Perfusion interval and myocardial injury in minimally invasive mitral valve surgery: the modifying role of aortic cross-clamp duration

OBJECTIVES: To assess how perfusion interval relates to myocardial injury and whether this is modified by aortic cross-clamp duration in minimally invasive mitral valve surgery. METHODS: We retrospectively analysed 556 patients receiving blood-enriched modified del Nido cardioplegia. The primary exposure and outcome were longest perfusion interval and base-10 logarithm-transformed peak cardiac troponin I within 48 hours. Analyses included multivariable regression, interaction and subgroup analysis, restricted cubic splines, sensitivity analysis, and logistic regression. RESULTS: Longer perfusion intervals were initially associated with higher cardiac troponin I (regression coefficient 0.0097, 95% confidence interval 0.0035-0.0159; P = 0.002). This association disappeared after adjustment for factors including aortic cross-clamp time and number of perfusions (regression coefficient -0.0006, 95% confidence interval -0.0109-0.0097; P = 0.913). Aortic cross-clamp time remained independently associated with cardiac troponin I (regression coefficient 0.0099, 95% confidence interval 0.0013-0.0185; P = 0.024). In patients with prolonged aortic cross-clamp time, exploratory analysis suggested a non-linear increase beyond 80 min. In patients with aortic cross-clamp time of 90 min or less, perfusion interval was not clearly associated with peak cardiac troponin I. No significant associations were found with the composite of adverse events. CONCLUSIONS: The association between perfusion interval and myocardial injury depended on aortic cross-clamp duration. Single-dose blood-enriched modified del Nido cardioplegia appeared adequate when aortic cross-clamp time was 90 min or less. Longer intervals in prolonged procedures may matter, but the 80-minute threshold remains exploratory. These findings support a context-dependent myocardial protection strategy.