Home Is Where the Heart Is: A Case of a Cardiac Pseudomass in a Patient with Acute Coronary Syndrome

Clinical History

Figure 1. 12-lead ECG demonstrating t-wave inversion in inferior leads.

On admission, her troponin levels were markedly elevated (5418.5 ng/L, reference range: 0-19 ng/L).The patient was treated on the lines of acute coronary syndrome with intravenous enoxaparin, anti-platelets and statins following which she underwent coronary angiography. Coronary angiography revealed a dominant right coronary artery (RCA) circulation. A contrast filled saccular aneurysm was seen arising from the proximal posterior descending artery (PDA). A short segment filling defect with contrast staining in its periphery was seen in proximal posterolateral ventricular branch without associated luminal narrowing, which was thought of as a coronary thrombus/embolus or a type I spontaneous coronary artery dissection (SCAD, Figure 2). Due to the diagnostic dilemma between thrombus/embolus and SCAD, the cardiologist decided to manage it conservatively and follow it up on a repeat coronary angiography. Since there was ongoing myocardial ischemia, the aneurysm was considered for interventional management by elective coil embolization as per institutional expertise. A transthoracic 2D echocardiography revealed good systolic ejection fraction and an echogenic mass like lesion with tiny internal cystic spaces just inferior to the annular attachment of posterior leaflet of tricuspid valve within right ventricular (RV) cavity. (Figure 3, Movie 1)

Figure 2. Catheter angiography showing a filling defect with peripheral contrast staining in posterolateral ventricular branch (black arrow in a and b) and an eccentric contrast filled saccular aneurysm arising from posterior descending artery (asterix in a, b and c). Left main, LAD and left circumflex were normal (d). LAD = left anterior descending; LMA = left main coronary artery; PDA = posterior descending artery; PLV = posterolateral ventricular; RCA = right coronary artery.

Figure 3. 2D transthoracic echocardiogram showing an echogenic mass like lesion with tiny internal cystic spaces in posterior sub tricuspid region of right ventricular cavity, with no demonstrable internal vascularity.

Movie 1. Subcostal and four chamber view in 2D and color Doppler transthoracic echocardiogram demonstrating the echogenic lesion in close relation to the posterior leaflet of tricuspid valve. There was no associated tricuspid regurgitation or stenosis.

CMR Findings

Cardiac MRI was performed at 1.5 T (Philips Multiva) for studying the tissue characteristics of the lesion found on echocardiogram by adopting the standard institutional protocol for cardiac masses consisting of a double inversion stack of black blood axial images, T1WI axial stack, balanced turbo field-echo (s-BTFE) cine sequences in 2 chamber, 4 chamber and short axis views, first pass rest perfusion, early and delayed enhancement. An additional RV inlet-outlet cine sequence was also obtained. The patient heart rate was 89 bpm at the time of acquisition with sinus rhythm.

Normal sized cavities with good LV systolic ejection fraction of 61%. A 15×15 mm rounded structure was seen within the subtricuspid basal inferior RV cavity near the posterior RV insertion point appearing isointense to adjacent myocardium on double inversion recovery (DIR) black blood sequences and on T1WI weighted images. On short tau inversion recovery (STIR) images, the lesion appeared mildly hyperintense. There was mild hyperintensity in basal inferior and inferoseptal myocardium of left ventricle (Figure 4).

Figure 4. A rounded lesion (red asterix) isointense to myocardium on (a) DIR- black blood images and (b) T1 axial images and mildly hyperintense on (c) STIR images. Also note the mild myocardial hyperintensity in basal inferior and infero-septal segments (black arrow).

On s-BTFE cine images, the lesion appeared centrally bright with a thin wall that was isointense to the myocardium. An additional RV inlet-outlet view helped to optimally demonstrate the spatial relationship between the lesion and the posterior tricuspid leaflet superiorly and the posterior interventricular groove posteroinferiorly. (Figure 5, Movie 2) In addition, regional wall motion abnormality was detected in the form of hypokinesia of the basal inferior myocardial segment (AHA segment 4).

