Key words cardiac - CT - coronary angiography - health policy and practice
Table of contents
1. Preamble
2. Introduction
3. Clinical evidence for coronary computed tomography
3.1 Guidelines
3.2 Calcium scoring
3.2.1 Calcium scoring in asymptomatic patients
3.2.2 Calcium scoring in symptomatic patients
3.2.3 Calcium scoring for risk reclassification and for treatment management
3.3 Coronary CT angiography
3.4 Additional parameters
4. Examination technique
4.1 CT calcium scoring
4.2 Coronary CT angiography
4.3 Special considerations for pediatric patients
5. Patient safety
5.1 Ionizing radiation
5.2 Contrast agent
5.3 Allergic reaction
5.4 Contrast-induced nephropathy
5.5 Effects on thyroid function
5.6 Medication-based vessel dilation
5.7 Medication-based heart rate control
6. Reporting
6.1 Qualification recommendations
6.2 Reporting
6.3 Structured reporting
6.4 CAC-DRS, MESA percentile, and CAD-RADS
6.4.1 CAC-DRS
6.4.2 MESA percentiles
6.4.3 CAD-RADS
6.5 Extracardiac findings
6.6 Opinion regarding radiology reporting
7. Quality of care
8. Reimbursement
9. Summary
1. Preamble
This position paper is a joint statement of the German Radiological Society (DRG)
and the Professional Association of German Radiologists (BDR), which reflects the
current state of knowledge about coronary computed tomography. It is based on preclinical
and clinical studies that have investigated the clinical relevance as well as the
technical requirements and fundamentals of cardiac computed tomography.
2. Introduction
Coronary computed tomography (CT) was first used in the 1980 s to evaluate the perfusion
of saphenous aortocoronary-bypass grafts [1 ]. However, by the end of the millennium, in spite of the worse spatial resolution,
the focus was primarily on electron beam CT (EBT) because of the higher temporal resolution
of up to 50 ms [2 ]
[3 ]. As a result of the further technical development of CT, particularly the introduction
of spiral CT, coronary CT-angiography (cCTA) has been able to be performed since the
2000 s in selected patients. However, since the introduction of the 64-slice CT scanner,
cCTA can now be performed in the majority of patients to be examined in clinical practice
with sufficiently high diagnostic image quality. The constant technical innovations
in CT in recent years have further improved the image quality, thereby allowing implementation
in previously unsuitable constellations, e. g. tachycardia and arrhythmia in atrial
fibrillation [4 ].
In the same time period, a significant increase in the number of invasive diagnostic
coronary angiography examinations was observed in Germany. In 2019 in Germany, approx.
726 300 invasive coronary angiography examinations (1999: 561 623) were performed.
However, a percutaneous coronary intervention (PCI) was also performed in only approx.
41 % of cases (absolute: 295 799) compared to approx. 30 % of cases (absolute: 166 132)
in 1999 [5 ]
[6 ]. Even though the mortality rate of ischemic cardiomyopathy in Germany decreased
between 1999 and 2014 from 356 to 189 per 100 000 inhabitants, Germany was still only
in 15th place in the European comparison in 2014 despite the high number of coronary
angiography examinations [7 ]
[8 ].
Even the National Disease Management Guidelines on Chronic Coronary Artery Disease
(2016), which were modified for the first time with respect to noninvasive methods
and particularly cCTA and which indicate the importance of cCTA particularly in patients
with a pretest probability between 15 % and 50 % due to the method's high negative
predictive value, have had little effect on the number of invasive examinations in
Germany [9 ].
The results of prospective clinical studies in recent years with large patient populations
that underwent cCTA examination, for example the SCOT-HEART trial [10 ], the PROMISE trial [11 ], and the ISCHEMIA trial [12 ], and the pretest probabilities for coronary artery disease, which were adjusted
based on the results of these studies [13 ], caused a paradigm shift in the current European ESC guidelines “Chronic Coronary
Syndrome” (CCS) [14 ]. In these ESC guidelines published in 2019, noninvasive coronary assessment, generally
in the form of functional tests like stress Magnetic Resonance Imaging (MRI), stress
echocardiography, and single-photon emission computerized tomography (SPECT), and
the morphological method cCTA are assigned a more important role in the workup of
chronic coronary syndrome. cCTA continues to be primarily recommended in the group
with low-intermediate pretest probability. The DISCHARGE study published in 2022 also
supports and confirms this paradigm shift. This large prospective multicenter study
examined the value of coronary CT and the use of an invasive cardiac catheter for
the detection of relevant chronic heart disease in patients with stable chest pain
and intermediate risk [15 ].
The determination of the amount of coronary calcium with “calcium scoring” (CASC)
is also increasingly taken into consideration in the guidelines with respect to risk
stratification. The CASC is used in the current ESC guidelines [11 ]
[12 ]
[13 ] primarily for estimating the “clinical probability” for coronary artery disease
[13 ] ([Fig. 1 ]).
Fig. 1 Pretest-probability and clinical likelihood [16 ].
For these reasons, an increase in cCTA examinations and a decrease in exclusively
diagnostic coronary angiography examinations can be expected in the coming years.
This position paper discusses the current state of knowledge about coronary CT with
respect to clinical evidence, quality of care, patient safety, legal aspects, and
reimbursement and provides an overview of future developments.
3. Clinical evidence for coronary computed tomography
3. Clinical evidence for coronary computed tomography
3. 1 Guidelines
The ESC guidelines regarding the diagnosis and management of chronic coronary syndrome
and the National Disease Management Guidelines on Chronic Coronary Artery Disease
were updated in 2019. To include the pathophysiology of coronary artery disease as
a dynamic process of a chronic progressive but also regressive disease in the nomenclature,
the original term “stable coronary artery disease” was retained in the ESC guidelines.
The categorization of the disease based on clinical manifestation as acute coronary
syndrome (ACS) and CCS is new [14 ].
In patients with suspicion of CCS, after the first impression, a detailed patient
history including symptoms, comorbidities, and other possible causes for symptoms
is first taken. A physical examination is then performed to evaluate the probability
of coronary artery disease. If there is a probability of coronary artery disease,
an ECG is performed, and the probability of ACS is evaluated. One possible approach
is described in the guidelines “Chest Pain” (being updated) of the German College
of General Practitioners and Family Physicians (DEGAM) [16 ]. Transthoracic echocardiography and lab tests can additionally be performed if necessary.
In the case of persistent suspicion of CCS, the pretest probability of coronary artery
disease can be assessed based on the patient's age, sex, and symptoms. The pretest
probability of coronary artery disease was recalculated based on the CT data of the
PROMISE and SCOT-Heart trials among other things. In general, this resulted in a reduction
in pretest probabilities of up to 66 % compared to the values in the ESC guidelines
from 2013 [17 ]. The pretest probabilities provide the basis for the selection of further diagnostic
procedures, for example, an invasive cardiac catheter examination is indicated in
the case of a pretest probability > 85 %. This threshold is no longer reached or exceeded
when using the updated values ([Fig. 2 ]) so that, based on the new updated pretest probabilities, there is, as a rule, initially
no primary indication for an invasive cardiac catheter examination in patients with
suspicion of CCS. The pretest probability can be modified by determining the newly
introduced “clinical probability” which includes the known triad of age, sex, and
symptoms as well as cardiac risk factors or prior examinations (echocardiography,
stress ECG, or calcium scoring) ([Fig. 1 ]). However, since consideration of the classic risk factors does not result in a
better prediction of the presence of coronary stenoses [18 ], “it is difficult to assess the performance of the 'clinical probability' concept”
[19 ]. According to the CCS guidelines, invasive cardiac catheter examination is only
recommended as an “alternative test to diagnose coronary artery disease in patients
with high clinical probability and severe treatment-refractory symptoms or in the
case of typical angina even at a low stress level and clinical evaluation indicating
a high risk of a cardiovascular event” [20 ]
[21 ].
