Cardiac resynchronization therapy update: evolving indications, expanding benefit?
C Butcher1, Y Mareev, V Markides
1Royal Brompton and Harefield NHS Foundation Trust, London, UK.
Insights
Cardiac resynchronization therapy (CRT) benefits heart failure patients, but its exact mechanisms remain unclear. New strategies aim to enhance CRT effectiveness and expand its use in heart failure management.
Area of Science:
- Cardiology
- Medical Devices
- Heart Failure Research
Background:
- Cardiac resynchronization therapy (CRT) is established for heart failure but its precise mechanisms of action are not fully understood.
- Current evidence suggests left ventricular dyssynchrony may not be the primary driver of CRT benefits.
- Alternative mechanisms like atrio-ventricular resynchronization and mitral regurgitation reduction are being explored.
Purpose of the Study:
- To explore the uncertain mechanisms underlying the effectiveness of cardiac resynchronization therapy (CRT).
- To identify reliable predictors of CRT benefit beyond QRS duration.
- To review emerging technologies and future directions for improving CRT.
Main Methods:
- Review of recent data and clinical observations regarding CRT efficacy.
- Analysis of potential mechanisms of benefit including electrical and mechanical factors.
- Evaluation of current and novel technological advancements in CRT.
Main Results:
- The benefits of CRT may stem from mechanisms other than solely left ventricular dyssynchrony correction.
- Atrio-ventricular resynchronization, mitral regurgitation reduction, and bradycardia prevention are potential contributors to CRT's effectiveness.
- A QRS duration exceeding 140 ms is the most consistent clinical predictor of CRT benefit.
- Numerous innovative approaches are under development to optimize CRT outcomes.
Conclusions:
- The multifaceted nature of CRT benefits suggests that no single metric can accurately predict patient response.
- Ongoing research and technological advancements are crucial for refining CRT and broadening its application in heart failure.
- Further evidence is required to determine CRT's efficacy in patients with atrial fibrillation and the added value of defibrillator functionality.
Abstract:
Cardiac resynchronisation therapy (CRT) is an effective intervention for appropriately selected patients with heart failure, but exactly how it works is uncertain. Recent data suggest that much, or perhaps most, of the benefits of CRT are not delivered by re-coordinating left ventricular dyssynchrony. Atrio-ventricular resynchronization, reduction in mitral regurgitation and prevention of bradycardia are other potential mechanisms of benefit that will vary from one patient to the next and over time. Because there is no single therapeutic target, it is unlikely that any single measure will accurately predict benefit. The only clinical characteristic that appears to be a useful predictor of the benefits of CRT is a QRS duration of >140 ms. Many new approaches are being developed to try to improve the effectiveness of and extend the indications for CRT. These include smart pacing algorithms, better pacing-site targeting, new sensors, multipoint pacing, remote device monitoring and leadless endocardial pacing. Whether CRT is effective in patients with atrial fibrillation or whether adding a defibrillator function to CRT improves prognosis awaits further evidence.
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