Treadmill 1-km walk test predicts prognosis in cardiac disease



ROME – A moderate walk on a treadmill for 1 km proved useful for calculating a patient’s peak oxygen uptake and cardiopulmonary exercise capacity, and provided significant prognostic information for patients with cardiac disease, in a study with more than 1,200 Italian men.

The treadmill walk test "is a low-cost and simple tool for the indirect evaluation of cardiorespiratory fitness in cardiac outpatients," Dr. Giorgio Chiaranda said in a poster at the annual meeting of the European Association for Cardiovascular Prevention and Rehabilitation.

Cardiac patients in the highest quartile for cardiorespiratory fitness measured by the walk test had a two-thirds reduction in their mortality, compared with patients in the lowest fitness quartile during a median follow-up of 8 years.

The researchers had previously reported the development of a new submaximal protocol to predict peak oxygen uptake using a moderate, perceptually regulated 1-km treadmill walk test (J. Cardiopulm. Rehabil. Prev. 2012;32:262-9). They developed the walk test as an alternative to the standard maximal cardiopulmonary exercise test, which is relatively expensive and can be impractical in some settings. The investigators initially developed the walk test in 178 men with cardiac disease; the new study was performed to validate the walk test using prospectively collected follow-up data.

After a cardiac event, 1,255 outpatient men were referred to a cardiac rehabilitation program. They averaged 61 years of age, with a range from 25 to 85 years. Their average body mass index was 27.6 kg/m2, and their average left ventricular ejection fraction was 56%(range, 21%-80%. Their index cardiac disease event was coronary artery bypass surgery in 49%, myocardial infarction in 28%, percutaneous coronary intervention in 9%, valve replacement in 9%, and other procedures in 5%.

All patients underwent a 1-km treadmill walk test, during which they were reminded to maintain a moderate pace. Testing produced no complications. Patients in the lowest quartile for their predicted peak oxygen uptake had a level of 19.6 mL/kg per minute or less. Patients in the highest quartile had a rate of at least 25.1 mL/kg per minute.

During a median follow-up of 8 years, 141 (11%) of the patients died. A multivariate analysis adjusted for several demographic and clinical factors including age, body mass index, ejection fraction, smoking status, hypertension, family history, cholesterol levels, glucose level, and renal function. Patients in the fittest quartile had a follow-up mortality rate that was 67% lower than that of patients in the least-fit quartile. Patients in the next most-fit quartile had a mortality rate that was 50% lower than that of the least-fit group. Both between-group differences were statistically significant, Dr. Chiaranda of the University of Ferrara (Italy) Center for Sports Medicine and his associates found. Cardiorespiratory fitness could account for 71% of the variability in mortality during follow-up.

The researchers found the lowest mortality rate among patients from the fittest quartile who further improved their peak oxygen uptake during follow-up, based on a second 1-km walk test performed 1 year following their baseline test in 964 patients. Patients with increased fitness on follow-up had an 89% reduced mortality rate compared with patients from the least-fit quartile who did not show improvement in their fitness after the first follow-up year.

Dr. Chiaranda and his associates said they had no relevant financial disclosures.

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