Effect of sotalol on ischemic myocardial pH in the dog heart

In dogs anesthetized with pentobarbital, the left anterior descending coronary artery (LAD) was occluded partially so that the LAD flow could be reduced to 1/2 to 1/3 the original flow (partial occlusion). Myocardial pH was recorded continuously by the use of a micro glass pH electrode inserted in the area to become ischemic by partial occlusion. Before partial occlusion, myocardial pH was 7.51--7.66. Partial occlusion reduced the pH by 0.63--0.72. Sotalol (5 mg . kg-1, i.v.) increased the pH (by 0.45) that had been reduced by partial occlusion, with a marked decrease in heart rate (about 70 beats . min-1) and a slight decrease in blood pressure (about 10 mm Hg in systolic pressure). Even when the sotalol-induced decrease in heart rate was prevented by pacing the heart, sotalol (5 mg . kg-1, i.v.) increased the pH (by 0.43) of myocardium in which LAD was partially occluded. The pH of the non-ischemic normal heart, however, was not influenced by the injection of sotalol (5 mg . kg-1, i.v.). It is concluded that the effect of sotalol to increase the pH of the ischemic heart is not related to the decrease in heart rate produced by the drug injection.