Systolic anterior motion of the posterior mitral leaflet in obstructive hypertrophic cardiomyopathy with Noonan syndrome

Excerpt

A 36-year-old man who had been diagnosed with Noonan syndrome with hypertrophic cardiomyopathy in his teens presented at our hospital with dyspnea on effort. Physical findings included short stature below the third percentile for his age. He had mild intellectual disabilities and distinctive facial features including a high forehead, orbital hypertelorism, ptosis and low set, and posteriorly rotated ears, findings which were all consistent with the diagnosis of Noonan syndrome [1]. Transthoracic echocardiography revealed a unique pattern of left ventricular hypertrophy that was notable only around the basal segments (Fig. 1a, Movie 1–4). At end diastole, the anterior leaflet coapted with the basal portion of the posterior leaflet; at systole, the residual portion of distal posterior leaflet got in contact with the ventricular septum, demonstrating systolic anterior motion (SAM) of the posterior leaflet (Fig. 1b). Color Doppler revealed left ventricular outflow tract (LVOT) stenosis with a pressure gradient of 97 mmHg with mild mitral regurgitation (Fig. 1c, 1d) and no pulmonary stenosis. The length of a posterior mitral leaflet was 26 mm. The aorto-mitral angle, defined as the angle between the aortic and mitral annulus, was 107°. Cardiac magnetic resonance imaging showed no abnormality of the papillary muscles (Fig. 1e, Movie 5). The patient was diagnosed with obstructive hypertrophic cardiomyopathy and beta-blocker administration was initiated, resulting in no improvement. Therefore, percutaneous transluminal septal myocardial ablation was performed, resulting in a marked improvement in his symptom from NYHA class 3 to 2 s and in a pressure gradient at LVOT from 97 to 17 mmHg (Fig. 1f).

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