Acquired Annular Subvalvular Aneurysm Complicated by a Fistulous Tract

Abstract

We report a case of an annular subvalvular left ventricular aneurysm in a 60-year-old Caucasian woman with a history of rheumatoid arthritis, hypertrophic cardiomyopathy and methicillin-resistant Staphylococcus aureus bacteremia. Initial transthoracic echocardiography failed to identify the aneurysm, but trans-esophageal echocardiography and cardiac magnetic resonance imaging confirmed the diagnosis. The patient underwent repair of left ventricular pseudoaneurysm with bovine pericardium patch and is doing well postoperatively with residual pulmonary hypertension, left ventricular intracavitary gradient, and right ventricular dysfunction.

Graphical Abstract

Left ventricular subvalvular aneurysms (SVAs) are a rare cardiac anomaly that has mostly been reported in patients of African descent. They are classically seen as subaortic and submitral aneurysms, with submitral aneurysms being more common.¹ Because the disease predominantly affects a specific ethnicity, it has been speculated that the cause may be congenital. However, in recent years, a few cases have been reported in patients of Caucasian origin. Our case involves a Caucasian identifying patient who presented with a submitral aneurysm complicated by an intracardiac fistula (an abnormal connection between the left ventricle and atrium).

Take-Home Messages

• •This case highlights the necessity of considering rare diagnoses like SVAs in atypical patients.
• •It also emphasizes the importance of recognizing the limitations of imaging techniques such as TTE, and the need for advanced modalities like TEE and cardiac MRI for accurate diagnosis and management of complex abnormalities like SVA.

History of Presentation

A 60-year-old women with a history of hypertrophic cardiomyopathy (HCM) presented to the cardiology clinic with progressive shortness of breath, palpitations, and a subjective sensation of chest pressure. The patient reported experiencing sporadic palpitations since childhood, which led to a diagnosis of HCM at the age of 30 years. The shortness of breath, which had emerged 6 months before presentation, had progressively worsened. Notably, the patient denied experiencing chest pain, syncope, edema, or orthopnea.

Past Medical History

Her medical history is significant for hypothyroidism, well-controlled on levothyroxine, and rheumatoid arthritis (RA), which has been challenging to manage despite medical therapy. She also has a history of paroxysmal atrial fibrillation and a “heart murmur” identified during childhood. In 2021, the patient developed a methicillin-resistant Staphylococcus aureus (MRSA) infection involving a knee prosthesis and hip joint, which progressed to bacteremia; however, there was no echocardiographic evidence of infective endocarditis at that time. She was started on chronic suppressive cefpodoxime. The patient's familial history is limited because of her adoption; however, she states that her son has also been diagnosed with a heart murmur. Her current medication regimen includes metoprolol. Cardiac magnetic resonance imaging (CMR) performed 5 years earlier to assess HCM had shown concentric hypertrophy of right ventricular and left ventricular (LV) myocardium. Although no region of myocardium was spared, more prominent hypertrophy was noted in the interventricular septum, LV anterior wall, and anterolateral region, particularly in the more basilar/mid portions of the chamber (thickness: 19 mm). CMR also reported mild systolic anterior motion of the anterior leaflet of with trace regurgitation of the mitral valve and LV outflow tract/subvalvular stenosis jets. The left atrium (LA) was dilated and LV myocardial mass was approximately 241 g with an ejection fraction of 68% (Video 1). She was never tested for genetic alterations associated with HCM.

Differential Diagnosis

A worsening of HCM was suspected in addition, cardiac/respiratory manifestations of uncontrolled RA were also considered.

Investigations

Given the progression of her symptoms, a transthoracic echocardiogram (TTE) was obtained, revealing severe mitral regurgitation (MR) and severe LV hypertrophy, mild to moderate aortic insufficiency, and moderate-severe tricuspid regurgitation. Right heart catheterization confirmed elevated pressures. Average right atrial pressure was 22 mm Hg, and right ventricular and mean pulmonary artery pressures were: 80/4 and 51 mm Hg, respectively. Subsequent left heart catheterization revealed normal coronary arteries. Benign finding of myocardial bridge was noted in the left circumflex artery, likely not the cause of shortness of breath (Video 2).

A transesophageal echocardiogram was performed, which uncovered a significant finding: an abnormal connection between the LA and LV with substantial regurgitant flow into the LA (Figure 1, Videos 3 and 4). This connection was identified as a pseudo-aneurysm, located on the posterolateral aspect of the mitral valve (MV) annulus with openings into both the LA and LV.

Figure 1.

Transesophageal Echocardiogram Still Image Showing Jets of Regurgitant Blood Flow Through the Abnormal Fistulous Cavity

LA = left atrium; LV = left ventricle; SVA = subvalvular aneurysm.

Notably, the MV was structurally normal, with only trace regurgitation, and the morphology of both the LA and LV was unremarkable. CMR was done to further locate the fistula, demonstrating a blood-filled cavity measuring 4.5 cm anteroposterior by 3.5 cm transverse by 3.0 cm craniocaudal in the left atrioventricular groove in close association to the mitral valve. Fistulous connections were identified with both the basal anterolateral LV and the LA as evidenced by dephasing jets (Figure 2, Videos 5 and 6). Moreover, it reported bilateral atrial dilatation left > right and concentric LV hypertrophy markedly in basal and anterior/anterolateral wall (ie, 20-mm thickness at end-diastole compared with other areas of LV myocardium that measure 13-14 mm thick). No myocardial late gadolinium enhancement was identified. Chest computed tomography angiography confirmed the findings of CMR in addition to reported marked peripheral wall calcification in the pseudoaneurysm. Review of unenhanced computed tomography from 3 years prior demonstrated bulky and lobulated calcifications associated with the mitral valve, suspicious for caseous calcification of the mitral annulus.

