Prognostic significance of prolonged PR interval in the general population

Aims Prolonged PR interval, or first degree AV block, has been traditionally regarded as a benign electrocardiographic finding in healthy individuals, until recent studies have suggested that it may be associated with increased mortality and morbidity. The aim of this study was to further elucidate clinical and prognostic importance of prolonged PR interval in a large middle-aged population with a long follow-up. Methods and results We evaluated 12-lead electrocardiograms of 10 785 individuals aged 3059 years (mean age 44 years, 52 males) recorded between 1966 and 1972, and followed the subjects for 30 +/- 11 years. Prolonged PR interval was defined as PR >= 200 ms, with further analysis performed using PR > 220 ms. Main endpoints were all-cause mortality, cardiovascular mortality, and sudden cardiac death, and other endpoints included hospitalizations due to cardiovascular causes. During the baseline examination, prolonged PR interval > 200 ms was present in 2.1% of the subjects, but PR interval normalized to <= 200 ms in 30% of these individuals during the follow-up. No increase in mortality or in hospitalizations due to coronary artery disease, heart failure, atrial fibrillation, or stroke was associated with prolonged PR interval (P = non-significant for all endpoints). These results were not changed after multivariate adjustment or in several subanalyses. Conclusion In the middle-aged general population, prolonged PR interval normalizes in a substantial proportion of subjects during the time course, and it is not associated with an increased risk of all-cause or cardiovascular mortality.