Cardiac Resynchronization Therapy in Heart Failure: Patients with Narrow QRS
Keywords:
dyssynchrony, cardiac resynchronization therapy, biventricular pacing, narrow QRS, heart failureAbstract
Heart failure remains a significant health problem in the Western countries despite the evolution achieved in terms of heart disease prevention and medical treatment. Its incidence and its prevalence reach 550,000/year and 5 million respectively in the United States. As a consequence, heart failure causes about 287,000 deaths in the US each year and puts a financial burden to the health system of $29.6 billion dollars due to the increasing number of hospitalizations especially in elderly patients.
Cardiac resynchronization therapy (CRT) is a relatively recent advance in the management of heart failure patients, which has been very hopeful since its development. Large trials have established the efficacy of CRT in improving functional capacity (MUSTIC, MIRACLE) and reducing mortality (COMPANION, CARE HF) in patients with advanced heart failure (NYHA III-IV), reduced ejection fraction (EF<35%) and wide QRS complex >120 - 130 ms (MIRACLE). Data from meta-analyses also confirm the beneficial effect of CRT with respect to mortality from worsening heart failure and all cause mortality in patients with wide QRS complex.
Nevetheless, not all patients suffering from heart failure have a prolonged QRS. On the contrary, it has been reported that nearly 50% of heart failure patients have a QRS < 120 ms. Moreover, CRT has been shown to improve haemodynamic variables in patients with heart failure and narrow QRS. Achilli et al, who studied 52 patients, reported that CRT produced similar clinical and functional benefit in patients with wide or narrow QRS, the cut-off point being 120 ms provided they had mechanical dyssynchrony. Bleeker at al came up with similar results when they compared 33 patients with normal QRS duration with an equal number of subjects with wide QRS. All participants ought to have mechanical dyssynchrony >65 ms on tissue Doppler imaging (TDI) study... (excerpt)Downloads
Downloads
Published
Issue
Section
License
Authors who publish with this journal agree to the following terms:
a. Authors retain copyright and grant the journal right of first publication with the work simultaneously licensed under a Creative Commons Attribution License that allows others to share the work with an acknowledgement of the work's authorship and initial publication in this journal.
b. Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgement of its initial publication in this journal.
c. Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) prior to and during the submission process, as it can lead to productive exchanges, as well as earlier and greater citation of published work (See The Effect of Open Access).