NORMOTHERMIC CONTINUOUS BLOOD CARDIOPLEGIA IMPROVES ELECTROPHYSIOLOGIC RECOVERY AFTER OPEN-HEART-SURGERY

Background: Myocardial protection during open heart surgery is based o n administration of oxygenated blood cardioplegia, the preferred tempe rature of which is still under debate. The current randomized study wa s designed to prospectively evaluate the quality of myocardial protect ion and the functional recovery of the heart with either normothermic (group N) or hypothermic (group H) oxygenated blood cardioplegia. Meth ods: Under continuous electrocardiographic Holter monitoring, 42 patie nts were randomly scheduled to receive either normothermic (33.5 degre es C) or hypothermic (10 degrees C) cardioplegia solutions during coro nary bypass grafting surgery. Blood samples for creatinine phosphokina se, creatinine phosphokinase-MB, lactate, epinephrine, and norepinephr ine were withdrawn during cardiopulmonary bypass via a coronary sinus cannula. Results: Active cooling in group H on initiation of cardiopul monary bypass was characterized by transition through ventricular fibr illation in 75% of patients, whereas in group N atrial fibrillation oc curred In 65% of patients, On myocardial reperfusion, sinus rhythm spo ntaneously resumed in 95% of group N patients compared to 25% In group H (P = 0.0003). In the latter, 75% of patients developed ventricular fibrillation often followed by complete atrioventricular block, which necessitated temporary pacing for a mean duration of 168 +/- 32 min. B oth groups showed a similar incidence of intraventricular block and ST segment changes. However, the Incidence of ventricular premature belt s in the first 16 h after cardiopulmonary bypass was significantly gre ater in group H (P < 0.05), 20 +/- 26/h, compared to 3 +/- 5/h in grou p N. Blood concentrations of lactate, creatinine phosphokinase, epinep hrine, and norepinephrine increased gradually during the operation, bu t the differences between the groups were not significant. Conclusions : The current prospective human study suggests that the Increased susc eptibility for ventricular fibrillation and dysrhythmia, and the delay ed recovery of the conduction system after hypothermic myocardial prot ection, are related to temperature-induced changes In vital cellular f unctions of the conduction tissue in the postischemic period. Both car dioplegic methods provide adequate myocardial protection but normother mic oxygenated blood cardioplegic may accelerate recovery of the heart after cardiopulmonary bypass.