Safety of prolonged ischemic arrest using hypothermic cardioplegia

Abstract

An evaluation was carried out of 200 consecutive patients undergoing elective cardiac operations. Hypothermic potassium (25 mEq/L) crystalloid cardioplegia was used for myocardial preservation during ischemic arrest. The purpose of this study was to determine if the length of cardioplegic arrest correlated with any parameter of myocardial injury, operative morbidity, or mortality. There were 154 patients undergoing coronary revascularization (CBG) and 46 valve replacement of repair (VR/R). The duration of cardioplegic arrest varied from 17 to 187 minutes. Eighteen patients (12%) in the CBG group and 11 (24%) in the VR/R group had arrest times of greater than 2 hours. In the CBG group, serum enzyme measurements, the incidence of inotropic support, perioperative myocardial infarction, and operative mortality rate did not correlate with the duration of ischemic arrest. In the VR/R group, however, the CPK-MB level increased in proportion to the duration of ischemia; none of the other parameters changed significantly. Myocardial infarction was diagnosed in 3.7% of the coronary bypass (CBG) patients having cardioplegic arrest times of less than 120 minutes and in none of the 18 patients having longer arrest times. Three operative infarcts occurred in the VR/R group, two between 60 and 90 minutes of arrest and one between 120 and 150 minutes. The only clinical manifestation of prolonged cardioplegic arrest in the CBG patients was an increase in the incidence of postoperative arrhythmias. The results of this study support the safety of prolonged (3 hour) cardioplegic arrest under appropriate hypothermic conditions in the CBG group, but not necessarily in the VR/R group, where increased myocardial enzyme generation was noted. The proper reduction of myocardial temperature in the use of multidose cardioplegia is considered essential for optimal preservation.