Background: First-degree atrioventricular (AV) block [PR interval exceeding 200 milliseconds (ms)] on a 12-lead electrocardiogram is a common finding. Previous studies suggested that first-degree AVB has a benign prognosis, but more recent reports suggest that first-degree AVB may be associated with adverse outcomes. We investigated the relationship between PR interval and long term morality in U.S. Veterans with atherothrombotic risk factors.
Methods: We retrospectively collected and analyzed data from a Veterans Affairs (VA) medical center for consecutive patients (October 2001 to January 2005) who presented for coronary angiography.
Results: Of 1193 charts, 1082 had a PR interval reading recorded (mean = 172.5±30.5 ms; median = 168 ms [range 59-334]). Mean follow-up period was 103±52 months. Mean age was 63.2±10.8 years with 98% male. Mean body mass index was 30.0±5.9. The prevalence of selected comorbidities was: hypertension (88%), hyperlipidemia (79%), obstructive coronary artery disease (73%), diabetes mellitus (45%), smoker (39%), history of peripheral vascular disease (17%), and history of cerebrovascular accident (8%). Mean left ventricular ejection fraction was 47%±13%. Eighty-two percent were on beta-blockers (BB), and 25% were on calcium channel blockers (CCB) while intraventricular conduction delay was seen in 6%. In a comparison of patients with PR interval ≤200 ms (n=936) vs. >200 ms (n=146), long term mortality was higher with PR interval >200 ms (58.2% vs. 44.4%, p=0.002). Mortality rate was also higher with patients on BB or CCB vs. not on either (49.8% vs 39.7%, p=0.024). While PR interval was a significant univariate predictor of mortality, it was not significant when adjusted for the covariates listed above [not including BB and CCB] (odds ratio = 1.08 [95% Cl = 0.70 to 1.66], p = 0.73).
Conclusion: In this study of US Veterans with atherothrombotic risk factors, the long term mortality rate was higher with first-degree AV block. PR interval has prognostic value within this specific cohort.