Mechanical and metabolic determinants of myocardial stunning in extracorporeally perfused pig hearts.
The purpose of this study was to apply step-wise multiple linear regression analysis retrospectively to an array of mechanical and metabolic measurements chosen because they had the potential to predict the extent of contractile recovery from a prescribed duration of myocardial ischemia. Data were acquired from the extracorporeally perfused, intact, working pig heart which was rendered regionally ischemic (60% reduction in anterior descending coronary flow) for 45 minutes and reperfused to aerobic levels for a final 30-50 minutes. Mechanical recovery was defined by the percentage systolic shortening and the area circumscribed by left ventricular pressure-segment length loops. Data were taken from 39 control hearts and from 16 hearts treated with oxfenicine, an agent which we have previously used to alter mechanical function by its interference with fatty acid metabolism. Despite the fixed nature of the protocol in affecting ischemic hypoperfusion, a wide range of mechanical responses encompassing hypo- and dyskinesis was produced during ischemia, followed by mechanical stunning during reflow. Of the parameters surveyed, regional indices of mechanical performance, together with perfusate pH and PCO2, best predicted recovery. Along with the heart rate, these predictors gave correlations of 0.875 for percentage systolic shortening and 0.766 for the length-pressure loop in control hearts. The analyses were also sensitive to the influence of pharmacological intervention with oxfenicine in that several parameters lost statistical significance for percentage systolic shortening and two were added (heart rate and end-diastolic length) for the length-pressure loop. Separate statistical models for oxfenicine-treated hearts gave correlations of 0.905 for percentage systolic shortening and 0.915 for the length-pressure loop. The data suggest that step-wise multiple linear regression analysis provides new insights toward our understanding of the mechanisms of mechanical stunning in myocardial reperfusion.
Eggleston
A M
AM
Section of Cardiology, University of Wisconsin, Madison 53792.
Bolukoglu
H
H
Liedtke
A J
AJ
Nellis
S H
SH
D000818:Animals; D005112:Extracorporeal Circulation; D005998:Glycine / Q000031:analogs & derivatives / Q000627:therapeutic use; D006439:Hemodynamics / Q000502:physiology; D009200:Myocardial Contraction / Q000502:physiology; D015425:Myocardial Reperfusion; D015428:Myocardial Reperfusion Injury / Q000453:epidemiology / Q000209:etiology* / Q000517:prevention & control; D011237:Predictive Value of Tests; D012044:Regression Analysis; D013552:Swine; D013997:Time Factors
C023010:4-hydroxyphenylglycine; D005998:Glycine