PR Interval and the Risks of Recurrent Syncope and All-Cause Mortality in Patients Presenting With Syncope

BACKGROUND: Risk assessment of patients with syncope does not consider a short PR interval despite its association with increased risk of atrial fibrillation and all-cause mortality. This study aimed to explore the association between the PR interval and all-cause mortality and recurrent syncope in patients admitted to the hospital with syncope.

METHODS: We included patients with a diagnosis of syncope and an ECG recorded within 24 hours of hospital admission from the Danish Nationwide Electrocardiogram Cohort and divided patients into short (<120 ms), normal (120-200 ms), or long PR interval (>200 ms). Patients with ECG abnormalities or comorbidities influencing the PR interval or outcomes were excluded.

RESULTS: A total of 52 038 patients were included. Adjusting for age, sex, and relevant covariates the highest hazard ratio (HR) was observed in patients with short PR interval with an HR of 1.50 (95% CI, 1.24-1.80, P<0.001). A long PR interval did not show an association with all-cause mortality (HR, 1.02 [95% CI, 0.97-1.08], P=0.3566). Adjusted 5-year cumulative incidence of all-cause mortality was 18% for short PR interval, 14% for normal PR interval, and 13% for long PR interval. Regarding recurrent syncope, a HR of 1.14 (95% CI, 1.09-1.20. P<0.001) was seen for long PR interval. Adjusted 5-year cumulative incidence of recurrent syncope was 23% in patients with a long PR interval.

CONCLUSION: In patients with syncope, a short PR interval was associated with higher risk of all-cause mortality; however, a long PR interval was associated with increased rate of recurrent syncope.