Simple Test Predicts Health Risk
03 Mar 2006
You may have an electrocardiogram today, but it’s no guarantee you won’t drop dead tomorrow. Today, in an increasingly complex electronic world, we can have a barrage of sophisticated tests done in an hour or so. But they do not ensure you will live out the day. So why not follow the rule, "keep it simple stupid" (kiss). A study published in The New England Journal of Medicine reports a simple prognostic gem that helps to predict the risk of death.
Dr. Michael S. Lauer, Director of Clinical Research at The Cleveland Clinic, says the heart’s recovery rate is the important factor in assessing mortality. The key factor is how quickly the heart rate returns to normal following exertion.
In this study 2,400 patients were referred to the clinic for exercise tests on a treadmill. They were all suspected of having coronary artery disease. These patients were then followed for six years.
The result? Those whose heart rate recovered slowly, falling by 12 beats or less during the first minute after exercise, were four times more likely to die of any cause than those whose heart rate recovered quickly.
It’s a simple calculation. Suppose your peak rate is 180 beats a minute and one minute later it drops to 160 the recovery rate is 20 (180-160). The higher the recovery rate the greater the prospect for a longer life.
This was a startling finding. So researchers decided to do exercise tests on those without any known heart problems. They discovered that those whose hearts recovered slowly from a treadmill test were twice as likely to die.
Factors that affect recovery of the heart include poor physical condition, advancing age and high blood sugar levels.
Two nervous systems control heart rate. If you run up a flight of stairs or are about to be mugged or shot (it used to be New York, now it’s Toronto) the sympathetic nervous system speeds up the heart. How quickly the heart rate returns to normal is determined by the parasympathetic nervous system which signals the heart to slow down once stress has ended.
Dr. Lauer says it’s the parasympathetic system that plays the major role in keeping us alive. He says it’s vital role is to protect the heart from stress.
For instance, if the heart is deprived of oxygenated blood due to coronary heart disease or by the stress of exercise, the parasympathetic nervous system slows the heart down. This protects the heart from a potentially serious abnormal rhythm.
At this point many readers are probably wondering about the condition of their heart. Possibly considering running up and down the stairs in an attempt to get their heart rate to maximum level, waiting a minute to see how much the heart’s rate has dropped, then doing the calculation.
But don’t do it, for two reasons. I don’t want anyone with unsuspected heart disease to drop dead while running up stairs. The purpose of this column is to save, not end lives. Moreover, it’s impossible to test your own heartbeat recovery at home as it’s difficult to determine how hard you’ve been exercising.
There may come a time, however, when you’re scheduled for an exercise stress test. This is the time to ask the doctor if he will also include the recovery test. This is not asking for the moon as it only takes a minute longer.
This test has other practical clinical implications. Calculating the recovery rate helps to separate those with minimal heart disease from those at higher risk. This would allow those with life-threatening problems, such as severe narrowing of the heart’s major artery, to get speedy treatment.
We also know that patients with diabetes have a high risk of coronary heart disease. Studies show that 50 per cent of diabetes patients die of a heart attack. The heart rate recovery test could help to detect people with diabetes or even pre-diabetes who are at exceptional risk. This may prompt them to get into better physical shape or be more conscientious in controlling their blood sugar levels.
