What is the level of evidence for combined cardiac resynchronization and defibrillation therapy in heart failure?
Chi Lin Medical Centre
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Hong Kong
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Email: simon.lam{at}medsci.oxon.org
Department of Cardiology
Kent and Canterbury Hospital
Ethelbert Road
Canterbury
Kent CT1 3NG
UK
The recently published ESC Guidelines for cardiac pacing and cardiac resynchronization therapy1 (CRT-P) are comprehensive and very welcome. We would like to comment on the strength of evidence given for combined cardiac resynchronization and defibrillation therapy (CRT-D).
Section 3.2.1 of the guideline gives a class I, level of evidence B for the implantation of a CRT-D device in patients with NYHA classes III–IV heart failure who have an LVEF of <35% and a wide QRS complex (>120 ms). The efficacy of CRT-D relative to optimal medical therapy is supported by direct evidence of survival benefit from a randomized control trial (COMPANION) as well as a network meta-analysis specifically examining the evidence base for CRT-D.2 There is therefore sufficient current evidence to support a class I, level of evidence A recommendation for CRT-D when compared with optimal medical therapy.
Section 3.2.3 also gives a class I, level of evidence B recommendation for CRT-D for patients who fulfil the criteria for CRT-P and who also have a class I indication for an implantable cardioverter defibrillator (ICD) (first implant, upgrading, or device change). This recommendation is only based on randomized control trial evidence (MIRACLE-ICD; CONTAK-CD) that demonstrated functional (but not survival) incremental benefits of CRT-D when compared with ICD alone. We know that CRT-P alone improves function, as well as reducing sudden deaths and overall survival (CARE-HF). The important clinical question, therefore, is whether CRT-D offers any survival benefit over CRT-P in this group of patients (given the additional cost of the combined device and potential for inappropriate shocks). Evidence from individual trials comparing CRT-D with either device alone, and from a network meta-analysis incorporating the major CRT-P, CRT-D, and ICD trials,2 however has not demonstrated any survival benefit of CRT-D when compared with either device alone. There is therefore no current evidence to suggest that a combined device is better than CRT-P to improve mortality and morbidity among heart failure patients suitable for both CRT-P and ICD. We would therefore suggest that the current evidence base only supports a class IIa, level of evidence C recommendation for CRT-D when compared with CRT-P.
These points concerning the level of evidence given to a particular recommendation are of great importance to practising clinicians when considering the appropriate device or treatment generally for an individual patient.
References
- Vardas PE, Auricchio A, Blanc JJ, Daubert JC, Drexler H, Ector H, Gasparini M, Linde C, Morgado FB, Oto A, Sutton R, Trusz-Gluza M. Guidelines for cardiac pacing and cardiac resynchronization therapy: the task force for cardiac pacing and cardiac resynchronization therapy of the European Society of Cardiology. Developed in collaboration with the European Heart Rhythm Association. Eur Heart J (2007) 28:2256–2295.
[Free Full Text] - Lam SKH, Owen A. Combined resynchronization and defibrillation therapy in left ventricular dysfunction: Bayesian network meta-analysis of randomized controlled trials. BMJ (2007) 335:925–928.
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