  Objective: Heart rate variability (HRV) has been proven to be an important
indicator of physiological status for numerous applications. Despite the
progress and active developments made in HRV metric research over the last few
decades, the representation of the heartbeat sequence upon which HRV is based
has received relatively little attention. The recently introduced heart rate
n-variability (HRnV) offers an alternative to R-to-R peak interval
representations which complements conventional HRV analysis by considering HRV
behavior on varying scales. Although HRnV has been shown to improve triage in
pilot studies, there is currently no open and standard software to support
future research of HRnV and its broader clinical applications. We aimed to
develop an open, reliable, and easy to use software package implementing HRnV
for further research and improvements of HRnV. This package has been designed
to facilitate collaborative investigations between clinicians and researchers
to study HRnV in various contexts and applications. Approach: We developed an
open-source software, HRnV-Calc, based on the PhysioNet Cardiovascular Signal
Toolbox (PCST), which features comprehensive graphical user interfaces (GUIs)
for HRnV and HRV analysis. Main results: While preserving the core
functionalities and performance of PCST, HRnV-Calc enables step-by-step manual
inspection and configuration of HRV and HRnV analysis, so that results can be
debugged, easily interpreted, and integrated to downstream applications.
Significance: The open-source HRnV-Calc software, an accessible and
standardized HRV and HRnV analysis platform, enhances the scope of HRV
assessment and is designed to assist in future improvements and applications of
HRnV and related research.
