The prognostic value of cardiopulmonary exercise testing with a peak respiratory exchange ratio of < 1.0 in patients with chronic heart failure

BackgroundPeak oxygen consumption derived from a maximal cardiopulmonary exercise test (CPET) is a standard prognostic indicator in patients with chronic heart failure (CHF). Tests with a peak respiratory exchange ratio (pRER) < 1.0 are often taken to be submaximal, and data from such tests are treated as less helpful. The aim of the current study was to compare the prognostic value of CPETs with a peak respiratory exchange ratio (pRER) < 1.0 versus a pRER ≥ 1.0 in a large, representative sample of patients with CHF.Methods and results445 patients underwent a symptom-limited, treadmill-based CPET using the modified Bruce protocol, [82% males; age 72 (65–79) years]. 255 patients completed the CPET with a pRER ≥ 1.0. 121 patients died, and in survivors, the median follow-up period was 42 months. 42% of patients could not perform a CPET with pRER ≥ 1.0 using a modified Bruce protocol. Independent predictors of mortality were peak oxygen uptake, and the VE/VCO2 ratio. 190 patients completed the CPET with a pRER < 1.0. Independent predictors of mortality were age, peak oxygen pulse, and history of angina. RER group (pRER < 1.0 versus pRER ≥ 1.0) remained an independent predictor of mortality in all patients.ConclusionsIndependent predictors of mortality were different in patients with a pRER < 1.0 compared to those with a pRER ≥ 1.0. In CHF patients with a pRER < 1.0, traditional prognostic markers (VE/VCO2 slope, peak oxygen uptake) were not independently predictive of mortality.