Cardiopulmonary bypass in a model of acute myocardial infarction and cardiac arrest

Cardiopulmonary bypass (CPB) reperfusion has demonstrated improved resuscitation rates in ventricular fibrillation cardiac arrest models. To investigate the effectiveness of CPB reperfusion in an ischemic cardiac arrest setting, simulating the clinical scenario of myocardial ischemia preceding sudden cardiac death, we developed a canine model of acute myocardial infarction followed by ventricular fibrillation. Sixteen dogs were randomly assigned to two groups. Group 1 (eight) had ventricular fibrillation induced without left anterior descending coronary artery occlusion. Group 2 (eight) had a thrombogenic copper coil placed in the left anterior descending artery and showed ECG evidence of acute myocardial infarction before induction of ventricular fibrillation. CPR commenced after eight minutes of ventricular fibrillation. Epinephrine 0.05 mg/kg and NaHCO₃ 1.0 mEq/kg were administered at ten minutes. CPB was begun at 12 minutes and continued for one hour. Myocardial ischemic and necrotic areas were determined in four-hour survivors by dual histochemical staining. All animals were resuscitated; all eight group 1 and six of eight group 2 animals survived to four hours. With the onset of CPB, coronary perfusion pressures increased significantly by 68.6 ± 31.8 (SD) mm Hg in group 1 and 56.2 ± 34.6 mm Hg in group 2 over those obtained with CPR (P < .001). This increase in coronary perfusion pressure correlated with the angiographic appearance of retrograde aorta filling, followed by antegrade coronary artery perfusion. Group 1 animals had 0.16 ± 0.32% necrotic myocardium versus group 2 animals, which had 5.24 ± 6.03% necrotic myocardium (P < .05). Infarct size, expressed as the ratio of necrotic to ischemic tissue weight, was 0.01 ± 0.02 in group 1 and 0.22 ± 0.25 in group 2 (P < .03). Cardiac arrest without prearrest ischemia yields minimal myocardial necrosis. The highly reproducible resuscitation rates obtained in this model may facilitate testing of postarrest myocardial and cerebral salvage therapies.