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QRS morphology more important predictor of response to CRT than QRSd
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In a comparison of QRS morphology and QRS duration as baseline characteristics for patients receiving cardiac resynchronization therapy, researchers concluded that QRS morphology is the more important baseline electrocardiographic determinant of cardiac resynchronization therapy response.
Researchers conducted a retrospective study examining the records of 496 patients. Baseline characteristics, clinical and echocardiographic response and outcomes were assessed for all patients included in the study. All patients received CRT at the Cleveland Clinic in Ohio between December 2003 and July 2007. Patients were divided into four groups according to the baseline QRS morphology and QRS duration (QRSd) recorded: 43.5% of the patients had left bundle branch block (LBBB) and QRSd ≥150 ms, 17.1% had LBBB and QRSd <150 ms, 18.5% had non-LBBB and a QRSd ≥150 ms, and 20.8% had non-LBBB and QRSd <150 ms.
Researchers found the change in ejection fraction was better in patients with LBBB and QRSd ≥150 ms (12 ± 12%) than in those in any of the other groups (P<.0001).
“The key findings of this study can be summarized as follows: 1) non-LBBB, as the baseline ECG morphology before CRT implantation, is much more prevalent in real-world practice than in randomized clinical trials; 2) echocardiographic and clinical response to CRT is determined by baseline QRS morphology in the first place and to a lesser degree by QRSd; 3) event-free survival (from death, heart transplantation, or LVAD) is better in CRT-treated patients with baseline LBBB and QRS ≥150 ms. However, this difference is not significant after adjusting for other baseline characteristics,” the researchers said in the study discussion.
CRT has been shown to improve cardiac function and HF symptoms, but it is unclear why at least one-third of all patients with CRT fail to benefit. The researchers aimed to “shed more light on the interaction between QRS morphology and QRSd and to determine echocardiographic response and outcome after CRT implantation as stratified according to both baseline electrocardiographic characteristics.”
Disclosure: See the full study for the researchers’ relevant financial disclosures.
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