Key Words
Aortic dissection - Hemodynamics - Surgery
Introduction
Acute Type A aortic dissection exists as a medical crisis with heightened mortality
attributable to an increased risk of aortic rupture or malperfusion[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]. Patients presenting with hemodynamic instability after Type A aortic dissection
have been documented to have excessive operative mortality ranging from 31.4% to 55%[11]. This operative mortality is not different from medical management alone, which
has been cited as high as 60% in-hospital[8]
[9]. There is a paucity of studies investigating the effect of hemodynamic instability
on early clinical outcomes and late survival, as well as the importance of surgical
decision making in patients with acute Type A aortic dissection. Our study sought
to evaluate whether patients presenting with hemodynamic instability have worse early
clinical outcomes and late actuarial survival following repair of acute Type A aortic
dissection compared to patients presenting without hemodynamic instability.
Materials and Methods
Patients
The Society of Thoracic Surgeons Databases at Beth Israel Deaconess, Carolinas Medical
Center, Missouri Baptist Medical Center, and Meijer Heart and Vascular Institute were
queried to identify all patients who underwent repair of aortic dissection between
January 2000 and October 2010. A total of 251 patients underwent repair for acute
Type A aortic dissections. Of those, 30 presented with hemodynamic instability and
221 presented without hemodynamic instability. Patients who presented with a Type
A dissection but did not have surgery were excluded.
A preoperative diagnosis of aortic dissection was accomplished using computed tomographic
angiography (CTA) or transesophageal echocardiography (TEE). The diagnosis was later
confirmed at the time of operation. A database was created for entry of demographics,
procedural data, and preoperative outcomes. These were prospectively entered by dedicated
data-coordinating personnel. Long-term survival data were obtained from the Social
Security Death Index (http://www.genealogybank.com/gbnk/ssdi/). Follow-up was 97% complete.
Prior to this analysis, study approval from the Institutional Review Board of each
center was obtained. Consistent with the Health Insurance Portability and Accountability
Act of 1996 (HIPAA), patient confidentiality was consistently maintained.
Definitions
Definitions for this study were obtained from the Society of Thoracic Surgeons' national
cardiac surgery database (available online at http://www.sts.org). Hemodynamic instability was defined as hypotension (systolic blood pressure < 80
mm Hg) or the presence of cardiac tamponade, shock, acute congestive heart failure,
myocardial ischemia, and/or infarction. Acute Type A dissection was defined as any
dissection involving the ascending aorta with presentation within 2 weeks of symptoms.
Cerebrovascular accident was defined as a history of central neurological deficit
persisting for more than 24 hours. Diabetes was defined as a history of diabetes mellitus
regardless of duration of disease or need for antidiabetic agents. Prolonged ventilation
was defined as pulmonary insufficiency requiring ventilatory support. Operative mortality
includes all deaths occurring during the hospitalization in which the operation was
performed (even if death occurred after 30 days from the operation), and those deaths
occurring after discharge from the hospital, but within 30 days of the procedure.
Operative Technique
The surgical approach did not differ between patients presenting with and without
hemodynamic instability. The diagnosis of Type A aortic dissection was confirmed by
TEE intraoperatively for all patients. Access was provided via a median sternotomy.
Total cardiopulmonary bypass was initiated with venous cannulation of the right atrium
and arterial cannulation of the femoral or right axillary artery. Myocardial protection
was ensured by cold blood cardioplegia administration through an antegrade approach
via the ostia of the coronary arteries and/or a retrograde approach through the coronary
sinus. Access through the right superior pulmonary vein was utilized for vent placement
in the left ventricle. The aortic root was restored by resection of the intimal tear
followed by replacement of the ascending aorta and resuspension or repair of the aortic
valve. The aortic clamp was removed and the aortic arch was inspected after attaining
a mean cooling temperature range of 15 to 18°C. The distal anastomosis was then completed
and antegrade aortic perfusion was established. Patients with irreparable damage of
the aortic root or valve underwent either a root replacement with a composite valve
graft and coronary button reimplantation, or a valve replacement with mechanical or
tissue prosthesis. If the aortic root could not be repaired, a root replacement was
performed. Reinforcement of the proximal and distal suture lines was accomplished
using Teflon (polytetrafluoroethylene) strips. Some patients required biological glue
(BioGlue surgical adhesive, Cryolife, Kennesaw, GA) to reapproximate the dissected
layers.
