SELF ASSESSMENT ANSWERS A patient with recurrent syncope

A transthoracic echocardiogram showed marked hypertrophy of the left ventricular apex (fig 1). There was no septal hypertrophy, systolic anterior motion of the mitral valve, or evidence of left ventricular outflow tract obstruction. A 24 hour ECG detected asymptomatic episodes of non-sustained ventricular tachycardia. On treadmill exercise testing he managed 10 minutes of the Bruce protocol without exercise induced arrhythmias. Immediately after exercise, he developed profound hypotension and bradycardia (fig 2) with transient loss of consciousness. During tilt table testing he became symptomatic at 14 minutes and dropped his systolic blood pressure from 110 mm Hg to 70 mm Hg followed by a drop in heart rate from 70 to 40 beats/min. The ECG rhythm strip of leads I, II, and III progressively changed from sinus rhythm to sinus bradycardia to nodal bradycardia getting slower and then to a wide complex slow idioventricular type rhythm similar to the postexercise ECG. Changes occurred in the reverse order when tilt was terminated.