Prognosis of CRT-treated and CRT-untreated unselected population with LBBB in Stockholm County

Abstract

Aims: Left bundle branch block (LBBB) might be the first finding of cardiovascular diseases but also the prerequisite for cardiac resynchronization therapy (CRT) in heart failure (HF) with reduced ejection fraction (HFrEF). The prognosis for patients with LBBB and the implications of CRT in an unselected real-world setting are the focus of our study.

Methods and results: A central electrocardiogram (ECG) database and national registers have been screened to identify patients with LBBB. Predictors of HF and the use of CRT were identified with Cox models. The hazard ratios (HRs) of death, cardiovascular death (CVD), and HF hospitalization (HFH) were estimated according to CRT use. Of 5359 patients with LBBB and QRS > 150 ms, median age 76 years, 36% were female. At the time of index ECG, 41% had a previous history of HF and 27% developed HF. Among 1053 patients with a class I indication for CRT, only 60% received CRT with a median delay of 137 days, and it was associated with a lower risk of death [HR: 0.45, 95% confidence interval (CI): 0.36-0.57], CVD (HR: 0.47, 95% CI: 0.35-0.63), and HFH (HR: 0.56, 95% CI: 0.48-0.66). The age of over 75 years and the diagnosis of dementia and chronic obstructive pulmonary disease were predictors of CRT non-use, while having a pacing/defibrillator device independently predicted CRT use.

Conclusion: In an unselected LBBB population, CRT is underused but of great value for HF patients. Therefore, it is crucial to find ways of better implementing and understanding CRT utilization and characteristics that influence the management of our patients.

Keywords: CRT; Heart failure; LBBB.

Graphical abstract

Figure 1

Flowchart of cohort selection from adults in the MUSE ECG database from 2000 to 2018. CRT, cardiac resynchronization therapy; ECG, electrocardiogram; EF, ejection fraction; HF, heart failure; LBBB, left bundle branch block; n, number.

Figure 2

Timeline of index ECG, first HF diagnosis, LVEF below 35%, indication for CRT, and CRT in patients with HF before or after index ECG. Index ECG = first ECG with QRS ≥ 150 ms and LBBB morphology, without paced QRS. CRT indication = if ECG with QRS ≥ 150 ms and LBBB morphology, without paced QRS, HF duration ≥ 90 days, LVEF ≤ 35%, without previous history of permanent AF and follow-up ≥ 12 months. AF, atrial fibrillation; CRT, cardiac resynchronization therapy; ECG, electrocardiogram; HF, heart failure; LBBB, left bundle branch block; LVEF, left ventricular ejection fraction; n, number.

Figure 3

Predictors of developing HF after LBBB with QRS ≥ 150 ms. CKD, chronic kidney disease; COPD, chronic obstructive pulmonary disease; CRT, cardiac resynchronization therapy; HF, heart failure; ICD, implantable cardioverter defibrillator; LBBB, left bundle branch block; PM, pacemaker; TIA, transient ischaemic attack.

Figure 4

Predictors of CRT use at the time of CRT indication. AF, atrial fibrillation; CKD, chronic kidney disease; COPD, chronic obstructive pulmonary disease; CRT, cardiac resynchronization therapy; ICD, implantable cardioverter defibrillator; PM, pacemaker; TIA, transient ischaemic attack. *Paroxysmal or undefined AF.

Figure 5

Survival function for all-cause of death (A), CVD (B), and first HFH (C) between patients with or without CRT despite the indication. With CRT (grey), without CRT (green). CI, confidence interval; CRT, cardiac resynchronization therapy; CVD, cardiovascular death; HFH, heart failure hospitalization.