REFLEX CONTROL OF ATRIOVENTRICULAR NODAL REFRACTORY PERIODS BY CARDIOPULMONARY RECEPTORS IN HUMANS

Abstract

The effects of selective cardiopulmonary receptor unloading on atrioventricular (AV) conduction were examined in 7 patients undergoing electrophysiologic testing. During -35 mmHg lower body negative pressure (LBNP) before autonomic blockade with propranolol and atropine, the AV nodal conduction time (AH interval), the effective and functional refractory periods of AV node decreased at paced cycle length, when systemic arterial and central venous pressures decreased and heart rate increased. These responseses to -35 mmHg LBNP except reductions in systemic arterial and central venous pressures disappeared after autonomic blockade. During -10 mmHg LBNP before autonomic blockade, both effective and functional refractory periods of AV node at paced cycle length decreased by 11±3% (mean±SEM) and 6±1% respectively with the reduction of central venous pressure while AH interval, systemic arterial pressure and heart rate remained unchanged. After autonomic blockade, -10 mmHg LBNP reduced central venous pressure but all the other parameters remained unchanged. These results suggest that cardiopulmonary baroreceptors participate in the reflex control of AV nodal refractoriness in humans.