[Septal Myectomy for Obstructive Hypertrophic Cardiomyopathy Due to Noonan Syndrome;Report of a Case].

A 15-year-old boy with Noonan syndrome, who had been diagnosed with hypertrophic cardiomyopathy (HCM) at 4 and treated by drugs, was referred to our hospital because of progression of left ventricular outflow tract obstruction (LVOTO). Transthoracic echocardiogram (TTE) revealed left ventricular hypertrophy( LVH), LVOTO( systolic gradient:102 mmHg), and systolic anterior motion of the mitral valve( SAM) with mild mitral regurgitation(MR). We performed septal myectomy by transaortic and transapical approaches. Postoperative TTE revealed significant reduction in left ventricular outflow tract (LVOT) gradient (9 mmHg), resolution of SAM, and reduction in MR grade. The postoperative course was uneventful except for transient atrial tachyarrhythmia. Myectomy for HCM in a patient with Noonan syndrome is rare. This case suggests that myectomy is useful for the patients with Noonan syndrome.