Diagnostic Utility of Cardiac Magnetic Resonance Imaging in Monozygotic Twins With Hypertrophic Cardiomyopathy and Identical Pattern of Left Ventricular Hypertrophy

Female, 18-year-old, monozygotic twins, had cardiac evaluations as a result of the suspicion of hypertrophic cardiomyopathy (HCM). Each was asymptomatic with active normal lifestyle. Both twins had normal 2-dimensional echocardiograms, which did not identify wall thickening in any segment of the left ventricular (LV) chamber (Figure). Mild systolic anterior motion of the mitral valve (associated with normal LV outflow tract velocities) and mitral regurgitation were present in both patients. LV end-diastolic cavity dimensions (40 and 34 mm, respectively) and left atrial dimension (20 and 28 mm, respectively) were similar. In each twin, 12-lead ECGs were abnormal but showed …