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.
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.
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 (I(2) = 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).
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.
"A meta-analysis was performed to evaluate the effect of CRT on clinical events with regards to different types of baseline conduction abnormalities using data from randomized controlled trials. Four randomized trials totaling 5,356 patients met the inclusion criteria and they concluded that 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.15 In the Comparison of Medical Therapy, Pacing, and Defibrillation in Heart Failure (COMPANION) trial, patients without LBBB did not have a statistically significant benefit, and those with QRS duration ≤147 ms had absolutely no benefit.16 "
[Show abstract][Hide abstract] ABSTRACT: The QRS represents the simultaneous activation of the right and left ventricles, although most of the QRS waveform is derived from the larger left ventricular musculature. Although normal QRS duration is <100 millisecond (ms), its duration and shape are quite variable from patient to patient in idiopathic dilated cardiomyopathy (IDCM). Prolongation of QRS occurs in 14% to 47% of heart failure (HF) patients. Left bundle branch block (LBBB) is far more common than right bundle branch block (RBBB). Dyssynchronous left ventricular activation due to LBBB and other intraventricular conduction blocks provides the rationale for the use of cardiac resynchronization therapy with biventricular pacing in patients with IDCM. Fragmented QRS (fQRS) is a marker of depolarization abnormality and present in significant number of the patients with IDCM and narrow QRS complexes. It is associated with arrhythmic events and intraventricular dyssynchrony. The purpose of this manuscript is to present an overview on some clinical, echocardiographic and prognostic implications of various QRS morphologies in patients with IDCM.
"Patients with a prolonged QRS duration may have a left bundle-branch block (LBBB), right bundle-branch Block (RBBB), nonspecific intraventricular conduction delay (IVCD), or paced rhythm. The presence of typical LBBB morphology is a strong predictor of response compared with right bundle branch block (RBBB) morphology and non-specific intraventricular conduction delay (IVCD) that has a much lower probability of CRT response [39, 40]. "
[Show abstract][Hide abstract] ABSTRACT: Heart failure affects millions of patients all over the world, and its treatment is a major clinical challenge. Cardiac dyssynchrony is common among patients with advanced heart failure. Resynchronization therapy is a major advancement in heart failure management, but unfortunately not all patients respond to this therapy. Hence, many diagnostic tests have been used to predict the response and prognosis after cardiac resynchronization therapy. In this paper we summarize the usefulness of different diagnostic modalities with special emphasis on the role of surface electrocardiogram as a major predictor of response to cardiac resynchronization therapy.
The Scientific World Journal 03/2013; 2013:837086. DOI:10.1155/2013/837086 · 1.73 Impact Factor
"P = 0.003) than any of the echocardiographic parameters. Another metanalysis by Sipahi et al.  including four randomized trials totaling 5,356 patients with LBBB at baseline demonstrated that there was a highly significant reduction in composite adverse clinical events with CRT (RR = 0.64 [95% CI (0.52-0.77)], P = .00001). "
[Show abstract][Hide abstract] ABSTRACT: Based on the clinical trials so far, there is a major controversy regarding the benefit of CRT in patients with QRS≤150 milliseconds. Some studies have shown that a fair number of patients with QRS ≤150 milliseconds benefit from CRT and it is needless to say that careful attention should be paid to CRT non-responders considering the risk of complications and cost-benefit ratio. Lack of uniformity in QRS measurement in all these trials could have a major influence on variable study outcomes. This is of concern because when the QRS is close to 120 milliseconds in patients with NYHA class III/IV symptoms or QRS close to 150 milliseconds in NYHA class I/II patients, the decision to recommend CRT implantation or undertake further risk stratification investigations is critically dependent on the EKG interpretation. In this paper we intent to raise the important question for need of standardized electrocardiographic criteria (QRS measurement and LBBB) in patients enrolled in CRT trials considering the variability in study results, high rates of CRT non response in the eligible population and the associated health care cost burden.
Current Cardiology Reviews 10/2012; 9(1). DOI:10.2174/157340313805076269
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