Figure 5. s-BTFE cine images depicting the lesion (red asterix) in (a) 4 chamber , (b) SA and (c) RV inlet-outlet view.

Movie 2. s-BTFE SA cine demonstrating the lesion as well as mild hypokinesia of basal inferior wall.

On first pass perfusion images, the lesion showed no contrast enhancement in the RV and left ventricular cavity phase, followed by an appearance of intense homogenous central contrast enhancement surrounded by a hypointense wall just after the LV cavity phase persisting into the myocardial phase (Figure 6). Additionally, a sub-endocardial perfusion defect was detected in the basal inferior myocardial segment (AHA segment 4). On early enhancement images (Inversion Recovery Turbo Field Echo with breath holding (IR_TFE_BH), time delay: 5 min, TI: 440 msec), there was diminished intralesional contrast similar to LV blood pool and its wall could no longer be discerned separately. There was no evidence of blood clot in LV cavity or microvascular obstruction in LV myocardium.

On delayed enhancement (IR_TFE_BH, time delay: 10 min, TI: 320 msec with incremental TI values based on an IR_TFE Scout), the lesion remained indistinguishable from the blood pool. There was a subendocardial infarct of >75% transmurality  in LV basal inferior segment (segment 4) and a part of mid inferior segment (segment 10) of RCA territory (Figure 6).

Figure 6. (a) to (d) dynamic first pass perfusion images demonstrating no contrast enhancement in the lesion(white arrow) in (a) RV phase and (b) LV phase, followed by intense homogenous contrast enhancement in (c) an intermediate phase between LV and myocardial phase when contrast is seen in the descending aorta and in (d) myocardial phase. The lesion is indistinguishable in (e) early enhancement and (f) delayed enhancement images. Also note the subendocardial perfusion defect (red arrow) in inferior basal segment in (d) and a corresponding subendocardial scar of >75% transmurality (green arrow) in (e) LGE images.

By this time, we were almost certain of the diagnosis and performed a limited MR coronary angiography study (navigator gated, ECG-triggered, free breathing single volume 3D balanced turbo field echo (TFE) sequence using spectral presaturation with inversion recovery (SPIR) fat saturated prepulse and T2 preparation, TR: 5msec, TE: 3 msec, limiting the field of view (FOV) to 300X300X52 mm to cover the lesion and inferior surface of the heart thus reducing the acquisition time, acquired matrix size:240×240, slice gap: -0.75 mm, with ECG trigger delay at mid-diastole). This resulted in a 3D angiogram of the distal RCA and posterior descending artery with a reconstructed resolution of ~0.78 × 0.78 ×0.75 mm, which confirmed that the lesion was in fact the saccular aneurysm of the posterior descending coronary artery which had burrowed its way through the basal inferior myocardium of right ventricle and was protruding into the RV cavity (Figure 7).

Figure 7. Limited coronary MRA images of the base of the heart demonstrating the narrow necked eccentric saccular aneurysm (black asterix) from PDA penetrating through the inferior RV myocardium and protruding into the RV cavity. Also noted was mild focal ectasia of the PDA just proximal to the aneurysm (blue arrow).

RCA = right coronary artery; PDA = posterior descending artery.

Conclusion

We concluded that this was a case of a posterior descending coronary artery saccular aneurysm with an atypical location in the right ventricular cavity, associated with myocardial infarction of >75% transmurality in basal inferior wall of left ventricle rendering the segment non-viable. There were no signs of aneurysmal rupture or fistulisation. Prior to the CMR, the PDA aneurysm and the intra-cardiac lesion were considered as separate entities but CMR proved them to be the same lesion. The patient subsequently underwent percutaneous coil embolization (Figure 8). It was interesting to note that the filling defect in posterolateral ventricular branch observed in the first coronary angiography was completely resolved in the subsequent angiography performed at an interval of 4 days, suggesting that the filling defect was likely a coronary thrombus/embolus, whose spontaneous dissolution is more plausible than the complete spontaneous healing of a type I SCAD lesion, which can take at least 30 days. Follow up echocardiogram after 3 weeks confirmed the coil wires in situ and reduction in the size of the aneurysm (Figure 8).

