Recovery of left ventricular function after graded cardiac ischemia as predicted by myocardial P-31 nuclear magnetic resonance.
The purpose of this study was to determine noninvasively some critical level of high-energy phosphate stores that relates to the recovery of ventricular contractile function after graded cardiac ischemia. Rabbit hearts (n = 30) were equipped with an intraventricular balloon to monitor developed pressure and +/- dp/dt and placed in a nuclear magnetic resonance magnet (Bruker, 4.7 Tesla). Each heart underwent 10, 20, 40, or 60 minutes of global ischemia followed by 1 hour of reperfusion. The pH as determined by nuclear magnetic resonance dropped from 7.14 +/- 0.04 to 7.07 +/- 0.07 (p less than 0.02) at 1 minute and to 6.19 +/- 0.08 at 30 minutes of ischemia; pH ceased to fall thereafter. Phosphocreatine was depleted to 10% +/- 7% of its preischemic control in 10 minutes. Adenosine triphosphate (ATP) concentrations were 71% +/- 14% and 1% +/- 2% at 10 and 60 minutes. Regression analysis of recovered developed pressure on end-ischemic ATP (EIATP) revealed: developed pressure = 0.93 (EIATP) + 23 (r2 = 0.99). We conclude that: anaerobic metabolism as evidenced by a fall in pH appears to be active for 30 minutes after normothermic ischemia and then ceases; phosphocreatine buffers the fall in ATP during early ischemia; there is a tight correlation between EIATP and recovery of left ventricular contractile function with a threshold content of approximately 80% below which recovery of function will not be complete.
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D003327:Coronary Disease / Q000378:metabolism / Q000503:physiopathology*; D004734:Energy Metabolism; D006352:Heart Ventricles / Q000503:physiopathology; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D009682:Magnetic Resonance Spectroscopy; D009200:Myocardial Contraction; D009206:Myocardium / Q000378:metabolism*; D010477:Perfusion; D010710:Phosphates / Q000378:metabolism*; D010725:Phosphocreatine / Q000378:metabolism; D011379:Prognosis; D011817:Rabbits; D013997:Time Factors
D010710:Phosphates; D010725:Phosphocreatine; D000255:Adenosine Triphosphate