[Modification of atrial natriuretic factor by the AV transmission time in pacemaker patients].

The possible relationship of variations in the programmed a-v interval on the peripheral-venous plasma level of the atrial natriuretic factor (ANF) was investigated in nine patients with dual-chamber pacemakers (DDD). During atrial and ventricular stimulation at 82 beats/min the pacemakers of the resting patients were programmed to give successive a-v intervals of 200, 175, 150, 125, 100, 50 and 15 ms. Blood samples were obtained from a peripheral arm vein ten minutes after each change of programme. ANF was extracted from each sample and determined by radioimmunoassay. Both the absolutely and relatively lowest plasma ANF level was obtained at an a-v interval of 175 ms. Lengthening the interval to 200 ms or shortening it to 150 ms or less increased the level. It is possible that both "too long" and "too short" a-v intervals produce an increase in atrial pressure and stretch, to which ANF reacts highly sensitively with an increase in peripheral-venous plasma levels of ANF.