Figure 8. (a) LAO view of RCA before coiling demonstrating filling defect in PLV (dashed arrows) and PDA aneurysm (white asterix). (b) LAO view of RCA post coiling (with EV 3 Helix Concerto detachable coil and Penumbra complex coil) demonstrating near complete resolution of the filling defect in PLV (black arrow) and coiled aneurysm of the PDA (black asterix).(c) Appearance of coiled aneurysm(black asterix) at the end of the procedure.(d) Follow up 2D-Echo after 3 weeks demonstrating coil wires in situ (white arrows) and reduced size of the aneurysm. PDA = posterior descending artery; PLV = posterolateral ventricular; RCA = right coronary artery.

Perspective

Coronary artery aneurysms, defined as a focal >1.5 fold increase in the size of the coronary artery are variably reported (prevalence ranging from 0.3-5.3%) in literature[1]. They are more common in men and are caused by a miscellaneous group of conditions that predispose an individual to vessel wall weakness, the leading cause being atherosclerosis followed by vasculitis, iatrogenic, traumatic, genetic and connective tissue disorder pathologies[1]. A solitary coronary aneurysm, no constitutional symptoms and a subsequent negative immunological workup led us to believe that the aneurysm could be congenital in origin, however further work up for vasculitis is warranted. Distal embolization of a thrombus originating in a coronary aneurysm is a known antecedent for myocardial infarction, however in our case, the aneurysm was in posterior descending artery and the suspected thrombus/embolus was in posterolateral ventricular branch which is intriguing. From the available literature, we did not find any similar case of a completely intraventricular small aneurysm of posterior descending artery that was unrelated to atherosclerosis, vasculitis or coronary manipulation. There have been isolated case reports citing the presentation of coronary aneurysms as cardiac and pericardiac masses on 2D echocardiography which were later confirmed on CT or catheter angiography and in few cases after surgical resection. Most of them were thrombosed giant coronary aneurysms arising from the right coronary artery that bulged into ventricular cavities, atria or the interventricular septum[2,3,4]. CMR either added to the confusion by ascribing them to a vascular neoplastic etiology or did not add any significant value to the conundrum. The utility of Coronary MRA has been sparingly mentioned in such cases.

Due to lower spatial resolution, long acquisition time and complex planning, coronary MRA is clinically limited to suspected anomalous coronary arteries, coronary aneurysms of Kawasaki’s disease and assessment of proximal coronary arteries[5]. However, in the coming years, the use of parallel imaging and compressed sensing to maintain high spatial resolution while reducing the total time of acquisition, self-gating techniques for motion correction and application of deep learning reconstruction is expected to improve signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR)[6]. Table 1 gives an insight into the current status of the multimodality imaging of coronary aneurysms[7,8,9].

(‘+’: poor, ‘++’: acceptable, ‘+++’: excellent)

Why CMR transcended from just being a complimentary diagnostic modality in our case was because of a) demonstration of the excellent spatial relationship of the lesion with the posterior interventricular groove in addition to the subtricuspid region b) reasonable evidence that the lesion was separate from the tricuspid valve by assessing the tricuspid valve mobility c) comparable shape, dimensions and  contrast enhancement of the lesion in question with the PDA aneurysm on catheter angiography d) diagnostic quality coronary MRA images that demonstrated a direct communication of the intracardiac aneurysm with the epicardial posterior descending artery through a narrow neck, obviating the need for a CT angiography and an additional radiation dose e) ascribing the patient’s chest pain to myocardial infarction- a complication likely to have ensued following a thromboembolic event as evidenced by a non-viable basal inferior segment with further implications in patient management, prognosis and follow up.

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References

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2. Mutha V, Asrar ul Haq M, Anavekar NS, et al. Giant coronary aneurysm presenting as a cardiac mass on transthoracic echocardiogram. BMJ Case Rep. 2014;2014:bcr2013202536.
3. Teng P, Ni C, Sun Q, Ni Y. Giant right coronary artery aneurysm mimicking a right intra-ventricular mass: a case report. J Cardiothorac Surg. 2020;Dec;15:1-4.
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