Background: Ischemic stroke after coronary artery bypass (CABG) has been often linked to aortic manipulation during surgery.

Objectives: The objective of the study was to estimate the rate of postoperative ischemic stroke within 30 days from CABG by surgical risk factors alone or in combination.

Methods: The multinomial propensity score for multiple treatments was used to create six models with a total of 16,255 consecutive patients undergoing isolated CABG. For each model, a different classification variable was used to stratify patients.

Results: Balance achieved in all models was substantial, enabling unbiased estimation of the treatment estimand. Both off-pump techniques with (0.009; 95% CI 0.006–0.011) or without proximal anastomoses (0.005; 0.005–0.003), and surgery performed on the beating heart using cardiopulmonary bypass with (0.009; 0.006–0.011) or without proximal anastomoses (0.024; 0.021–0.029) showed a mean stroke estimate significantly lower than the other techniques. Off-pump surgery and on-pump surgery without an aortic cross-clamp yielded nearly equal incidences of stroke (0.012; 0.008–0.015 and 0.018; 0.012–0.023, respectively). Using an aortic cross-clamp significantly increased the stroke estimate (0.075; 0.061–0.088), whereas using a side-biting clamp did not (0.039; 0.033–0.044). The number of aortic touches (0.029; 0.026–0.031) and the number of proximal anastomoses (0.044; 0.035–0.047) did not significantly increase the incidence of stroke.

Conclusions: Aortic cross-clamping was found to be the primary cause of post-CABG ischemic stroke. Instead, additional aortic manipulation from a side-biting clamp, on-pump surgery, multiple aortic touches, number of proximal anastomoses, and aortic cannulation were found not to increase the estimate of stroke significantly. Further research on this topic is warranted.