Left ventricular mechanics during synchronous left atrial-aortic bypass.
The purpose of this study was to analyze left ventricular mechanics during asynchronous, pulsatile left atrial-aortic bypass before and after microsphere injection with the pressure-volume relationship. In 14 anesthetized Holstein calves, left ventricular pressure was measured with a micromanometer and ultrasonic dimension transducers measured left ventricular orthogonal diameters. Ellipsoidal geometry was used to calculate simultaneous left ventricular volume. Contractility index, pressure-volume area, external work, and potential energy were calculated during steady-state contractions. These measurements were repeated during pulsatile left atrial-aortic bypass. To induce heart failure, we injected microspheres into the left main coronary artery, and the protocol for baseline and pulsatile left atrial-aortic bypass was repeated. Despite the significant differences in the baseline contractility index (7.4 +/- 0.7 mm Hg/ml versus 4.7 +/- 0.5 mm Hg/ml), contractility index remained the same during pulsatile left atrial-aortic bypass in control and heart failure modes, respectively. Pulsatile left atrial-aortic bypass significantly decreased end-diastolic volume (22% and 17%), pressure-volume area (58% and 48%) and external work (74% and 69%, all p < 0.05) during control and heart failure measurements, respectively. However, it did not change end-systolic volume or potential energy. In conclusion, asynchronous pulsatile left atrial-aortic bypass did not affect left ventricular contractile state in either the normal or failing heart. Although decreased pressure-volume area accounts for the reduction in myocardial oxygen consumption, unchanged potential energy suggested a limited unloading of the ventricle.
Kawaguchi
O
O
Department of Surgery, Pennsylvania State University, College of Medicine, Milton S. Hershey Medical Center, Hershey 17033.
Sapirstein
J S
JS
Daily
W B
WB
Pae
W E
WE
Pierce
W S
WS
D000818:Animals; D002417:Cattle; D006333:Heart Failure / Q000503:physiopathology* / Q000628:therapy; D006352:Heart Ventricles / Q000378:metabolism; D006353:Heart-Assist Devices; D006439:Hemodynamics; D009200:Myocardial Contraction / Q000502:physiology*; D010101:Oxygen Consumption; D016276:Ventricular Function; D016277:Ventricular Function, Left