Effect of QRS morphology on clinical event reduction with cardiac resynchronization therapy: Meta-analysis of randomized controlled trials

Abstract

Background Cardiac resynchronization therapy (CRT) is effective in reducing clinical events in systolic heart failure patients with a wide QRS. Previous retrospective studies suggest only patients with QRS prolongation due to a left bundle-branch block (LBBB) benefit from CRT. Our objective was to examine this by performing a meta-analysis of all randomized controlled trials of CRT. Methods Systematic searches of MEDLINE and the Food and Drug Administration official website were conducted for randomized controlled CRT trials. Trials reporting adverse clinical events (eg, all-cause mortality, heart failure hospitalizations) according to QRS morphology were included in the meta-analysis. Results Four randomized trials totaling 5,356 patients met the inclusion criteria. In patients with LBBB at baseline, there was a highly significant reduction in composite adverse clinical events with CRT (RR = 0.64 [95% CI (0.52–0.77)], P = .00001). However no such benefit was observed for patients with non-LBBB conduction abnormalities (RR = 0.97 [95% CI (0.82–1.15)], P = .75). When examined separately, there was no benefit in patients with right-bundle branch block (RR = 0.91 [95% CI (0.69–1.20)], P = .49) or non-specific intraventricular conduction delay (RR = 1.19 [95% CI (0.87–1.63)], P = .28). There was no heterogeneity among the clinical trials with regards to the lack of benefit in non-LBBB patients (I2 = 0%). When directly compared, the difference in effect of CRT between LBBB versus non-LBBB patients was highly statistically significant (P = .0001 by heterogeneity analysis). Conclusions While CRT was very effective in reducing clinical events in patients with LBBB, it did not reduce such events in patients with wide QRS due to other conduction abnormalities.

QRS duration versus morphology and survival after cardiac resynchronization therapy

“…In addition, the sub‐study of the Multicenter Automatic Defibrillator Implantation Trial‐Cardiac Resynchronization Therapy (MADIT‐CRT) trial, including 1817 patients with sinus rhythm at baseline ECG, showed that the presence of LBBB morphology was associated with a 53% reduction in the risk of heart failure events or all‐cause mortality of patients randomized to CRT with defibrillator compared with patients treated with implantable cardioverter defibrillator (ICD) alone whereas patients with non‐LBBB QRS morphology did not show clinical benefit from CRT 7. Subsequent meta‐analysis pooling data from 5356 patients enrolled in four randomized trials showed that LBBB morphology was associated with significant reduction in the composite adverse clinical events of patients treated with CRT (risk ratio 0.64, 95% CI 0.52–0.77; P  < 0.0001) whereas patients with non‐LBBB configuration failed to show clinical benefit 9. Recently, the analysis of data from 31 892 heart failure patients treated with CRT (76% with LBBB QRS morphology) included in the National Cardiovascular Data Registry and the ICD registry showed that after a median follow‐up of 3 years, patients with LBBB morphology had 24% lower mortality risk than patients with non‐LBBB morphology (HR 0.76, 95% CI 0.72–0.80; P  < 0.001) 22.…”

“…However, the individual prognostic benefit is not consistent, and selection of patients who will benefit from CRT remains challenging. Sub‐analyses from randomized controlled trials and meta‐analyses pointed out that QRS duration and morphology are relevant for prognosis of patients treated with CRT 5, 6, 7, 8, 9. Patients with shorter QRS duration and/or non‐left bundle branch block (LBBB) morphology appear to benefit less than patients with longer QRS duration and/or LBBB morphology 5, 6, 7, 8, 9.…”

“…Sub‐analyses from randomized controlled trials and meta‐analyses pointed out that QRS duration and morphology are relevant for prognosis of patients treated with CRT 5, 6, 7, 8, 9. Patients with shorter QRS duration and/or non‐left bundle branch block (LBBB) morphology appear to benefit less than patients with longer QRS duration and/or LBBB morphology 5, 6, 7, 8, 9. However, the patients included in randomized trials with non‐LBBB configuration represent a minority (5–30%), and approximately one third has a QRS duration between 120–150 ms 1, 2, 3, 4.…”

The Prognostic Impact of New‐Onset Persistent Left Bundle Branch Block Following Transcatheter Aortic Valve Implantation: A Meta‐analysis

“…27 Cardiac resynchronization therapy (CRT) has shown to be effective in reducing adverse events in LBBB patients. 28 The benefit of CRT in NOP-LBBB after TAVI is widely unknown. Meguro et al reported an effective CRT therapy for a patient with worse cardiac function with NOP-LBBB after TAVI.…”

Six Sigma DMAIC for Shaking Stagnant Construction Cultures – A Conceptual Perspective

“…However, sub-group analyses based on QRS morphology [30,31,56] and a metaanalysis [57] suggested that patients with complete LBBB showed a greater benefit on the composite of morbidity/mortality from CRT, compared with patients with non-specific intraventricular conduction delay or right bundle branch block. Based on this evidence, current class I recommendations were restricted to patients with complete LBBB.…”