Value of Frontal QRS Axis for Risk Stratification of Individuals with
Prolonged PR Interval
Abstract
Introduction There is ongoing controversy regarding the
prognostic value of PR prolongation among individuals free of
cardiovascular diseases. It is necessary to risk-stratify this
population according to other electrocardiographic parameters.
Methods and Results This study based on the Third National
Health and Nutrition Examination Survey. A total of 6188 participants
(58.1±13.1 years; 55% women) were included. The median frontal QRS axis
of the entire study population was 37° (IQR: 11–60°). PR prolongation
was present in 7.6% of the participants, of whom 61.2% had QRS axis
≤37°. In a multivariable-adjusted model, mortality risk was highest in
the group with concomitant prolonged PR interval and QRS axis ≤37° (HR:
1.20, 95% CI: 1.04-1.39). In models with similar adjustment where
population were reclassified depending on PR prolongation and QRS axis,
prolonged PR interval and QRS axis ≤37° was still associated with
increased risk of mortality (HR: 1.18, 95% CI: 1.03-1.36) compared with
normal PR interval. Conclusion QRS axis is an important factor
for risk stratification in population with PR prolongation. The extent
to which this population with PR prolongation and QRS axis ≤37° is at
higher risk of death compared with the population without PR
prolongation.