Fig. 2 Pretest probability of obstructive coronary artery disease in symptomatic patients
according to age, sex, and type of symptoms [13 ]. Dark blue: Groups in which noninvasive tests are most advantageous (pretest probability
> 15 %). Light blue: Groups with a pretest probability for coronary artery disease
between 5 % and 15 % in which a test for diagnosis on the basis of the clinical evaluation
can be considered.
Thus, primary noninvasive imaging is currently recommended in patients with suspicion
of CCS. This applies to all patients with an intermediate risk (pretest probability
15–85 %). Depending on local availability and expertise, either noninvasive functional,
i. e., ischemia detection, methods like stress echocardiography, stress MRI, stress
PET, and stress SPECT, or the morphological method cCTA can be used for this purpose
[20 ]
[21 ]. According to the current National Disease Management Guidelines on Chronic Coronary
Artery Disease, coronary CT is preferred particularly in the case of a low-intermediate
pretest probability of 15–50 % [22 ].
3.2 Calcium scoring
A non-contrast low-dose CT examination for determining the calcium score can be a
standard component of a cCTA examination for the workup of coronary artery disease.
The most widely used and best studied calcium scoring method is the quantitative Agatston
method (see the “Examination technique” section).
3.2.1 Calcium scoring in asymptomatic patients
Numerous studies and meta-analyses were able to show that asymptomatic patients without
a measurable amount of coronary calcium (Agatston score 0) have only a low risk for
cardiovascular events and no elevated overall mortality in the medium and long term
[23 ]
[24 ]. For example, the Heinz-Nixdorf-Recall study was able to show that the relative
risk for a cardiovascular event in the case of a calcium score of 1–99, 100–399, 400–999
and ≥ 1000 is increased by a factor of 1.7, 4.0, 5.4, and 16.1, respectively [25 ]
[26 ]. In a meta-analysis of 13 studies including 71 595 asymptomatic patients, one cardiovascular
event occurred in only 0.47 % of 25 903 patients with a calcium score of 0 in the
medium-term follow-up period of 50 months. In contrast, there was one cardiovascular
event in 4.14 % of asymptomatic patients with a calcium score > 0 corresponding to
a relative risk of 0.15 (95 % CI: 0.11–0.21; p < 0.001) [27 ].
A higher percentage of atherosclerotic changes in the case of a CAC score of 0 was
seen in the prospective multicenter SCAPI (Swedish Cardiopulmonary Bioimage) study.
A cCTA examination and a CAC scan were evaluated in 25 182 randomly selected individuals
between the ages of 50 and 64 who were asymptomatic and without any known coronary
artery disease. Athersclerotic changes were seen in 5.5 % of those in the group with
a negative CAC score of 0. These changes were significant in 0.4 %. The percentage
of cases of atherosclerosis in participants with a negative calcium score and a moderate
10-year risk due to cardiovascular risk factors was higher. Atherosclerosis was seen
in 9.2 % of cases [28 ].
However, there is currently no study data allowing a final conclusion about calcium
scoring with respect to possible screening examinations. Since early detection examinations
for detecting non-communicable diseases, like calcium scoring examinations in asymptomatic
individuals, e. g. as part of regular checkups, may only be performed as part of controlled
screening programs approved by the German Federal Ministry for the Environment, Nature
Conservation, and Nuclear Safety in accordance with current regulations (§ 84 Radiation
Protection Act), there is currently no legal basis for performing calcium scoring
in this patient group.
3.2.2 Calcium scoring in symptomatic patients
The value of calcium scoring in symptomatic patients is unclear. A meta-analysis of
data from 10 355 patients who underwent coronary angiography due to suspicion of coronary
artery disease or acute coronary syndrome showed coronary stenosis > 50 % in 56 %
of these patients. Calcium scoring with a value > 0 had a sensitivity of 98 %, a specificity
of 40 %, a negative predictive value (NPV) of 93 %, and a positive predictive value
of 68 % [27 ].
Among other things, the high NPV in this study was often used as an argument for not
performing any additional examinations in the case of a CAC score of 0 (gatekeeper
function) [29 ] In contrast, a subgroup analysis of the CORE64 study showed an NPV of only 68 %
for coronary artery disease [30 ], and in the CONFIRM Register 3.5 % of patients with a CAC score of 0 had coronary
stenosis ≥ 50 % and 1.4 % ≥ 70 % [31 ].
Studies using CT scanners of the latest generation in patients with a significant
amount of coronary calcium, e. g. patients prior to planned TAVI [32 ]
[33 ], show that it is possible to rule out relevant coronary artery disease with cCTA
also in this patient population with a high percentage. Therefore, a function test
with an ischemia detection method is recommended as the next step in the recommendations
of the guidelines regarding CCS in the case of a high CASC in preliminary diagnostics
and thus a high clinical pretest probability [14 ].
3.2.3 Calcium scoring for risk reclassification and for treatment management
A retrospective cohort study including 13 644 patients showed the relationship between
the presence and extent of CAC and the use of statin therapy for risk reduction in
atherosclerotic cardiovascular diseases [34 ]. The data from the MESA study has shown that the coronary calcium score not only
provides superior discrimination and risk classification compared to other subclinical
imaging markers or biomarkers [35 ]
[36 ] but it is also strongly associated with the 10-year risk for atherosclerotic cardiovascular
diseases. This association is independent and incremental with respect to traditional
risk factors and can be seen in a graduated manner regardless of age, sex, and ethnic
group [37 ].
An analysis of the Heinz-Nixdorf-Recall study was able to show that the additional
determination of the calcium score (score = 0 vs. score ≥ 100) improves the stratification
of patients with a high and low risk for coronary events [38 ]. Presumably, calcium scoring can thus help to perform an intensive risk factor modification
adapted to the atherosclerotic plaque burden and the actual risk.
In patients with a borderline (5–7.4 %) or intermediate (7.5–19.9 %) risk for coronary
artery disease according to the AtheroSclerotic CardioVascular Disease (ASCVD) Risk
Score, calcium scoring can be used for individual risk evaluation for primary prevention,
e. g., with statin therapy [39 ]
[40 ]. In these groups, the determination of coronary artery calcification can result
in a reclassification in a significant percentage of patients. For example, patients
with an Agatston Score ≥ 100 or ≥ 75th age/sex/race percentiles can be reclassified
in a higher risk group and those with a score of 0 in a lower risk group [40 ]
[41 ].
The latest information regarding the use of calcium scoring for prevention in clinical
practice indicates that calcium scoring improves current risk stratification and treatment
decisions in people with hypertriglyceridemia without clinically relevant ASCVD risk
[42 ].
Therefore, the cumulative 5-year ASCVD incidence was 15.9 % for a calcium score over
100 and 7.2 % for a calcium score of 0 in patients who qualify for treatment with
icosapent ethyl (approved for lowering triglycerides since the end of 2021) and 13.9 %
and 1.5 %, respectively, in those who do not qualify for this medication. This results
in a number needed to treat of 29 for a calcium score greater than 100 and 64 for
a calcium score of 0 for those qualifying for treatment with icosapent ethyl and a
number needed to treat of 33 and 304, respectively, for patients who do not qualify
for treatment with icosapent ethyl. Therefore, the calcium score could be used, for
example, in the case of uncertainty regarding the use of statin therapy or for making
decisions about additional treatments. However, there is a risk of undertreatment
of patients with a calcium score of zero and overtreatment of patients with an elevated
calcium score [43 ]. Therefore, for example, the ASCVD incidence for patients with a calcium score of
0 meeting the treatment requirements for icosapent ethyl increased to 10.8 % over
a 10-year observation period. The results of the study by Cainzos-Achririca et al.
can therefore provide a basis for the planning of randomized controlled studies for
clarifying these questions [40 ].
