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Evolving indications of cardiac resynchronisation therapy

Heart Failure (HF)


CRT offers both substantial mortality and morbidity benefit for patients with Heart Failure. The pleiotropic effects of CRT are interventricular synchrony, atrioventricular synchrony and intraventricular synchrony.
Studies such as MUSTIK, CONTRAK, COMPANION, CARE-HF, MIRACLE etc showed beneficial effects in patients with HF after CRT implantation. The recent ESC guidelines (ESC 2013) reported a clear beneficial effect in patients with HF and with ejection fraction <35%, left bundle branch block (LBBB), QRS>150ms (class IA).

Frank Ruschitzka addressed the topic of narrow QRS complex (QRS <120 ms). Previous studies in patients with narrow QRS complex have shown controversial results. Hawkins et al (EHJ 2006) showed a symptomatic benefit. Also, the PROSPECT trial showed symptomatic benefit and left ventricular remodeling with an improvement on the 6 minute walk test.

The RETHINQ pilot study showed controversial results but with a smaller study population. From all these studies it is evident that bigger trials are necessary to elucidate CRT in patients with EF<35% and QRS<120ms. The use of imaging techniques such as echocardiography may be useful in this group of patients identifying specific parameters such as speckle-tracking and strain rate. 

Professor Rouleau examined the role of CRT in patients with class I symptoms according to the NYHA classification. He reported that the most important factors favoring CRT in such patients are the following: QRS>150ms, LBBB, few comorbidities, left atrial dilation, mitral regurgitation (favorable profile), and very low LVEF (great benefit), ischemic cardiomyopathy and de novo implantation.
Unfavorable factors in these class I patients are QRS<150ms, right bundle branch block (RBBB), little LA dilation and atrial fibrillation. In non-ischemic class I HF, we can use the above parameters. 

Dr Curtis presented the results of the BLOCK HF trial in patients with NYHA I, II, III and pacing indications. The patients were randomized in 2 groups. The first group received biventricular pacing and in the second group, only ventricular pacing was implanted. The findings of this study indicate that biventricular pacing leads to a 26% reduction in cardiac endpoints and symptoms.

In conclusion, CRT is clearly beneficial in symptomatic patients with QRS>150ms, LBBB, and EF<35%. However, in the other categories such as narrow QRS complex or patients with class I symptoms or with pacing and EF<50% or with AF, the results are controversial.

Therefore, further larger studies are indicated to elucidate the impact of CRT in these patients, and imaging parameters may be used to identify special subgroups of patients who may respond to CRT therapy. 

References


Session Title: Evolving indications of cardiac resynchronisation therapy

The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology.