Abstract
The pacing-induced heart failure model provides an opportunity to assess the structural and functional determinants of mitral regurgitation (MR) in dilated cardiomyopathy. This study aimed to evaluate MR to better understand the multitude of factors contributing to its development. Heart failure was induced by rapid ventricular pacing (230 beats/min) in 40 mongrel dogs. Left ventricular (LV) size and MR were evaluated echocardiographically. LV contractility was analyzed using a conductance catheter. MR increased to mild in 12 animals (regurgitant orifice area, 0.06±0.05 cm2), moderate in 15 (0.14±0.07 cm2), and severe in 13 (0.34±0.16 cm2). The grade of MR had an inverse relationships with Emax (the slope of the end-systolic pressure - volume relationship, p<0.01) and dE/dt (the slope of the maximum rate of change of pressure - end-diastolic volume [VED] relationship, p<0.01) and positive relationships with VED and end-diastolic cross-sectional areas and lengths (p<0.05) by univariate analysis. The dE/dt had an independently significant (p<0.01) relationship by multivariable logistic regression. Many factors influence the development of MR and because of its similarity to the clinical situation, this model can be used to investigate MR and heart failure, as well as new surgical therapies. (Circ J 2003; 67: 78 - 82)
