1350365 - Rare Mitral Valve Anomaly in Hypertrophic Cardiomyopathy: Trileaflet Mitral Valve

A 57-year-old female with no known medical conditions was admitted for left sided facial numbness and left arm pain. On evaluation she was found to have bilateral cerebellar acute ischemic stroke. A transthoracic echo (TTE) showed severe left ventricular hypertrophy suggestive of hypertrophic cardiomyopathy (HCM) with left ventricular outflow tract (LVOT) obstruction. There was also moderate eccentric mitral regurgitation with systolic anterior motion of the mitral valve leaflet, as well as an echogenic density in the posterior aspect of the mitral annulus suggestive of caseous mitral annular calcification (CMAC). Subsequently, she underwent a cardiac magnetic resonance (CMR) which confirmed the HCM diagnosis and also revealed as small apical aneurysm without evidence of thrombus. It also demonstrated trileaflet mitral valve with three separate papillary muscles. After discussion with neurology, anticoagulation and surgical referral were deferred, as the etiology of her stroke was unclear.

Diagnostic Techniques and Their Most Important Findings:

In this case, the TTE revealed left ventricular hypertrophy suggestive of HCM with a maximal septal thickness of 2.1 cm. It also demonstrated LVOT obstruction with a peak gradient of 40 mm Hg at rest, which increased to 82 mm Hg with Valsalva maneuver (Figure 2). In addition, there was evidence of systolic anterior motion of the mitral valve leaflets with moderate eccentric mitral regurgitation. The TTE also revealed the presence of CMAC on the posterior aspect of the mitral annulus measured at 2.5 x 2.5 cm. Her CMR confirmed the diagnosis of HCM with a maximal mid inferoseptum thickness of 2.0 cm. It also revealed a rare anomaly of the mitral valve apparatus as the mitral valve consisted of three leaflets with the separate papillary muscles. Moreover, it showed a small apical aneurysm measured 1.2 x 1.0 cm without evidence of thrombus.

Learning Points from this Case:

HCM is a genetic disease caused by a mutation in one of many sarcomere genes responsible for developing the myocardium. It affects as many as 1 in 500 people worldwide and while it is typically characterized by left ventricular hypertrophy, it presents in various morphologic patterns. While several rare variants of HCM have been seen and reported, the presence of HCM along with a trileaflet mitral valve is exceedingly rare. In addition, the long term hemodynamic effects of this have yet to be elucidated. In our case, our patient not only had HCM with a trileaflet mitral valve, but she also had presence of both CMAC as well as an apical aneurysm which are high risk features for adverse events. Each of these findings were diagnosed or confirmed with different imaging modalities. This highlights the importance of using multimodality imaging in doing a full assessment on a patient with a newly diagnosed cardiomyopathy.