Keywords
myocardial infarction - myxoma - cardiac catheterization/interventionpercutaneous
coronary intervention - cardiovascular surgery - echocardiography - tumor
Background
Primary cardiac tumors are relatively rare and fortunately, 80% are benign. Of the
latter, myxoma is the most common type (50% thereof).[1] Its incidence is under 0.2%; two-thirds of them are located in the left atrium (LA),
and less than a third in the right atrium (RA).[2] There is evidence that myxomas on the heart's left side can embolize and cause serious
complications. Myxomas on the heart's right side can also embolize, but they usually
cause a pulmonary embolism.[2] However, a paradoxical embolism is only possible in the presence of a cardiac-septum
defect. It can also cause embolization complications in the left circulation.
With this case, we describe an ST-segment elevation myocardial infarction (STEMI)
possibly caused by embolism fragments from a giant RA myxoma.
Case Presentation
A 64-year-old male patient suffering from a new onset of angina and nausea since the
previous day's evening was admitted to the emergency room at a primary-care hospital
not equipped to perform a percutaneous coronary intervention (PCI). After initial
noninvasive diagnostics (electrocardiogram, cardiac biomarkers), the patient was immediately
transferred to a clinic with a cardiac catheter laboratory because of ST-segment elevations
([Fig. 1]) and highly elevated cardiac biomarkers (CK max. 61.22 µmol/s.l., CK-MB max. 4.82
µmol/s.l.). Because of the delay since his first symptoms and their persistence, the
patient was immediately transferred from the stretcher to the catheter laboratory
table. Coronary angiography revealed an occluded proximal left anterior descending
(LAD) artery in segment 7 ([Fig. 2A, B]) and moderate-to-severe stenosis of the right coronary artery in segment 3.
Fig. 1 Electrocardiogram.
Fig. 2 Primary emergency percutaneous coronary intervention. (A and B) Left coronary artery with the arrow marking the total occlusion of the left anterior
descending artery. (C) Right coronary artery with the arrow marking the high-grade stenosis in segment
3.
After the guidewire was first passed through the completely occluded LAD where the
culprit lesion was located, the vessel was reopened almost completely and two drug-eluting
stents (DESs) were implanted. The patient was then given dual antiplatelet therapy
following guidelines.[3] Immediately after the emergency PCI, he underwent transthoracic echocardiography,
which surprisingly revealed a giant RA mass measuring 40 × 50 mm prolapsing into the
right ventricle ([Fig. 3]). His left ventricular ejection fraction was severely reduced after the STEMI with
apico- and anteroseptal hypokinesia. He underwent transesophageal echocardiography
to identify this intracardiac mass, confirming prior findings. Four days after the
culprit lesion's primary PCI, implanting a DES eliminated the remaining stenosis in
the right coronary artery's segment 3 ([Fig. 4C]). Eleven days after the STEMI, the patient was transferred to our department for
the resection of the RA's giant mass (occluding the tricuspid valve almost completely).
Fig. 3 Giant right atrial myxoma (*). (A) Transesophageal echocardiography. (B) Computed tomography scan. (C) Magnetic resonance tomography scan.
Fig. 4 (A) Initial left anterior descending artery's result after the first passage with the
guidewire through the total occlusion and finally (B) after implanting two drug-eluting stents. (C) Final result of the second inspection of the right coronary artery's percutaneous
coronary intervention.
Our department took additional computed and magnetic resonance tomographs to improve
surgical planning ([Fig. 3A, B]). The following day, the patient underwent a minimally invasive technique in an
usual manner via a right lateral mini-thoracotomy in the fifth intercostal space.
The heart was accessed via the RA, where the giant tumor became immediately visible.
The mass obstructed nearly the entire cavity. The tumor's macroscopic appearance revealed
an irregular, gelatinous exterior of friable, soft consistency corresponding to a
papillary myxoma confirmed later histopathologically ([Fig. 5]). It was broad-based, anchored to the septum primum, and approximately 50 mm in
diameter. In addition to the tumor, the patient also had a persistent foramen ovale
(PFO). The tumor was removed from the atrial myocardium, and then, the PFO could be
closed.
Fig. 5 Histopathological examination using light microscopy. Hematoxylin–eosin staining—inlay
Alcian blue staining with periodic acid-Schiff reaction. Tumor with few cells and
elements located subendothelial in loose, elongated structures, dominated by a myxoid
matrix.
A rethoracotomy complicated the patient's in-hospital postoperative course on the
first postoperative day due to diffuse postoperative bleeding, postoperative cognitive
dysfunction, and pneumonia. He was discharged on postoperative day 23 from the regular
ward to a rehabilitation facility. At the 1-year follow-up after surgery, he was clinically
free of complaints. His echocardiographs revealed good left ventricular function (55%)
with trivial mitral valve and mild tricuspid valve regurgitation.
