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Heart failure
Cardiac resynchronisation therapy in populations underrepresented in randomised controlled trials
  1. Ulas Höke,
  2. Victoria Delgado,
  3. Nina Ajmone Marsan,
  4. Jeroen J Bax
  1. Department of Cardiology, Leiden University Medical Centre, Leiden, The Netherlands
  1. Correspondence to Professor Jeroen J Bax, Department of Cardiology, Leiden University Medical Center, Albinusdreef 2, Leiden 2300 RC, The Netherlands; j.j.bax{at}

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Learning objectives

  • Cardiac resynchronization therapy (CRT) is an established treatment for heart failure patients. However, there remain subpopulations that were underrepresented in randomised controlled trials and for which the benefits of this therapy is less clear.

  • The present review article summarises the evidence on the effects of CRT in specific heart failure subpopulations such as patients with mild heart failure symptoms, non-left bundle branch block morphology of the QRS complex, diabetics or renal failure patients.

  • Based on current literature, dedicated randomised controlled trials in these subpopulations are needed to further determine which patients may benefit from CRT.

The benefits of cardiac resynchronisation therapy (CRT) on long term survival and left ventricular (LV) function of patients with heart failure symptoms have been demonstrated in several randomised controlled trials (RCTs).1–4 w1–w4 The data from those trials form the basis of current recommendations for CRT use.5 ,6 w5 w6 However, several subpopulations, such as elderly patients, diabetics, and patients with atrial fibrillation (AF), non-left bundle branch block QRS morphology or congenital heart disease, are underrepresented in randomised clinical trials, and the effects of CRT remain unclear. For example, the mean age of patients included in the majority of RCTs was <75 years, whereas in the European CRT survey 31% of patients were older than 75 years.7 Similarly, AF was an exclusion criterion in many RCTs, while 31% of patients included in the Medicare Implantable Cardioverter-Defibrillator Registry had AF.8 Table 1 summarises the frequency of specific subpopulations included in RCTs and recent registries.1–3 ,7 ,8 w1–w4 The present article provides an overview of the effects of CRT in subpopulations underrepresented in RCTs and underscores the unmet needs for evidence based treatment in these subpopulations.

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Table 1

Overview of the proportion of specific subgroups in real world registries and in the large randomised controlled …

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  • Contributors All authors have contributed to the manuscript, including elaborating the hypothesis, research of the literature, drafting and reviewing the manuscript, and giving final approval of the manuscript.

  • Competing interests In compliance with EBAC/EACCME guidelines, all authors participating in Education in Heart have disclosed potential conflicts of interest that might cause a bias in the article. The Department of Cardiology of Leiden University Medical Centre has received unrestricted research grants from Medtronic, Biotronik, and Boston Scientific. Victoria Delgado has received consulting fees from St Jude Medical and Medtronic.

  • Provenance and peer review Commissioned; externally peer reviewed.

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