Coherence between heart rate and dominant frequency of the time-frequency heart rate variability spectrum as ischemic marker in the exercise test

Observation on heart rate (HR) and heart rate variability (HRV) trends in exercise ECGs lead us to hypothesize that some correlation exists between the evolution of HR and the dominant HRV frequency, which may differ in ischemic and healthy subjects. The ECGs recordings from stress test trials were collected and clustered into four groups: ischemic (positive coronary angiography), non-ischemic, volunteers and healthy (non-ischemic patients with 10 year predicted risk of CAD < 5%, according to the Framingham index). A new index based on the coherence between HR and dominant frequency of the time-frequency HRV was proposed in this work to add diagnostic information to exercise testing, obtaining statistically significant differences (p<10^-5) between ischemic and rest of the groups.