Dual chamber cardiac pacing in hypertrophic cardiomyopathy

The aim of the study was to investigate effect of temporary cardiac pacing an clinical state, magnitude of left ventricular outflow tract pressure gradient obtained by echocardiography, characteristics of supraventricular and ventricular arrhythmias (Halter ECG), threshold load and exercise duration (exercise test) on the 7-th day of dual chamber pacing in 9 patients with hypertrophic cardiomyopathy and implanted temporary pacemaker. Decrease in the number of ventricular premature beats and Improvement of exercise tolerance were observed during pacing. Mean decrease in the number of ventricular premature beats was 61% compared to prepacing level and average for the group NYHA functional class was lowered from 2,7 to 2,3. Blood flow velocity in left ventricular outflow tract assessed by doppler echocardiography decreased in 7 and remained unchanged in 2 patients, Average value of left ventricular outflow tract blood flow velocity significantly decreased by 13% in all patients and by 8% in the subgroup of patients with outflow tract obstruction. In patients with atrioventricular delay exceeding 160 ms more pronounced lowering of this parameter (by 36%) was noted compared to other patients, As prediction of efficacy of cardiac pacing is at present impossible it is advisable to implement preliminary temporary cardiac pacing with assessment of hemodynamic parameters at rest and during exercise, Best short term results are expected in patients with PQ interval exceeding 160 ms, in patients with initially short PQ interval or in cases in which preexcitation appears at atrioventricular delay below 160 ms it is recommended to prolong PQ interval by drugs.