Ultrasonic diagnosis of anterior mitral leaflet aneurysm caused by aortic valve regurgitation jet: a case description

Introduction

Mitral valve aneurysm (MVA) is a rare but extremely serious disease. The initial description of this distinctive lesion was documented in the medical literature as early as 1729 by Morand (1,2). It is widely recognized that MVA is usually caused by infective endocarditis (IE) (2). However, other potential etiologies include connective tissue disease and myxomatous valvular disease. Meanwhile, a hypothesis exists that aortic regurgitation (AR) significantly contributes to MVA, particularly in non-infective patients. Our case description presents evidence that supports the hypothesis that MVA can also occur in patients without IE and rheumatic diseases (2,3).

Case presentation

A 50-year-old Asian man presented to the hospital with palpitations, chest tightness, and exertional dyspnea that had been present for 1 year, having worsened over the past 2 months. He was a heavy smoker, with a history a smoking for 20 years at an average of 40 cigarettes per day. He had previously been healthy, was of average height, had no special medical history, and had no genetic diseases. Physical examination showed a grade 3/6 systolic rumbling murmur, present at the apex, heard in the mid-late phase, which did not propagate to the neck or back. Meanwhile, another diastolic murmur could be heard at the left sternal border over the second intercostal space, without extending towards the neck or back. His blood pressure was 121/66 mmHg, with a pulse of 85 beats per minute. He was afebrile and exhibited normal white blood cell count and erythrocyte sedimentation rate values. An electrocardiogram revealed a high voltage in the left ventricular leads. He had no apparent risk factors for IE. A transthoracic echocardiogram (TTE) revealed a saccular structure on the anterior leaflet of the mitral valve (MV), measuring approximately 20.5 mm × 16.4 mm, with systolic expansion and diastolic collapse (Figure 1A). The aortic sinus exhibited a tumor-like dilation of approximately 63.9 mm, the ascending aorta was dilated by approximately 39 mm, and the sinotubular junction showed a widening of approximately 39 mm. The aortic valve was of a trileaflet design, with thickening of the aortic valve leaflets. Congenital elongation of the aortic valve leaflets resulted in prolapse during closure. In addition, the color flow Doppler imaging demonstrated moderate mitral regurgitation and moderate-to-severe AR (Figure 1B). Based on its echocardiographic appearance, MVA was diagnosed. The patient underwent computed tomography angiography (CTA) of the aorta, which revealed dilatation of the aortic sinus and ascending aorta, as well as atherosclerosis of the thoracic and abdominal aorta (Figure 2A-2C). It has been demonstrated that poor alignment of the MV caused by MVA exacerbates MV regurgitation, subsequently leading to the deterioration of cardiac function and ultimately resulting in heart failure. The patient was subsequently referred to the cardiac surgery department for surgical intervention. To gather more detailed information, the medical team conducted a transesophageal echocardiogram (TEE), which showed a saccular structure on the MV, expanding during systole and collapsing during diastole (Figure 3A,3B). The aortic sinus was significantly widened. Color flow Doppler imaging showed moderate to severe regurgitation of both the mitral and aortic valves. The parasternal long-axis view showed AR jets pointing toward the prominent anterior MV leaflet (Figure 4). To ensure a smooth postoperative follow-up, patients underwent measures aimed at enhancing myocardial contractility, promoting diuresis, and optimizing myocardial nutrition, thereby improving cardiac function. Surgery was then performed once the patients’ conditions had stabilized. A week later, the patient underwent Bentall surgery and mitral valve replacement (MVR) surgery. Intraoperatively, a chronic aortic dissection was identified 2 cm above the left and right coronary sinuses of Valsalva. The aortic valve leaflets were thin, redundant, and poorly coapted. A 20 mm × 15 mm saccular structure was noted on the anterior leaflet of the MV (Figure 5A,5B). Postoperative pathology showed fibrous proliferation, hyalinization, and myxoid degeneration in mitral and aortic valve tissues, with extensive lymphocytic infiltration (Figure 6). The patient’s postoperative follow-up is satisfactory. Follow-up examinations at one week, two weeks, and one year postoperatively revealed that, following Bentall surgery, the artificial valve functioned well. Similarly, after the MVR surgery, the artificial valve also performed well.

