Perioperative stroke is a devastating complication of cardiac surgery and is associated with prolonged ventilator support, delayed discharge from the intensive care unit, in-hospital mortality of up to 24% and impaired quality of life due to neurological sequelae [4]. The risk of major stroke during isolated CABG is 1.9–3.8% [5]. Clinically silent cerebral embolization detected by imaging is much more frequent [6]. Cerebrovascular occlusive disease increases the risk of stroke, especially if bilateral or symptomatic ICA stenoses are present [7]. Other risk factors for perioperative stroke are prior neurological events, duration of CPB and atrial fibrillation [8]. Age, left main coronary artery disease, PAD, T2DM, chronic kidney disease, smoking and arterial hypertension probably do not play a direct role in the pathogenesis of perioperative stroke but are associated with atherosclerosis of the ascending aorta, which has been identified as strong predictor for focal neurological deficit after isolated CABG [9, 10].

In patients scheduled for CABG, ICA stenosis is a frequent incidental finding during routine preoperative assessment. Because of concerns about impaired cerebral perfusion during CPB and the anticipated risk of procedural stroke in patients with high-grade ICA stenosis, we routinely performed CEA ahead of CABG. Moreover, untreated carotid artery disease has also been identified as a risk factor for stroke during long-term follow-up after CABG [11]. Due to the collaborative efforts of cardiac and vascular surgeons in one department, we preferred synchronous CEA and CABG. This approach requires only one anesthesia exposure and the risk of MI during awaiting CABG is reduced compared to staged CEA [12]. However, the operative time is prolonged and mortality may be increased in patients undergoing synchronous CEA and CABG; however, this was not a uniform finding in previous reports [13]. Compared to the reverse staged approach, the risk of stroke is reduced in CABG patients with prior (staged or synchronous) CEA [2].

The composite endpoint of death, MI and stroke within 30 days after surgery was 13.0% in our patients, which is comparable to community-wide outcomes of synchronous CEA and CABG [14]. In accordance with previous publications, we found that these patients are at increased risk of perioperative cardiovascular events including stroke, frequently undergo reinterventions from multi-territorial atherosclerosis and have reduced long-term survival. The risk of permanent stroke in our study, which included consecutive and unselected patients, was 5.4%. Half of the patients in our series had bilateral or symptomatic carotid artery disease, which is clearly associated with an increased risk of perioperative stroke [7]. Among patients with unilateral, asymptomatic ICA stenosis the stroke risk was 2% at 30 days, lower compared to single institutional reviews and controlled studies [1, 2]. However, staged or synchronous CEA for unilateral ICA stenosis is no longer recommended as routine clinical practice in current guidelines [15, 16]. Asymptomatic unilateral ICA stenosis is not a proven independent risk factor for procedural, ipsilateral ischemic stroke in patients undergoing CABG, and prophylactic CEA failed to demonstrate a clear benefit in those patients [7, 17]. Moreover, a substantial proportion of strokes after CABG occurs in patients without cerebrovascular occlusive disease, is bihemispheric or contralateral to the hemispheric distribution of a significant ICA stenosis or occurs after an uneventful recovery from surgery [8, 17, 18]. For the latter patients, arrhythmias in the perioperative period such as atrial fibrillation may play a causative role in the development of neurological events.

Cerebral hypoperfusion accounts for 8.8% of strokes after CABG [19]. Patients with impaired cerebral blood flow reserve due to extra- and/or intracranial cerebrovascular occlusive disease have an increased risk of brain hypoperfusion and watershed infarcts during CPB [20]. To improve patient selection for prophylactic CEA, we now routinely assess CABG patients with known high-grade ICA stenosis by means of magnetic resonance angiography and transcranial Doppler ultrasound performed by a specially trained neurologist. If cerebral blood flow reserve is impaired (increase in middle cerebral artery blood flow velocity < 10% on breath holding), we perform synchronous CEA and CABG. For remaining CABG patients with unilateral, asymptomatic 70–99% ICA stenosis, the carotid revascularization strategy is decided by multidisciplinary discussion and individualized. In general, we advise synchronous CEA for patients with an increased risk for late stroke, including those with ipsilateral silent cerebral embolization on neuroimaging, documented progression to an ≥ 80% ICA stenosis or high-risk morphological features of the carotid plaque. In all patients with high-grade ICA stenosis and especially in those not scheduled for CEA, general measures to reduce procedural stroke risk during CABG include a mean arterial pressure > 70 mmHg during CPB, avoiding intraoperative drops in blood pressure, avoiding a nadir hematocrit < 25%, optimizing perioperative hemodynamics, patient blood management strategies to avoid transfusions, aggressive treatment of arrhythmias and proper anticoagulation.

Seventy-three percent of strokes in our series occurred contra- or bilateral to the CEA distribution site, indicating that they were not caused by temporary hypoperfusion during carotid artery clamping (Fig. 1C). There is an increasing amount of evidence that points towards ascending aorta atherosclerosis as the principal culprit lesion for perioperative strokes in CABG patients. With a reported OR of 3 to 4.5, an atheromatous proximal aorta is the strongest independent predictor for perioperative strokes in isolated CABG procedures [4, 21, 22]. Uni- or bihemispheric plaque material embolization may occur during manipulation, cannulation, cross or side clamping of the aorta as well as a “sandblasting” effect of the jet derived from the inflow cannula [23,24,25]. We now routinely perform preoperative imaging of the aorta with computed tomography in patients > 60 years and those suspected to have severe generalized atherosclerosis (high cardiovascular risk profile, on dialysis, symptomatic PAD, visible aortic calcification on preoperative chest x-ray or angiography). Epiaortic ultrasonography is also highly sensitive in the detection of even non-calcified atheroma of the ascending aorta [26]. Ultrasound-guided aortic cannulation and cross clamping have been shown to reduce perioperative stroke and death rate associated with on-pump coronary surgery [27]. Additionally, porcelain aorta is present in up to 9.3% of patients undergoing elective CABG and may preclude any aortic manipulation [28]. If such severe calcifications in the ascending aorta are detected by preoperative imaging, we favor off-pump coronary artery bypass grafting (OPCAG) in hemodynamically stable patients with good quality target coronary vessels and on-pump beating heart CABG with direct axillary artery cannulation for unstable patients as well as those with diffuse carotid artery disease or poor quality target vessels. Preferentially all arterial in situ bypass conduits or Y-grafts are used. In patients with atheromatous aortas, OPCAG is associated with a reduced risk of stroke and in-hospital mortality [29]. However, the graft number is reduced and the risk of incomplete revascularization increased compared to on-pump surgery. Adequate patient selection is therefore mandatory for OPCAG. Axillary artery cannulation has been shown to reduce cerebral microembolization from the aorta, especially into the right hemisphere by flow reversal in the innominate artery [30]. Even in the presence of severe atherosclerosis of the aorta, the axillary artery is most often disease free. We prefer direct axillary artery cannulation; alternatively, a side graft can be used.

Nevertheless, the limitations of this single-center experience study include its retrospective nature. Additionally, the absence of a comparison group undergoing staged procedures makes it challenging to draw definitive conclusions about the superiority of synchronous CEA and CABG.