The interval time for the St. Thomas cardioplegia solution in mitral valve surgeries.

Background: There is a lack of consensus on the appropriate St. Thomas cardioplegia solution interval for cardiac surgeries. The objective of this study was to determine a safe cardioplegia interval.

Method: A total of 340 patients who underwent mitral valve surgery with St. Thomas solution were assessed and divided into 2 groups according to the average cardioplegia interval. In Group A, the average cardioplegia interval was < = 30 min; in Group B, the average cardioplegia interval was greater than 30 min. Propensity score matching was used to adjust for confounders between the two groups. After propensity score matching, Groups A and B contained 125 patients each. The primary endpoints were creatine kinase MB, left ventricular ejection fraction, and troponin levels after surgery. Threshold effect analysis was used to assess the association of the cardioplegia interval with the postoperative CK-MB mass level.

Results: After propensity score matching, postoperative CK-MB mass significantly differed between the two groups, and CK-MB levels were significantly greater in group B than in group A(Group A vs. Group B: 46.1 [46.1;48.3] ng/ml vs. 49.9 [46.1;62.7] ng/ml, p < 0.001). According to the threshold effect analysis, the interval needs to be above 27.6 min before it is associated with an increased risk of CK-MB mass level, and the interval needs to be above 31 min before it is associated with an increased risk of CK-MB mass level 7 h after surgery. There were no other significant differences between the two groups.

Conclusions: The multidose cardioplegia interval above 30 min during mitral valve surgery is associated with a greater risk of myocardial damage. The relationships between the cardioplegia interval and other myocardial markers require further research.