RIGHT AND LEFT-VENTRICULAR GEOMETRY AND MYOCYTE CONTRACTILE PROCESSESWITH DILATED CARDIOMYOPATHY - MYOCYTE GROWTH AND BETA-ADRENERGIC RESPONSIVENESS

Objectives: Comparison of the effects of supraventricular tachycardia- induced dilated cardiomyopathy on left and right ventricular isolated myocyte geometry and function. Background: Chronic ventricular tachyca rdia and supraventricular tachycardia cause left ventricular dilation and dysfunction in humans. However, it is unknown whether supraventric ular tachycardia-induced dilated cardiomyopathy is a homogenous proces s for both the left and right ventricles. Methods: Dilated cardiomyopa thy was induced by rapid atrial pacing (240 beats/min, 3 weeks) in 5 p igs. Five age- and weight-matched pigs served as controls. Ventricular mass was measured, myocyte dimensions were obtained, and isolated rig ht and left ventricular myocyte contractile performance was evaluated at baseline and after P-adrenergic receptor stimulation. Results: With the development of dilated cardiomyopathy, there was no change in lef t ventricular mass. In contrast, right ventricular mass was increased, as was right ventricular myocyte cross-sectional area. In the control group, baseline right ventricular myocyte contractile function was in creased compared to left ventricular myocytes. P-adrenergic receptor s timulation increased myocyte contractile function in both left and rig ht ventricular myocytes. With supraventricular tachycardia-induced car diomyopathy, both left and right ventricular myocyte contractile funct ion and beta-adrenergic responsiveness were reduced. Conclusions: This study demonstrated differences in left and right ventricular myocyte growth with supraventricular tachycardia-induced dilated cardiomyopath y and this differential growth response was associated with changes in contractile performance. Thus, in this model of cardiomyopathic disea se, left and right ventricular growth and changes in contractile perfo rmance are not a homogenous process.