Flaherty J T, Weisfeldt M L, Hollis D P, Schaff H V, Gott V L, Jacobus W E
Adv Myocardiol. 1980;2:487-99.
Previous studies from this laboratory utilized mass spectrometry to measure myocardial oxygen (PO2) and carbon dioxide (PCO2) tensions in isolated feline hearts subjected to periods of global ischemia and reperfusion. Myocardial carbon dioxide tension was found to increase during ischemia, and its rate of increase was found to correlate inversely with subsequent recovery of myocardial function following reflow. The present study utilized phosphorus-31 nuclear magnetic resonance (NMR) to assess whether the severity of intracellular acidosis or the depletion of high energy phosphate stores would show a similar correlation with recovery of function. Hyperkalemic cardioplegia employed as a myocardial preservation technqiue in combination with hypothermia was compared with hypothermia alone as the control intervention. The experimental results demonstrated that intracellular pH fell to 6.09 +/- 0.13 with hypothermia alone and to 6.31 +/- 0.09 with cardioplegia plus hypothermia. Furthermore, myocardial ATP content fell to 22% +/- 2% of control with hypothermia alone, while falling to 36% +/- 4% of control with the combined therapy. Recovery of myocardial performance was found to correlate inversely with the severity of intracellular acidosis and depletion of ATP during ischemia. In contrast, no relationship was observed between preservation of phosphoryl-creatinine levels either during ischemia or after reflow and recovery of ventricular function. These results suggest that, similar to mass spectrometry, which allows monitoring of myocardial PCO2, 31P NMR permits the on-line monitoring of intracellular pH as well as high energy phosphate compounds, and thereby provides useful metabolic indices of the severity of ischemia. Since tight coupling was found between changes in these parameters and subsequent recovery of contractile performance, further development of 31P NMR for evaluation of techniques designed to minimize the severity of ischemic damage would seem indicated.
该实验室之前的研究利用质谱法测量了经历全心缺血和再灌注的离体猫心的心肌氧分压（PO2）和二氧化碳分压（PCO2）。研究发现，心肌二氧化碳分压在缺血期间会升高，且其升高速率与再灌注后心肌功能的后续恢复呈负相关。本研究利用磷-31核磁共振（NMR）来评估细胞内酸中毒的严重程度或高能磷酸储存的耗竭是否与功能恢复呈现相似的相关性。将作为心肌保护技术与低温联合使用的高钾停搏液与单独使用低温作为对照干预措施进行比较。实验结果表明，单独低温时细胞内pH降至6.09±0.13，而停搏液加低温时降至6.31±0.09。此外，单独低温时心肌ATP含量降至对照值的22%±2%，而联合治疗时降至对照值的36%±4%。研究发现，心肌性能的恢复与缺血期间细胞内酸中毒的严重程度和ATP的耗竭呈负相关。相比之下，在缺血期间或再灌注后，磷酸肌酸水平的保存与心室功能的恢复之间未观察到相关性。这些结果表明，与允许监测心肌PCO2的质谱法类似，31P NMR能够在线监测细胞内pH以及高能磷酸化合物，从而提供缺血严重程度的有用代谢指标。由于发现这些参数的变化与随后收缩性能的恢复之间存在紧密耦合，似乎有必要进一步开发31P NMR以评估旨在最小化缺血性损伤严重程度的技术。
