The heart rate-PR interval relationship: a model for evaluating drug actions on SA and AV nodal function

The relationship between heart rate (HR) and PR interval (PR) has been investigated to determine inter-subject variability, within-subject variability and potential reference standards. Eight healthy male volunteers underwent upright graded submaximal treadmill exercise during eight separate study sessions. All subjects exhibited statistically significant negative linear relationships between PR and HR. Although there was considerable inter-subject variability, there was little within-subject variability in the interpolated PR at HR between 80 and 120 beats min-1. The HR-PR regression model has greatest validity within this HR range and for individual subjects rather than pooled or group data.