In summary, in every CCS workup, a non-contrast CT scan for calcium scoring can be
recommended prior to coronary CT angiography to determine an additional risk parameter,
to identify patients with an extremely large amount of coronary calcium, and to perform
a function test, e. g. a stress MRI, instead of coronary CT angiography, if applicable.
Calcium scoring examinations in asymptomatic individuals, e. g., as part of regular
checkups, are not allowed in accordance with current regulations.
3.3 Coronary CT angiography
With the adjusted pretest probabilities of coronary artery disease [13 ] that have been included in the current European Guidelines on Chronic Coronary Syndrome
[14 ], noninvasive coronary CT imaging has been given a significantly more important role
in the workup of chronic coronary syndrome.
The COURAGE trial [44 ], the SCOT-HEART trial [19 ], the PROMISE trial [45 ], and the ISCHEMIA trial [12 ], among others served as starting points for this development. With the publication
of the COURAGE trial in 2007, which examined coronary artery disease patients with
positive detection of ischemia and at least 70 % proximal coronary stenosis, the prognostic
advantage of coronary revascularization was examined for the first time. The results
showed that coronary intervention in addition to optimal medical treatment does not
reduce the risk of death, heart attack, or other severe cardiovascular events in this
patient population.
The SCOT-HEART trial showed that patients with stable chest pain who underwent coronary
CT in addition to standard diagnostics in the workup of suspicion of coronary artery
disease had a significantly lower rate of myocardial infarction (2.3 % vs. 3.9 %,
p = 0.004) after an average of 4.8 years due to more intensive preventive treatment
based on the CT results.
The results of the randomized ISCHEMIA trial were published in 2020 [10 ]
[12 ]. A total of 5179 patients with noninvasively detected myocardial ischemia received
either optimized medication-based treatment alone or in addition to invasive coronary
angiography and possibly revascularization [12 ]. In 73 % of patients, coronary CT served as a gatekeeper to rule out patients with
relevant left main artery stenosis (> 50 %) and to detect at least one single-vessel
coronary artery disease with stenosis ≥ 50 % in one of the 3 coronary arteries. The
agreement between cardiac catheter and CT was 97.1 % for the presence of a relevant
left main stenosis ≥ 50 % and 92.2 % for the presence of significant coronary heart
disease with stenosis ≥ 50 % in at least one coronary artery [46 ]. In the invasive group, 78 % of patients underwent revascularization. However, there
was no significant difference in the cumulative 5-year event rate (death due to cardiovascular
causes, myocardial infarction, hospitalization due to unstable angina pectoris, acute
cardiac insufficiency, or survived cardiac death) (16.4 % in the invasive group and
18.2 % in the conservative group). There was also no significant group difference
with respect to overall mortality (1.7 % vs. 1.0 % after one year and 9.0 % vs. 8.3 %
after 5 years) also with respect to the secondary end points cardiovascular death
and myocardial infarction. One advantage of the invasive approach was seen with respect
to disease symptoms. In patients suffering from angina pectoris at the start of the
study, complete freedom from symptoms could be achieved in 30 % more patients than
with medication-based treatment alone [12 ]. On the whole, the ISCHEMIA trial showed that patients with suspicion of coronary
artery disease benefit only symptomatically but not prognostically from an initial
invasive diagnosis and treatment strategy after exclusion of left main stenosis via
coronary CT compared to best medical treatment. As a limitation, it must be stated
that during the approximately 5-year course of the study, 23 % of patients initially
treated conservatively ultimately underwent coronary revascularization [12 ].
As mentioned above, there is currently no indication for calcium scoring alone as
a screening method. At present, the same is also true for coronary CT angiography.
However, for the future, cCTA is the only noninvasive method capable of detecting
or ruling out unstable, non-calcified plaques. This raises the question as to whether
coronary CT angiography could be useful in the future as a screening examination.
As a first step, an answer to this question can only be provided by scientific examination
of the topic in a narrowly defined group. This is also made possible by the changes
in the Radiation Protection Act regarding screening, which allow implementation after
scientific review within a narrow legal framework (§§ 84, 14 (3) Radiation Protection
Act) [47 ].
In summary, based on the indicated studies, it can be stated that cardiac CT is equivalent
to other invasive and noninvasive diagnostic methods with respect to its diagnostic
significance in the primary diagnosis of CCS. Cardiac CT reduces the number of invasive
catheter angiography examinations, the number of revascularization procedures, and
the number of myocardial infarctions [10 ]
[48 ]. Based on the current ESC guidelines, there is hardly a direct indication for invasive
diagnostic procedures in patients with suspicion of chronic coronary syndrome.
3.4 Additional parameters
In addition to classic and established parameters in the analysis of coronary CT examinations
like calcified, mixed, and non-calcified plaque, degree of stenosis, length and diameter
of stenosis, additional plaque parameters have become increasingly established for
evaluating cardiac risk. These parameters far exceed the simple degree of stenosis,
as seen in invasive coronary angiography, and allow a more differentiated characterization
of coronary lesions.
The ROMICAT II trial and the PROMISE trial were able to define various plaque parameters
as independent and incremental risk factors for the occurrence of a cardiac event.
These qualitative parameters are ([Fig. 3 ]):
Fig. 3 High-risk plaque features based on the finidings of the ROMICAT II- and PROMISE-trial:
positive remodeling a ; low attenuation b ; spotty calcifications c ; napkin ring sing d , marked with arrows.
Positive remodeling: Expansive, outward plaque growth without relevant stenosis of
the vessel.
Low attenuation plaque: Non-calcified atherosclerotic lesions with areas with low
density (< 30 HU). These correspond to a fatty core.
Spotty calcifications: Small calcifications (< 3 mm) with a high density (> 130 HU)
within the atherosclerotic lesion.
Napkin ring sign: Ring-shaped areas with increased density around a hypodense core
of a non-calcified atherosclerotic lesion.
These changes are associated with an elevated risk for a relevant cardiac event both
in patients with ACS and in those with CCS, and they are therefore also referred to
as vulnerable or high-risk plaque features. Treatment should be reviewed and adjusted
as needed [49 ].
The presence and extent of these high-risk plaque parameters should be an essential
part of a coronary CT report. This was already taken into consideration in the current
guidelines of the American Society of Cardiovascular Computed Tomography (SCCT) from
2021 [50 ]. The effect of these parameters on treatment regime is the current object of intensive
research.
In addition to morphological parameters, other quantitative functional parameters
will certainly become more important in the future for creating cardiac CT reports.
The determination of the CT-based fractional flow reserve or CT-FFR has the greatest
potential here. The FFR is determined via invasive pressure wire measurement during
a cardiac catheter examination. The FFR provides the ratio of the mean intraarterial
pressure of a coronary artery directly downstream from the stenosis (Pd) compared
to the maximum pressure without stenoses or upstream from the stenosis (Pa) under
maximum hyperemia. This is performed via the intravenous administration of adenosine
during a cardiac catheter examination. For years it has been the invasive gold standard
for determining the hemodynamic relevance of a coronary stenosis [51 ].
