Use of Free-Living Step Count Monitoring for Heart Failure Functional Classification: Validation Study

Abstract

BackgroundThe New York Heart Association (NYHA) functional classification system has poor inter-rater reproducibility. A previously published pilot study showed a statistically significant difference between the daily step counts of heart failure (with reduced ejection fraction) patients classified as NYHA functional class II and III as measured by wrist-worn activity monitors. However, the study’s small sample size severely limits scientific confidence in the generalizability of this finding to a larger heart failure (HF) population.ObjectiveThis study aimed to validate the pilot study on a larger sample of patients with HF with reduced ejection fraction (HFrEF) and attempt to characterize the step count distribution to gain insight into a more objective method of assessing NYHA functional class.MethodsWe repeated the analysis performed during the pilot study on an independently recorded dataset comprising a total of 50 patients with HFrEF (35 NYHA II and 15 NYHA III) patients. Participants were monitored for step count with a Fitbit Flex for a period of 2 weeks in a free-living environment.ResultsComparing group medians, patients exhibiting NYHA class III symptoms had significantly lower recorded 2-week mean daily total step count (3541 vs 5729 [steps], P=.04), lower 2-week maximum daily total step count (10,792 vs 5904 [steps], P=.03), lower 2-week recorded mean daily mean step count (4.0 vs 2.5 [steps/minute], P=.04,), and lower 2-week mean and 2-week maximum daily per minute step count maximums (88.1 vs 96.1 and 111.0 vs 123.0 [steps/minute]; P=.02 and .004, respectively).ConclusionsPatients with NYHA II and III symptoms differed significantly by various aggregate measures of free-living step count including the (1) mean and (2) maximum daily total step count as well as by the (3) mean of daily mean step count and by the (4) mean and (5) maximum of the daily per minute step count maximum. These findings affirm that the degree of exercise intolerance of NYHA II and III patients as a group is quantifiable in a replicable manner. This is a novel and promising finding that suggests the existence of a possible, completely objective measure of assessing HF functional class, something which would be a great boon in the continuing quest to improve patient outcomes for this burdensome and costly disease.

The detrimental effect of COVID‐19 nationwide quarantine on accelerometer‐assessed physical activity of heart failure patients

“…Indeed, the mean daily step count of the patients before the onset of the quarantine was higher than the step count usually observed in other studies focusing on HF populations. 8,16 However, when we entered the daily step count, the time elapsed since enrolment into the trial, and whether the patient was in the intervention or follow-up phase of the trial as covariates into the model, neither of them had a significant effect on the percentage change, suggesting that our results can possibly be generalized to the HF populations outside a trial setting.…”

The Role of Wearables in Heart Failure

“…Activity monitors could therefore be used to provide a more objective measure of functional limitation and one that relates more closely to the individual's usual activity patterns. A study of 50 heart failure patients with activity monitors measured "freeliving" step counts over 2 weeks [26]. Mean step counts were significantly different between NYHA classes, although there was some overlap in activity levels between the more sedentary class II and more active class III participants.…”

Mildly symptomatic heart failure with reduced ejection fraction: diagnostic and therapeutic considerations

“…16 Consequently, there is an urgent need for objective methods to assess functional capacity, such as wearable activity trackers that count patients' daily steps under free-living conditions. 20 A more precise definition of NYHA class is also warranted. Another challenge is that physicians are sometimes influenced by the general clinical status of their patients and the severity of the underlying disease, and thus they use NYHA classification system as an 'HF severity score' and not as a measure of symptom severity.…”