Perioperative myocardial infarction after coronary artery bypass grafting still presents a major cause of morbidity and mortality . Our study found that PMI patients had higher postoperative complications, including low cardiac output, pulmonary and renal complications, prolonged mechanical ventilation, ICU, and hospital stay. Additionally, PMI was associated with higher mortality. We identified risk factors for PMI in our cohort and included older age, female gender, low BSA, congestive heart failure, thrombolysis, and a higher number of distal anastomoses.
The incidence of PMI varies widely in the literature. A major cause for this variability is the different diagnostic criteria and techniques used . According to several reports, no optimal single diagnostic criteria for PMI are available, and combined diagnostic approaches are recommended . The debate between on-pump and off-pump CABG continues, and the practice varies in different centers. In a meta-analysis of studies comparing on-pump and off-pump CABG, no difference in myocardial injury was reported between groups .
Hospital and long-term sequelae risk could be improved if the risk factors are identified and properly managed. Several risk factors associated with PMI after off-pump CABG were reported. The presence of collaterals could protect the patients against PMI . We found that the risk of PMI was associated with increasing the number of distal anastomoses. This finding is similar to what was reported by Nathoe and colleagues . This observation could be attributed to the longer distal occlusion time, leading to PMI in patients with poor collaterals. Therefore, several strategies could be used to reduce distal ischemia or improve the collateral circulation, such as the use of intra-coronary shunts , coronary staplers , or ischemic preconditioning . Alkhouli and colleagues found that females, heart failure, dialysis, cirrhosis, emergency CABG, and mechanical circulatory support predicted early PMI after CABG . In our series, congestive heart failure and recent thrombolysis increased the risk of PMI. These factors indicated patients' instability with severe coronary artery disease. CABG in patients with cardiogenic shock or those who failed non-surgical revascularization was associated with high morbidity and mortality . In other series, the female gender was a risk factor for PMI, which was related to the smaller coronary arteries and poor collaterals . We confirmed this finding in our patients, and we found that females had a higher risk of PMI. Similarly, lower BSA was associated with PMI, which could be related to the coronary artery sizes.
PMI was associated with increased complications and mortality in our series. Patients with PMI had prolonged ventilation, ICU, and hospital stay. Another study reported a negative impact of PMI on hospital outcomes, while there was no difference in long-term outcomes . However, other studies showed that PMI negatively affected the incidence of long-term cardiovascular outcomes after CABG .
The study is limited by the retrospective design; however, PMI is a rare event, and this is the optimal study design to evaluate risk factors for PMI. Additionally, the study is a single-center experience, and several factors could be related to the operating surgeons and their expertise. Several unmeasured variables could have affected the outcomes and were not included in the analysis. Finally, we did not include invasive measures to diagnose PMI.