The accuracy of wearable, optically based HR monitors varies with exercise type and is greatest on the treadmill and lowest on elliptical trainer. Electrode-containing chest monitors should be used when accurate HR measurement is imperative.

Wrist-worn fitness and heart rate (HR) monitors are popular. 1,2

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Background The prognostic ability of a single measurement of peak oxygen uptake (VO2) is well established in patients with chronic heart failure (HF). The relation between a change in peak VO2 and clinical outcomes is not well defined. Methods and Results This investigation determined if an increase in peak VO2 was associated with a lower risk of the primary endpoint of time to all-cause mortality or all-cause hospitalization and three secondary endpoints. In Heart Failure and a Controlled Trial to Investigate Outcomes of Exercise Training (HF-ACTION), an exercise training trial for patients with systolic HF, cardiopulmonary exercise tests were performed at baseline and approximately three months later in 1620 participants. Median peak VO2 in the combined sample increased from 15.0 (11.9–18.0 Q1–Q3) to 15.4 (12.3–18.7 Q1–Q3) mL-kg−1-min−1. Every 6% increase in peak VO2, adjusted for other significant predictors, was associated with a 5% lower risk of the primary endpoint (HR = 0.95; CI = 0.93–0.98; p < 0.001); a 4% lower risk of the secondary endpoint of time to cardiovascular mortality or cardiovascular hospitalization (HR = 0.96; CI = 0.94–0.99; p < 0.001); an 8% lower risk of cardiovascular mortality or HF hospitalization (HR = 0.92; CI = 0.88–0.96; p < 0.001) and a 7% lower all-cause mortality (HR = 0.93; CI = 0.90–0.97; p < 0.001). Conclusions Among patients with chronic systolic HF, a modest increase in peak VO2 over three months was associated with a more favorable outcome. Monitoring the change in peak VO2 for such patients may have benefit in assessing prognosis.

BACKGROUND Data from a cardiopulmonary exercise (CPX) test are used to determine prognosis in patients with chronic heart failure (HF). However, few published studies have simultaneously compared the relative prognostic strength of multiple CPX variables. OBJECTIVES We sought to describe the strength of the association among variables measured during a CPX test and all-cause mortality in patients with HF with reduced ejection fraction (HFrEF), including the influence of sex and patient effort, as measured by respiratory exchange ratio (RER). METHODS Among patients (n = 2,100, 29% women) enrolled in the HF-ACTION (HF-A Controlled Trial Investigating Outcomes of exercise traiNing) trial, 10 CPX test variables measured at baseline (e.g., peak oxygen uptake [VO2], exercise duration, percent predicted peak VO2 [%ppVO2], ventilatory efficiency) were examined. RESULTS Over a median follow-up of 32 months, there were 357 deaths. All CPX variables, except RER, were related to all-cause mortality (all p < 0.0001). Both %ppVO2 and exercise duration were equally able to predict (Wald χ2: ~141) and discriminate (c-index: 0.69) mortality. Peak VO2 (mL·kg−1·min−1) was the strongest predictor of mortality among men (Wald χ2: 129) and exercise duration among women (Wald χ2: 41). Multivariable analyses showed that %ppVO2, exercise duration, and peak VO2 (mL·kg−1·min−1) were similarly able to predict and discriminate mortality. In men, a 10% 1-year mortality rate corresponded to a peak VO2 of 10.9 mL·kg−1·min−1 versus 5.3 mlkg−1/min−1 in women. CONCLUSIONS Peak VO2, exercise duration, and % ppVO2 carried the strongest ability to predict and discriminate the likelihood of death in patients with HFrEF. The prognosis associated with a given peak V2 differed by sex.