Cardiac resynchronization therapy improves myocardial conduction
Mei Yang1,2, Xuping Li2,3, Dachun Yang2
1Department of Cardiology, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
Insights
Cardiac resynchronization therapy (CRT) improves ventricular conduction, with continuous QRS narrowing indicating a super-response. This electrical marker of CRT is linked to reduced mortality risk post-generator replacement.
Area of Science:
- Cardiology
- Electrophysiology
- Medical Devices
Background:
- Cardiac resynchronization therapy (CRT) is known to improve left ventricular remodeling and systolic function.
- The impact of CRT on ventricular conduction, however, remains less understood.
Purpose of the Study:
- To investigate the relationship between patient response to CRT and changes in QRS duration.
- To determine if QRS narrowing serves as a marker for CRT efficacy.
Main Methods:
- A cohort of 114 patients receiving CRT with defibrillator (CRT-D) underwent assessment at 6 months post-implantation and at generator replacement (GR).
- Patients were categorized into super-responders (LVEF ≥ 50%), responders (LVEF 36-49% with >5% increase), and non-responders based on left ventricular ejection fraction (LVEF) changes.
- QRS duration was measured at baseline, 6 months, and at GR to evaluate changes.
Main Results:
- Significant QRS narrowing was observed at 6 months in both super-responders and responders.
- Super-responders demonstrated further QRS narrowing between 6 months and GR.
- QRS duration change post-6 months was independently associated with super-response, and a narrowing of ≥ 10 ms correlated with reduced all-cause mortality after GR.
Conclusions:
- Continuous QRS narrowing after CRT functions as an electrical marker of a super-response.
- Sustained QRS narrowing beyond 6 months post-CRT implantation is associated with a decreased risk of mortality.
Background:
Cardiac resynchronization therapy (CRT) reverses left ventricular remodeling and improves left ventricular systolic function. However, little is known about whether CRT improves ventricular conduction.
Objective:
To determine the relationship between CRT response and QRS narrowing.
Methods:
The study included consecutive patients who underwent CRT with defibrillator (CRT-D) implantation between January 2002 and December 2012 and had subsequent generator replacement (GR). At the time of GR, super-responder was defined as those who had left ventricular ejection fraction (LVEF) of 50% or more; patients who had an LVEF of 36-49% with an increase of more than 5% were considered responders, and the others were nonresponders. All patients were assessed 6 months after CRT-D implantation and at the time of GR.
Results:
Of 114 study patients, 58 (50.9%) were nonresponders, 29 (25.4%) responders, and 27 (23.7%) super-responders. QRS narrowing at 6 months was significant in super-responders (175.4 ± 21.4 to 159.7 ± 20.7 ms, P = 0.001) and responders (169.0 ± 21.3 to 157.7 ± 17.6 ms, P = 0.008). At time of GR, only super-responders had further QRS narrowing (159.7 ± 20.7 to 146.3 ± 19.2 ms, P < 0.001). QRS duration change after 6 months was independently associated with super-response (hazard ratio: 1.20 for every 5 ms QRS duration narrowing; 95% confidence interval, 1.06-1.38; P = 0.005), and QRS narrowing of 10 ms or more was associated with lower risk of all-cause mortality after GR.
Conclusion:
Continuous QRS narrowing after CRT, as an electrical marker, is associated with a super-response to CRT. Further QRS narrowing 6 months after CRT implantation was associated with lower risk of mortality after GR.
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