Value of Frontal QRS Axis for Risk Stratification of Individuals with Prolonged PR Interval

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.