Predictors of early and late stroke following cardiac surgery

Abstract

Background: Much is known about the short-term risks of stroke following cardiac surgery. We examined the rate and predictors of long-term stroke in a cohort of patients who underwent cardiac surgery.

Methods: We obtained linked data for patients who underwent cardiac surgery in the province of Ontario between 1996 and 2006. We analyzed the incidence of stroke and death up to 2 years postoperatively.

Results: Of 108,711 patients, 1.8% (95% confidence interval [CI] 1.7%-1.9%) had a stroke perioperatively, and 3.6% (95% CI 3.5%-3.7%) had a stroke within the ensuing 2 years. The strongest predictors of both early and late stroke were advanced age (≥ 65 year; adjusted hazard ratio [HR] for all stroke 1.9, 95% CI 1.8-2.0), a history of stroke or transient ischemic attack (adjusted HR 2.1, 95% CI 1.9-2.3), peripheral vascular disease (adjusted HR 1.6, 95% CI 1.5-1.7), combined coronary bypass grafting and valve surgery (adjusted HR 1.7, 95% CI 1.5-1.8) and valve surgery alone (adjusted HR 1.4, 95% CI 1.2-1.5). Preoperative need for dialysis (adjusted odds ratio [OR] 2.1, 95% CI 1.6-2.8) and new-onset postoperative atrial fibrillation (adjusted OR 1.5, 95% CI 1.3-1.6) were predictors of only early stroke. A CHADS2 score of 2 or higher was associated with an increased risk of stroke or death compared with a score of 0 or 1 (19.9% v. 9.3% among patients with a history of atrial fibrillation, 16.8% v. 7.8% among those with new-onset postoperative atrial fibrillation and 14.8% v. 5.8% among those without this condition).

Interpretation: Patients who had cardiac surgery were at highest risk of stroke in the early postoperative period and had continued risk over the ensuing 2 years, with similar risk factors over these periods. New-onset postoperative atrial fibrillation was a predictor of only early stroke. The CHADS2 score predicted stroke risk among patients with and without atrial fibrillation.

Figure 1:

Rate of stroke from time of hospital admission for cardiac surgery to 2 years after surgery, by CHADS₂ score. CHADS₂ = acronym for congestive heart failure, hypertension, age > 75 yr, diabetes mellitus, and prior stroke or transient ischemic attack; 1 point is given for the presence of each of the first 4 conditions and 2 points for a history of stroke or transient ischemic attack.

Figure 2:

Rate of stroke or death from time of hospital admission for cardiac surgery to 2 years after surgery, by CHADS₂ score. CHADS₂ = acronym for congestive heart failure, hypertension, age > 75 yr, diabetes mellitus, and prior stroke or transient ischemic attack; 1 point is given for the presence of each of the first 4 conditions and 2 points for a history of stroke or transient ischemic attack.