Dobutamine increased left ventricular restoring forces independently of changes in end-systolic volume, shifting the fully relaxed pressure-ESV relation by an average of -2.6 +/- 1.6 mmHg.
Does dobutamine increase left ventricular restoring forces independently of end-systolic volume in an open-chest dog model?
In an open-chest dog model, dobutamine increases left ventricular restoring forces independently of changes in end-systolic volume, an effect that may be partly related to increased coronary blood volume.
Effect estimate: Mean shift -2.6 mmHg
Restoring forces, which are generated when the left ventricle contracts below its equilibrium volume (Veq), are responsible for diastolic suction. Their magnitude is inversely related to end-systolic volume (ESV). In previous studies in which the mitral valve was replaced with a prosthesis, increased contractility was shown to augment restoring forces independently of ESV. In the present study, we quantified restoring forces in the presence of an intact mitral valve in open-chest dogs (n = 6) as the fully relaxed pressure (FRP) after completion of left ventricular pressure (LVP) fall during nonfilling diastoles produced by a servomotor system that clamped left atrial pressure below LVP. A negative FRP indicated a restoring force was present. We related FRP to ESV during control, intravenous, and left anterior descending coronary artery (intracoronary) administration of dobutamine. With intravenous dobutamine, we observed an approximately parallel downward and rightward shift of the FRP-ESV relation, indicating increased restoring forces at any ESV less than Veq. The downward shift averaged -2.6 +/- 1.6 (SD) mmHg at the control Veq. A similar shift occurred with intracoronary dobutamine. In additional experiments (n = 2), we found that over a common range of ESV dobutamine slightly increased wall thickness (<10%) during nonfilling diastoles, consistent with an increase in coronary blood volume. We conclude that dobutamine increases restoring forces independently of changes in ESV in conjunction with an increase in Veq. This effect may partly be related to increased coronary blood volume.
Bell et al. (Wed,) conducted a other in Left ventricular restoring forces in open-chest dogs (n=8). Dobutamine vs. Control was evaluated on Fully relaxed pressure (FRP) to end-systolic volume (ESV) relation (Mean shift -2.6 mmHg). Dobutamine increased left ventricular restoring forces independently of changes in end-systolic volume, shifting the fully relaxed pressure-ESV relation by an average of -2.6 +/- 1.6 mmHg.
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