BLOCK HF: how far does it extend indications for cardiac resynchronization therapy?
Giuseppe Boriani1, Matteo Ziacchi, Igor Diemberger
1aInstitute of Cardiology, Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, S. Orsola-Malpighi University Hospital, Bologna, Italy bCentre for Cardiovascular Sciences, Queen Elizabeth Hospital, University of Birmingham, Birmingham, UK.
Insights
The BLOCK HF trial found cardiac resynchronization therapy (CRT) offered a modest benefit for heart failure patients with atrioventricular block. Further research is needed to clarify CRT
Area of Science:
- Cardiology
- Electrophysiology
- Heart Failure Management
Background:
- The Biventricular versus Right Ventricular Pacing in Heart Failure Patients with Atrioventricular Block (BLOCK HF) trial investigated cardiac resynchronization therapy (CRT) in patients with atrioventricular block and systolic dysfunction.
- Previous CRT trials suggested significant benefits, but concerns regarding selection bias and trial validity were raised for the BLOCK HF study.
- The study focused on patients with conventional pacing indications, left ventricular dysfunction, and New York Heart Association (NYHA) class I-III.
Purpose of the Study:
- To determine if CRT is superior to conventional pacing in heart failure patients with atrioventricular block.
- To evaluate the treatment effect and clinical utility of CRT in this specific patient population.
- To assess the implications of the BLOCK HF trial findings for current clinical practice and recommendations.
Main Methods:
- The BLOCK HF trial was an 8-year study comparing biventricular pacing (CRT) with right ventricular pacing.
- Patient enrollment averaged two patients per center per year, raising concerns about potential selection bias.
- The study assessed outcomes including death or hospitalization due to heart failure.
Main Results:
- The BLOCK HF trial demonstrated a relatively low treatment effect for CRT compared to other CRT trials.
- The absolute risk reduction for death or heart failure hospitalization was 4.8%, with a number needed to treat (NNT) of 21.
- An estimated one-third of participants may have met current indications for CRT, suggesting potential under-enrollment of eligible patients.
Conclusions:
- The BLOCK HF trial suggests a modest benefit of CRT in heart failure patients with atrioventricular block.
- The study's findings raise uncertainties regarding the broad implementation of CRT and its cost-effectiveness due to unconsidered risks and costs.
- Further evaluation is needed to clarify the role of CRT in current clinical guidelines and practice for this patient group.
Abstract:
The Biventricular versus Right Ventricular Pacing in Heart Failure Patients with Atrioventricular Block (BLOCK HF) trial, published in April 2013 [Curtis AB, Worley SJ, Adamson PB, et al; Biventricular versus Right Ventricular Pacing in Heart Failure Patients with Atrioventricular Block (BLOCK HF) Trial Investigators. Biventricular pacing for atrioventricular block and systolic dysfunction. N Engl J Med 2013; 368:1585-1593], explored whether cardiac resynchronization therapy (CRT) was superior to conventional pacing in patients with conventional indications for pacing, left ventricular dysfunction and NYHA (New York Heart Association) class I-III. The trial took 8 years and a source of concern is selection bias, because participating centers had an average of two patients enrolled per center, per year. Both the internal and external validity of the trial merit some comments. BLOCK HF showed a relatively low treatment effect of CRT as compared with other CRT trials. As a matter of fact, the absolute risk reduction for death or hospitalization because of heart failure was 4.8%, in a relatively long follow-up, with a number needed to treat (NNT) of 21, much higher than the NNT of other CRT trials. We estimate that at least one third of patients in BLOCK HF could meet current indications for CRT. Moreover, the study did not consider the additional risks and costs of CRT versus conventional pacing, both having important implications for cost-effectiveness estimates. For these and other reasons, uncertainties arise as to how far BLOCK HF extends current recommendations for CRT and how much it should be implemented in daily clinical practice.
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