Intracellular myocardial pH measured in vivo with sustained and reperfused coronary occlusion

Intracellular pH provides an important measure of the adequacy of local tissue perfusion. The purpose of this study was to measure regional intracellular myocardial pH (impH) in the ischemic zone in vivo during experimental canine coronary occlusion, with and without coronary reperfusion. Twenty adult dogs were studied. Ten dogs underwent permanent ligation of the proximal anterior left descending coronary artery (group L), five dogs had coronary reperfusion after 1 hour of total coronary occlusion (group R), and five dogs did not undergo ligation and served as controls (group C). Intracellular myocardial pH was measured by ³¹phosphorus nuclear magnetic resonance spectroscopy at baseline and then at 15-minute intervals for 6 hours after coronary occlusion (or after sham occlusion in group C). Baseline impH did not differ among groups (group C, 7.22 ± 0.12 mean ± standard error of mean; group L, 7.17 ± 0.07; group R, 7.22 ± 0.09). During hour 1 of total occlusion, the impH of both groups L (6.58 ± 0.05) and R (6.55 ± 0.08) was significantly reduced as compared with the impH of group C (7.3 ± 0.12; p < 0.05). At 0 to 1, 1 to 3, and 3 to 5 hours of reperfusion, the impH of group R (7.34 ± 0.08, 7.27 ± 0.07, and 7.29 ± 0.06, respectively for these times) did not differ from group C (7.26 ± 0.11, 7.21 ± 0.07, and 7.25 ± 0.10). At these same times, the impH of group L (6.47 ± 0.05, 6.57 ± 0.04, and 6.75 ± 0.04) was significantly reduced as compared with both groups R and C (p < 0.05). Thus a severe, persistent regional intracellular myocardial acidosis occurs in the ischemic zone with coronary occlusion but is rapidly corrected by reperfusion within 1 hour.