ardiac resynchronization therapy (CRT) in patients with advanced heart failure (HF) and a ventricular conduction delay improves symptoms and functional capacity, induces reverse remodeling, and reduces morbidity, and probably mortality. [1][2][3][4] It is well known that although the vast majority of CRT recipients present with left bundle branch block (LBBB), up to 10% of the minority have nonspecific conduction delays or right bundle branch block (RBBB). 2,5 Recently, RBBB was proven to be an important predictor of mortality in patients with congestive HF, just as has LBBB. 6 However, patients with RBBB and congestive HF have not been adequately evaluated because of an under-representation in the referenced studies. Therefore, which type of patients with RBBB has ventricular conduction delays, and thus are good candidates for CRT, has not been fully clarified.
Methods
Study PopulationThis study included 104 patients (34 women, 70 men; mean age, 59±15 years) who underwent conventional echocardiography, including tissue Doppler imaging (TDI) and tissue tracking imaging (TTI) between January 2002 and December 2004. Of these, 49 consecutive patients had complete RBBB (CRBBB) with a duration of the QRS complex of ≥120 ms (RBBB-Gr). The remaining 55 had normal morphology of the QRS complex and narrow QRS (<120 ms; Control-Gr), and were randomly selected so that the data collected would be statistically matched to the RBBB-Gr patients in terms of age and gender (Table 1). In total, 33 patients had hypertension, 5 dilated cardiomyopathy, 5 mitral valvular diseases, 2 hypertrophic cardiomyopathy, 1 congenital heart disease, 3 ischemic heart disease, and the remaining 93 (89%) had no structural heart disease. Echocardiography demonstrated that the mean left ventricular ejection fraction (LVEF) was 64.2±11.8% (range, 12-83), and left ventricular end-diastolic diameter (LVEDD) 46.5± 8.5 mm (range, 34-75). All patients were in sinus rhythm, and the mean QRS duration was 113.8±33.3 ms (range, 70-200). All patients in the Control-Gr had LVEF >50% (range, 51-83).
Echocardiographic Examination Including TDI and TTIThe left ventricular (LV) dimensions were measured by M-mode echocardiography in the parasternal long-axis view. The LVEDD was measured at the onset of the QRS Background The indications and efficacy of cardiac resynchronization therapy (CRT) have not been sufficiently clarified in patients with right bundle branch block (RBBB).
Methods and ResultsThis study included 55 patients with normal QRS morphology and duration (ControlGr) and 49 patients with complete RBBB (CRBBB-Gr). Using tissue Doppler imaging, the time difference (TD) between the electromechanical delay of the septal wall, left ventricular (LV) lateral wall, and right ventricular free wall were measured. Using tissue tracking imaging, the coefficient of the time variation from the beginning of the QRS to the peak displacement time of 6 regions of the LV (CV-PMDLV) was calculated. The TD between the septal wall and that of the LV lateral wall (TDSEPT-LAT)...
