Fascicular conduction disturbances following aortocoronary bypass surgery: The role of hypothermia versus potassium-arrest cardioplegia

Two hundered and sixty six consecutive patients who underwent aorto-coronary bypass surgery at our institution were studied to assess the incidence of developing new fascicular conduction disturbance. The first 66 patients (Group I) were operated on using systemic hypothermia and ventricular fibrillation while the next 200 patients (Group II) were operated on using systemic hypothermia plus 4° C potassium cardioplegia. Twelve patients in Group I (18%) developed new fascicular conduction defects, an incidence similar to previous studies of patients operated on using similar conditions. A significantly higher incidence of new fascicular conduction defects occurred in Group II patients where 87 patients (43.5%) developed new defects (p < .001). The most likely explanations for the marked increase in fascicular conduction defects in Group II patients were either local effects of high concentrations of potassium on the conduction system or excessive cooling of the posterior wall of the heart.