Early vs Late Stroke Risk Factors Similar Post–Cardiac Surgery

July 22, 2014

HAMILTON, ON — Patients who develop AF following cardiac surgery are at early risk of stroke, but that risk does not persist long term, new research suggests. In fact, with the exception of new postop AF, the risk factors for stroke following cardiac surgery are largely the same in the early and late periods, conclude researchers who reviewed health records from patients across the province of Ontario.[1]

The findings may have implications for the duration of anticoagulation needed to treat AF in these patients.

A patients' CHADS2 score, they found, predicted stroke and stroke or death for two years after cardiac surgery regardless of whether there was new postoperative AF or even a history of AF, according to the study, published July 21, 2014 in CMAJ with first author Dr Richard Whitlock (McMaster University, Hamilton, ON).

The population consisted of 108 711 patients who underwent isolated CABG surgery (77% of patients), isolated cardiac valve surgery (13%), or combined CABG and valve surgery (10%) in the province over 10 years starting in 1996. Of the 91.2% of patients without a history of AF, 18% developed AF postoperatively.

Over the entire cohort, 1.8% had a stroke within 48 hours of surgery and 3.6% had a stroke during the subsequent two years.

The strongest significant predictors of stroke over two years in adjusted analysis were age >65 years, history of stroke or transient ischemic attack, peripheral vascular disease, history of AF, combined CABG and valve surgery vs isolated CABG, and isolated valve surgery vs isolated CABG.

The same factors were among the strongest significant predictors of early stroke, with the addition of new postoperative AF and a preoperative dependence on dialysis, the authors reported.

Predictors of Early Stroke and Stroke at Two Years After Cardiac Surgery, Hazard Ratio (95% CI)

Predictor HR (95% CI) for early stroke HR (95% CI) for stroke at 2 years
Age >65 years 1.1 (1.0–1.2) 1.2 (1.1–1.4)
Prior stroke or TIA 2.1 (1.8–2.5) 2.2 (1.9–2.5)
Preoperative dialysis 2.1 (1.6–2.8) 1.3 (0.9–1.8)
Peripheral vascular disease 1.6 (1.4–1.8) 1.6 (1.4–1.8)
History of AF 1.2 (1.1–1.4) 1.4 (1.3–1.6)
New postoperative AF 1.5 (1.3–1.6) 1.1 (1.0–1.2)
CABG plus valve surgery (vs isolated CABG) 1.7 (1.5–1.9) 1.5 (1.4–1.8)
Isolated valve surgery (vs isolated CABG) 1.3 (1.1–1.5) 1.3 (1.1–1.5)

As patients' CHADS2 scores rose, so did their risk of stroke and of stroke or death over two years among patients without any AF, those with a preoperative history of AF, and those with new-onset AF after surgery, respectively.

Rate (%) of Stroke or Death by CHADS2 Score in Ontario Patients Undergoing Cardiac Surgery

End points CHADS2 0–1 CHADS2 >2
Absence of AF 5.8 14.8
New-onset postoperative AF 7.8 16.8
History of AF 9.3 19.9
CHADS 2 index based on presence of congestive heart failure, hypertension, age >75 years, presence of diabetes, and history of stroke or transient ischemic attack

"The finding that new-onset postoperative atrial fibrillation was an independent predictor of early stroke but not of late stroke suggests that patients with postoperative atrial fibrillation should be considered for a short course of anticoagulation," according to the authors.

The authors had no disclosures.


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