Patients with antibodies to heparin have nearly double the risk of death or serious complication after heart surgery, according to an article in the December issue of the Journal of Thoracic and Cardiovascular Surgery.

“Complications after heart surgery are typically attributed to the surgery alone,” said Thomas Slaughter, MD, co-principal investigator on the project and a professor of anesthesiology at Wake Forest University Baptist Medical Center. “Our study examined whether development of heparin antibodies before surgery poses an independent risk.”

The study, which involved 466 patients scheduled to undergo either coronary artery bypass or valve replacement surgery, was conducted by investigators at Wake Forest University Baptist and Duke University medical centers. It is the first study to convincingly demonstrate a relationship between heparin antibodies and complications after cardiac surgery.

Estimates suggest that nearly half of patients treated with heparin develop antibodies, which may last for months. The researchers theorize that in patients with heparin antibodies, subsequent treatment with heparin activates blood components that cause clotting and inflammation, increasing the risk for myocardial infarction, dysrhythmias, strokes and other complications.

“While it is too early to recommend universal testing for the antibodies, our study is the most definitive evidence to date that heparin antibodies increase the risk for death and complications associated with cardiac surgery,” said Slaughter.

The researchers tested heparin antibody levels in all study patients before surgery. They found that patients with the antibodies experienced a nearly twofold greater risk of death or hospitalization extending longer than 10 days. The researchers used an extended hospital stay as a surrogate marker for other complications after surgery such as heart attacks, strokes, infection, and kidney problems.

To ensure that patients’ baseline health status did not influence results, the researchers assessed each patient’s predicted surgical risk using a standardized risk scoring system called the Parsonnet risk score. This system is based on 19 factors known to be associated with death or other complications after heart surgery. The researchers found that regardless of Parsonnet score, patients with heparin antibodies before surgery fared worse than patients without the antibodies.

More than 350,000 adult cardiac surgical procedures are performed in the United States each year. In this study, as many as13 percent of surgical patients were found to have heparin antibodies before undergoing surgery.

“Researchers are at the cutting edge of learning about heparin antibodies and how they affect surgical outcomes,” said Slaughter. “We need to understand more about mechanisms underlying the adverse effects of heparin antibodies and whether alternative anti-clotting medications will prove safer before informed recommendations can be made to patients and surgeons.”