Last Updated: 2008-02-07 10:39:30 -0400 (Reuters Health)

NEW YORK (Reuters Health) – In patients referred for exercise treadmill testing, exercise capacity is independently associated with nonfatal cardiac events as well as mortality, according to findings published in the January 28th issue of the Archives of Internal Medicine.

"Exercise capacity is one of many important prognostic factors measured during ETT (exercise treadmill testing)," Dr. Pamela N. Peterson, of the University of Colorado at Denver and Health Sciences Center, and colleagues write. "Little is known about the association between exercise capacity among patients referred for ETT and nonfatal cardiac events," they note.

The researchers assessed the prognostic value of exercise capacity for nonfatal cardiac events in 9191 patients referred for ETT and who were followed for a median of 2.7 years.

Exercise capacity was quantified as the proportion of age- and sex-predicted metabolic equivalents achieved, categorized as less than 85%, 85%-100%, and greater than 100%.

Patients with lower exercise capacity were more likely to be female and to have comorbid conditions such as diabetes and hypertension compared to those with greater exercise capacity. Those with lower exercise capacity were also more likely to have chest pain on the treadmill, abnormal heart rate recovery, and an abnormal chronotropic index during ETT.

During follow-up, there were 119 hospitalizations for myocardial infarction, 259 hospitalizations for unstable angina, 749 revascularization procedures, and 132 deaths.

Results of multivariate analysis adjusting for demographic, clinical, and treadmill variables, showed that exercise capacity less than 85% predicted was associated with an increased risk of myocardial infarction (hazard ratio (HR), 2.36), unstable angina (HR, 2.39), and coronary revascularization (HR, 1.75), compared with exercise capacity greater than 100% predicted.

"In fully adjusted models, exercise capacity was significantly associated with increased risk of all-cause mortality (HR, 2.90) for those who achieved less than 85% compared with those who achieved greater than 100% of age- and sex-predicted exercise capacity," Dr. Peterson and colleagues report.

Exercise capacity in the 85%-100% predicted range was also significantly associated with increased risk of all-cause mortality (HR, 1.78).

The findings have important implications, the researchers conclude, suggesting that "aggressive risk factor modification and close follow-up should be considered for patients with impaired exercise capacity."

Arch Intern Med 2008;168:174-179.

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