Stress Test Recovery Rate: two articles from same doctor. added 09/30/01

Researchers Find Heart Rate Worth a Thousand Words 
    Simple Test Tells Even Healthy People Their Heart Disease Risk

By Liz Meszaros  WebMD Medical News  Reviewed by Dr. Gary D. Vogin
   from http://my.webmd.com/content/article/1728.61455

Sept. 19, 2000 -- For those worried about their heart, here's some good news: A person's risk for having a life-threatening bout with heart disease can be determined easily and accurately using two simple, noninvasive tests. You've probably heard of one -- exercise stress testing, also known as treadmill testing. The other you probably aren't familiar with: heart rate recovery. Researchers at the Cleveland Clinic report their results with these two tests in the Sept. 20 (2000) issue of the Journal of the American Medical Association.

Heart rate recovery is a measurement of how much the heart rate falls during the first minute after peak exercise. It is routinely measured during millions of exercise tests every year. Doctors usually order these tests when they suspect that a patient may have a heart in trouble.

Patients are put on a treadmill and exercise to the point that they can't go on. It is then that the heart rate recovery is taken. Afterward, it's added to the picture created by how long the person can exercise and what the heart rate was doing during the exercise test. This big picture can give doctors a pretty accurate idea of how well the heart is working.

The healthier a person's heart is, the quicker it returns to its normal beat; the less healthy the heart is, the longer it takes it to recover from something like an exercise stress test.

"One simply subtracts the heart rate two minutes after exercise from the heart rate at the end of exercise," says Michael S. Lauer, MD, director of the Cleveland Clinic Exercise Laboratory in Ohio and the lead researcher of the study.

Lauer and colleagues found that people with an abnormal heart rate recovery, which consists of a score -- or decrease -- of 12 or less beats per minute, were at a greater risk for death from heart disease than those with normal heart rate recovery, which is a decrease of 15 to 25 beats per minute.

Both tests are very simple and, according to these authors, will give a good picture of who should be treated aggressively for heart disease and who should be reassured that they are at little risk.

"If a patient has a normal heart rate recovery and normal exercise stress test, I tell them that everything looks great for them, that they have a risk for having a major life-threatening problem of less than one half of 1% per year," he says. "If the test is abnormal, the risk moves up to 3% or 5% per year. That means we really have to get to work."

So what are those who have abnormal heart rate recovery times to do? According to Lauer, they should be even more motivated to become healthier and reduce their risk for heart disease.

"People who had abnormal heart rate recovery times are at increased risk for [heart disease] so that everything that can be fixed, should be," Lauer says. He suggests:

• Smokers should break the habit.
• High cholesterol levels should be brought down.
• Diabetes should be kept under control.
• Overweight should people lose weight.
• Those with blockages in the blood vessels should seek aggressive treatment.

Lauer has done several studies of heart rate recovery, but he tells WebMD that this one is different because it was done in such a large number of patients who had no symptoms of heart disease.

"Most of them were referred for testing as part of screening, meaning that they didn't have any symptoms of heart disease, but for whatever reason, their doctors thought they may be at risk for heart disease," he explains.

He adds that as a result, he now orders stress tests more readily in his own patients. "Since our original paper came out over a year ago, we now routinely incorporate heart rate recovery into virtually every stress test that we do," Lauer says. "In my own practice, I send patients for exercise stress tests with a lot more enthusiasm than I used to because I know that the test has a lot more information than I used to think that it did," he concludes.

Also convinced is Gerald F. Fletcher, MD, professor at the Mayo Clinic in Jacksonville, Fla., who says that these results and those previously seen from these same researchers have convinced him that heart rate recovery should be added to all stress testing.

"If the heart rate recovery is not rapid enough, it's a marker of not-so-good things to come," he tells WebMD, but adds that this information needs to be seen in the bigger picture created by the other factors in testing. "If heart rate recovery is not so good, but everything else is [good], you can't put too much into it."

Fletcher adds, "Heart rate response, heart rate recovery, [blood pressure] response, [blood pressure] recovery, time on the treadmill -- all these things are very important. We can get a lot of information out of a relatively inexpensive test," he concludes.

  - - - - - abstract of the JAM article follows - - - - - - -

Objective  To assess the associations among abnormal heart rate recovery, treadmill exercise score, and death in patients referred specifically for exercise electrocardiography.

Design and Setting  Prospective cohort study conducted in an academic medical center between September 1990 and December 1997, with a median follow-up of 5.2 years.

Patients  A total of 9454 consecutive patients (mean [SD] age, 53 [11] years; 78% male) who underwent symptom-limited exercise electrocardiographic testing. Exclusion criteria included age younger than 30 years, history of heart failure or valvular disease, pacemaker implantation, and uninterpretable electrocardiograms.

Main Outcome Measures  All-cause mortality, as predicted by abnormal heart rate recovery, defined as failure of heart rate to decrease by more than 12/min during the first minute after peak exercise, and by treadmill exercise score, defined as (exercise time) - (5 maximum ST-segment deviation) - (4 treadmill angina index).

Results  Three hundred twelve deaths occurred in the cohort. Abnormal heart rate recovery and intermediate- or high-risk treadmill exercise score were present in 20% (n = 1852) and 21% (n = 1996) of patients, respectively. In univariate analyses, death was predicted by both abnormal heart rate recovery (8% vs 2% in patients with normal heart rate recovery; hazard ratio [HR], 4.16; 95% confidence interval [CI], 3.33-5.19; ² = 158; P<.001) and intermediate- or high-risk treadmill exercise score (8% vs 2% in patients with low-risk scores; HR, 4.28; 95% CI, 3.43-5.35; ² = 164; P<.001). After adjusting for age, sex, standard cardiovascular risk factors, medication use, and other potential confounders, abnormal heart rate recovery remained predictive of death (among the 8549 patients not taking -blockers, adjusted HR, 2.13; 95% CI, 1.63-2.78; P<.001), as did intermediate- or high-risk treadmill exercise score (adjusted HR, 1.49; 95% CI, 1.15-1.92; P = .002). There was no interaction between these 2 predictors.

Conclusions  In this cohort of patients referred specifically for exercise electrocardiography, both abnormal heart rate recovery and treadmill exercise score were independent predictors of mortality. Heart rate recovery appears to provide additional prognostic information to the established treadmill exercise score and should be considered for routine incorporation into exercise test interpretation.

JAMA. 2000;284:1392-1398

Author Affiliations: Departments of Cardiology (Drs Nishime, Cole, Pashkow, and Lauer), Cardiothoracic Surgery (Dr Blackstone), and Biostatistics and Epidemiology (Dr Blackstone), Cleveland Clinic Foundation, Cleveland, Ohio.
 
Corresponding Author and Reprints: Michael S. Lauer, MD, Clinical Research and Exercise Laboratory, Department of Cardiology, Desk F25, Cleveland Clinic Foundation, Cleveland, OH 44195 (e-mail: lauerm@ccf.org).

Funding/Support: Dr Lauer is the recipient of an Established Investigator Grant from the American Heart Association.