DYNAMIC LEFT-VENTRICULAR OUTFLOW TRACT OBSTRUCTION DUE TO CONCENTRIC LEFT-VENTRICULAR HYPERTROPHY - EFFECT OF PACING WITH A SHORT AV INTERVAL

Dual chamber pacing with a short atrioventricular (AV) interval has emerged as a novel therapeutic approach in dynamic left ventricular outflow tract obstruction. A morbidly obese 65-year-old man with previous borderline hypertension and documented normal coronary arteries and concentric left ventricular hypertrophy who underwent uneventful elective hip replacement is reported. Eight hours postoperatively the patient developed junctional tachycardia and hypotension. Echocardiogram revealed concentric left ventricular hypertrophy with dynamic left ventricular outflow tract obstruction and peak gradient of 262 mmHg. The patient improved with intravenous fluid replacement. The gradient fell to 112 mmHg 14 days later. Twelve days later the patient developed symptomatic sinus pauses and a dual chamber pacemaker was implanted. After testing various AV intervals, the lowest gradient of 138 mmHg was associated with an AV interval of 100 ms. One year later the gradient was 37 mmHg at the same AV interval, with a higher gradient at shorter and longer AV intervals. Dual chamber pacing with a short AV interval has been associated with improvement in hypertrophic obstructive cardiomyopathy. This case suggests the benefit of this therapy may extend to acquired forms of dynamic left ventricular outflow tract obstruction such as concentric left ventricular hypertrophy.