Stroke risk of carotid stenosis and impaired cerebrovascular autoregulation at cardiac surgery with extracorporeal circulation

Aims: Carotid stenosis at cardiac surgery with cardiopulmonary bypass (CPBS) is linked to an increased stroke risk. We aimed to assess this risk in relation to the degree of stenosis and whether stenosis related haemodynamic compromise predicts perioperative stroke.

Methods: 2809 of 7120 (39.5%) patients (pts) who underwent CPBS between Jan 1996 and Oct 2005 had carotid duplex before surgery (73.3% coronary artery bypass graft, 14.1% valve repair, 12.6% both). Transcranial Doppler with carbon dioxide testing for cerebrovascular reserve capacity was performed in all pts with high-grade stenosis (>/=80% local diameter reduction) and occlusion. 12 pts underwent synchronous carotid endarterectomy and were excluded from further analyses.

Results: 2.2% of pts had (bilateral) occlusion, 4% high-grade (0.6% bilaterally or with contralateral occlusion), 12.6% medium-grade (0.9% with contralateral occlusion), 81.1% low-grade/no stenosis. Reserve capacity was found exhausted in 11 (0.4%) pts distal to 9 occlusions and 2 high-grade stenoses. 2.4% of pts suffered an ischemic stroke. Stroke occurred distal to an occluded, high-grade, medium-grade and low-grade/not stenosed artery in 5.7, 0.8, 1.3, and 0.9%, respectively. When arteries with exhausted reserve capacity were considered as a separate category, corresponding percentages were 27.3, 1.3 (occlusion), 0 (high-grade), 1,3 (medium-grade), and 0.9 (low-grade/no stenosis). An exhausted reserve capacity was the strongest of all selected predictors for an ischemic stroke (adjusted hazard ratio 20.6, 95% CI 4.7–90.8; p<0.001; adjusted for sex, age, prior cardiac surgery, prior (ipsilateral) stroke, peripheral arterial disease, and atrial fibrillation).

Conclusion: An exhausted reserve capacity distal to high-grade carotid stenosis/occlusion is infrequent in pts undergoing CPBS. Doppler carbon dioxide testing can be used to identify pts, who have an increased stroke risk at CPBS from carotid stenosis/occlusion.