Regional contractile performance during acute ischemia in porcine right ventricle.
Studies of regional ischemia in the canine left ventricle (LV) have shown augmented systolic segmental shortening in nonischemic regions. To characterize these responses in the right ventricle (RV), acute occlusions of the right coronary artery (RCAO) were produced in anesthetized pigs. Orthogonal pairs of ultrasonic segment-length crystals were implanted in the mid-RV free wall (ischemic region) and in the outflow tract (nonischemic region). RV pressure-area work loops were generated during inferior vena caval occlusions, and both slope (M) of the preload recruitable stroke work relationship and elastance (Ees) of the end-systolic pressure-area relationship were determined by linear regression. Under control conditions, there was no significant difference in M or Ees of the two regions. After RCAO, fractional area shortening decreased by 84% in the ischemic region but increased by 21% in the nonischemic region. Although RV end-diastolic pressure and areas in both regions increased, M was significantly reduced by 78% only in the ischemic region. There was no change in contractile function in the nonischemic region as described by M and Ees despite the increase in systolic fractional area shortening. Therefore the nonischemic region of the porcine RV exhibits an apparent compensatory hyperkinesis in response to regional ischemia similar to that shown for the canine LV, consistent with the Frank-Starling mechanism.
Chow
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Department of Cardiovascular Surgery, California Pacific Medical Center, San Francisco 94115.
Foppiano
L
L
Farrar
D J
DJ
D000208:Acute Disease; D000818:Animals; D003327:Coronary Disease / Q000503:physiopathology*; D006352:Heart Ventricles; D006706:Homeostasis; D009200:Myocardial Contraction; D013552:Swine