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Published on: June 12, 2021
Association between myocardial substrate, implantable cardioverter defibrillator shocks and mortality in MADIT-CRT
Nitesh Sood1, Anne-Christine H Ruwald, Scott Solomon
1Cardiac Arrhythmia Services, Southcoast Health System, Fall River, MA, USA.
Insights
Appropriate implantable cardioverter defibrillator (ICD) shocks in patients with cardiac resynchronization therapy were linked to higher mortality risk. This association was not seen with anti-tachycardia pacing alone, suggesting compromised myocardium contributes to mortality.
Area of Science:
- Cardiology
- Electrophysiology
- Clinical Trials
Background:
- Implantable cardioverter defibrillators (ICDs) are crucial for managing sudden cardiac death.
- Understanding factors influencing outcomes after ICD implantation, such as device shocks and myocardial substrate, is essential.
- The Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy (MADIT-CRT) provided a large dataset to investigate these associations.
Purpose of the Study:
- To investigate the relationship between myocardial substrate, implantable cardioverter defibrillator (ICD) shocks, and subsequent mortality.
- To determine if the type and appropriateness of ICD therapy influence patient outcomes.
- To explore the role of cardiac structural disease in patients receiving ICD shocks.
Main Methods:
- Analysis of data from 1790 patients in the MADIT-CRT trial.
- Utilized multivariate Cox regression and landmark analyses at 1-year follow-up.
- Examined associations between myocardial substrate, ICD shocks (appropriate and inappropriate), and mortality.
Main Results:
- Appropriate ICD shocks were associated with a 2.3-fold increased mortality risk (HR = 2.3; P < 0.001), persisting after adjustment for echocardiographic remodeling.
- Appropriate anti-tachycardia pacing (ATP) alone did not significantly increase mortality (P = 0.42).
- Inappropriate shocks and inappropriate ATP were not associated with increased mortality. Advanced myocardial structural disease was observed in patients with appropriate shocks.
Conclusions:
- Receiving appropriate ICD shocks is linked to increased subsequent mortality in the MADIT-CRT population.
- The association between ICD shocks and mortality appears related to the underlying compromised myocardium.
- Appropriate ATP alone does not carry the same mortality risk, highlighting the importance of shock delivery in this context.
Objective:
The aim of the present study was to assess a possible association between myocardial substrate, implantable cardioverter defibrillator (ICD) shocks, and subsequent mortality.
Methods:
Within the multicentre automatic defibrillator implantation trial-cardiac resynchronization therapy (MADIT-CRT) population (n = 1790), we investigated the association between myocardial substrate, ICD shocks and subsequent mortality using multivariate Cox regression analyses and landmark analyses at 1-year follow-up.
Results:
The 4-year cumulative probability of ICD shocks was 13% for appropriate shock and 6% for inappropriate shock. Compared with patients who never received ICD therapy, patients who received appropriate shock had an increased risk of mortality [HR = 2.3 (1.47-3.54), P < 0.001], which remained increased after adjusting for echocardiographic remodelling at 1 year (HR = 2.8, P = 0.001). Appropriate anti-tachycardia pacing (ATP) only was not associated with increased mortality (P = 0.42). We were not able to show an association between inappropriate shocks (P = 0.53), or inappropriate ATP (P = 0.10) and increased mortality. Advanced myocardial structural disease, i.e. higher baseline echocardiographic volumes and lack of remodelling at 1 year, was present in patients who received appropriate shocks but not in patients who received inappropriate shocks or no shocks.
Conclusion:
In the MADIT-CRT study, receiving appropriate ICD shocks was associated with an increased risk of subsequent mortality. This association was not evident for appropriate ATP only. These findings, along with advanced cardiac structural disease in the patients who received appropriate shocks, suggest that the compromised myocardium is a contributing factor to the increased mortality associated with appropriate ICD shock therapy. Clinical trials.gov identifier: NCT00180271.
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