Effects of inspiration, expiration, and apnea upon pacemaking and block in atrial fibrillation.

Abstract

The effects of inspiration, expiration, and apnea on A-V transmission system block and on A-V junctional and idioventricular pacemakers were studied in 53 examinations on 29 patients with atrial fibrillation. The severity of block and the location, prevalence, and firing frequency of subsidiary pacemakers were measured separately in each phase of respiration and compared by quantitative methods. In most patients, apnea increased the severity of A-V block, the prevalence of A-V junctional escape and ventricular automaticity but reduced the prevalence of A-V junctional tachycardia. The firing frequency of the subsidiary pacemakers was not affected. Occasionally apnea shortened the coupling interval of premature ventricular contractions. Cheyne-Stokes respiration markedly accentuated the effects of apnea and often produced bursts of ventricular tachycardia in patients who had only isolated ventricular ectopic beats during regular respiration. The data indicate that intermittent respiration has deleterious effects upon cardiac activity and should be corrected whenever possible.