With the help of mathematical models known as computational fluid dynamics (CFD),
the principle was applied to CT data thus allowing noninvasive evaluation of hemodynamic
conditions with respect to the relevance of a stenosis [52 ]. This plays a role particularly in intermediate stenoses [53 ]
[54 ]. The PLATFORM study was able to show in patients with suspicion of coronary artery
disease that the rate of cardiac catheterization without detection of obstructive
coronary artery disease can be significantly reduced by using the CT-FFR (CT-FFR:
12 % vs. ICA: 73 %) [55 ]. This is limited by a lack of broad availability since to date only one clinically
approved application is commercially available. This application can only be used
off-site in the form of a cloud-based solution. Not yet commercially available software
solutions based on machine learning from various manufacturers [56 ]
[57 ] that can be used on-site also show very promising results and may soon be commercially
available. Nevertheless the use of this comparably expensive method can already be
helpful in individual cases from the standpoint of patient wellbeing and with respect
to economic aspects.
4. Examination technique
Quality standards regarding the examination technique used in non-contrast cardiac
CT for calcium scoring and coronary CTA provide the basis for good diagnostic significance.
The image quality of the examination should be assessed by a specialist immediately
after completion of the reconstructions on the CT scanner. Various anatomical landmarks
which are listed in detail in the two sections “CT calcium scoring” and “coronary
CT angiography” are used for visual quality assessment.
The two examination techniques have the following in common: To avoid motion artifacts,
CT scans must be acquired with at least 64 detector rows and a rotation time of < 0.35
seconds. Prospective ECG triggering or retrospective ECG gating should be used depending
on heart rate and the presence of arrhythmia. The patient is in a supine position
with arms over the head. The heart should be in the isocenter of the scanner. Both
the topogram and the scan should be acquired in inspiration. The CTDIvol is based on the current reference values, adapted to the particular medical question.
The standard matrix for visualization of the heart should be a small Field-of-View
(FOV) 512 × 512 pixels adapted to the size of the heart. Moreover, an additional scan
with a “large” FOV completely covering the thorax and the surrounding soft tissues
must be acquired to visualize secondary findings. The heart is reconstructed with
a smooth (soft) kernel. The thorax is additionally reconstructed with a hard kernel.
Cardio or stent-specific kernels are also available depending on the manufacturer.
4.1 CT calcium scoring
The patient is positioned and prepared as described above. The artifact-free visualization
of calcifications of the coronary arteries and the heart valves and the identification
of the coronary ostia are the basis for the visual quality assessment of the image.
The boundaries of the scan region are the carina and the cardiac apex. The recommended
scan parameters are 100–120 kV, a rotation time of < 0.35 seconds, and a collimation
of < 1 mm in spiral mode. In the case of scanners with a corresponding detector width,
individual rotations with complete acquisition are also possible. For calcium scoring,
an individual series in end-diastole is needed. For the reconstruction of images of
the heart and the thorax, the slice thickness and the increment should be 3 mm to
ensure comparability with the published calcium scores, mainly the Agatston score
[58 ]. For example, windowing can be performed with a width (w) of 400 HU and a center
(c) of 100 HU, but these can vary as needed.
4.2 Coronary CT angiography
Optimal image quality is reliably achieved when the patient has a low heart rate of
≤ 65 beats/minute and a regular heart rhythm during the examination. If this requirement
is not met, a beta blocker should be administered (see the section “Medication-based
heart rate control”). In addition, nitrates should be administered to improve vessel
lumen evaluation (see the section “Medication-based vessel dilation”). Heart rhythm,
rate, blood pressure, and all administered medications must be documented.
The basis for the visual quality assessment of the image is the ability to identify
coronary plaques and the leaflets and cusps of the heart valves. To ensure adequate
enhancement of the coronary arteries (blood pool > 250 HU), the contrast agent should
be adapted to the patientʼs weight (0.2–0.4 g iodine/kg body weight). An iodine delivery
rate of 1.2–2.0 g iodine/second is recommended [59 ]. Using a contrast agent with 300 mg iodine/ml results in a volume of 60–80 ml contrast
agent and an injection rate of 4–6 ml/s for the average patient. The standard for
the triggering of a scan is bolus tracking (cutoff value 120–180 HU), with the positioning
of the region of interest (ROI) depending on the scanner type. Alternatively, a test
bolus strategy can be used. [60 ]
The scan region should extend at least from the aortic bulb to the cardiac apex in
patients after bypass operations when an arterial in-situ bypass is to be visualized.
Prior to TAVI, the region can be expanded to include the subclavian artery. Typical
scan parameters are 70–120 kV, rotation time of < 0.35 seconds (360°), and a collimation
of < 0.7 mm. In the case of a regular, low heart rate (< 65 beats/minute), dose-sparing,
prospective ECG triggering can be used. If these requirements are not met, the more
robust, retrospective ECG gating with or (in exceptional cases with pronounced arrhythmia)
without ECG-adjusted dose modulation should be used. However, this is associated with
higher radiation exposure. The reconstructed slice thickness for evaluating CTA should
be ≤ 0.7 mm. In the case of prospective ECG triggering, multiple cardiac phases should
be reconstructed to identify the phases with minimal motion artifacts or various phases
for every coronary artery. The minimum requirements for retrospective ECG gating are
two spatially overlapping reconstructions (increment < slice thickness) of the heart.
Moreover, curved or straightened MPRs of the LAD, CX, and RCA should be created. For
example, the window width can be 600 HU and the window center 200 HU. This can be
adjusted as needed. Supporting reconstruction algorithms, e. g. for artifact reduction
or quality improvement, with iterative reconstruction are optional.
4.3 Special considerations for pediatric patients
For the pediatric patient population, suitable, age-adapted protocols with a reduced
dose should be used (e. g., the lowest possible tube voltage). In the case of optimal
examination conditions, high-pitch/single-shot protocols are also available depending
on the scanner. The amount of contrast and flow rate should be reduced based on age
and size. Non-contrast examinations for calcium scoring are usually not indicated
in young patients.
5. Patient safety
When the safety measures recommended when using ionizing radiation are taken into
consideration and when properly indicated, computed tomography is a safe examination
technique. Possible risks can result from the use of ionizing radiation, the administration
of iodinated contrast agents and nitroglycerin, and the use of medication-based heart
rate control.
5.1 Ionizing radiation
Like every examination using ionizing radiation, CT is subject to the Radiation Protection
Act and the Radiation Protection Ordinance [61 ]. When used properly, CT does not result in any acute deterministic radiation effects
due to the low doses used by modern CT scanners. Chronic and delayed radiation effects
require a differentiated assessment.
McCollough et al. estimate that a CT scan with a dose between 1 and 10 mSv is associated
with a risk of fatal cancer of 1:2000 [62 ]. The natural incidence of fatal cancer of approx. 400:2000 (20 %) increases in this
dose range by 0.2 % to 20.02 % (401:2000) [63 ]. For certain tumor entities, there may be other additive risks depending on the
total dose. However, there was no increased cancer risk also in this case for doses
less than 30 mSv [64 ]. In the case of an average dose of approx. 4.4 mSv for a diagnostic coronary angiography
examination [65 ] and an average dose of 0.63–4.7 mSv for a coronary CT examination [66 ], the risk of fatal cancer for coronary CT is lower than or approximately equal to
an invasive diagnostic coronary angiography.
However, there is an additional complication risk for invasive diagnostic coronary
angiography due to the invasiveness of the examination. The risk of non-fatal complications
(e. g., asymptomatic occlusion of the radial artery, hematoma at the puncture site)
in coronary angiography is 1–30 % and the risk of fatal complications is 0.08–0.1 %
[67 ]
[68 ]
[69 ]. Therefore, regardless of possible therapeutic consequences, coronary CT has a significantly
better safety profile for the patient when comparing complication frequency and severity.
