A two-in-one test can determine who is in danger of further heart problems following a heart attack, researchers at the University of Calgary say.

In the REFINE study, which stands for Risk Estimation Following Infarction Noninvasive Evaluation, researchers found measuring nervous system function and the heart's electrical function provided an indication of which heart attack patients were most at risk for future heart problems.

Researchers found measuring T-wave alternans (TWA) and elevated heart-rate turbulence (HRT) provided a sign of future heart attack risk.
(CBC)

The University of Calgary researchers studied 322 patients immediately following their heart attacks. At two to four weeks after the attack, and then at 10 to 14 weeks, the patients wore all-day electrocardiograms to measure those two key factors in the development of heart arrhythmias, which are disturbances in a person's heartbeat.

The heart's electrical system can throw off a heart's rhythm after being damaged during a cardiac arrest. A person's nervous system can make an arrhythmia spiral out of control.

Dr. Derek Exner, a heart rhythm specialist in Calgary who worked on the study, said until now, tests performed on heart attack patients haven't provided an accurate measurement of future risk. 

"If you happen to have one of these episodes [a heart attack] and you're not near a hospital or ambulance, your chance of surviving is only about one in 20. So it's really important that we identify these people before rather than [when] it's too late," he told CBC News.

Two measures tell the tale

The University of Calgary researchers looked for signs of T-wave alternans (TWA) — an abnormality in the heart's rhythm — and heart-rate turbulence (HRT) — the return to a regular heartbeat after a premature ventricular contraction, which is a type of arrhythmia.

The participants were subsequently tracked over a period of four years.

The researchers found that the biggest indicator of future heart attack risk was TWA and lowered HRT at the 10- to 14-week mark. The patients who had these characteristics, who made up 20 per cent of the study group, were six times more likely to suffer another heart attack or die in the followup period than other patients.

One in five people who have suffered a heart attack are at high risk of more heart complications. The new test regime will allow doctors to accurately identify which patients are at greatest risk.

"The one in five patients in our study who had abnormal tests were at high risk of serious problems," Exner said in a release. "Close followup with a physician and the use of medications known to be beneficial after a heart attack — aspirin, beta blockers, ACE inhibitors and statins — are very strongly recommended."

The study is published in the Dec. 11 issue of the Journal of the American College of Cardiology.