Associations between left bundle branch block with different PR intervals, QRS durations, heart rates and the risk of heart failure: a register-based cohort study using ECG data from the primary care setting

Abstract

Aim: Left bundle branch block (LBBB) is associated with an increased risk of heart failure (HF). We assessed the impact of common ECG parameters on this association using large-scale data.

Methods and results: Using ECGs recorded in a large primary care population from 2001 to 2011, we identified HF-naive patients with a first-time LBBB ECG. We obtained information on sex, age, emigration, medication, diseases and death from Danish registries. We investigated the association between the PR interval, QRS duration, and heart rate and the risk of HF over a 2-year follow-up period using Cox regression analysis.Of 2471 included patients with LBBB, 464 (18.8%) developed HF during follow-up. A significant interaction was found between QRS duration and heart rate (p<0.01), and the analyses were stratified on these parameters. Using a QRS duration <150 ms and a heart rate <70 beats per minute (bpm) as the reference, all groups were statistically significantly associated with the development of HF. Patients with a QRS duration ≥150 ms and heart rate ≥70 bpm had the highest risk of developing HF (HR 3.17 (95% CI 2.41 to 4.18, p<0.001). There was no association between the PR interval and HF after adjustment.

Conclusion: Prolonged QRS duration and higher heart rate were associated with increased risk of HF among primary care patients with LBBB, while no association was observed with PR interval. Patients with LBBB with both a prolonged QRS duration (≥150 ms) and higher heart rate (≥70 bpm) have the highest risk of developing HF.

Keywords: 12 lead ECG; epidemiology; primary care.

Figure 1

Patient selection flow chart. Selection of the study population. bpm, beats per minute; CGPL, Copenhagen General Practitioners Laboratory; HF, heart failure; LBBB, left bundle branch block.

Figure 2

Cumulative incidence of heart failure by QRS duration and heart rate and by PR interval. Cumulative incidence of heart failure in patients with LBBB (A) with (1) QRS duration <150 ms and heart rate <70 bpm (black line), (2) QRS duration <150 ms and heart rate ≥70 bpm (blue line), (3) QRS duration ≥150 ms and heart rate <70 bpm (green line), and (4) QRS duration ≥150 ms and heart rate ≥70 bpm (red line); and (B) patients with PR interval <200 ms (blue line) and with PR interval ≥200 ms (red line). Solid lines represent heart failure. Dotted lines represent death from other causes. bpm, beats per minute; LBBB, left bundle branch block.

Figure 3

Risk of heart failure by QRS duration and heart rate. Multivariable Cox regressions showing HRs with 95% CI of associations between heart failure in patients with LBBB within four subgroups: (1) QRS duration <150 ms and heart rate <70 bpm, (2) QRS duration <150 ms and heart rate ≥70 bpm, (3) QRS duration ≥150 ms and heart rate <70 bpm, and (4) QRS duration ≥150 ms and heart rate ≥70 bpm. Adjusted for age groups, sex, hypertension, diabetes, previous acute myocardial infarction, chronic ischaemic heart disease, renal disease, beta-blockers and PR groups. bpm, beats per minute; LBBB, left bundle branch block.

Figure 4

Association between QRS duration and the risk of heart failure by heart rate. Restricted cubic splines with three knots at 10th, 50th and 90th percentiles showing the association between QRS duration (continuous) and the risk of heart failure represented by HR and stratified by (A) heart rate <70 bpm and (B) heart rate ≥70 bpm. Grey area indicates 95% CI. The reference values of 150 ms was used. The distribution of patients is represented by blue bars. Adjusted for age groups, sex, hypertension, diabetes, previous acute myocardial infarction, chronic ischaemic heart disease, renal disease, beta-blockers and PR groups. bpm, beats per minute.

Figure 5

Risk of heart failure by PR interval. Multivariable Cox showing HRs with 95% CI of associations between heart failure in patients with LBBB with PR interval <200 ms and ≥200 ms, respectively. Adjusted for age groups, sex, beta-blockers, cardiac glycosides, calcium channel blockers and heart rate groups. LBBB, left bundle branch block.