Figure 1 TTE findings. (A) A saccular aneurysm (20.5 mm × 16.4 mm) on the anterior mitral leaflet, exhibiting systolic expansion and diastolic collapse (white arrow). (B) Color Doppler imaging shows moderate mitral regurgitation and moderate-to-severe aortic regurgitation. TTE, transthoracic echocardiogram.

Figure 2 Aortic CTA. Coronal (A), sagittal (B), and axial (C) views demonstrate dilatation of the aortic sinus and ascending aorta. No evidence of aortic dissection is observed. CTA, computed tomography angiography.

Figure 3 TEE findings. (A) A saccular structure (white arrow) is visualized on the anterior leaflet of the mitral valve, demonstrating dynamic systolic expansion. (B) The same saccular structure (white arrow) exhibits diastolic collapse, confirming its phasic variation with the cardiac cycle. TEE, transesophageal echocardiogram.

Figure 4 Parasternal long-axis echocardiographic view demonstrating AR. The parasternal long-axis image reveals AR jets directed toward the prominent anterior mitral valve leaflet, highlighting the spatial relationship between the regurgitant flow and mitral valve morphology. AR, aortic regurgitation.

Figure 5 Intraoperative view of the mitral valve lesion. (A,B) A saccular structure is noted on the anterior leaflet of the mitral valve.

Figure 6 Histopathological features of mitral and aortic valve tissues (hematoxylin and eosin staining, 40× magnification). Postoperative pathology showed fibrous proliferation, hyalinization, and myxoid degeneration in mitral and aortic valve tissues, with extensive lymphocytic infiltration.

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration and its subsequent amendments. Written informed consent was obtained from the patient for publication of this article and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Discussion

MVAs are a rare but extremely serious disease. MVAs manifests as a thin-walled, saccular structure on the MV, exhibiting expansion during systole and collapse during diastole (4). The pathogenic mechanism of MVAs remain unclear. It is widely recognized that MVA is usually caused by IE. However, other potential etiologies include connective tissue, myxomatous valvular disease, as well as massive AR. The following mechanisms may be responsible for the formation of MVA: (I) infection of the MV can be classified into two distinct categories: infiltration by aortic-mitral intervalvular fibers and direct extension of aortic valve vegetation into the left ventricular outflow tract. (II) Injury to the anterior mitral leaflet due to massive regurgitant impingement of the aortic valve. (III) Connective tissue or myxomatous valvular disease, such as rheumatic disease, Marfan syndrome (MFS), pseudoxanthoma elasticum (PXE), and so on, causing structural damage and subsequent aneurysm formation (2-5).

