Blood test identifies increased risk of death following surgery

A simple blood test can help identify people who are at high risk of dying within a month after non-cardiac surgery, a study by McMaster researchers has found.

Knowing who is at risk through the test called Troponin T (troponin is a protein marker of heart injury) can help physicians target patients who need enhanced observation or interventions, says the major study published in the Journal of the American Medical Association. Currently, troponin levels are not commonly measured after surgery.

Worldwide, more than 200 million adults have major non-cardiac surgery each year. Despite the benefits of surgery, many patients suffer serious complications and more than one million of those patients die within 30 days of surgery.

The results are from the VISION study, the largest international prospective study evaluating complications after surgery.

VISION enrolled 15,133 adult patients in North and South America, Asia, Australia and Europe who had a Troponin T measurement daily for the first three days after surgery. Patients were followed in hospital and at 30 days after surgery.

“VISION demonstrated that a simple blood test strongly identifies which non-cardiac surgery patients are at high risk of dying in the next 30 days,” said Dr. P.J. Devereaux, VISION’s principal investigator and associate professor of medicine, clinical epidemiology and biostatistics at McMaster’s Michael G. DeGroote School of Medicine.

Devereaux said the results also demonstrated that most patients did not die until an average of six or more days after their Troponin T blood test was identified as elevated. “This holds out great hope that there is time to intervene.”

Surgery activates pathways of inflammation, stress and clotting that predispose the heart to injury. As a result, many patients suffer heart attacks after surgery. The majority of these patients, however, will not experience chest pain.

Devereaux said although there is encouraging observational data that aspirin and cholesterol-lowering statins save lives in patients suffering heart injury after surgery, clinical trials are needed to establish whether interventions can alter patients’ risk of death based upon an elevated troponin measurement after surgery.

“Small studies have suggested that measuring troponin blood tests after surgery may identify patients at-risk of dying in the short-term,” said Dr. Gordon Guyatt, professor of clinical epidemiology & biostatistics and medicine of the Michael G. DeGroote School of Medicine and a VISION steering committee member. “We undertook VISION to provide a clearer understanding of the prognostic capabilities of Troponin T tests after surgery.”

“This study has substantial potential to change how patients are monitored after surgery,” said Dr. Jean Rouleau, scientific director of the Institute for Circulatory and Respiratory Health of the Canadian Institutes of Health Research.

“These results hold substantial promise that through measuring troponin blood tests after surgery, physicians can identify which patients are at high-risk of dying and this can allow them to consider enhanced monitoring and interventions in an attempt to improve outcomes. This is a good example of how a carefully conducted clinical study can impact on patient care,” Rouleau said.

“This study had more than 60 international funding sources. Such efforts are rare, but large studies like VISION are essential in order to have enough data to see signals clearly and to make progress,” said Dr. Salim Yusuf, a professor of medicine at the Michael G. DeGroote School of Medicine, vice-president of research at Hamilton Health Sciences and a member of the VISION Steering Committee.

Major funders of the VISION Study include the Canadian Institutes of Health Research and the Heart and Stroke Foundation of Ontario.