Simultaneous Evaluations of Contractility and Energy Metabolism of Stunned Myocardium Using 31P Magnetic Resonance Spectroscopy.

Abstract

A canine model of postischemic myocardial dysfunction (15 min ischemia, 60 min reperfusion) was used to evaluate the relationship between energy metabolism and myocardial contractile function by on-line measurements of ECG, left ventricular pressure, coronary blood flow and regional segment shortening (%SS) with the continuous acquisition of 31PMR spectra. Two groups emerged from these studies; the first (n=7) in which regional myocardial %SS remained significantly depressed after 60 min of reperfusion (stunned) and the second (n=5) in which regional %SS returned to control levels after 60 min of reperfusion (non-stunned). Both groups exhibited rapid, similar decreases in %SS and parallel rapid decreases in the phosphocreatine to inorganic phosphate (PCr/Pi) ratio with the onset of ischemia. The PCr/ATP ratio exceeded control levels in the stunned group immediately upon reperfusion and remained significantly above control after 60 min of reperfusion. Measurements of tissue myocardial creatine kinase (CK) revealed a significant decrease in total tissue CK activity in stunned myocardium compared to control. A significant inverse relationship (r=-0.904, p<0.003) was found between myocardial tissue CK specific activity and the PCr/ATP ratios. We postulate that the elevated PCr/ATP ratio caused by the impairment of energy transfer to the contractile apparatus constitutes a contractile dysfunction in the postischemic heart.

Participation of Na/Ca‐exchanger and sarcoplasmic reticulum in the high [K]o‐protection against ischaemia‐reperfusion dysfunction in rat hearts

“…This increase suggests that ATP was consumed more rapidly during ischaemia and restored more slowly during reperfusion than PCr. This result agrees with the buffer energetic role of PCr and was also described in stunned reperfused canine hearts, where was attributed to alteration in creatine kinase reaction that supports PCr over ATP formation (Geshi et al. 1998).…”

“…2001). Cytosolic PCr/ATP ratio at initial (2.61 ± 0.23) was comparable with that (2.1) described by NMR studies (Geshi et al. 1998, Zhang et al.…”

“…Contractile performance was evaluated throughout ischaemia‐reperfusion. The energetic metabolic state of hearts, which is expected to be compromised (Geshi et al. 1998, Zhang et al.…”