Left ventricular pump efficiency in long-term mitral regurgitation assessed by means of left ventricular-arterial coupling relations

Abstract

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.