Multimodality imaging of tuberculous aortomitral intervalvular fibrosa aneurysm: A case report

INTRODUCTION

The aortomitral intervalvular fibrosa (AMIVF), also known as the mitral-aortic intervalvular fibrosa (MAIVF), is a slender, fibrous structure that lies between the anterior mitral leaflet and the non-coronary cusp of the aortic valve. Its location and lack of vascularity make it especially prone to injury from infection, mechanical stress, or surgical procedures. Although pseudoaneurysms in this region are quite rare, they carry the potential for serious complications. They are most frequently seen in association with infective endocarditis or a history of valve replacement surgery. With the increased use of advanced imaging techniques – particularly transesophageal echocardiography (TEE) and multidetector computed tomography (CT) – these lesions are now more frequently identified, often before major complications develop.

CASE REPORT

A 27-year-old retroviral-positive male presented with complaints of shortness of breath and palpitations for 1 week. He had cough with an episode of hemoptysis. Echocardiography [Figure 1] revealed a thin-walled, dilated, sac-like structure, likely a pseudoaneurysm, arising from the aortomitral continuity protruding into the left atrium, severe MR, AR noted with reduced ejection fraction.

Close

Figure 1:

Echocardiogram images (a and b) shows a defect between anterior mitral leaflet and non-coronary cusp with flow through the defect in the doppler images.

Export to PPT

Then, the patient was referred to the radiology department for CT aortogram. Aortogram was performed with GE Optima CT660 128-slice scanner at 120 kVp, automatic dose modulation, and slice thickness of 0.625 mm. Iohexol 350 mg/mL was injected at a rate of 5 mL/sec using a power injector, followed by 40 mL saline flush.

CT aortogram [Figure 2] revealed a large aneurysm seen arising from the aortic root, protruding to LA. A defect was seen immediately posterior to non-coronary cusp and anterior mitral leaflet. There was no evidence of thrombus or any obvious fistulous tract. The coronary cusps were normal. Following aortogram, the patient was subjected to magnetic resonance imaging (MRI) which was performed in 1.5 T MRI scanner (MAGNETOM Avanto, Siemens Healthineers, Erlangen, Germany). For morphologic imaging, the standard institute cardiac magnetic resonance protocol was used, with true fast imaging with steady-state free precision for white blood and half Fourier single-shot turbo spin-echo for black blood. Axial and coronal sections were taken. Cine images were obtained in two-chamber, four-chamber, and short-axis views to assess cardiac function and abnormal wall motion.

Close

Figure 2:

(a) A contrast-enhanced computed tomography sagittal section shows a defect (white arrows) in the aortomitral continuity, (b) shows a volume rendered image of the pseudoaneurysm. (c-d) there is a contrast-filled outpouching seen projecting into the left atrium with a defect (white arrows) between the anterior leaflet of mitral valve and the noncoronary cusp.

Export to PPT

Cardiac MRI [Figure 3] revealed a large sac-like structure with a neck seen arising between the aortic and mitral intervalvular region, appearing as a cystic structure, protruding and compressing the left atrium. There was no evidence of flow between the sac and outflow tract. Severe mitral regurgitation and paradoxical septal motion were found.

Close

Figure 3:

Serial axial TRUFI images in (a) show pseudoaneurysmal sac (white asterisks) with defect (white arrow head) noted protruding into the left atrium and image (b) shows filling in of the sac on contrast with no filling defect within it.

Export to PPT

Using the imaging findings, a diagnosis of AMIVF aneurysm was made. Following this, the patient underwent aneurysm resection with aortic valve replacement. Histopathology and cultures came positive for Mycobacterium tuberculosis. Now, the patient has been started on antiretroviral therapy with anti-tuberculosis therapy.

DISCUSSION

Pseudoaneurysm involving the AMIVF is an uncommon but clinically significant entity. Because of its subtle and sometimes silent presentation, diagnosis can be delayed or missed entirely. Anatomically, the fibrosa lies between the non-coronary cusp of the aortic valve and the anterior leaflet of the mitral valve. The tissue here is avascular and thin, which contributes to its vulnerability – especially in the context of infection or repeated surgical manipulation.

Among known causes, aortic valve endocarditis remains the most common, while tuberculosis should be suspected in immunocompromised patients. The infection can track through the fibrosa, leading initially to abscess formation. If the process is contained, it may evolve into a pseudoaneurysm. In other cases, the lesion may arise after valve replacement surgery, or, less commonly, as a result of congenital weakness or trauma.^[1,2]

Clinical presentation varies. Some patients may have only vague symptoms – fatigue, breathlessness, or low-grade fever. A newly detected murmur can sometimes be the first clue. In more advanced stages, patients may develop heart failure or present with embolic complications. On rare occasions, a fistula may form, such as between the left ventricular outflow tract and the left atrium, which can significantly alter hemodynamics. Although rupture is not frequent, when it does occur, the outcome can be catastrophic.^[3]

TEE remains a key tool for early detection. It allows detailed visualization of the pseudoaneurysm, which typically expands during systole and collapses in diastole. Doppler imaging is helpful in identifying abnormal blood flow patterns, including regurgitation or evidence of fistulous tracts.^[4] Where available, 3D TEE provides even more detailed anatomical understanding and assists in surgical planning.