Discussion
Wherever it is located, embolization from a myxoma is a life-threatening complication.
When located on the heart's right side, these tumors usually cause embolization in
the lungs. However, a paradoxical embolization is possible in the presence of a PFO.
In our case, fragments of a giant RA myxoma may have embolized and caused STEMI. To
the best of our knowledge, there are no published case reports on such a scenario.
The probability that a myxoma will embolize is 30 to 40%.[4] Other reports have described embolization rates that differ markedly between an
LA myxoma (45–60%) and RA myxoma (8–10%).[5] Therefore, we can assume that the numbers of undetected embolisms are certainly
higher than those described. Furthermore, embolization from an LA myxoma into the
coronary arteries has a reported probability of just 0.06%,[4] while various authors assume a more probable rate between 10 and 30% in patients
with myxoma embolisms.[6]
[7]
[8] While all the published reports so far consistently refer to LA myxomas, paradoxical
embolisms in the coronary arteries from an RA myxoma have not been described.[2]
[9] Similar to the paradoxical embolism of thrombotic material in deep vein thrombosis,
a slight increase in right atrial pressure (e.g., Valsalva maneuvers) suffices to
produce a short-term shunt reversal that can transport tumor tissue into the LA. Our
patient's RA myxoma of papillary type (known as a predictor for embolization itself[10] with its irregular, gelatinous exterior and friable, soft consistency) was immediately
adjacent to the concomitant PFO. The myxoma's immense size is potentially why the
PFO remained undetected on transesophageal echocardiography done immediately after
the STEMI.
Myxoma-related myocardial infarctions (MRMIs) are extremely difficult to discriminate
without echocardiographic evidence. However, there is often a substantial discrepancy
between the extent of the infarction and angiographic images because stenoses and
occlusions can only be documented angiographically in approximately 30% of cases or
they disappear in early follow-up.[2]
[10] A stenosis from an acute MRMI can naturally resemble an ordinary total or subtotal
occlusion of a coronary vessel. A recent literature search on the topic of myocardial
infarction as a complication of an LA myxoma revealed that only in approximately 15%
of cases were myxoma fragments obtainable for histopathological examination to support
the diagnosis.[2] Braun et al. assume that myxoma fragments may be subject to further fragmentation,
followed by distal dispersion of the myxomatous material. The histological composition
of myxomas, consisting of an amorphous tumor mass containing glycosaminoglycans with
no structural cellular organization, promotes the emboli's subsequent fragmentation.[2]
Additionally, substantial increases in cardiac biomarkers, also after spontaneous
recanalization, suggest that reperfusion often occurs too late to preserve the heart's
integrity.[2] In retrospect, our patient's culprit lesion behaved precisely like that of an MRMI.[2]
[10]
[11] The angiograph clearly showed how the total LAD occlusion disappeared after the
guidewire's passage, leaving no residual stenosis. In addition, we observed no typical
intracoronary “slow flow”—phenomenon, which is usually generally present after the
fragmentation of a thrombotic lesion with the visible, fragmented material entering
microvascular structures. We, therefore, believe that there is sufficient evidence
in the patient we describe here (e.g., high cardiac enzymes, severely increased ST
elevations, and strongly reduced left ventricular pump function despite the rapid
reopening of the occluded artery) that this was an acute coronary syndrome (ACS) possibly
caused by a paradoxical embolism from an RA myxoma.
If our patient had undergone echocardiography once before his catheter examination,
his treatment course might have been somewhat different. For the sake of fairness,
we should mention that PCI is unquestionably the method of choice in STEMI, even when
caused by a myxoma.[3] Although the guidelines no longer recommend thrombus aspiration,[3] the latter might have been another option under these circumstances, even knowing
echocardiographically that these were myxoma fragments. Thus, without dual platelet
therapy via acetylsalicylic acid and ticagrelor and without foreign material in the
coronary arteries, our patient could have undergone a myxoma resection and coronary
artery bypass surgery and would have carried a significantly lower risk of postoperative
bleeding.
Conclusion
An STEMI resulting from paradoxical embolization from a giant RA myxoma into the coronary
arteries is possible. Successful treatment entailing primary PCI followed by surgical
tumor resection via minimally invasive cardiac surgery is feasible, although if the
patient has already been on dual platelet therapy, their postoperative bleeding risk
is high. An ultrafast emergency transthoracic echocardiograph taken for orientation
before primary PCI in ACS may save the physician from unpleasant surprises before
primary PCI.
