Comparison of ECG HRV measures obtained from monitor and wearables
| Feature | Monitor ECG, n=836* | ECG wearable, n=863* | Q value† | Monitor PPG, n=775* | PPG wearable, n=923* | Q value† |
| HR | 100 (92–108) | 103 (94–111) | <0.001 | 105 (97–113) | 103 (95–111) | <0.001 |
| Time domain | ||||||
| pNN50 | 0.5 (0.0–2.0) | 0.6 (0.0–3.7) | 0.007 | 2 (0–7) | 1 (0–6) | 0.078 |
| SDNN | 30 (18–56) | 28 (17–47) | 0.014 | 32 (22–52) | 29 (19–48) | 0.005 |
| SDSD | 15 (8–51) | 16 (9–41) | 0.4 | 24 (13–45) | 21 (14–39) | 0.039 |
| rMSSD | 15 (8–51) | 16 (9–41) | 0.4 | 24 (13–45) | 21 (13–39) | 0.039 |
| IRRR | 25 (16–41) | 27 (20–39) | 0.4 | 32 (24–48) | 30 (20–41) | 0.011 |
| MADRR | 4.10 (4.10–8.20) | 3.91 (3.91–7.81) | <0.001 | 8.00 (8.00–8.00) | 8.00 (8.00–9.00) | <0.001 |
| TINN | 81 (61–109) | 84 (64–117) | 0.043 | 99 (77–131) | 90 (69–119) | <0.001 |
| HRVi | 5.16 (3.89–6.96) | 5.38 (4.10–7.50) | 0.043 | 6.32 (4.90–8.39) | 5.73 (4.40–7.60) | <0.001 |
| Frequency domain | ||||||
| VLF | 0.53 (0.28–0.75) | 0.55 (0.36–0.75) | 0.072 | 0.46 (0.31–0.65) | 0.47 (0.30–0.66) | >0.9 |
| LF | 0.22 (0.13–0.29) | 0.19 (0.10–0.30) | 0.009 | 0.24 (0.17–0.32) | 0.24 (0.16–0.33) | >0.9 |
| HF | 0.15 (0.05–0.47) | 0.15 (0.05–0.36) | 0.5 | 0.24 (0.11–0.39) | 0.24 (0.10–0.39) | >0.9 |
| LFnu | 0.59 (0.31–0.78) | 0.57 (0.30–0.78) | 0.3 | 0.49 (0.37–0.67) | 0.49 (0.37–0.67) | >0.9 |
| HFnu | 0.41 (0.22–0.69) | 0.43 (0.22–0.70) | 0.3 | 0.51 (0.33–0.63) | 0.51 (0.33–0.63) | >0.9 |
| LF:HF | 1.4 (0.4–3.4) | 1.3 (0.4–3.6) | 0.3 | 0.97 (0.58–2.06) | 0.97 (0.58–2.08) | >0.9 |
*Statistics presented: median (IQR).
†Statistical tests performed: Wilcoxon rank-sum test, adjusted for multiple testing.
HF, high frequency; HFnu, high frequency normalised units; HR, heart rate; HRV, heart rate variability; HRVi, integral of the density of the RR interval histogram divided by height; IRRR, IQR of RR intervals; LF, low frequency; LF:HF, low to high frequency ratio; LFnu, low frequency normalised units; MADRR, median of the absolute differences between RR intervals; pNN50, percentage of successive RR intervals that differ by more than 50 ms; PPG, photoplethysmography; rMSSD, route mean square of successive; RR, interval difference; SDNN, SD of NN intervals; SDSD, SD of successive RR intervals; TINN, baseline width of the RR interval histogram; VLF, very low frequency.