A metric for evaluating the cardiac response to resynchronization therapy
Yidi Ge1, Anne-Christine Huth Ruwald2, Valentina Kutyifa1
1Heart Research Follow-up Program, University of Rochester Medical Center, Rochester, New York.
Insights
Cardiac resynchronization therapy with a defibrillator (CRT-D) significantly improved heart failure (HF) outcomes in most patients. Approximately 90% of CRT-D recipients showed favorable left ventricular end-systolic volume reduction, leading to fewer cardiac events.
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.
Abstract:
We hypothesized that the response to cardiac resynchronization therapy with a defibrillator (CRT-D) in patients with mildly symptomatic heart failure (HF) is more favorable than the commonly referenced figure of 70%. This study involves the Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy (MADIT-CRT) study population in which paired echocardiograms from baseline and 1-year follow-up were available in 621 implantable cardioverter-defibrillator-treated patients and 749 patients treated with CRT-D. We prespecified CRT-D responders as the patients who at 1-year follow-up had a reduction in left ventricular end-systolic volume (LVESV) that corresponded to the top (best) quintile of LVESV reduction in the implantable cardioverter-defibrillator-treated patients, that is, a ≥17% reduction in LVESV. Using this metric, 88% of patients treated with CRT-D and 91% of the patients treated with CRT-D with left bundle branch block (LBBB) were identified as cardiac resynchronization therapy responders. Landmark multivariate Cox model analyses revealed a significant interaction (p=0.038) involving LVESV (responders vs nonresponders) and LBBB (present vs not present) in risk reduction for HF or death. The interaction finding indicates that cardiac resynchronization therapy responders with LBBB have a significantly lower risk for HF or death (hazard ratio [HR] 0.24) than patients without LBBB (HR 0.62). In the patients treated with CRT-D, LVESV response was associated with reduction in the risk of death (HR 0.20, p<0.001). An increasing percent reduction in LVESV was associated with progressively lower rates of HF or death, a finding consistent with a dose-response relation. In conclusion, approximately 90% of CRT-D-treated patients in MADIT-CRT had a significant and meaningful reduction in LVESV, and these LVESV responders had reduced rates of cardiac events during long-term follow-up.