Data Analysis
Univariate Analysis. Univariate comparisons of preoperative, operative, and postoperative
variables were performed between patients presenting with hemodynamic instability
(n = 30) and those presenting without hemodynamic instability (n = 221). Normal distribution of continuous variables was assessed using the Kolmogorov-Smirnov
test. Continuous variables were tested using either the Student t test or the Mann-Whitney test, depending on the distribution of data. Categoric variables
were assessed by the χ2 or Fisher exact test, depending on the distribution of the data.
All tests were two-sided and a p-value < 0.05 was considered statistically significant.
Survival Analysis. Kaplan-Meier unadjusted survival estimates were calculated and
compared for patients presenting with hemodynamic instability versus patients presenting
without hemodynamic instability using a log-rank test. All analyses were conducted
using SPSS statistical software version 21 (IBM Corp, Armonk, NY).
Results
Preoperative Characteristics
Preoperative characteristics are summarized in [Table 1]. Creatinine was higher in patients with hemodynamic instability compared to those
without hemodynamic instability (P = 0.005).
Table 1.
Preoperative Patient Characteristics
|
Variable[a]
|
Hemodynamic instability
|
|
|
Yes (n = 30)
|
No (n = 221)
|
P-value
|
|
Age (years)
|
63 (38-82)
|
60 (19-87)
|
0.595
|
|
Diabetes
|
3 (10%)
|
14 (6%)
|
0.453
|
|
Hypertension
|
23 (79%)
|
175 (80%)
|
0.976
|
|
Ejection fraction
|
55 (35-75)
|
55 (15-73)
|
0.642
|
|
COPD
|
1 (3%)
|
18 (8%)
|
0.799
|
|
Creatinine
|
1.3 (0.8-3.8)
|
1.1 (0.4-12.5)
|
0.005
|
|
Female gender
|
9 (30%)
|
70 (32%)
|
0.853
|
|
Arrhythmias
|
5 (17%)
|
27 (12%)
|
0.493
|
|
NYHA class
|
|
|
0.319
|
|
I
|
3 (14%)
|
17 (11%)
|
|
|
II
|
2 (9%)
|
10 (6%)
|
|
|
III
|
1 (4%)
|
34 (21%)
|
|
|
IV
|
16 (73%)
|
101 (62%)
|
|
|
History of cerebrovascular accident
|
2 (7%)
|
16 (7.2%)
|
0.909
|
|
Number of diseased vessels
|
|
|
0.413
|
|
Zero
|
24 (80%)
|
191 (87%)
|
|
|
One
|
4 (14%)
|
12 (5%)
|
|
|
Two
|
1 (3%)
|
7 (3%)
|
|
|
Three
|
1 (3%)
|
11 (5%)
|
|
|
EF < 40
|
1 (3%)
|
13 (6%)
|
0.568
|
a Continuous data are shown as median (range) and categoric data are shown as percentage.
COPD = chronic obstructive pulmonary disease; EF = ejection fraction; NYHA = New York
Heart Association.
Operative Characteristics
Operative patient characteristics of patients with hemodynamic instability and without
hemodynamic instability who underwent repair for acute Type A aortic dissection are
presented in [Table 2]. Patients presenting with hemodynamic instability had a lower cardiopulmonary bypass
time compared to patients without hemodynamic instability (P = 0.039). A hemiarch technique was employed more frequently for patients with hemodynamic
instability compared to patients without hemodynamic instability (P = 0.002).
Table 2.
