INTERMITTENT WARM BLOOD CARDIOPLEGIA

Background Warm heart surgery implies continuous perfusion with normot hermic blood cardioplegia. Interruption of cardioplegia, however, faci litates construction of distal coronary anastomoses and is the method practiced by many surgeons. To determine whether intermittency is harm ful, we present results from 720 coronary bypass patients, protected w ith intermittent antegrade warm blood cardioplegia, that were derived from a previous study of normothermic versus hypothermic cardioplegia. Methods and Results Mean+/-SD age was 60.8+/-9.0 years; 27% of cases were urgent; 16% of patients had >50% left main stenosis, and 19% had grade III or IV ventricles. A mean of 3.2+/-0.9 grafts was constructed . The average aortic cross-clamp time was 61.8+/-22.2 minutes. The lon gest single time off cardioplegia (LTOC) averaged 11.4+/-4.0 minutes p er patient. The cumulative time off cardioplegia as a percentage of th e cross-clamp time (PTOC) was 48.2+/-18.6% per patient. LTOC and PTOC were divided into quartiles (LTOC, <10, 10 to 11, 12 to 13, and >13 mi nutes; PTOC, <36%, 36% to 39%, 50% to 62%, and >62%) and related to th e prespecified composite outcome of mortality, myocardial infarction a ccording to serial CK-MB sampling, and low-output syndrome (LOS). Long er LTOC was harmful (event rates per quartile, 13.5%, 10.3%, 10.9%, an d 19.0%; P=.046), whereas longer PTOC was protective (16.1%, 17.2%, 9. 4%, and 10.6%; P=.07). Stepwise logistic regression was performed, con trolling for demographic and angiographic predictors. In the multivari ate models, LTOC remained detrimental (P=.07) and PTOC remained benefi cial (P=.053). Additional modeling after entering surgeon identity (P< .001) into the risk equation eliminated the PTOC effect, whereas LTOC remained predictive of adverse outcomes (P=.053; odds ratio, 1.06; 95% CI, 1.00, 1.13). Conclusions The data indicate that a reasonable marg in of safety exists with intermittent, antegrade warm blood cardiopleg ia. Repeated interruptions of warm blood cardioplegia are unlikely to lead to adverse clinical results if single interruptions are less than or equal to 13 minutes.