Alterations in Cardiac Synchrony Induced by the Cardiac Sympathetic Nerves

Abstract

While pressures were recorded separately from the four chambers of the heart in openchest dog preparations, together with a standard limb lead of the ECG, the right and left stellate ganglia were stimulated. Measurements from the beginning of the P wave to the initial rise in chamber pressures revealed that pressure in the left ventricle began to rise approximately 20 msec prior to that in the right ventricle. This interval was significantly shortened during electrical stimulation of the stellate ganglion. Although the interval between P wave and the initial pressure elevations in the right atrium (RA) and the left atrium (LA) both shortened during stellate stimulation, P-RA decreased considerably more than P-LA. The P wave, PR interval, and the QRS complex all shortened markedly, indicating increased conduction velocity over the atria, the nodal conducting tissue, and the ventricles during stellate stimulation. These events occurred with or without alterations in heart rate and were correlated with large increases in the rate of change of ventricular pressures. Simple algebraic summation of individual muscle segment contractions may achieve significantly greater intraventricular pressure as the contractions become more synchronous. The total pressure developed is further augmented when each individual unit contracts with greater force and greater velocity. The recruitment of additional functional units would result in further summation and thus in still greater augmentation in total force and pressure. Alterations in pacemaker site are common during stellate stimulation.

Electrophysiologic Effects of Isoproterenol and Beta Blocking Agents in Awake Dogs

“…The effects of anesthesia alone are shown in table 1 (expt. 7,8,9). In anesthetized animals propranolol decreased heart rate slightly to moderately, lengthened A-V conduction time, and produced no change of conduction velocity in Purkinje tissue.…”

Interrelationships Between Automaticity and Conduction in Purkinje Fibers

“…A great part of the effectiveness of catecholamines in improving conduction in depressed hearts (33) and in suppressing certain types of ventricular tachycardias (34)(35)(36), despite their propensity for enhancing automaticity, is almost certainly due to the hyperpolarizing actions of these agents on partially depolarized fibers (see Figs. 9 and 10).…”

Sympathetic activity and myocardial damage after stimulation of dorsal medulla and vagotomy in a novel animal model

“…doi:10.1016/j.ijcard.2004.08.026 catecholamine cardiotoxicity have involved the administration of catecholamines to in vitro cardiomyocytes or in vivo animals [8][9][10][11][12][13][14][15]. Some studies have investigated the cardiac response after the electrical stimulation of sympathetic nervous system [16][17][18]. However, they lack of detailed pathological exploration.…”