Operative Patient Characteristics
|
Variable[a]
|
Hemodynamic instability
|
|
|
Yes (n = 30)
|
No (n = 221)
|
P-value
|
|
CPB time >200 min
|
8 (27%)
|
92 (42%)
|
0.116
|
|
CPB time (minutes)
|
156 (5-411)
|
186 (64-684)
|
0.039
|
|
Circulatory arrest time (minutes)
|
15 (0-73)
|
16 (0-90)
|
0.591
|
|
Aortic valve procedure
|
|
|
0.609
|
|
Nothing
|
7 (23%)
|
55 (25%)
|
|
|
Replacement
|
2 (7%)
|
19 (9%)
|
|
|
Resuspension
|
17 (57%)
|
94 (43%)
|
|
|
Aortic root replacement
|
4 (13%)
|
52 (23%)
|
|
|
Distal anastomotic technique
|
|
|
|
|
Distal with cross-clamp
|
5 (17%)
|
59 (29%)
|
0.156
|
|
Open distal
|
24 (83%)
|
143 (71%)
|
0.278
|
|
Hemiarch technique
|
23 (77%)
|
102 (46%)
|
0.002
|
|
Total arch replacement
|
1 (3%)
|
24 (11%)
|
0.196
|
|
Arterial cannulation
|
|
|
0.340
|
|
Axillary
|
4 (16%)
|
46 (26%)
|
|
|
Femoral
|
12 (48%)
|
86 (50%)
|
|
|
Other
|
9 (36%)
|
42 (24%)
|
|
|
Retrograde cerebral perfusion
|
5 (17%)
|
24 (11%)
|
0.351
|
|
Antegrade cerebral perfusion
|
7 (23%)
|
56 (25%)
|
0.812
|
|
Bioglue/Felt Strip
|
|
|
0.321
|
|
Bioglue
|
14 (47%)
|
110 (50%)
|
|
|
Felt strip
|
10 (33%)
|
43 (20%)
|
|
|
Both
|
2 (7%)
|
23 (10%)
|
|
|
None
|
4 (13%)
|
45 (20%)
|
a Continuous data are shown as median (range) and categoric data are shown as percentage.
CPB = cardiopulmonary bypass.
Postoperative Characteristics
Postoperative characteristics are depicted in [Table 3]. Operative mortality (47% versus 14%) and cardiac arrest (30% versus 6%) were significantly
higher for patients presenting with hemodynamic instability (P < 0.001), compared to patients without hemodynamic instability. More patients with
hemodynamic instability experienced acute renal failure (43% versus 17%) compared
to patients presenting without hemodynamic instability (P = 0.001).
Table 3.
Postoperative Patient Characteristics
|
Variable[a]
|
Hemodynamic instability
|
|
|
Yes (n = 30)
|
No (n = 221)
|
P-value
|
|
Deep sternal wound infection
|
0
|
3 (1%)
|
0.521
|
|
Prolonged ventilation
|
19 (63%)
|
96 (47%)
|
0.087
|
|
Acute renal failure
|
13 (43%)
|
37 (17%)
|
0.001
|
|
Hemodialysis
|
5 (17%)
|
16 (7%)
|
0.080
|
|
Hemorrhage-related re-exploration
|
6 (20%)
|
37 (17%)
|
0.657
|
|
Cardiac arrest
|
9 (30%)
|
12 (6%)
|
<0.001
|
|
Stroke
|
5 (17%)
|
38 (17%)
|
0.943
|
|
Atrial fibrillation
|
7 (23%)
|
52 (25%)
|
0.832
|
|
Hospital length of stay (days)
|
15 (0-62)
|
10 (0-99)
|
0.569
|
|
Operative mortality
|
14 (47%)
|
30 (14%)
|
<0.001
|
a Continuous data are shown as median (range) and categoric data are shown as percentage.
Survival Analysis
Unadjusted Kaplan-Meier survival estimates are presented in [Figure 1]. There was a difference in the follow up time between groups (p = 0.007). Patients with hemodynamic instability had a median follow-up time of 1542
days (range = 1-4082), while those without hemodynamic instability had a median follow
up time of 2154 days (range= 1-4800). Actuarial 10-year survival was lower for patients
with hemodynamic instability, compared to those without (44% versus 63%, respectively,
log-rank P = 0.007).
Figure 1. Actuarial unadjusted 10-year survival curves for patients with hemodynamic instability
versus patients without hemodynamic instability.
Discussion
Our study is among few studies comparing operative characteristics and early and late
postoperative outcomes between patients presenting with and without hemodynamic instability
following acute Type A aortic dissection repair. Hemodynamic instability negatively
impacted the postoperative outcomes and survival of patients who underwent surgical
repair of Type A aortic dissection, compared to hemodynamic instability presentation.
