Atrial pacing in patients with sinus node dysfunction

Abstract

Sinus node recovery time (SNRT) at paced atrial rates of 100 (SNRT 100) and 120 (SNRT 120) beats/min, atrial effective refractory periods at spontaneous heart rates (AERP) and at paced rates of 100 (AERP 100) and 120 (AERP 120) beats/min, and premature atrial stimulation were among the studies used in evaluating 33 patients with symptomatic sinus node disease and 42 normal subjects. Although mean SNRT 100 and SNRT 120 were statistically significantly greater in patients than in control subjects, there was a significant overlap between patient and control groups, and SNRT 100 or SNRT 120 was associated with a 30.3 per cent false-negative and 5 per cent false-positive incidence. Correction for heart rate (SNRT-spontaneous cycle length) failed to improve the sensitivity or specificity of this test. There was no significant difference in mean AERP, AERP 100 or AERP 120, or in sinoatrial conduction time in patients compared with control subjects. Analyses of curves derived from plots of test and return cycles showed abnormal curves in only five of the 24 patients studied by progressively premature atrial stimulation. Two of these five patients showed normal zones I and II phenomena followed by a progressive linear increase in the return cycle that was thought to be due to abnormal refractoriness of the perinodal fibers.