Inverse association between mortality and estimated functional capacity in hypertensive male outpatients with established coronary artery disease

BACKGROUND: Exercise capacity has been inversely associated with the incidence and severity of hypertension and cardiovascular disease. Cardiopulmonary exercise testing (CPET) is the gold standard for the determination of exercise capacity (i.e. peak oxygen consumption [VO2peak]). However, CPET is not always readily available in clinical settings. A moderate 1-km treadmill walking test (1k-TWT) has been demonstrated to be a valid and simple tool for the assessment of exercise capacity in outpatients with cardiovascular disease. The aim of this study was to examine the association between VO2peak estimated during a 1k-TWT and all-cause mortality in patients with hypertension and stable coronary artery disease. METHODS: A total of 597 patients aged 63 ± 9 years underwent the 1k-TWT, and were followed up for all-cause mortality. The 1k-TWT was individualized at a moderate perceptually-regulated exercise intensity (11-13 on the 6-20 Borg scale). Age, body mass index, heart rate, and time to complete the 1k-TWT were entered into the equations originally validated for VO2peak estimation. Subjects were stratified into quartiles according to baseline VO2peak, and mortality risks were calculated. RESULTS: During a median follow-up of 7.7 years, 79 deaths from any cause occurred, and resulted 36, 28, 10 and 5 for the first, second, third, and fourth quartile respectively. Compared to the lowest quartile (average VO2peak 18.1 ml/kg/min, n=149), the full-adjusted hazard ratios were 0.80 (p=0.49), 0.31 (p=0.02), and 0.13 (p=0.005) for the second (average VO2peak 21.8 ml/kg/min, n=150), third (average VO2peak 24.4 ml/kg/min, n=149), and fourth quartile (average VO2peak 28.7 ml/kg/min, n=149), respectively. CONCLUSIONS: VO2peak estimated by the 1k-TWT is a strong and independent predictor of all-cause mortality in patients with hypertension and coronary artery disease. Assessing VO2peak by the 1k-TWT can be a useful, simple and low-cost tool to stratify and follow up hypertensive patients with cardiovascular disease through cardiac rehabilitation and secondary prevention programs.