Early effects of right ventricular volume overload on ventricular performance and β-adrenergic signaling

Abstract

Objective: Right ventricular dysfunction is a poorly understood but persistent clinical problem. This study was undertaken to evaluate ventricular performance and β-adrenergic receptor signaling in a tricuspid regurgitation model of right ventricular overload. Methods: Seventeen dogs were chronically instrumented with epicardial dimension transducers. By means of the shell-subtraction model, right ventricular pressure-volume relationships were evaluated in normal and right ventricular overload states. Right ventricular chamber performance was quantified by the stroke work at an end-diastolic volume relationship. Results: Right ventricular volume overload caused a 28% ± 11% and 31% ± 9% decline in chamber performance acutely and at 1 week, respectively, whereas end-diastolic volume increased from 45 ± 21 to 60 ± 30 mL (P =.019). β-Adrenergic receptor signaling in myocardial samples was assessed, examining adenylyl cyclase and G-protein–coupled receptor kinase activity. Stimulated adenylyl cyclase activity significantly decreased, and G-protein–coupled receptor kinase activity significantly increased in both left and right ventricular samples caused by increased levels of β-adrenergic receptor kinase 1. No change in β-adrenergic receptor density was seen at 1 week. Conclusions: Early right ventricular overload is associated with impaired right ventricular chamber contractility, dilation, and, importantly, a biventricular alteration of β-adrenergic receptor signaling. (J Thorac Cardiovasc Surg 2000;119:342-9)