Left ventricular pump efficiency in long-term mitral regurgitation assessed by means of left ventricular-arterial coupling relations.
The left ventricular-arterial coupling relationship was used in patients with long-term mitral regurgitation to test the hypothesis that the low impedance left atrial contribution to left ventricular ejection obscures an impairment in left ventricular-arterial coupling and forward left ventricular pump efficiency. Twenty-two control patients and 26 patients with long-term mitral regurgitation were studied. Micromanometer left ventricular pressures and radionuclide angiograms for left ventricular volumes were acquired over a range of loading conditions. Left ventricular-arterial coupling was assessed by the ratio of left ventricular chamber elastance, E(es), to total arterial elastance, E(a). Forward left ventricular pump efficiency was calculated as the ratio of forward left ventricular stroke work to the corresponding pressure-volume area. There was a progressive decrease in E(es) in the patients with long-term mitral regurgitation (p < 0.001), but there was no significant difference in E(a) in comparison to the control patients. Consequently, E(es)/E(a) demonstrated a progressive decrease (p < 0.001). Although the efficiency of performing total left ventricular stroke work was only reduced when left ventricular contractile function was severely impaired (p < 0.001), there was a progressive reduction in left ventricular pump efficiency for performing forward left ventricular stroke work in the patients with long-term mitral regurgitation (p < 0.001). Further, normalized left ventricular stroke work was reduced for any left ventricular-arterial coupling ratio in the patients with long-term mitral regurgitation compared with the control patients. These data indicate that despite the outward evidence for normal left ventricular ejection in patients with long-term mitral regurgitation, a progressive deterioration in left ventricular contractile state leads to impaired left ventricular-arterial coupling and to an impairment in the efficiency of performing forward left ventricular stroke work. Once the left ventricle begins to dilate in patients with long-term mitral regurgitation, the progressive deterioration in left ventricular-arterial coupling and pump efficiency suggests that an earlier consideration of mitral valve surgery may be warranted to preserve left ventricular contractile function.
Starling
M R
MR
Department of Internal Medicine, University of Michigan, Ann Arbor 48105.
D000328:Adult; D000368:Aged; D001158:Arteries / Q000503:physiopathology; D002637:Chest Pain / Q000175:diagnosis / Q000503:physiopathology; D002908:Chronic Disease; D004526:Efficiency / Q000502:physiology*; D005260:Female; D006334:Heart Function Tests / Q000379:methods / Q000706:statistics & numerical data; D006352:Heart Ventricles / Q000503:physiopathology; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D008944:Mitral Valve Insufficiency / Q000175:diagnosis / Q000503:physiopathology*; D016277:Ventricular Function, Left / Q000502:physiology*