Of course, only physicians with the corresponding CT expertise can correctly determine
the indication for CT and perform coronary CT examinations. In addition to the regulations
in the Radiation Protection Act, Section 299a of the German Criminal Code prohibits
the taking of bribes in the health care sector. Therefore, the referring physician,
usually a general practitioner, internist, or cardiologist, may not receive any direct
or indirect personal advantage as a result of a CT examination. Critical review of
the indication helps to ensure patient safety and use of the 4-eyes principle ensures
economic efficiency. In statutory health insurance, in accordance with the Quality
Assurance Agreements per § 135 Paragraph 2 of the German Social Code Book V (in connection
with the Regulations on Continuing Medical Education of the State Chambers of Physicians),
radiological methods like MRI, CT, and angiography can only be performed by specially
qualified radiologists [70 ]
[71 ].
5.2 Contrast agent
In general, the non-ionizing, low-osmolar, iodinated contrast agents typically used
today are very safe. The incidence of acute side effects is approx. 0.2–0.7 % [72 ]
[73 ]
[74 ] and the incidence of severe acute side effects is approx. 0.04 %. Fatal contrast
agent reactions are very rare with an incidence of 1:170 000 [75 ].
5.3 Allergic reaction
The incidence of allergic reactions is estimated to be 0.05–0.1 % after intravenous
administration of iodinated contrast agents and is even lower (0.03–3 %) for non-ionizing
contrast agents as normally used today [76 ]
[77 ]
[78 ]
[79 ]. The risk factors for hypersensitivity to iodinated contrast agent are not fully
understood [78 ].
5.4 Contrast-induced nephropathy
Compared to invasive coronary angiography, cardiac CT has an advantageous safety profile
with respect to the risk for contrast-induced nephropathy. At present, contrast-induced
nephropathy is believed to be extremely rare, particularly in CT. However, the actual
incidence of contrast-induced nephropathy is still not sufficiently known in spite
of numerous studies. However, the available data indicate that the intravenous administration
of an iodinated contrast agent in patients with an eGFR ≥ 45 ml/min/1.73 m2 is not an independent risk factor for post-contrast acute kidney failure and that
post-contrast acute kidney failure in patients with an eGFR between 30 and 45 ml/min/1.73 m2 is very rare [80 ]
[81 ]
[82 ]
[83 ]. Two studies showed an elevated risk for contrast-induced nephropathy in patients
with an eGFR < 30 ml/min/1.73 m2
[80 ]
[81 ]
.
In comparison to other examinations using contrast agent, invasive coronary angiography
seems to have an elevated risk for contrast-induced nephropathy. The intraarterial
and suprarenal contrast injection resulting in a short and insignificantly diluted
contrast bolus in the kidneys may be responsible for this. In addition, the risk of
arterio-arterial thromboembolisms due to catheter manipulation should be mentioned
[82 ]
[84 ]
[85 ]
[86 ].
5.5 Effects on thyroid function
Iodinated contrast agents can disrupt thyroid function, e. g., hyperthyroidism, or,
in the presence of latent hyperthyroidism, can trigger manifest hyperthyroidism. Moreover,
the use of scintigraphy to diagnose thyroid diseases, e. g., an autonomous adenoma,
is blocked for at least 3 months by the administration of iodine.
Although clinically relevant, the prevalence of thyroid dysfunction caused by iodinated
contrast agents has not been sufficiently studied. The published data shown a prevalence
between 0.05 % and 5 % but this rate is higher in patients with preexisting thyroid
disease [87 ]
[88 ]
[89 ]
[90 ]. Although it is rare, the disease can have severe or even life-threatening consequences
if it goes untreated. Therefore, as a rule, thyroid dysfunction is ruled out prior
to the administration of an iodinated contrast agent. This is usually done by performing
a lab test to determine the patient's basal TSH level. However, there are currently
no generally accepted recommendations in this regard [89 ]
[91 ].
5.6 Medication-based vessel dilation
Provided that there are no contraindications, nitrates should be administered prior
to CTA to cause vasodilation thereby allowing optimal vessel lumen evaluation [92 ]. 400–800 mg sublingual nitroglycerin that can be administered either as a tablet
or spray (typically 1–2 tablets or 1–2 sprays) are commonly used [93 ]. The 800 mg dose and the spray form are typically preferred due to the ease of application
[94 ]. To ensure optimum effectiveness, the spray should be administered sublingually
approximately 5 minutes prior to the examination. After administration, the duration
of action is approximately 20–30 minutes [95 ]. It is recommended to administer the spray after measuring the patientʼs blood pressure
on the CT table to avoid syncopal episodes caused by a sudden drop in blood pressure
[96 ]. An overview of contraindications and common side effects is provided in [Table 1 ].
Table 1
Contraindications and common side effects of the administration of nitroglycerin premedication.
HOCM, hypertrophic obstructive cardiomyopathy.
Contraindications
Phosphodiesterase inhibitors
Severe hypotension (systolic blood pressure under 90 mm Hg)
Severe aortic valve stenosis, HOCM
Allergy to nitrates or other ingredients
Side effects
Drop in blood pressure, syncope
Headache, dizziness, lightheadedness
Tachycardia
Allergic reaction
Asthenia at the administration site
5.7 Medication-based heart rate control
For optimal image quality, a heart rate ≤ 65 beats per minute with the lowest possible
variability should be targeted even in the case of modern CT scanners [97 ] (see the section “Examination technique”). Heart rate is typically controlled by
the administration of cardioselective beta blockers (e. g., metoprolol) prior to the
start of the examination [98 ]. Under the consideration of comorbidities and contraindications ([Table 2 ]), no clinically relevant complications were seen in multiple large studies. Raju
et al. retrospectively evaluated the data of 662 patients, who received an average
of 19 mg metoprolol (maximum 67 mg) until the target heart rate of less than 60 beats
per minute was reached [99 ]. No unwanted side effects were seen. Kassamali et al. reported similar results in
679 patients who underwent coronary CT angiography. The average metoprolol dose was
20 mg (maximum: 70 mg). Complications were seen in 10 (1.47 %) patients, with the
complications requiring intervention in only 3 (0.44 %) patients [99 ]. The complications included a second-degree atrioventricular block in two patients.
Table 2
Contraindications and side effects with respect to the administration of ß-blockers
for heart rate control.
Contraindications
(Allergic) bronchial asthma or severe chronic obstructive pulmonary disease
Mobitz type II or III atrioventricular block
Bradycardia (under 50 beats/minute)
Severe hypotension (systolic blood pressure under 100 mm Hg)
Acute congestive heart failure
Allergy to beta blockers or their ingredients
Side effects
Bronchospasm
Bradycardia
Atrioventricular block
Hypotension
Raynaud's phenomenon
Allergic reaction
Titrated intravenous administration of metoprolol has become established. One possible
dosing scheme is initial i. v. administration of 5 mg followed by 2.5 mg i. v. every
3–5 minutes until the target heart rate is achieved. The recommended highest dose
is 15 mg i. v. To reduce the preparation time in the scanner, oral administration
of 100 mg one hour prior to the examination is also possible if local conditions allow
[98 ]. The cardioselective beta blocker esmolol i. v. can be used as an alternative in
patients with bronchial asthma requiring treatment. It has a rapid onset of action
but a short half-life of only 9 minutes. Administration is adapted to body weight.
50–100 µg/kg body weight is recommended here. The slightly less favorable risk profile
compared to metoprolol must be taken into consideration. Therefore, it should only
be used in the indicated patient population. A further possibility for lowering heart
rate is to administer benzodiazepines, e. g., 1 mg lorazepam sublingual, or ivabradine
(If -channel inhibitor) per os.