Cross-sectional imaging is often used as a complementary approach. CT angiography is useful for assessing the size and extent of the lesion and for identifying features such as thrombus or calcification. Cardiac MRI offers additional benefits, particularly in patients who cannot receive iodinated contrast, by providing both anatomical and functional information.^[5]

Treatment depends on several factors, including the size of the pseudoaneurysm, symptoms, and risk of complications. Surgical intervention is generally advised for large or expanding lesions, those with ongoing infection, or when rupture is a concern. Procedures often include patch repair and, when needed, valve replacement. In contrast, small, asymptomatic lesions without hemodynamic compromise may be observed with periodic imaging. However, many of these ultimately require surgery due to progressive enlargement or the emergence of symptoms.^[6]

In rare cases, pseudoaneurysms arise without any clear history of infection or surgery. These idiopathic or congenital aneurysms may come to light during evaluation for unrelated conditions. Although their natural history tends to be less aggressive, close monitoring is still recommended.^[7]

Given the potential for severe complications, a high index of suspicion is needed, especially in patients with prosthetic valves, prior episodes of endocarditis, or unexplained cardiovascular findings. In such scenarios, radiologists and echocardiographers have a crucial role in ensuring that the diagnosis is not overlooked.

DIFFERENTIAL DIAGNOSIS

• Pseudoaneurysm of the Left Ventricular Outflow Tract (LVOT)

• Sinus of Valsalva Aneurysm (SOVA)

• Abscess at the aortic root or intervalvular fibrosa (infective endocarditis).

• Perivalvular hematoma (post-surgical or post-trauma).

• Left atrial myxoma or other cardiac tumors bulging into atrial–aortic region.

• Thrombus in LA roof or perivalvular region.

• Membranous ventricular septal aneurysm.

• Subaortic diverticulum.

CONCLUSION

Pseudoaneurysm of the MAIVF, though uncommon, poses significant clinical risks. Tuberculous etiology should be considered in an immunocompromised individual with similar clinical presentation and imaging findings. If left undetected, it can lead to rupture, fistula formation, or progressive hemodynamic instability. Early and accurate diagnosis – made possible through echocardiography, CT, or MRI – is a key to preventing complications. Clinician awareness and appropriate imaging are essential, particularly in patients with known risk factors. As more cases are recognized and reported, there is hope that future research will lead to clearer management guidelines for this complex condition.

TEACHING POINTS

1. Anatomical vulnerability - The aortomitral intervalvular fibrosa (AMIVF) is a thin, avascular structure, making it highly susceptible to infection or mechanical insult.

2. Common etiologies - Aortic valve endocarditis is the most frequent cause of AMIVF pseudoaneurysm; in immunocompromised patients, tuberculosis must be strongly suspected.

3. Imaging diagnosis –

   • Transesophageal echocardiography: Best for early detection; pseudoaneurysm expands in systole and collapses in diastole

   • Computed tomography angiography: Defines sac size, extent, and complications

   • Cardiac magnetic resonance imaging: Provides both anatomical and functional assessment.

4. Clinical presentation - Ranges from mild non-specific symptoms (fatigue, murmur, and breathlessness) to severe heart failure, regurgitation, embolic events, fistula, or rupture.

5. Management strategy - Large or symptomatic pseudoaneurysms require surgical resection with/without valve replacement, whereas small, stable ones may be monitored but often progress to needing intervention.

MCQs

1. Which of the following is the most common cause of pseudoaneurysm of the aortomitral intervalvular fibrosa?

   1. Trauma

   2. Tuberculosis

   3. Aortic valve endocarditis

   4. Congenital weakness

   Answer key: c

2. On transesophageal echocardiography, a pseudoaneurysm of the aortomitral intervalvular fibrosa typically shows which of the following features?

   1. Expands in diastole and collapses in systole

   2. Expands in systole and collapses in diastole

   3. No cyclical change in size

   4. Always shows thrombus formation

   Answer key: b

3. Which imaging feature on computed tomography angiography best supports the diagnosis of an aortomitral intervalvular fibrosa pseudoaneurysm?

   1. Expanding sac with systolic-diastolic variation

   2. Sac-like outpouching between the non-coronary cusp and anterior mitral leaflet

   3. Filling defect in left atrium

   4. Calcified mitral annulus

   Answer key: b