Heart failure monitoring using the wearable cardioverter defibrillator in patients with newly diagnosed heart failure
Authors: Hillmann HAK , Eiringhaus J , Hohmann S , Mueller-Leisse JL , Zormpas C , Veltmann C , Duncker D 
Published: May 2021

Abstract

Funding Acknowledgements
Type of funding sources: None.

Background
The wearable cardioverter-defibrillator (WCD) can be prescribed in patients with newly diagnosed heart failure. The WCD provides additional heart failure parameters, like heart rate, step count and body position, accessible via remote monitoring.
The purpose of this study was to evaluate clinical relevance of additionally recorded data in patients using the WCD.

Methods
Patients with newly diagnosed heart failure and WCD, an average wear time with at least 20 hours per day and available heart failure parameters were included. The heart failure parameters were provided in 5-minute data intervals. An approximate for the heart rate variability was calculated via the standard deviation of the cycle length of the given heart rate per 5-minute data interval (HRV5).

Results
276 patients (68% male) were included between 04/2013 and 12/2017. Mean age was 57.4 ± 15.3 years. 174 patients (63%) suffered from non-ischemic and 102 patients (37%) from ischemic cardiomyopathy. Mean NYHA functional class at prescription was 2.6 ± 0.8. Mean left ventricular ejection fraction (LVEF) was 25.3 ± 8.5%. Mean wear time of the WCD was 111.8 ± 74.5 days. Recorded median heart rate using the WCD was 70.8 (IQR 63.1 - 78.7) beats per minute on the first wear day and 64.5 (IQR 59.7 - 71.3) on the last wear day. Median step count amounted to 4294 (IQR 2283 - 7092) steps on the first wear day compared to 5688 (IQR 3153 - 8263) steps on the last wear day. Median HRV5 was 85.4 (IQR 60.1 - 109.8) ms on the first wear day and 110.4 (IQR 78.6 - 134.9) ms on the last wear day.
Between the first and last seven days of usage, median heart rate was significantly reduced (69.5 (IQR 62.0 - 76.8) to 65.9 (IQR 60.4 - 72.2) beats per minute; p &lt; 0.001), while median step counts per day (4657 (IQR 2778 – 6918) to 5562 (IQR 3890 – 8446) steps; p &lt; 0.001) and HRV5 (89.0 (IQR 64.8 - 110.7) to 111.0 (IQR 83.7 - 134.7) ms; p &lt; 0.001) were significantly elevated. A higher delta of heart rate correlated with a higher delta of HRV5A (p &lt; 0,001; rs = 0.488) between the first and last seven days of usage. A higher delta of step counts per day in the first and last seven days correlated with a higher HRV5 (p &lt; 0.001; rs = 0.320). Patients with a higher delta of step count per day (p = 0,005; rs = 0,189) and patients with a higher delta of HRV5 (p = &lt; 0.001; rs = 0.255) showed a higher delta of LVEF measured at prescription and three months follow-up.

Conclusion
The WCD provides heart failure monitoring using additional heart failure parameters. Patients with newly diagnosed heart failure show a significant difference in heart rate, step count per day and heart rate variability approximate between beginning and end of prescription time. Step count and heart rate variability correlate with LVEF reverse remodeling. Remote monitoring for parameters regarding heart failure might be helpful for close monitoring and further heart failure therapy optimization during WCD wearing.