In summary, cCTA has a very favorable risk-benefit profile compared to invasive coronary
angiography when properly indicated according to the CCS guidelines. This is true
with regard to both the possible consequences of ionizing radiation and unwanted contrast
agent side effects. The application of contrast agent during CT imaging is established
globally and has a very low complication rate. Predisposing factors must be investigated
during the informed consent discussion and taken into consideration accordingly. Contrast
agents should be applied in accordance with the approved uses, and the contrast administration
protocol should be adjusted to the particular medical question and CT scanner.
Sufficient heart rate control during cardiac CT imaging is important for ensuring
good diagnostic image quality. Various medications and application forms can be used
here. These should be selected based on individual experience, the patient, and applicability.
All of these drugs have a favorable risk profile and are established in the clinical
routine. Major complications caused by the administration of medication were not observed
[99 ]. In contrast, the frequency of relevant complications during diagnostic coronary
angiography (death, myocardial infarction, stroke, pericardial effusion or tamponade,
percutaneous coronary intervention due to iatrogenic coronary dissection, or unplanned
bypass operation within 72 hours after diagnostic left hearth catheter examination)
is 0.082–0.44 % [100 ]
[101 ].
6. Reporting
6.1 Qualification recommendations
Cardiac CT is an integral part of the advanced training curriculum published by the
German Radiological Society and the German Young Radiology Forum, and the module “M5
heart and vessels” describes in detail the cardiac imaging training content [102 ] (https://www.forum-junge-radiologie.de/de-DE/4927/curriculum/ ). The ensure the quality standards of cardiac cross-sectional imaging, the Cardiac
and Vascular Diagnostics working group of the German Radiological Society created
a level-based certification program for cardiac imaging, which, starting with the
second qualification level, far exceeds the knowledge needed to become a board-certified
radiologist. The qualification levels can be achieved separately for CT and MRI and
include the following levels:
Qualification level Q1 corresponds to fundamental knowledge of the heart anatomy,
the (patho)physiology, the indications, technical implementation, and reporting in
adults.
Qualification level Q2 indicates an ability to independently perform and interpret
cardiac cross-sectional imaging. The Q2 qualification level builds on level Q1 and
requires a thorough understanding of the subjects listed above.
Qualification level Q3 requires comprehensive knowledge of cross-sectional cardiac
imaging. Achieving this level also means that the physician is qualified to review
applications submitted to the certification program of the Cardiac and Vascular Diagnostics
working group.
The prerequisites for achieving each qualification level are a certain number of CME
points from a Q-course certified by the Cardiac and Vascular Diagnostics working group,
a fixed number of interpreted and documented examinations, and, starting at Q2, successful
completion of an exam. Details can be found on the website of the Cardiac and Vascular
Diagnostics working group (https://www.ag-herz.drg.de/de-DE/1201/ueberblick/ ). The examination numbers can be documented online using the case collections on
the CONRAD platform or optionally using the European Cardiac MR/CT Registry (https://www.mrct-registry.org/ ) of the European Society of Cardiovascular Radiology. Registry in the ESCR MR/CT
Registry is mandatory.
In addition to the certification of medical personnel, centers and courses can also
be certified. As part of the consolidation of medical technical professions in the
German Radiological Society, certification for radiographers is also offered. Detailed
information and documentation regarding the individual certification processes can
be found online on the homepage of the Cardiac and Vascular Diagnostics working group
(https://www.ag-herz.drg.de/de-DE/129/zertifizierung/ ).
6.2 Reporting
The examination report should contain at least the following: Clinical data for determining
the proper indication and estimating the pretest probability of coronary artery disease,
like symptoms, onset of symptoms, cardiovascular risk factors, and known prior examinations.
Data regarding the examination technique including acquisition technique and administered
medication, image postprocessing, examination quality, and findings: Calcium score,
presence of coronary anomalies, type of coronary circulation, plaques (calcified,
mixed, not calcified, high-risk), coronary stenoses, heart valves, pericardium, extracardiac
findings. Information regarding radiation exposure. In addition, decision aids that
are important for the referring physician should be included in the report in the
form of a classification or percentiles so that important clinical consequences are
standardized and easy to identify.
6.3 Structured reporting
In addition to traditional reports written in free form, structured reporting has
become increasingly established in the clinical routine. Various studies have shown
that structured reporting results in a lower rate of diagnostic errors, a higher level
of completeness and understandability of the radiology report, and a higher level
of satisfaction on the part of the referring physician and other colleagues [103 ]
[104 ]. Ghoshhajra et al. were able to show in a study on cCTA that the agreement between
radiologists and referring physicians with respect to the number of coronary arteries
with severe stenosis increased significantly (53 % (free form) vs. 68 % (structured
report); p = 0.04; κ = 0.31 vs. 0.52) [105 ]. Especially in the context of medically and technically demanding examinations with
intensive interdisciplinary communication like cardiac CT, these characteristics are
significantly more important.
In addition to numerous general radiological societies [106 ]
[107 ], multiple cardiovascular imaging societies have expressed their support for structured
reporting in a joint consensus paper [108 ]. The European Society of Cardiovascular Radiology issued a concrete recommendation
for structured reporting in the case of pre-transcatheter aortic valve replacement
(TAVR) cross-sectional imaging [109 ].
To make structured reporting templates broadly available, the Cardiac and Vascular
Diagnostics working group created a number of templates during a consensus conference
[110 ]. They are based on the corresponding recommendations of the professional societies
depending on the pathology with the goal of promoting a high-quality standard for
reporting. All templates created to date are available online via an open-source license
(www.befundung.drg.org ) and can be used directly for reporting. English-language reporting templates of
the Radiological Society of North America (RSNA) and the European Society of Radiology
(ESR) can be found on the platform www.radreport.org .
6.4 CAC-DRS, MESA percentile, and CAD-RADS
For calcium scoring and cCTA, structured decision support tools have also become established
in the clinical routine in the form of the Coronary Artery Calcium Data and Reporting
System (CAC-DRS) and Coronary Artery Disease Reporting and Data System (CAD-RADS)
classification systems [111 ]. The CAD-RADS classification in particular is important for reporting. With respect
to the amount of coronary calcium, the MESA percentiles are given preference over
the CAC-DRS classification for the reasons mentioned above.
6.4.1 CAC-DRS
The CAC-DRS allows classification of the Agatston values for structured reporting,
however without adjustment for age and sex [58 ] ([Table 3 ]). Classification is performed preferably based on the Agatston score (A0: score
0, A1: score 1–99, A2: score 100–299, A3 ≥ 300) or alternatively visually (V0: no
coronary calcifications to V3: significant amount of coronary calcium) primarily in
the case of non-ECG-gated examinations [112 ]
[113 ]. The modifier N describes the number of affected coronary vessels (example: Agatston
score 287 in 2 vessels = CAC-DRS 2/3). In addition, pharmacopreventive measures can
be derived from the CAC-DRS classification.
Table 3
Classification according to CAC-DRS and treatment recommendations (according to [105 ]). ASA, acetylsalicylic acid.
CAC-DRS
Agatston Score
Risk
Treatment recommendation
0
0
Very low
No statin therapy (exception: familial hypercholesterolemia)
1
1–99
Slightly elevated
Moderate statin therapy
2
100–299
Elevated
Moderate to intensive statin therapy plus ASA 100 mg
3
> 300
Elevated to extremely elevated
Intensive statin therapy plus ASA 100 mg
The standardization of the classification makes it possible to ensure a standardized
and targeted evaluation of the amount of coronary calcium and to provide information
in a compact and clear manner to the disciplines providing further treatment.
Alternatively, in clinical practice and in studies like the analysis of the SCOT-Heart
Study [114 ], the calcium score is divided into six categories: 0: none; 1–10: minimal; 11–100:
low; 101–400: moderate; > 400: pronounced; > 1000: severe coronary sclerosis.
