Has the ideal and universal prognostic index in cardiorespiratory exercise testing been identified?

Cardiopulmonary exercise testing (CPET), although of limited availability in many countries, provides data on various parameters with clinical, diagnostic and prognostic implications that are of particular interest in heart failure. 1 These parameters include maximum oxygen consumption (VO 2 max), 2,3 oxygen pulse curve (both absolute and adjusted for body weight), 4,5 the ventilatory anaerobic threshold (VAT), 6 ventilatory equivalent for CO 2 (VE/VCO 2 ) and VE/VCO 2 slope, 7,8 and oxygen uptake efficiency slope. 9he question is which of these are the most reliable, easiest to obtain and prognostically most useful for predicting overall mortality.There are limitations in the assessment of these variables, including low reproducibility, 10 differences in methods of calculation and identification, 11 and the need in most cases to achieve maximal exercise to obtain results, 12 which depends on the motivation of patients, technicians and physicians alike.Exercise tests frequently do not reach maximal levels, particularly in patients with heart failure and most elderly people.The study by Ramos et al. 13 in this issue of the Journal analyzes a new parameter, the cardiorespiratory optimal point (COP), calculated as the minimum oxygen ventila-