QRS duration on electrocardiography and cardiovascular mortality (from the National Health and Nutrition Examination Survey-III).

The relation of bundle branch block (BBB) with adverse outcome is controversial. We hypothesized that increased QRS duration is an independent predictor of cardiovascular (CV) mortality in a cross-sectional US population. This is a retrospective cohort study on prospectively collected data to assess the relationship between QRS duration on routine ECG and CV mortality. Participants included 8,527 patients with ECG data available from the National Health and Nutrition Examination Survey data set, representing 74,062,796 individuals in the United States. Mean age was 60.5 ± 13.6 years. Most subjects were white (87%) and women (53%). During the follow-up period of 106,244.6 person-years, 1,433 CV deaths occurred. Multivariate analysis revealed that the highest quartile of QRS duration was associated with higher CV mortality than lowest quartile (hazard ratio [HR] 1.3, 95% confidence interval [CI] 1.01 to 1.7, p = 0.04) after adjustment for established risk factors. Both left BBB (HR 2.4, 95% CI 1.3 to 4.7, p = 0.009) and right BBB (HR 1.90, 95% CI 1.2 to 3.0, p = 0.008) were significantly associated with increased CV mortality. The addition of the QRS duration in 10-millisecond increments to the Framingham Risk Score model resulted in 4.4% overall net reclassification improvement (95% CI 0.02 to 0.04; p = 0.00006). In conclusion, increased QRS duration was found to be an independent predictor of CV mortality in this cross-sectional US population. A model including QRS duration in addition to traditional risk factors was associated with improved CV risk prediction.

Comparison of rate versus rhythm control in patients with atrial fibrillation and a pacemaker.

The effect of rate versus rhythm control in patients with atrial fibrillation who have undergone previous pacemaker (PM) implantation is unknown. We evaluated the mortality in patients with atrial fibrillation and a PM randomized to rate or rhythm control treatment strategies. The Atrial Fibrillation Follow-up Investigation of Rhythm Management data set was stratified by the presence (n = 250) or absence (n = 3,810) of a PM at randomization into the rate or rhythm control arm. Kaplan-Meier curves were used for univariate analysis, and proportional hazards were used for multivariate analysis. The subjects with a PM (n = 250) were older (73 vs 69 years, p <0.01) and had a greater prevalence of coronary artery disease (53% vs 37%, p <0.01) and congestive heart failure (33% vs 23%, p <0.01). All-cause mortality was significantly greater in the PM patients who were randomized to the rhythm control arm (n = 128) than in the patients enrolled in the rate control arm with or without a PM (n = 2,027, p <0.01) and those in the rhythm control arm without a PM (n = 1,905, p <0.01). Multivariate analysis revealed that predictors of all-cause mortality included PM patients randomized to the rhythm control arm (hazard ratio 2.59, 95% confidence interval 1.46 to 4.58, p <0.01) and the presence of congestive heart failure (hazard ratio 2.42, 95% confidence interval 1.40 to 4.16, p <0.01). In conclusion, all-cause mortality was greater among patients with atrial fibrillation with a PM, who were randomized to the rhythm control arm of the Atrial Fibrillation Follow-up Investigation of Rhythm Management study compared with all other patients enrolled in the Atrial Fibrillation Follow-up Investigation of Rhythm Management study. The rhythm control strategy in patients with a PM was an independent predictor of mortality.