Experimental coronary air embolism. Assessment of time course of myocardial ischemia and the protective effect of cardiopulmonary bypass.

In 74 mongrel dogs 0.02 ml air/kg of body weight was injected into the left anterior descending coronary artery (LAD). Forty-three dogs were studied without (group I) and 31 with (group II) extracorporeal circulation (ECC). Time course and extent of myocardial ischemia were assessed by continous thermographic measurements as well as by fluorescence techniques. Coronary air embolism resulted in an immediate decrease of myocardial temperature associated with transmural ischemia. In 31 surviving dogs (72%) of group I this phenomenon was fully reversible within 8.7 minutes as compared with 5.4 minutes in 100% of the surviving dogs from group II. No postembolic death occurred in the group II animals. In group II the postembolic temperature decrease was significantly less than that in group I, and, in addition, the myocardial area involved was significantly smaller. The results indicate that the extent of myocardial ischemia following coronary air embolism and its time course can be well-documented by means of thermocardiography; using extracorporeal circulation survival can be improved and myocardial damage minimized.