Effect of dual chamber pacing on raised plasma atrial natriuretic peptide concentrations in complete atrioventricular block.

Effect ofdual chamber pacing on raised plasma atrial natriuretic peptide concentrations in complete atrioventricular block Atrial natriuretic peptide is released into the circulation in normal humans in situations of increased central blood volume and hence atrial pressure, such as head out immersion in water.' The same stimulus of raised atrial pressure is also responsible for the increased plasma concentrations of atrial natriuretic peptide observed in pathological states of fluid overload, including cardiac and renal failure.2 Raised atrial pressures also occur in patients with complete atrioventricular block because of the frequent occurrence of atrial systole during ventricular systole. In theory this could provide an adequate stimulus for a sustained rise in plasma atrial natriuretic peptide concentrations. Dual chamber pacing restores the normal sequence of atrial and ventricular contraction, whereas ventricular pacing leaves atrial and ventricular systole uncoordinated. We used these pacing modes to determine the relative effects on plasma atrial natriuretic peptide concentration of coordinated and dissociated atrial and ventricular chamber contraction. Patients, methods, and results Thirty two patients (17 men and 15 women, aged 44-85) with complete atrioventricular block were studied. All had normal atrial activity and none had retrograde atrioventricular conduction, cardiac failure, or renal failure. Six of these patients (aged 72 (SEM 14)), who presented acutely with complete atrioventricular block, had a dual chamber mode programmable pacemaker implanted. Plasma atrial natriuretic peptide concentrations (determined by radioimmunoassay3) were measured before pacing and at the end of each of two consecutive 30 day periods. During these periods patients were paced in ventricular demand mode at 70 beats/min and in dual chamber mode (back up 70 beats/min, upper rate 125-150 beats/min, and atrioventricular delay of 150 ms) in randomised order. Plasma atrial natriuretic peptide concentration was also estimated in 13 patients (aged 71 (2), atrial rate 78 (2) beats/min) paced in ventricular demand mode at 70 beats/min for 43 (6) months and in 13 patients (aged 63 (4), atrial rate 72 (3) beats/min) paced in dual chamber mode (programmed as above) for 40 (4) months. Thirteen of the patients were paced with ventricular demand pacing rather than the preferred dual chamber mode, either because dual chamber pacing had not yet become available (seven patients) or because of disease in other systems (six patients). Atrial natriuretic peptide values were compared with those from 13 age and sex matched convalescent hospital patients with no cardiac or renal disease. The mean plasma atrial natriuretic …