Stroke Risk Lingered Two Years After Heart Surgery

Diabetes and high blood pressure were risk factors for stroke after cardiovascular surgery

/ Author:  / Reviewed by: Joseph V. Madia, MD Beth Bolt, RPh

(RxWiki News) Most people who have cardiac surgery are aware of the risks — irregular heart beats, infection and stroke. What many may not realize is the risk for stroke may last long after the surgery is over.

A new study showed that stroke remained a risk for up to two years after cardiovascular surgery.

Researchers have developed tools to predict who may be most at risk.

"Speak to your cardiologist about your risk for stroke after surgery."

This research was conducted by Richard Whitlock, MD, of the Population Health Research Institute in Hamilton, Ontario, Canada, and colleagues.

Dr. Whitlock and team looked at cardiac surgery performed in Ontario between 1996 and 2006. They also examined the risk for stroke or death for up to two years after the surgery.

These researchers identified 108,711 people who had heart surgery during the study period. Most had coronary artery bypass grafting (76.8 percent), while 13 percent had isolated valve surgery and 10.2 percent had a combination of the two.

Coronary artery bypass grafting is a procedure that improves blood flow to the heart by connecting a healthy artery or vein in the body to the blocked portion of another artery, giving blood a new route to travel.

Stroke risk is generally high during and after heart surgeries like coronary artery bypass grafting. It is exceptionally high for people with diabetes or high blood pressure.

Only 1.8 percent of those who had cardiac surgery had a stroke during their time in the hospital, either having surgery or recovering from surgery. But 3.6 percent of those who had heart surgery had a stroke within two years.

Following surgery, more patients also died. While in the hospital, 2.8 percent of patients died. In the two years after surgery, 6.8 percent died.

There were several strong predictors of stroke at any time following heart surgery, such as being 65 or older, having a history of stroke or transient ischemic attacks (mini strokes, when the blockage of blood flow is temporary) or peripheral vascular diseases (diseases of the arteries or veins outside the heart).

Needing dialysis before surgery or being newly diagnosed with an irregular heartbeat (atrial fibrillation) predicted stroke while in the hospital but not after release.

The authors of this study used a tool to predict stroke called CHADS2. Using this tool, the researchers assigned points to people based on whether they had congestive heart failure, diabetes or high blood pressure; were 75 or older; or had a history of stroke, transient ischemic attack or blood clots.

The researchers found that patients who scored 2 points or higher on CHADS2 had a higher risk for stroke or death than those who scored lower. Those who scored two or higher had a 14.8 percent risk for stroke, compared with only 5.8 percent if they scored zero or one.

For those with a history of atrial fibrillation or those newly diagnosed with atrial fibrillation, having a score of two or more on CHADS2 was even deadlier.

The study authors noted that “patients with an elevated score should be the focus for preventive strategies in future research irrespective of heart rhythm.”

Sarah Samaan, MD, cardiologist and physician partner at the Baylor Heart Hospital in Plano, TX, told dailyRx News that risk factors for heart disease also contribute to stroke risk.

"People who have undergone open heart surgery tend to be those with more advanced heart disease, so they are also more likely to have serious risk factors,” Dr. Samaan said. "Many cases of atrial fibrillation are silent, meaning that some people may be unaware of an irregular heart beat. While this study does not present any surprises, it does highlight the importance of continuing to monitor an individual's risk for stroke, and to be proactive in taking measures to lower that risk wherever possible.”

This study was published in the Canadian Medical Association Journal on July 21.

The study was funded by a grant from the Canadian Network and Centre for Trials Internationally. The researchers reported no other potential conflicts of interest.

Review Date: 
July 22, 2014
Last Updated:
July 24, 2014