EFFECTS OF PERMANENT DUAL-CHAMBER PACING ON MYOCARDIAL PERFUSION IN SYMPTOMATIC HYPERTROPHIC CARDIOMYOPATHY

Objective-Angina and the presence of myocardial ischaemia are common i n hypertrophic cardiomyopathy. Dual chamber pacing results in clinical improvement in these patients. This study evaluates the effects of pe rmanent dual chamber pacing on absolute regional myocardial perfusion and perfusion reserve. Setting-University hospital. Patients and desig n-Six patients with hypertrophic cardiomyopathy and severe symptoms of angina received a dual chamber pacemaker. Absolute myocardial regiona l perfusion and perfusion reserve (dipyridamole 0.56 mg/kg) were measu red by dynamic positron emission tomography with N-13-ammonia both dur ing sinus rhythm and 3 months after pacemaker insertion. Results were compared with those from 28 healthy volunteers. Results-Pacing resulte d in a reduction of anginal complaints and a reduction in intraventric ular pressure gradient from 65 (SD 30) mmHg to 19 (10) mm Hg. During s inus rhythm, baseline perfusion was higher in patients with hypertroph ic cardiomyopathy than controls (184 (31) v 106 (26) ml/min/100 g, P < 0.01), and perfusion reserve was lower (1.6 (0.4) v 2.8 (1.0), P < 0. 05). During pacing myocardial perfusion decreased to 130 (27) ml/min/1 00 g (P < 0.05), with variable responses in terms of perfusion reserve . Pacing caused a redistribution of myocardial stress perfusion and pe rfusion reserve. The coefficient of regional variation of myocardial s tress perfusion decreased from 19.7 (7.0)% to 14.6 (3.9)% during pacin g (12.9 (3.8)% in controls, P < 0.01). The coefficient of regional var iation of perfusion reserve decreased from 16.7 (6.6)% to 11.4 (2.6)% during pacing (9.8 (4.1)% in controls, P < 0.01). Conclusions-Pacing c aused a decrease of resting left ventricular myocardial blood flow and blood flow during pharmacologically induced coronary vasodilatation. Although global perfusion reserve remained unchanged, myocardial perfu sion reserve became more homogeneously distributed.