Cardiac Resynchronisation Therapy in Patients With Heart Failure and a Normal QRS Duration: The RESPOND Study
What is the clinical response to cardiac resynchronization therapy (CRT) in heart failure and a normal QRS duration (<120 ms)?
This single-center study enrolled 60 patients with heart failure and a normal QRS duration receiving optimal pharmacological treatment (OPT). The study investigators randomly assigned patients to CRT (n = 29) or to a control group (OPT, n = 31). They utilized cardiovascular magnetic resonance to avoid scar at the site of left ventricular (LV) lead deployment. The primary endpoint was a change in 6-minute walking distance (6MWD). Other measures included a change in quality-of-life scores (Minnesota Living with Heart Failure questionnaire) and New York Heart Association (NYHA) class.
The investigators found that in 93% of implantations, the LV lead was deployed over nonscarred myocardium. At 6 months, the 6MWD increased with CRT compared with OPT (p < 0.0001), with more patients reaching a ≥25% increase (51.7% vs. 12.9%, p = 0.0019). Compared with OPT, CRT led to an improvement in quality-of-life scores (p = 0.0265) and a reduction in NYHA class (p < 0.0001). The composite clinical score (survival for 6 months free of heart failure hospitalizations plus improvement by one or more NYHA class or by ≥25% in 6MWD) was better in CRT than in OPT (83% vs. 23%, respectively; p < 0.0001). Although no differences in total or cardiovascular mortality emerged between OPT and CRT, patients receiving OPT had a higher risk of death from pump failure than patients assigned to CRT (hazard ratio, 8.41; p = 0.0447) after a median follow-up of 677.5 days.
The authors concluded that CRT leads to an improvement in symptoms, exercise capacity, and quality of life in patients with heart failure and a normal QRS duration.
This small unblindeded study suggests that echocardiographic assessment of dyssynchrony adds incremental value to electrocardiogram parameters in the management of heart failure. Larger studies are needed to validate these important findings.
Clinical Topics: Arrhythmias and Clinical EP, Diabetes and Cardiometabolic Disease, Heart Failure and Cardiomyopathies, Noninvasive Imaging, Prevention, Implantable Devices, Acute Heart Failure, Echocardiography/Ultrasound, Exercise
Keywords: Walking, Follow-Up Studies, Minnesota, Heart Failure, Electrocardiography, Myocardium, New York, Magnetic Resonance Spectroscopy, Echocardiography, Cardiac Resynchronization Therapy
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