Postoperative conduction disturbances: A comparison of blood and crystalloid cardioplegia

Conduction system disturbances after cardioplegia am well described. Our four-man group changed in mid-1987 from standard crystalloid cardioplegia (35 mEq/L of KCl) to blood cardioplegia 44 parts blood to 1 part cardioplegia) (18 mEq/L of KCl) based on experimental and clinical evidence that blood cardioplegia provides better myocardial protection- Shortly thereafter, we anecdotally noted increased conduction abnormalities. This prompted us to compare serially all patients undergoing coronary artery bypass grafting during 1987 for perioperative and late conduction system disturbances after either crystalloid or blood cardioplegia. Surgeons and techniques including topical cooling did not differ. Forty-one (23%) of 179 patients with crystalloid cardioplegia had conduction disturbances versus 141 (49%) of 289 patients with blood cardioplegia (p < 0.001). Perioperative complete heart block squiring atrioventricular sequential pacing occurred in 20 patients with crystalloid cardioplegia versus 67 patients with blood cardioplegia (p < 0.002), and atrioventricular block requiring permanent pacing was present in 4 and 12 patients (p < 0.001), respectively. Left bundle-branch block was found in 8 patients given crystalloid cardioplegia and 28 patients with blood cardioplegia (p < 0.05); right bundle-branch block, 12 and 68 patients (p < 0.001); left anterior hemiblock, 8 and 37 patients (p < 0.001) and interventricular conduction delay, 15 and 53 patients (p < 0.005), respectively. Bifascicular block occurred in 4 patients receiving crystalloid cardioplegia versus 23 receiving blood cardioplegia (p < 0.001). There was no difference in cross-clamp times, number of grafts, or amount of cardioplegia solution between patients with and patients without conduction disturbances within each group. Except for perioperative complete heart block, most conduction disturbances were present at discharge. We conclude that the use of blood cardioplegia is associated with significantly more postoperative conduction disturbances than is the use of crystalloid cardioplegia. This suggests that patients with preexisting conduction defects should not receive blood cardioplegia. Further investigation is indicated to confirm and elucidate the causes of this phenomenon.