Can We Minimise the Risk of Stroke After Coronary Artery Bypass Graft? Techniques and Patient Selection
Accurate risk stratification and careful selection of the strategy of revascularisation are key factors to minimise the risk of stroke. The presence of severe atherosclerotic disease of the ascending aorta may be associated with a stroke rate up to 45 % if no modifications in the operative technique are implemented.37 Depending on the individual risk profile of patients, several options can be considered to minimise the risk of stroke. If the risk of stroke appears prohibitive with CABG, and anaortic approaches cannot be used, PCI should be considered as an alternative. In case of severe atherosclerotic disease of the ascending aorta, off-pump CABG with anaortic approaches should be implemented. Total arterial revascularisation with in situ grafting using both mammary arteries and/or T- or Y-grafting should be considered the gold standard to minimise the risk of stroke.
When complete revascularisation cannot be achieved with total arterial revascularisation, use of the HEARTSTRING device may help in minimising aortic manipulation. Use of intra-operative epiaortic ultrasound, which can precisely characterise site and extension of atherosclerotic disease, may help the surgical decision-making approach. In the study by Bolotin et al., intra-operative findings of atherosclerotic disease of the ascending aorta with epiaortic ultrasound led to a change in the surgical strategy in 28 % of cases.10 Moreover, in cases in which on-pump CABG cannot be avoided, epiaortic ultrasound may help in identifying a relatively disease-free portion of the aorta to minimise the risk of atheroembolism when clamping or cannulating the aorta.
Despite some studies suggesting a potential benefit of anaortic approaches for high-risk patients, this technique has not been widely embraced. For several reasons, including the technical requirements for performing graft anastomoses with the beating heart and the concern for long-term patency, most surgeons worldwide still prefer to perform CABG with cardiopulmonary bypass.38 Thus, much of the evidence derived from the aforementioned studies has been contributed by highly experienced centres with surgeons that have developed high proficiency in performing off-pump CABG. Whether this technique can be safely extended to all cardiac surgical centres, remains to be determined.
Use of epiaortic filters has also been advocated as another possible strategy to minimise the risk of cerebral embolism in patients with severe atherosclerotic disease of the ascending aorta, who are not deemed suitable for anaortic approaches. The filter is inserted through a modified arterial cannula immediately before releasing the cross-clamp, and it remains in the aorta until cardiopulmonary bypass is discontinued. In a study involving 77 patients, implantation of the filters proved to be feasible, safe and uneventful.39 Particulate emboli were retrieved in 44 patients, the predominant origin of which was atheromatous. In a randomised trial including 1,289 patients, particulate emboli were detected in 598 (96.8 %) of 618 successfully deployed filters.40 In addition, a significant reduction in post-operative renal complications was apparent in patients in whom filters were implanted compared with the control group.
More controversial appears the management of patients with carotid artery disease that have to undergo CABG. The prevalence of severe carotid disease in this setting is around 6–12 %.41 Three approaches are commonly used: carotid endarterectomy followed by CABG, combined carotid endarterectomy and CABG, and more recently carotid stenting followed by CABG. In a propensity matched analysis of 350 patients in which these three approaches were compared, Shishehbor et al. showed significantly lower long-term rates of all-cause death, myocardial infarction and stroke in patients treated with carotid stenting followed by CABG in comparison with both carotid endarterectomy followed by CABG (adjusted hazard ratio [HR] 0.33, 95 % CI 0.15–0.77; p=0.01) and combined carotid endarterectomy and CABG (HR 0.35, 95 % CI 0.18–0.70).42 However, due to the observational nature of the study, these data should be considered hypothesis generating, and further randomised trials are warranted.
Optimal blood pressure management, prompt recognition and treatment of new onset atrial fibrillation, prevention of rewarming temperature >37°C,43 use of alpha-stat pH management44 and prevention of hyperglycaemia during surgery45 are other recommendations that should be considered depending on the individual risk profile of patients.