Figure 2.

Cardiac Magnetic Resonance Imaging Snapshot During Ventricular Systole Showing 2 Jets of Regurgitant Blood Flow

The 2 jets of regurgitant blood flow are jet “a” LV through an opening in aneurysm, and jet “b” aneurysm through an opening in LA. Abbreviations as in Figure 1.

Management

The patient sought surgical consultation at an outside hospital, eventually undergoing septal myectomy, mitral valve repair with epic plus mitral valve 29 mm, and repair of LA-LV fistula and left ventricular pseudoaneurysm with bovine pericardium patch. She had a successful procedure and is doing well with residual pulmonary hypertension, LV intracavitary gradient, and right ventricular dysfunction.

Discussion

SVAs of the left side of the heart are rare and have been primarily reported in patients of African origin. This predilection suggests a congenital cause, possibly a defect or weakness in the posterior portion of the mitral annulus.² Additionally, these aneurysms have been observed in association with diseases such as ischemic heart disease, rheumatic heart disease, infective endocarditis, tuberculosis, and syphilis. Some researchers propose that a combination of genetic predisposition and infectious or inflammatory insults explains their etiology.³

In our patient, the submitral aneurysm was most likely acquired, because a CMR performed 5 years earlier showed no abnormalities. There was no recent history or clinical evidence of infective endocarditis, although the patient’s MRSA bacteremia in 2021 remains a notable aspect of her history and cannot be entirely excluded as a contributing factor. Additionally, the patient’s RA, an inflammatory condition linked to various cardiac valvular manifestations, may have played a role. Chronic inflammation and interleukin-6 up-regulation in RA increase the risk of valvular thickening and nodule formation, potentially weakening the posterior mitral annulus and contributing to the development of the aneurysm.^4,5

According to the available literature, the most common presenting symptom of mitral SVAs is MR. Arrythmias such as atrial fibrillation and ventricular tachycardias are another symptom that is caused by the compression of surrounding structures by the aneurysm. SVAs can lead to heart failure, sudden cardiac death caused by rupture of the aneurysm, and life-threatening arrhythmias. Therefore, prompt surgical management for the aneurysm repair is indicated.⁶

TTE may not always detect SVAs, as demonstrated in our case (Video 7). Initially, the flow through the associated fistula was interpreted as severe MR rather than an extravalvular regurgitation. Therefore, transesophageal echocardiogram is warranted for this condition when it is suspected.⁷

We believe that the myocardial bridge observed in left circumflex, as seen on the angiogram, is probably caused by the pseudoaneurysm in close proximity to the artery. Possibly, as the cavity expands caused by regurgitant blood during systole, it abuts to compress the adjacent vessel.

Finally, the relationship between HCM and the presence of this aneurysm remains unclear. Although no direct link can be established based on the current evidence, further investigation into the possible associations between these conditions may be warranted.

Follow-Up

The patient is scheduled for follow-up with the surgical team at an outside hospital and plans to continue care with us. During our last phone encounter, 25 days postprocedure, she reported that she was doing well—afebrile, with reduced shortness of breath, and no edema, palpitations, syncope, or chest pain. A TTE is planned for 1 month postprocedure.

Conclusions

This case highlights the rarity of an SVA, especially one with a concomitant fistulous tract in a patient of non-African descent. Despite initial challenges in diagnosis with TTE, advanced imaging techniques were instrumental in identifying the SVA and fistula. The patient’s history of HCM, RA, and MRSA bacteremia adds complexity to the case, although no definitive link to the SVA was confirmed. A multidisciplinary approach and the utility of advanced imaging is paramount in managing such rare conditions. Further studies exploring the links among SVA, HCM, and autoimmune conditions such as RA are warranted.

Funding Support and Author Disclosures

The authors have reported that they have no relationships relevant to the contents of this paper to disclose.

Appendix

Video 1

Left Heart Catheterization

LHC showing a normally patent LAD and a Myocardial bridge in proximal LCX likely to be exacerbated because of the aneurysmal cavity in proximity. Arrow: Myocardial bridge

Video 2

TEE With Doppler Showing Inflow and Outflow Openings of the Fistulous Cavity

Blue asterisk: outflow (towards LA) opening, red asterisk: inflow (from LV) opening

Video 3

CMR Showing the Cavity and Jets of Blood Flow Through the Fistula

Asterisk: cavity; blue dotted arrow: regurgitant jet into LA; red dotted arrow: regurgitant jet from LV into the cavity

Video 4

TTE Showing an Abnormal Cavity Adjacent to Mitral Valve

Video 5

3D Echo With Doppler Highlighting the Cavity (Asterisk)

Video 6

Cardiac MRI Images From 2019 Demonstrating Hypertrophic LV and Trace MR

The recently discovered abnormal cavity was absent

Video 7

Additional Images of the Recent CMR (2024) Demonstrating the Pseudoaneurysm Along With the Fistulous Openings