Differences in myocardial performance and load between patients with similar amounts of chronic aortic versus chronic mitral regurgitation

Abstract

It is not known if the favorable changes in preload and afterload that augment ejection performance in acute experimental aortic and mitral regurgitation are also present in patients with chronic regurgitation. Additionally, observations that patients with mitral versus aortic regurgitation respond differently to valve replacement suggest that differences exist preoperatively between these two types of volume overload. Therefore, ventricular mechanics were compared in nine patients with severe aortic regurgitation, eight patients with severe mitral regurgitation and seven normal subjects. The amount of volume overload was similar in both groups with regurgitation. In both aortic and mitral regurgitation, ejection performance was reduced compared with findings in normal subjects. Preload estimated as enddiastolic stress was comparably elevated above normal in both groups with regurgitation: 69 ± 24 dynes × 10³/cm²in mitral regurgitation compared with 81 ± 34 dynes × 10³/cm²in aortic regurgitation and 36 ± 11 dynes × 101/cm²in normal subjects. However, afterload estimated as mean systolic stress was normal in mitral regurgitation (186 ± 34 dynes × 10³/cm²) but markedly elevated in aortic regurgitation (260 ± 41 dynes × 10³/cm²) (p < 0.01). Contractile depression tended to be more severe in mitral regurgitation despite similar ejection performance in mitral and aortic regurgitation.

Thus, in mitral regurgitation favorable loading conditions may mask contractile dysfunction, and in aortic regurgitation excessive afterload contributes to poor pump performance, possibly accounting for previously observed differences in the response to valve replacement.