A metric for evaluating the cardiac response to resynchronization therapy

Area of Science:

• Cardiology
• Electrophysiology
• Heart Failure Management

Background:

• Cardiac resynchronization therapy with a defibrillator (CRT-D) is a treatment for heart failure (HF).
• Previous studies suggested a 70% response rate to CRT-D, but this may underestimate its effectiveness in mildly symptomatic patients.

Purpose of the Study:

• To re-evaluate the response rate to CRT-D in patients with mildly symptomatic HF.
• To assess the impact of CRT-D response on cardiac event risk, particularly in relation to left ventricular end-systolic volume (LVESV) reduction and left bundle branch block (LBBB).

Main Methods:

• Analysis of the Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy (MADIT-CRT) population.
• Paired echocardiograms from baseline and 1-year follow-up were used to measure LVESV reduction.
• CRT-D responders were defined as patients in the top quintile of LVESV reduction (≥17%) compared to defibrillator-only treated patients.

Main Results:

• Approximately 88% of CRT-D patients and 91% of CRT-D patients with LBBB met the responder criteria (≥17% LVESV reduction).
• CRT-D responders, especially those with LBBB, showed significantly reduced risk of HF or death (HR 0.24 for LBBB responders vs. 0.62 for non-LBBB responders).
• LVESV response was strongly associated with reduced mortality risk (HR 0.20) and a dose-response relationship was observed between LVESV reduction and cardiac event rates.

Conclusions:

• A high percentage (around 90%) of CRT-D-treated patients in the MADIT-CRT trial demonstrated significant LVESV reduction.
• These LVESV responders experienced a substantial decrease in major cardiac events during long-term follow-up.
• The findings suggest CRT-D is highly effective in improving outcomes for a broad range of heart failure patients.