Heart rate fragmentation (HRF) is a new method for assessing cardiac neuroautonomic integrity based on the analysis of short-term (high-frequency) heart rate dynamics.

The materials in this publication include:

1. Source code in AWK for the computation of three HRF metrics: PIP, PNNLS, and PNNSS, as described in Costa et al. Front Physiol, 2017;8:255. doi: 10.3389/fphys.2017.00255. The program can be run in different operating systems: Windows (using Cygwin), Mac and Linux.

2. Three time series test files: (A) timeseries_1PVC.txt; (B) timeseries_1PVC_1outlier.txt; and (C) timeseries_1PVC_2outliers.txt. The results for each of these test files are: 
(A) PIP = 0.623; PNNSS = 0.558; PNNLS = 0.373
(B) PIP = 0.620; PNNSS = 0.525; PNNLS = 0.404
(C) PIP = 0.652; PNNSS = 0.583; PNNLS = 0.349

3. Three figures accompanying the sections on “Background” (Fig. 1 and 2) and “Technical Implementation” (Fig. 3).

NN intervals < 0.3 s or > 1.5 s were excluded. Users can change these thresholds by modifying the values of the variables NN_min and NN_max. Additionally, the default ECG sampling frequency is 250 Hz, which can be modified by updating the value of the variable SF.