Augmentation of Left Ventricular Contractility by Cardiac Sympathetic Neural Stimulation

Abstract

Background— Electric stimulation of mediastinal sympathetic cardiac nerves increases cardiac contractility but is not selective for the left ventricle because it elicits sinus tachycardia and enhanced atrioventricular conduction. The aim of this study was to identify sympathetic neural structures inside the heart that selectively control left ventricular inotropy and can be accessed by transvenous catheter stimulation. Methods and Results— In 20 sheep, high-frequency stimulation (200 Hz) during the myocardial refractory period with electrode catheters inside the coronary sinus evoked a systolic left ventricular pressure increase from 97±20 to 138±32 mm Hg ( P P =0.004) and rate of diastolic relaxation (531±128 versus 888±331 mm Hg/s; P =0.001) increased. The slope of the end-systolic pressure-volume relationship increased (2.3±0.8 versus 3.1±0.6 mm Hg/mL; P =0.04), as did cardiac output (3.5±0.8 versus 4.4±0.8 L/min; P Conclusions— Cardiac nerve fibers that innervate the left ventricle are amenable to transvenous electric catheter stimulation. This may permit direct interference with and modulation of the sympathetic tone of the left ventricle.