Simultaneous cardiac mechanics and phosphorus‐31 NMR spectroscopy during myocardial ischemia and reperfusion in the intact dog

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Abstract
To investigate the high‐energy phosphate metabolic correlates of left ventricular (LV) dysfunction during the onset and recovery from severe, global myocardial ischemia in vivo, seven preinstrumented closed‐chest dogs had ECG‐gated phosphorus‐31 (31P) NMR‐spectroscopy (NMR‐S) studies performed and LV micromanometer and sonomicrometer data measured before, during, and every 5 min following severe occlusive global myocardial ischemia. Ischemic LV + dP/dtmax fell from 2396 ± 576 mm Hg/s at baseline to 2185 ± 478 mm Hg/s (p < 0.05) and did not normalize until after 30 min of reperfusion. LV ejection fraction (EF) decreased significantly (0.32 ± 0.07 EF units to 0.12 ± 0.13 EF units; P < 0.05) and did not recover by 30 min of reperfusion (0.27 ±0.09 units; P < 0.05 vs baseline). Simultaneous 31P NMR‐S studies demonstrated excellent β ‐ATP signal‐to‐noise (10 ± 4:1). Myocardial acidosis occurred during global ischemia (ApH = −0.22 ± 0.23 units; p < 0.05), with recovery at 30 min of reperfusion. Inorganic phosphate/ phosphocreatine ratio (Pi/PCr) increased significantly during ischemia (0.46 ± 0.07 to 0.61 ± 0.07; P < 0.05), with delayed normalization of this ratio at 30 min of reperfusion. β‐ATP peak area did not change during ischemia. Pi/PCr and LV contractility ( + dP/ dtmax ) were significantly correlated at baseline (r = −0.70) and during global ischemia (r = −0.78; p < 0.01), but not during recovery (r = 0.006; p = NS). Therefore, the simultaneous evaluation of high‐fidelity hemodynamic data and topical 31P NMR‐S can be performed in the intact State. © 1991 Academic Press, Inc.