Heart Stress Test Study Better Predicts RisksAccording to a study reported in February 27, 2003 New England Journal of Medicine, treadmill tests are given to millions of Americans each year. Their hearts are analyzed while they walk at a steadily increasing pace. But doctors concentrate almost entirely on what happens while the patient is actually exercising.
[Journal abstract follows]
The study of more than 29,000 patients over ten years showed that the presence of irregular heartbeats in the minutes after a treadmill test is a better indicator of death within five years than irregular heartbeats during the test itself.
An irregular heartbeat after exercise on the treadmill "will be considered a marker of risk," said Dr. Daniel M. Shindler, a cardiologist at Robert Wood Johnson Medical School in New Jersey. "Before, it was not clear."
That information could, in turn, help doctors decide which patients need invasive testing, aggressive treatment and close monitoring.
Cardiologists at the Cleveland Clinic found that 11 percent of patients with irregular heartbeats after a stress test were dead within five years, compared with 5 percent of those who did not have such irregular rhythms.
Nine percent of patients with irregular heartbeats during the test itself died within five years, compared with 5 percent who did not have irregular beats during the exercise.
"What we're showing is that plain old, simple exercise tests that people have been doing for decades can show evidence of problems that identify people who are at risk of death," said Dr. Michael S. Lauer, director of clinical research in cardiac medicine at the Cleveland Clinic.
The irregular heartbeats, called ventricular ectopy, are caused by a disturbance in the heart's electrical system. Such irregular beats are not uncommon, but they usually disappear soon after a person stops exercising.
Three percent of the study patients had those irregular beats only during exercise, 2 percent had them only during recovery and 2 percent had them during both periods.
"I think Lauer and other people who are working on this are appropriately refocusing us" on irregular beats after the tests, said American Heart Association spokesman Dr. Richard Stein, the chief of cardiology at Brooklyn Hospital Center. "I think it's a very important piece of information for a doctor to have."
Over an average follow-up of 5.3 years, 1,862 of the 29,244 patients died. The study included deaths from all causes.
In a typical heart stress test, a person walks on a treadmill, with the pace gradually increasing to the patient's maximum endurance. Meanwhile, the person's blood pressure, pulse rate, electrical activity of the heart and any signs of inadequate blood flow through the heart are all monitored and recorded.
Treadmill tests have been around for five decades and are still widely used, despite the growing popularity of more expensive and sophisticated heart imaging techniques.
New England Journal of Medicine - Volume 348:781-790 February 27, 2003 Number 9
Frequent Ventricular Ectopy after Exercise as a Predictor of Death
Joseph P. Frolkis, M.D., Ph.D., Claire E. Pothier, M.S., Eugene H. Blackstone, M.D., and Michael S. Lauer, M.D.
Background: Exercise-induced ventricular ectopy predicts an increased risk of death in population-based cohorts. We sought to examine in a clinical cohort the prognostic importance of ventricular ectopy immediately after exercise, when reactivation of parasympathetic activity occurs. We hypothesized that ventricular ectopy after exercise (i.e., during the recovery phase) would predict an increased risk of death better than ventricular ectopy during exercise.
Methods: We studied 29,244 patients (mean [±SD] age, 56±11 years; 70 percent men) who had been referred for symptom-limited exercise testing without a history of heart failure, valve disease, or arrhythmia. Frequent ventricular ectopy was defined by the presence of seven or more ventricular premature beats per minute, ventricular bigeminy or trigeminy, ventricular couplets or triplets, ventricular tachycardia, ventricular flutter, torsade de pointes, or ventricular fibrillation.
Results: Frequent ventricular ectopy occurred only during exercise in 945 patients (3 percent), only during recovery in 589 (2 percent), and during both exercise and recovery in 491 (2 percent). There were 1862 deaths during a mean of 5.3 years of follow-up. Frequent ventricular ectopy during exercise predicted an increased risk of death (five-year death rate, 9 percent, vs. 5 percent among patients without frequent ventricular ectopy during exercise; hazard ratio, 1.8; 95 percent confidence interval, 1.5 to 2.1; P<0.001), but frequent ventricular ectopy during recovery was a stronger predictor (11 percent vs. 5 percent; hazard ratio, 2.4; 95 percent confidence interval, 2.0 to 2.9; P<0.001). After propensity matching for confounding variables, frequent ventricular ectopy during recovery predicted an increased risk of death (adjusted hazard ratio, 1.5; 95 percent confidence interval, 1.1 to 1.9; P=0.003), but frequent ventricular ectopy during exercise did not (adjusted hazard ratio, 1.1; 95 percent confidence interval, 0.9 to 1.3; P=0.53).
Conclusions: Frequent ventricular ectopy during recovery after exercise is a better predictor of an increased risk of death than ventricular ectopy occurring only during exercise.
Healing Heart Foundation