Electrocardiographic PR Interval Duration and Cardiovascular Risk: Results From the Copenhagen ECG Study.

Background: Because of ambiguous reports in the literature, we aimed to investigate the association between PR interval and the risk of all-cause and cardiovascular death, heart failure, and pacemaker implantation, allowing for a nonlinear relationship.

Methods: We included 293,111 individuals, corresponding to one-third of the population in the greater region of Copenhagen. These individuals had a digital electrocardiogram recorded in a general practitioner's core facility from 2001-2011. Data on drug use, comorbidities, and outcomes were collected from Danish registries. We divided the population into 7 groups based on the population PR interval distribution. Cox models were used, with reference to a PR interval between 152 and 161 ms (40th to < 60th percentile).

Results: During follow-up, we identified 34,783 deaths from all causes, 9867 cardiovascular deaths, 9526 cases of incident heart failure, and 1805 pacemaker implantations. A short PR interval (< 125 ms; hazard ratio [HR], 1.23; 95% confidence interval [CI], 1.08-1.41; P = 0.001) as well as a long PR interval (> 200 ms; HR, 1.23; 95% CI, 1.14-1.32; P < 0.001) was associated with an increased risk of cardiovascular death after multivariable adjustment. A long PR interval conferred an increased risk of heart failure (> 200 ms; HR, 1.31; 95% CI, 1.22-1.42; P < 0.001). An increasing PR interval conferred an increased risk of pacemaker implantation, in a dose-response manner, with the highest risk associated with a PR interval > 200 ms (HR, 3.49; 95% CI, 2.96-4.11; P < 0.001).

Conclusions: PR interval was significantly associated with the risk of the adverse outcomes investigated. The nonlinear relationships, in combination with relatively weak associations, could contribute to previously reported conflicting results on the subject.