Determinants of the Development of Mitral Regurgitation in Pacing-Induced Heart Failure

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