Comparison of the Relation Between Left Ventricular Anatomy and QRS Duration in Patients With Cardiomyopathy With Versus Without Left Bundle Branch Block

摘要

QRS duration (QRSd) is used to diagnose left bundle branch block (LBBB) and is important for determining cardiac resynchronization therapy eligibility. The same QRSd thresholds established decades ago are used for all patients. However, significant inter-individual variability of normal QRSd exists and individualized QRSd thresholds may improve diagnosis and intervention strategies. Prior work reported left ventricular (LV) mass and papillary muscle location predicted QRSd in healthy subjects, but the relationship in diseased ventricles is unknown. We aimed to determine the association between LV anatomy and QRSd in cardiomyopathy patients. Patients referred for primary prevention implantable defibrillators (n=166) received cardiac magnetic resonance imaging and those with normal conduction (without bundle branch or fascicular block) and LBBB were studied. LV mass, length, internal diameter, end diastolic volume (LVEDV), septal and lateral wall thickness, and papillary muscle location were measured. In normal conduction patients, LV length (r=0.35, p<0.001), mass (r=0.32, p<0.001), diameter (r=0.20, p=0.03) and septal wall thickness (r=0.20, p=0.03) had positive correlations with QRSd. In LBBB patients, LV length (r=0.32, p=0.03), mass (r=0.39, p=0.01), diameter (r=0.34, p=0.02), and LVEDV (r=0.32, p=0.04) had positive correlations with QRSd. Contrary to prior studies in healthy subjects, papillary muscle angle (location) was not associated with QRSd in normal conduction or LBBB cardiomyopathy patients. In conclusion, increasing LV anatomical measurements are associated with increasing QRSd in cardiomyopathy patients. Future work should investigate the use of LV anatomical measurements in developing individualized QRSd thresholds for diagnosing conduction abnormalities such as LBBB and identifying candidates for cardiac resynchronization therapy.