Diseases commonly associated with aortic dilatation encompass hypertension, IE, rheumatic conditions, syphilis, and MFS. However, this patient exhibited none of the following: hypertension, fever, elevated white blood cell count, a history of IE or rheumatic disease, or a history of syphilis or a family history of genetic disorders. Furthermore, there were no discernible signs of MFS, such as tall and lanky frame, skeletal anomalies such as “spider-like” fingers and toes, chest wall deformities, or scoliosis, and there were there no ocular abnormalities, such as lens dislocation. Although our evaluation adhered to the 2010 revised Ghent nosology for MFS, the diagnostic certainty remains limited in this case. For individuals without a family history of MFS, the criteria mandate an aortic root diameter Z-score ≥2 (or dissection) combined with either: (I) lens dislocation, (II) a confirmed pathogenic ‘FBN1’ variant, or (III) a systemic score ≥7 points. This patient demonstrated no lenticular abnormalities, with a systemic score substantially below the threshold (specifically 2 points). Crucially, the absence of comprehensive genetic testing precludes definitive exclusion of a Marfan spectrum disorder. Additionally, the aortic valve appeared long and slender, suggesting a congenital developmental anomaly may be the cause of the aortic dilatation. Our literature review corroborates that a congenital sinus of Valsalva aneurysm (SVA) is pathologically defined as a localized dilation typically confined to a single aortic sinus, resulting from developmental defects characterized by separation between the aortic media and annulus fibrosus at the aortoventricular junction, frequently accompanied by elastic tissue deficiency and abnormal bulbus cordis development. In contrast, aneurysmal dilation involving multiple sinuses with preserved sinotubular junction architecture constitutes aortic root dilation, which is pathognomonic of syndromic connective tissue disorders such as MFS (6). Regrettably, suboptimal imaging planes during echocardiography precluded definitive characterization of the number of involved sinuses. Moreover, the absence of histopathological examination of the aortic tissue precludes histologic confirmation of our hypothesis. After comparing both conditions and synthesizing all clinical findings, we consider ‘atypical MFS’ the more likely diagnosis. The aortic root dilation associated with atypical MFS may have further contributed to the severe AR, which subsequently led to the formation of an MVA. In this case of ultrasonic diagnosis, the missed diagnosis of the old dissection may be attributed to the following 2 reasons: (I) non-floating thrombotic intima, causing subtle ultrasonic lesion display; (II) overfocusing on mitral valve lesions, neglecting ascending aorta dilation-related dissection. The underlying cause for the oversight in diagnosing old dissection via CTA stems from the nature of the dissection being chronic, which may be accompanied by internal thrombus formation. This obstruction hinders the passage of contrast agent into the dissection through the entry tear, ultimately resulting in the lesion remaining undetected on the CTA examination.

MVAs needs to be differentiated from conditions such as mitral valve hemorrhagic cyst (MVHC), mitral-aortic intervalvular fibrosa (MAIVF) and accessory mitral valve tissue (AMVT), and subpulmonic type VSD. MVHCs have round cysts with a thin, smooth wall and a “petal-like” or “bulb-like” shape. They oscillate freely and periodically at the site of attachment (7,8). An MVHC differs from an MVA in that its wall is intact and it does not typically change with heart contractions and dilations. MAIVF is characterized by the following: (I) the presence of a saccular structure located between the anterior leaflet of the mitral valve and the posterior wall of the aorta, and (II) the filling of this structure during systole and its collapse during diastole (9). MAIVF differs from MVA due to its unique positioning and the normal anatomical structure of the mitral valve. An MAIVF differs from an MVA in that its wall AMVT is a seldom congenital heart disease. It is frequently associated with other congenital heart disease. In some cases, this can lead to obstruction of the left ventricle outflow tract. During ultrasound examinations, AMVT has been described in different ways, resembling a sail, a sac, a balloon, or a parachute (10,11). The ultrasound imaging in the patient confirmed the integrity of the interventricular septum, and the color Doppler ultrasound did not detect any evidence of shunted blood flow during systole. Consequently, it was reasonable to conclude that the patient was not experiencing a subpulmonic VSD.

Conclusions

It is widely recognized that MVA is usually caused by IE. However, other potential etiologies include connective tissue, myxomatous valvular disease, as well as massive AR. Regrettably, there is currently a paucity of evidence to suggest that MVA can be caused by massive AR. Our case description presents evidence that supports the hypothesis that MVA can also occur in patients without IE and rheumatic diseases. Echocardiography is the method of choice for diagnosis (2). In conclusion, the presence of MVA should be considered in patients with IE involving the aortic valve, and also in those with obvious eccentric AR without IE. In our subsequent work, we will endeavor to observe smaller MVA from multiple planes and various angles, and when necessary, utilize regional magnification for a more detailed view.

Acknowledgments

None.

Footnote

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-24-2281/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration and its subsequent amendments. Written informed consent was provided by the patient for publication of this article and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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