Assessing a Warping Methodology for the Identification of Increased Cardiovascular Risk Based on the HR Profile Morphology

Heart rate (HR) response to exercise and recovery are strong predictors of cardiovascular mortality, but the HR profile morphology may add useful information for the identification of subjects at risk. Our aim was to characterise the HR profile morphology and assess its cardiovascular risk predictive value. 1-lead ECG recordings of 17,691 participants from the general population in an exercise stress test from the UK Biobank study were analyzed. A methodology based on time warping of the HR profile was applied to compute the average HR profile morphology along the exercise test. Then, two series of warping-based morphological differences in amplitude, d
_a
, and time, d
_w
, were calculated by comparing each individual HR profile morphology with respect to this average HR profile. Subjects who suffered one or more cardiovascular events showed significantly lower values of d
_a
than survivors (median of -10.5% vs -7.5%, p=0.009). Also, d
_a
was significantly associated with cardiovascular mortality in a Cox model after adjusting for clinical variables, resting HR, difference between peak and resting HR, or between peak and recovery HR after a follow-up period of five years (p<;0.0001). Individuals at risk show HR dynamics with slower adaptation to exercise than healthier subjects, possibly due to autonomic nervous system dysfunction.