These results affirm the notion that patients presenting with hemodynamic instability
fare worse than those without hemodynamic instability after surgical repair for acute
Type A dissection.
Principal Findings
Operative Mortality. Patients in our study presenting with hemodynamic instability
had significantly higher operative mortality rates compared to patients without hemodynamic
instability (P < 0.001). Previous studies have also documented worse survival for patients with
hemodynamic instability[11]
[12]. Specifically, Trimarchi et al.[11] documented 31.4% in-hospital mortality among patients with hemodynamic instability
compared to 16.7% for stable patients (P < 0.001). The even higher operative mortality for hemodynamically unstable patients
in our study could be explained by the fact that Trimarchi et al.[11] consolidated patients with neurologic instability, mesenteric ischemia, and acute
renal failure into their hemodynamic instability cohort, whereas our hemodynamic instability
cohort did not include patients with neurologic instability or intestinal malperfusion.
Operative Characteristics. Hemodynamically unstable patients had shorter cardiopulmonary
bypass time and more hemiarch repairs. The shorter cardiopulmonary bypass time in
hemodynamically unstable patients is due to the lower rate of patients requiring aortic
root replacements (a more time consuming operation compared to the resuspension or
replacement of the aortic valve), compared to the patients without hemodynamic instability.
The higher incidence of hemiarch repairs in patients with hemodynamic instability
may be attributed to the more extensive aortic dissection in this subset of patients
compared to the patients without hemodynamic instability.
Postoperative Outcomes and Survival. Early postoperative outcomes such as atrial fibrillation
and stroke rates were comparable between patients with and without hemodynamic instability.
However, acute renal failure was higher for patients with hemodynamic instability
compared to those without hemodynamic instability, secondary to preoperative hypotension
in patients with hemodynamic instability. Actuarial 10-year survival was worse for
patients who presented with hemodynamic instability than those without ([Fig. 1]). However, most of the mortalities in the hemodynamic instability group occurred
in the early postoperative phase, compared to the later phase where the differences
in survival between groups were less pronounced.
Timing of Surgery versus No Surgery
Our study documented an excessive operative mortality of patients who presented with
hemodynamic instability compared to those without. The mortality of patients presenting
with hemodynamic instability is similar to the mortality for medical management of
patients with Type A aortic dissection, according to recent data documenting a 42%
30-day survival in medically treated acute Type A dissections[7]. Our present data, with a 47% operative mortality in Type A dissection patients
presenting with hemodynamic instability, suggests that therapy in this subgroup should
be individualized and some patients may be candidates for surgery. However, patients
with significant comorbidities may be candidates for medical or possibly delayed surgery.
Clinical Implications
We conducted a multi-institutional observational study to assess the impact of hemodynamic
instability on operative characteristics and on short- and long-term outcomes following
repair of acute Type A aortic dissection. In this study we examined an unselected
cohort of patients from four academic institutions. This is among few studies comparing
early clinical outcomes and 10-year actuarial survival between patients with and without
hemodynamic instability following repair of acute Type A aortic dissection. In our
study, hemodynamic instability adversely affected early clinical outcomes and survival
following repair of acute Type A aortic dissection. Based on the results of our study,
treatment of patients with hemodynamic instability should be individualized because
of the excessive early operative mortality. However, long-term survival is comparable
between patients with hemodynamic instability and those without hemodynamic instability.
Study Limitations
Inherent limitations of a retrospective multi-institution investigation unavoidably
affected our study. The analysis may also have introduced bias since nine different
surgeons from four different institutions performed the operations. Patients who were
lost to follow-up were not contacted for this study. Further examination regarding
reoperations on the remaining dissected aorta, the causes of late mortality, and the
fate of the false lumen were outside the scope of our analysis. These should be the
focus of future studies evaluating long-term outcomes of acute Type A aortic dissection
repair.
Conclusions
Hemodynamic instability has a profoundly negative impact on early outcomes and operative
mortality in patients with acute Type A aortic dissection. However, late survival
is comparable between hemodynamically unstable and non-hemodynamically unstable patients.
