Abstract and Introduction
Objectives To evaluate the clinical response to cardiac resynchronisation therapy (CRT) in patients with heart failure and a normal QRS duration (<120 ms).
Setting Single centre.
Patients 60 patients with heart failure and a normal QRS duration receiving optimal pharmacological treatment (OPT).
Interventions Patients were randomly assigned to CRT (n=29) or to a control group (OPT, n=31). Cardiovascular magnetic resonance was used in order to avoid scar at the site of left ventricular (LV) lead deployment.
Main outcome measures The primary end point was a change in 6 min walking distance (6-MWD). Other measures included a change in quality of life scores (Minnesota Living with Heart Failure questionnaire) and New York Heart Association class.
Results In 93% of implantations, the LV lead was deployed over non-scarred myocardium. At 6 months, the 6-MWD 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 hospitalisations plus improvement by one or more NYHA class or by ≥25% in 6-MWD) 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 (HR=8.41, p=0.0447) after a median follow-up of 677.5 days.
Conclusions CRT leads to an improvement in symptoms, exercise capacity and quality of life in patients with heart failure and a normal QRS duration.
(ClinicalTrials.gov number, NCT00480051.)
Cardiac resynchronisation therapy (CRT) is an established treatment for selected patients with heart failure. In the Cardiac Resynchronization Heart Failure (CARE-HF) study, CRT was associated with 36% reduction in all-cause mortality. Other benefits of CRT include an improvement in symptoms, exercise capacity and quality of life.
A QRS complex duration ≥120 ms has been adopted as the cut-off point for electrical dyssynchrony in CRT trials and, consequently, by treatment guidelines. The emerging recognition that mechanical dyssynchrony is present in patients with a QRS<120 ms has provided a conceptual basis for extending CRT to this patient population, which comprises the majority of patients with heart failure. Several observational studies have so far shown a benefit from CRT in patients with a QRS<120 ms. The only randomised controlled trial of CRT in patients with a QRS<130 ms, however, failed to show a benefit for peak oxygen uptake on cardiopulmonary exercise testing.
We sought to determine whether CRT leads to a symptomatic improvement in patients with heart failure and a QRS<120 ms. The 6 min walking distance (6-MWD) using the 6 min walk test is sensitive to changes in the symptoms of heart failure and reflects activities of daily living, particularly after CRT. In addition, it is highly reproducible and easily quantifiable. Its utility has been extensively evaluated in systematic reviews. It is on this basis that a change in 6-MWD was adopted as the primary end point in this study.