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Benefits of Cardiac Resynchronization Therapy in an Asynchronous Heart Failure Model Induced by Left Bundle Branch Ablation and Rapid Pacing
Published on: December 11, 2017
Effectiveness of implantable cardioverter defibrillators and cardiac resynchronization therapy in heart failure
James V Freeman1, Frederick A Masoudi
1Division of Cardiovascular Medicine, Stanford University School of Medicine, Stanford, CA 94305-5406, USA. jfreeman@stanford.edu
Insights
Implantable cardioverter-defibrillators (ICDs) and cardiac resynchronization therapy (CRT) benefit select heart failure (HF) patients. Further research is needed to optimize device selection and patient outcomes.
Area of Science:
- Cardiology
- Medical Devices
Background:
- Randomized trials and observational data confirm the benefits of implantable cardioverter-defibrillators (ICDs) for primary prevention of sudden cardiac death (SCD) in heart failure (HF) patients with left ventricular systolic dysfunction (LVSD) and for secondary prevention in those with prior ventricular arrhythmias or aborted SCD.
- Secondary analyses and observational data indicate ICD effectiveness in subpopulations like the elderly and NYHA class IV patients, but potential reduced efficacy in women and those with severe comorbidities (e.g., end-stage renal disease) warrant further investigation.
- Dual-chamber ICDs are frequently used despite limited evidence of incremental benefit over single-chamber devices.
Purpose of the Study:
- To review the current evidence on the efficacy and optimal use of ICDs and cardiac resynchronization therapy (CRT) in patients with heart failure.
- To identify patient subpopulations that benefit most from these devices and factors influencing procedural and long-term outcomes.
Main Methods:
- Review of randomized trials and observational data regarding ICD and CRT therapy in heart failure patients.
- Analysis of secondary and post hoc trial data, as well as real-world observational studies.
- Examination of factors influencing device effectiveness, including patient demographics, comorbidities, device type, and implantation characteristics.
Main Results:
- ICDs are effective for primary and secondary prevention of SCD in selected HF patients, with varying efficacy in specific groups.
- Cardiac resynchronization therapy (CRT) improves quality of life, reduces HF hospitalizations, and may offer a mortality benefit in symptomatic HF patients with LVSD and prolonged QRS.
- CRT may benefit mildly symptomatic patients, but cost-effectiveness is unclear. QRS morphology (LBBB vs. RBBB) may influence CRT response, though guidelines do not yet specify recommendations based on this.
- Procedural outcomes for ICD implantation are better with electrophysiologist operators and high-volume hospitals.
Conclusions:
- ICDs, CRT-pacemakers (CRT-P), and CRT-defibrillators (CRT-D) are crucial for select HF patients.
- Further research is essential to refine patient selection criteria for ICDs and CRT.
- Optimizing outcomes requires understanding which patient populations benefit most and identifying ideal device, physician, and hospital characteristics for implantation.
Abstract:
Randomized trials and observational data have consistently demonstrated the benefit of ICDs for primary prevention of SCD in patients with HF and LVSD or secondary prevention in patients with a history of prior ventricular arrhythmias or aborted SCD, most of whom have HF. Secondary and post hoc analyses of trial data, as well as observational data, generally suggest that ICD therapy is effective in most selected subpopulations, such as the elderly and patients with NYHA class IV HF symptoms, but some studies suggest that ICDs may not be as effective in women and those with severe comorbidities, such as ESRD. Although there is limited evidence for an incremental benefit achieved with dual-chamber compared with single-chamber ICDs, the former devices are placed almost twice as frequently in the United States. Finally, observational data have recently shown that ICD procedural outcomes are improved when the device is placed by an electrophysiologist and at a high-volume hospital. More recently, clinical trials have demonstrated that cardiac resynchronization therapy improves quality of life and lowers rates of HF hospitalization in patients with symptomatic HF, LVSD, and a prolonged QRS complex already receiving optimal medical management; recent trial results have also suggested a mortality benefit with CRT in this population. In addition, recent trial data suggest that CRT reduces nonfatal events among mildly symptomatic patients (NYHA class I-II); however, the cost-effectiveness of CRT in this population remains unclear. As with ICDs, secondary and post hoc analyses of trial data as well as observational data suggest that CRT remains effective in most selected subpopulations, including stable NYHA class IV patients, the very elderly, and women. Recent observational work has suggested that CRT may not benefit patients with an RBBB QRS morphology to the same extent as those with an LBBB pattern, although because more conclusive studies are currently lacking, the guidelines do not tailor the recommendations based on QRS morphology. In summary, ICDs, CRT-P, and CRT-D represent important and effective treatment modalities for select patients with HF. Additional investigation is required to better determine which patient populations most benefit from these cardiac devices and which device, implanting physician, and hospital characteristics optimize outcomes with these cardiac devices.
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