Cardiac Vagal Stimulation Eliminates Detrimental Tachycardia Effects of Dobutamine Used for Inotropic Support

Abstract

Many patients require temporary inotropic support after cardiac surgery, and dobutamine is one of the commonly used drugs for this purpose. However, dobutamine infusion is frequently associated with unwanted sinus tachycardia. Selective sinus node electrical vagal stimulation through a discrete epicardial ganglionic plexus (fat pad) approach can achieve sinus rate slowing. Because sinus node fat pad vagal stimulation (SNFP-VS) can easily be applied during or after cardiac surgery, we hypothesized that combining selective SNFP-VS with dobutamine could produce desired hemodynamic improvement while avoiding sinus tachycardia in patients when inotropic drug support is needed. This exploratory experimental study was performed in 7 open-chest dogs. Dobutamine (2.5 to 10 microg x kg(-1) x min(-1)) was infused at a rate producing at least 30% increase in sinus rate and cardiac output. Then electrical SNFP-VS was applied in the epicardial ganglionic plexus located at the right pulmonary vein-atrial junction, to slow the sinus rate back to control level. Hemodynamic data during control, with steady-state dobutamine infusion, and with dobutamine plus SNFP-VS were collected and compared. Dobutamine significantly increased heart rate, systolic and diastolic blood pressures, peak left ventricular systolic pressure, positive and negative maximal derivatives of left ventricular pressure, and cardiac output. Combining SNFP-VS with dobutamine eliminated sinus rate increase while preserving all major hemodynamic benefits. Selective SNFP-VS itself had no direct effect on cardiac contractility during atrial pacing. Combining SNFP-VS with dobutamine could achieve hemodynamic improvement while avoiding sinus tachycardia in this dog model, suggesting that similar strategy may also be applied in patients.