Heart rate variability follow-up during COVID-19 -a case report-

Fig. 1.. Patient clinical course. HRV was recorded from day 8 to 12 when symptoms worsened and the last record was on day 19, when the patient had almost recovered. CRP: C-reactive protein.

Fig. 2.. Q-Q Plot (quantile-quantile: standard distribution quantiles vs. sample quantiles plot). Q-Q Plot: quantile-quantile plot. Day 19 sample is skewed to the left (might be caused by an artifact in the first seconds of the sample [Fig. 3., day 19 sample]).

Fig. 3.. RR intervals over time with 2 minutes samples, each of which corresponds to a different day. RR: interbeat intervals between all successive heartbeats, IBI, interbeat intervals between all successive heartbeats. There might be an artifact in the first 10 s on Day 19 sample.

Fig. 4.. Exploratory analysis PNS (orange) vs. SNS (blue). PNS: parasympathetic nervous system, SNS: sympathetic nervous system, LF: low-frequency band (0.04–0.15 Hz), HF: high-frequency band (0.15–0.40 Hz). Day 8 to 12 SNS (blue outer circle) predominates over PNS (orange inner circle) when the patient was in stage II of Covid-19 (Fig. 1). Day 19 shows otherwise, a higher parasympathetic activity, although it might also be due to sympathetic depletion [4].

Fig. 5.. Time-domain results using Kubios© software (2 min measurements). RR: interbeat intervals between all successive heartbeats, SD: standard deviations, HR: heart rate, RMSSD: root square of successive interval differences, PNS: parasympathetic branch of the nervous system, SNS: sympathetic branch of the nervous system, SD1: standard deviation (hence SD) of the distance of each point from the y = x axis, perpendicular to the line of identity, SD2: standard deviation of each point from the y = x + average RR interval, along the line of identity, Kubios software was developed by Kubios Oy, founded in 2016 in Kuopio, Finland as a spin-off company from University of Eastern Finland.

Fig. 6.. Kubios©: Nonlinear Results. SD1, standard deviation (hence SD) of the distance of each point from the y = x axis, perpendicular to the line of identity; SD2: standard deviation of each point from the y = x + average RR interval, along the line of identity; Kubios software was developed by Kubios Oy, founded in 2016 in Kuopio, Finland as a spin-off company from University of Eastern Finland.