Electrophysiologic and myocardial metabolic changes in the acute phase of partial coronary occlusion.

The acute effects of the partial reduction of coronary blood flow (CBF) on electrical and metabolic changes in myocardium were studied in 59 dogs. In seven dogs with a CBF reduction of 20% to 49%, the adenosine triphosphate (ATP) content (3.59 +/- 0.45 mumol/gm) and the width of the composite electrogram (54 +/- 5 msec) were not significantly different from those of 14 control dogs. In 14 dogs with a CBF reduction of 50% to 74%, ATP decreased significantly (3.09 +/- 0.30 mumol/gm, p less than 0.01); however, widening of the composite electrogram was not noted. Malignant ventricular arrhythmias developed in 5 of 10 dogs with a CBF reduction of 75% to 90% and 6 of 14 dogs with a 100% occlusion, but in none of the dogs with a CBF reduction of less than 75%. Marked widening of the composite electrogram (94 +/- 42 msec, p less than 0.05; and 115 +/- 54 msec, p less than 0.001) and further decrease in ATP (2.49 +/- 0.28 mumol/gm, p less than 0.001; and 2.66 +/- 0.45 mumol/gm, p less than 0.05) were noted in these two groups with a CBF reduction of greater than or equal to 75%. In conclusion, more advanced ischemia was mandatory for electrical derangements than for metabolic deterioration.