6.4.2 MESA percentiles
Moreover, structured categorization on the basis of percentile curves based on the
results of the Multi-Ethnic Study of Atherosclerosis (MESA) study is recommended [113 ]. These thus allow classification of the Agatston Score in the appropriate reference
group weighted according to age, sex, and ethnicity. While an Agatston Score of 100
would be classified as low for an 84-year-old patient within the framework of the
atherosclerotic aging process, the same Agatston Score would be high for a 45-year-old
patient. Doubling of the Agatston Score is associated with a 15–35 % higher probability
of a relevant cardiac event (stroke, myocardial infarction, cardiovascular death)
[27 ]
[113 ].
An online tool for calculating MESA percentiles is available free of charge (at https://www.mesa-nhlbi.org/Calcium/input.aspx ). The report should include the calculated percentiles.
6.4.3 CAD-RADS
The CAD-RADS classification depends on the degree of stenosis and the number of affected
vessels. The degree of stenosis is classified based on the percentage lumen diameter
stenosis ([Table 4 ]). All vessels with a diameter of more than 1.5 mm should be used for the evaluation.
The CAD-RADS classification does not apply to vessels with a diameter of less than
1.5 mm. Evaluation is not recommended. Allocation to one of the CAD-RADS classes is
performed largely based on the maximum detected degree of stenosis ([Table 5 ]) [115 ]. The category “CAD-RADS 4” is divided into the subcategories 4A (70–99 % stenosis)
and 4B (stenoses in 3 coronary arteries > 70 % or > 50 % stenosis of the left main
coronary artery) [115 ]. The CAD-RADS categories are accompanied by recommendations regarding the further
diagnostic approach and patient management ([Table 5 ]) [115 ].
Table 4
The degree of stenosis is determined based on the percentage lumen diameter stenosis
(according to [110 ]).
Lumen diameter stenosis [%]
Nomenclature
0
No stenosis
1–24
Minimal stenosis
25–49
Minor stenosis
50–69
Moderate stenosis
70–99
Severe stenosis
100
Occlusion
Table 5
CAD-RADS categories in chronic coronary syndrome (according to [109 ]). CAD, coronary artery disease.
Maximum degree of stenosis [%]
Interpretation
Further diagnostic workup
Patient management
CAD-RADS 0
0 (no stenosis or plaque)
CAD ruled out
None
CAD-RADS 1
1–24
Minimal non-obstructive CAD
None
Preventive therapy
Risk modification
CAD-RADS 2
25–49
Mild non-obstructive CAD
None
Preventive therapy
Risk modification
Particularly in the case of plaques and multiple affected segments
CAD-RADS 3
50–69
CAD with moderate coronary stenosis
Consider function testing
CAD-RADS 4
A: 70–99
CAD with severe coronary stenosis
A: Consider function testing or invasive coronary angiography
Symptom-based, anti-ischemic, and preventative pharmacotherapy
Risk factor modification
Consider further treatments, incl. revascularization, according to guidelines
B: Left main > 50 % or 3 coronary arteries > 70 %
B: Invasive coronary angiography
CAD-RADS 5
100 (occlusion)
CAD with complete occlusion of a coronary artery
Consider invasive coronary angiography or vitality diagnostics
CAD-RADS N
Non-diagnostic examination quality
Not possible to rule out CAD
Consider alternative/additional diagnostic workup
–
The CAD-RADS classification system also uses modifiers. The category “CAD-RADS N”
is used for examinations with non-diagnostic quality. The modifier can be used alone
or in combination with one of the numeric categories (example: CAD-RADS 4/N = left
main stenosis > 50 %, the remaining coronary segments cannot be evaluated). Other
modifiers that can be added in an analogous manner are “S” (stent), “G” (graft = bypass),
and “V” (vulnerable). The V modifier is used when a plaque has two or more of the
high-risk plaque features mentioned above (low-density plaque, positive remodeling,
microcalcifications, napkin ring sign) and is therefore a vulnerable plaque ([Fig. 3 ]).
6.5 Extracardiac findings
In addition to the heart, other anatomical structures are always also imaged during
cardiac cross-sectional imaging examinations resulting in incidental and secondary
findings in a significant number of examinations [116 ]. According to the literature, the rate of incidental findings is 6–58.5 % [117 ]
[118 ]. The type of imaging that is performed affects the prevalence of incidental findings.
They are seen most rarely in the case of non-contrast CT for calcium scoring and more
frequently in examinations to evaluate bypass vessels or pulmonary veins [119 ]. According to a systematic review of 13 studies, the frequency of incidental findings
in cardiac CT angiography is 41 % with 16 % being clinically relevant [120 ]. Suspicious pulmonary masses (26.6 %), hiatal hernias (20.8 %), aortic anomalies
(10.8 %) were most common with a cumulative frequency of 58.2 % among the 2160 clinically
significant extracardiac incidental findings. In one study on emergency care by Onuma
et al., an alternative extracardiac disease was able to be identified as the cause
of acute angina pectoris symptoms in 16 % of patients based on cardiac cross-sectional
imaging so that further imaging was not necessary [121 ]. Dewey et al. were able to confirm this with 12.9 % detected extracardiac causes
for atypical angina pectoris [122 ]. In a further study by Lehmann et al., extracardiac findings changed management
in 1.3 % of patients and provided an alternative explanation for angina pectoris symptoms
in 4.1 % of patients [123 ]. Moreover, the detection rate of incidental findings is higher if a large field
of view representing the entire acquired anatomy was reconstructed [124 ].
While life-threatening diseases like lung cancer can be detected early, follow-up
examinations can result in additional radiation exposure and costs without proven
benefit [119 ]
[125 ]. Due to their comprehensive specialist training and broad medical knowledge, radiologists
are uniquely qualified to evaluate corresponding incidental findings and to minimize
the above-described disadvantages. The reconstruction of a large field of view for
complete coverage of the entire scan volume and all relevant findings is therefore
mandatory.
6.6 Opinion regarding radiology reporting
In summary, to ensure high-quality patient care, cardiac computed tomography requires
the competence of a radiology specialist in order to meet the method- and content-related
demands regarding cardiac CT and structured reporting, to comply with radiation protection
regulations, to interpret extracardiac findings, and to possess the necessary overview
of non-organ-related pathophysiological relationships between the thorax and upper
abdomen. Care provided by those outside the discipline cannot fully meet these demands.
In addition to professional competence in radiology, the 4-eyes principle should be
employed when determining the indication for cardiac CT in order to ensure examination
quality. The ability to correctly determine indication and to estimate radiation exposure
and consequences with respect to not only the heart but also the other organs included
in the scan is an essential skill of radiology specialists. Regular continuing and
advanced training in this very dynamic area of medicine is also important. To interpret
cardiac CT examinations, a radiologist must have reached at least Q2 status according
to the Cardiac and Vascular Diagnostics working group of the German Radiological Society.
For quality assurance, not only regular discussion of the findings with the referring
non-radiology colleague(s) but also incorporation of the corresponding selective expertise
of the other cardiovascular disciplines from cardiac surgery, pediatric cardiology,
and cardiology is useful. This exchange makes a significant contribution to mutual
quality assurance in patient care and helps to ensure targeted diagnostic workup of
every patient that is as comprehensive as possible.
