Osborn (J) wave appearance on the electrocardiogram in relation to potassium transfer and myocardial metabolism during hypothermia.

The genesis of the J wave during hypothermia has been attributed to injury current, delayed ventricular depolarization and early repolarization, tissue anoxia, and acidosis. To our knowledge, no studies have addressed the appearance of the J wave in relation to the myocardial K+ transfer and metabolism during hypothermia. Dogs (n = 9) were progressively cooled, blood samples were taken from the aorta and coronary sinus, and myocardial tissue samples were obtained for adenosine triphosphate (ATP), creatine phosphate (CP), and glycolytic intermediate determination. In every instance, the appearance of the J wave was preceded by a net loss of K+ from the myocardium. In one dog, there was no myocardial K+ loss and the J wave was absent. The J wave appeared when the esophageal temperature was between 27 degrees and 24 degrees C (26.6 +/- 0.73 degrees C). At that temperature, the animals were hypotensive and bradycardic, but arterial oxygen partial pressure, carbon dioxide partial pressure, and pH were within the physiologic range at that temperature. The myocardial ATP and CP from the hypothermic dogs was lower compared with the value obtained from dogs at 37 degrees C (p < .025 and p < .005, respectively). The levels of the glycolytic intermediates, fructose-1,6-diphosphate, dihydroxyacetone phosphate, and pyruvate, were lower and the level of lactate was higher compared with those from the normothermic dogs (not significant; p < .007, p < .02, p < .001, respectively). These findings suggest that the appearance of the J wave on electrocardiography during cooling is a result of depression of the metabolic process concerned with maintenance of the partition of ions across the cell membrane, as evidenced by decreased myocardial energy content and K+ loss during the hypothermic state.