Effects of heart rate on experimentally produced mitral regurgitation in dogs |
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Authors: | Chaim Yoran MD Edward L. Yellin PhD Masatsugu Hori MD PhD Katsuhiko Tsujioka MD Sholomo Laniado MD Edmund H. Sonnenblick MD Robert W.M. Frater MD |
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Affiliation: | From The Department of Surgery Cardiovascular Research Laboratory and the Departments of Medicine and Physiology, Albert Einstein College of Medicine and the Bronx-Lebanon Hospital, Bronx, New York, USA |
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Abstract: | The effects of increasing heart rate (HR) on the hemodynamics of acute mitral regurgitation (MR) were studied in 8 open-chest dogs. Filling volume, regurgitant volume and stroke volume were calculated from electromagnetic probe measurements of mitral and aortic flows. The left atrial-left ventricular systolic pressure gradient was measured with micromanometers. The calculated effective mitral regurgitant orifice area varied from 10 to 128 mm2, with a consequent regurgitant fraction (regurgitant volume/filling volume) of 24 to 62%. After crushing the sinus node, HR was increased stepwise from 90 to 180 beats/min by atrial pacing while maintaining aortic pressure constant. With increasing HR, filling volume, stroke volume, regurgitant volume and regurgitant time decreased; total cardiac output, forward cardiac output, regurgitant output, systolic pressure gradient, regurgitant fraction and the regurgitant orifice did not change; left ventricular end-diastolic pressure decreased; and left atrial v-wave amplitude increased. These results indicate that in acute experimental MR with a wide spectrum of incompetence, the relative distribution of forward and regurgitant flows did not change with large increases in HR. At rates >150 beats/min the atrial contraction occurs early and increases the amplitude of the left atrial v wave. This may contribute to the severity of pulmonary congestion in patients with MR. |
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Keywords: | Address for reprints: Chaim Yoran MD Albert Einstein College of Medicine 1300 Morris Park Avenue Forchheimer Building Bronx New York 10461. |
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