Coronary CT has numerous diagnostic possibilities, but the limitations must also be
taken into consideration. In classic coronary CT as in invasive coronary angiography,
diagnostic evaluation of the myocardium is not possible. Inflammatory changes of the
myocardium, e. g., in the case of myocarditis, fibrosis, and myocardial scars, cannot
be diagnosed. Adjustments to the CT protocol for specific medical questions are possible
in principle, e. g. when acquiring a late contrast phase to evaluate myocardial contrast
enhancement in the case of inflammation, when performing dynamic contrast-enhanced
imaging to detect a hypoperfused region when diagnosing ischemia, or when using functional
imaging to detect movement abnormalities in the case of myocardial scars [126 ]
[127 ]
[128 ]. However, this is the exception in the clinical routine. It is important to have
sufficient knowledge of the advantages and disadvantages of the additionally available
diagnostic methods like MRI and SPECT and to use them accordingly. Only in this way
can patients be directed to the best possible diagnostic method for their clinical
symptoms and particular medical issue which is decisive for correctly determining
the indication.
7. Quality of care
The quality of care in Germany with respect to coronary CT is ensured on various levels
and by various structures, for example, the German Radiological Society under the
guidance of the Cardiac and Vascular Diagnostics working group, and the Professional
Association of German Radiologists. In these societies, radiologists are categorized
as clinical or academic-scientific, and participate in regular training and continuing
education programs. This is implemented in all organizational forms of outpatient
and inpatient radiology in Germany.
This broad and high-quality clinical care is provided by the 86 cardiovascular centers
and 1750 people in Germany currently certified by the Cardiac and Vascular Diagnostics
working group of the German Radiological Society (status 11/20). 11.7 % attain cardiovascular
training status Q3, 16.6 % reach level Q2, and 71.7 % receive the initial certificate
Q1. Since 2015, the number of certified centers has increased by 300 % (2015: 21)
and the number of certified specialists by 235 % (2015: 475). The data from the previous
year with the corresponding growth is shown in [Fig. 4 ]
[129 ]. 56 of the 99 (56.6 %) postal code regions in Germany have direct access to a certified
center with 2 centers being located in 9 regions and 3 centers in 4 regions. [Fig. 5 ] shows the coverage in Germany based on a 30-minute, 45-minute, and 60-minute driving
time [129 ]. These numbers show that for coronary CT the transition from limited local availability
to widely available expertise has already been successfully accomplished.
Fig. 4 Number of DRG centers and individuals certified for cardiovascular imaging (2015–2021).
Fig. 5 Overview of the cardiovascular imaging certified centers (red crosses) in Germany
in November 2022 and their corresponding catchment areas in 30/45/60 minutes driving
time (dark blue/light blue/turquoise). Triangles represent CT Q2- and Q3-certified
radiologists, circles for MRI Q2- and Q3-certified radiologists.
In the future, quality-assuring measures for coronary CT examinations should be created,
established, and continuously further developed as in the case of other already established
quality-assuring measures (e. g. the methods used for stroke treatment or chest pain
units which have recognized certification methods) ([130 ]
[131 ]). Possible benchmarking parameters could be, for example, good or very good image
quality in > 90 % or > 95 % in patients receiving sublingual administration of nitroglycerin
and/or ß-blockers.
As a result of the creation of the Cardiac and Vascular Diagnostics working group
in 2001 and the establishment of continuous certified training, continuing education,
and advanced training programs in 2010, quality-assured cardiac and vascular imaging
is now widely available in Germany. The steady increase in certified centers and people
([Fig. 4 ]) is a strong indicator of an established effective specialization process and the
success of the dedicated training, continuing education, and advanced training programs.
This development was also supported by a structured continuing education program of
the German Radiological Society as the foundation for the certification of centers.
Cardiovascular continuing education programs are offered throughout Germany, locally
and nationally, as separate continuing education courses and workshops and in the
form of conventions (e. g. annual convention of the ESCR, German Cardiodiagnostic
Days (https://www.kardiodiagnostik.de )) and the German X-ray Congress). This is supported by a comprehensive online program
both in Germany and internationally, e. g., the courses of the ESR. In addition, the
fully digital learning platform CONRAD with selected and diverse DICOM data-based
real cardiovascular case presentations allows flexible training, continuing education,
and advanced training as well as certification not just during the global COVID-19
pandemic restrictions.
In summary, radiology in private practice and in the hospital ensures broad availability
of high-quality, specialized patient care. Key elements for ensuring this quality
of care have been established since 2010 by the Cardiac and Vascular Diagnostics working
group of the German Radiological Society and have been continuously further developed.
The certification of both individuals and centers is a further important component
of quality assurance. The multilevel course system with the necessary requirements
ensures a nationwide high level of quality in radiology and cardiac imaging. Further
quality assurance measures are regular scientific conventions, continuing education
events, and a digital learning platform of the Cardiac and Vascular Diagnostics working
group of the German Radiological Society.
8. Reimbursement
Cardiac CT examinations are not yet sufficiently represented in the GOÄ (medical fee
schedule) and the EBM (uniform value scale). As part of ongoing work to update the
two physicianʼs fee scales, concrete service legends and assessment proposals were
provided by the Professional Association of German Radiologists. The report from the
Institute for Quality and Efficiency in Health Care from 2020 recommended a benefit
assessment for cardiac CT [133 ]. It was then classified in 2021 as a new examination method by the Federal Joint
Committee in accordance with § 135 Paragraph 1 Sentence 1 of the Fifth Book of the
Social Code. In 2022, the Federal Joint Committee examined whether cCTA improves the
current diagnostic process in the case of suspicion of chronic coronary artery disease
and will be available in the future as a service covered by statutory health insurance
[134 ]. However, it is still unclear when corresponding updates would actually be implemented.
Therefore, in the outpatient sector, billing for this service is only currently possible
based on the GOÄ (medical fee schedule).
For this purpose, together with the German Radiological Society, the Cardiac and Vascular
Diagnostics working group, and the FuNRAD (Forum of Radiologists in Private Practice),
the Professional Association of German Radiologists published a joint recommendation
for the billing of cardiac CT and MRI examinations [135 ]. The recommendation is limited to the representation of regularly billable fee schedule
items and services that are additionally necessary or billable in the individual case.
Coronary CT angiography is thus currently billed as chest CT with supplementary images,
multiple contrast-enhanced high-pressure injections, ECG, computer-aided analysis,
as well as a detailed report, possibly supplemented by pulse oximetry. The fee amount
is to be determined in the individual case by determining the suitable increase factor
(§ 5 GOÄ).
9. Summary
In national and international guidelines on the diagnosis of chronic coronary syndrome
and chronic coronary artery disease, coronary CT has become the diagnostic method
of first choice in all patients with an intermediate risk and has replaced diagnostic
coronary angiography particularly in patients with a low-intermediate risk (15–50 %).
This development was based on the PROMISE study, the SCOT-HEART study, and the ISCHEMIA
study and on the risk tables derived from these studies.
In the case of correct determination of indication and correct technical implementation,
coronary CT has a low risk for complications, particularly compared to diagnostic
invasive coronary angiography.
The minimal technical requirement for implementation is a CT scanner with at least
64 rows and a rotation time of less than 0.35 s.
As part of the CCS workup, a non-contrast CT scan should be performed prior to coronary
CTA for calcium scoring.
Coronary CT requires the skills of a competent, specialized, and Q2- or Q3-certified
radiologist to meet the method-related demands regarding cardiac CT, structured reporting,
radiation protection, and extracardiac findings in order to ensure high-quality patient
care.
Reimbursement must currently be considered insufficient.
The quality of care in Germany is already very good thanks to good spatial coverage
with specially qualified radiologists.
Nationwide care by qualified radiologists is ensured even in the case of increasing
demand. Since no additional CT units need to be installed and services can only be
rendered upon GP and specialist referral in order to prevent non-indicated volume
increases, this process is also economically viable.
