Clinical Response to Resynchronization Therapy: Conduction System Pacing vs Biventricular Pacing: The CONSYST-CRT
Margarida Pujol-López1, Freddy R Graterol1, Roger Borràs2
1Institut Clínic Cardiovascular (ICCV), Hospital Clínic, Universitat de Barcelona, Catalonia, Spain; Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Catalonia, Spain.
Insights
Conduction system pacing (CSP) proved noninferior to biventricular pacing (BiVP) for cardiac resynchronization therapy, demonstrating similar clinical and echocardiographic responses. This suggests CSP is a viable alternative for patients with systolic dysfunction and wide QRS.
Area of Science:
- Cardiology
- Electrophysiology
- Medical Devices
Background:
- Randomized trials comparing conduction system pacing (CSP) with biventricular pacing (BiVP) are limited, particularly regarding clinical outcomes.
- There is a need to evaluate alternative pacing strategies for cardiac resynchronization therapy (CRT).
Purpose of the Study:
- To assess the noninferiority of CSP compared to BiVP in patients indicated for CRT.
- To evaluate clinical and echocardiographic endpoints at 1-year follow-up in the CONSYST-CRT trial.
Main Methods:
- A randomized, controlled, noninferiority trial (CONSYST-CRT) involving 134 patients with CRT indication.
- Patients were randomized to BiVP or CSP, with optimized atrioventricular intervals for intrinsic conduction fusion.
- Primary endpoint included mortality, transplant, heart failure hospitalization, or LVEF improvement <5 points; secondary endpoints focused on LVEF, LVESV, QRS duration, and functional class.
Main Results:
- CSP demonstrated noninferiority to BiVP for the primary combined endpoint (23.9% vs 29.8%) and key secondary endpoints including mortality/transplant/hospitalization (11.9% vs 17.9%), echocardiographic response (66.6% vs 59.7%), NYHA class, and QRS shortening.
- While LVEF, LVESV, and septal flash values were similar, noninferiority was not met for these specific echocardiographic measures.
- A significant crossover rate was observed, with 26.9% crossing from CSP to BiVP and 7.5% from BiVP to CSP.
Conclusions:
- Conduction system pacing (CSP) is noninferior to biventricular pacing (BiVP) in achieving combined clinical and echocardiographic response in patients requiring CRT.
- CSP presents a potential alternative pacing strategy to BiVP for selected patient populations.
- Further research may explore long-term outcomes and optimal patient selection for CSP.
Background:
Randomized studies comparing conduction system pacing (CSP) with biventricular pacing (BiVP) are scarce and do not include clinical outcomes.
Objectives:
The CONSYST-CRT (Conduction System Pacing vs Biventricular Resynchronization Therapy in Systolic Dysfunction and Wide QRS) trial aimed to test the noninferiority of CSP as compared with BiVP in patients with an indication for cardiac resynchronization therapy, with respect to a combined clinical endpoint at 1-year follow-up.
Methods:
A total of 134 patients with cardiac resynchronization therapy indication were randomized to BiVP or CSP and followed up for 12 months. Crossover was allowed when the primary allocation procedure failed. The atrioventricular interval was optimized to obtain fusion with intrinsic conduction. The primary combined endpoint was all-cause mortality, cardiac transplant, heart failure hospitalization, or left ventricular ejection fraction (LVEF) improvement <5 points at 12 months. Secondary endpoints were LVEF increase, LV end-systolic volume (LVESV) decrease, echocardiographic response (≥15% LVESV decrease), QRS shortening, septal flash correction, NYHA functional class improvement, and a combined endpoint of all-cause mortality, cardiac transplantation, and heart failure hospitalization.
Results:
Sixty-seven patients were allocated to each group. Eighteen patients (26.9%) crossed from CSP to BiVP; 5 (7.5%) crossed over from BiVP to CSP. Noninferiority (NI) was observed for CSP compared with BiVP for the primary endpoint (23.9% vs 29.8%, respectively; mean difference -5.9; 95% CI: -21.1 to 9.2; P = 0.02) and for the combined endpoint of all-cause mortality, cardiac transplantation, and heart failure hospitalization (11.9% vs 17.9%; P < 0.01 NI); echocardiographic response (66.6% vs 59.7%; P = 0.03 NI); NYHA functional class (P < 0.001 NI); and QRS shortening (P < 0.01). LVEF, LVESV, and septal flash endpoint values were similar, but noninferiority was not met (14.1% ± 10% vs 14.4% ± 10%, -27.9% ± 27% vs -27.9% ± 28%, -2.2 ± 2.7 mm vs -2.7 ± 2.4 mm, respectively).
Conclusions:
CSP was noninferior to BiVP in achieving clinical and echocardiographic response, suggesting that CSP could be an alternative to BiVP. (Conduction System Pacing vs Biventricular Resynchronization Therapy in Systolic Dysfunction and Wide QRS [CONSYST-CRT]; NCT05187611).
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