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

Abstract

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.

Relationship between QRS measurements and left ventricular morphology and function in asymptomatic individuals

“…Our results confirm previous findings in showing that the three QRS measurements, duration, amplitude and area correlate with LV mass and end‐diastolic dimension in a modest size cohort of asymptomatic individuals with no overt heart disease. Also, QRS modestly correlated with markers of dyssynchrony, shown as prolonged T‐IVT and raised Tie index, particularly when values exceeded 9 s/min and 0.3, respectively.…”

“…The QRS complex reflects the time and speed of myocardial depolarization which is related to LV structure much more than function . The myocardium requires coherent electric stimulation to guarantee efficient mechanical function.…”

“…Clinically, prolonged QRS duration and increased amplitude (voltage) are interpreted as signs of slow depolarization of an enlarged left ventricle (LV) and the prolonged activation of thickened ventricular wall, respectively . The effect of LV size on QRS morphology is normally affected by gender, cavity geometry, and myocardial fiber orientation, as well as pathologically by ischemic heart disease, cardiomyopathies, myocardial fibrosis and pulmonary diseases . However, the diagnostic concordance between QRS morphology and echocardiographic or magnetic resonance estimation of LV mass and volume is limited and the direct association between changes in QRS amplitude and LV size remains controversial …”

Sex Differences in Device Therapy for Heart Failure: Utilization, Outcomes, and Adverse Events

“…This may in part be due to women having higher prevalence of nonischemic cardiomyopathy, as previously discussed, and less dense areas of scar. 128,129 The similarity in NYHA heart failure class improvement between sexes despite a difference in LVESV reduction supports the notion that LVESV is likely not a direct measure of clinical symptoms or long term outcome. Furthermore, a more standardized clinical assessment of LV volumes and function among women and men, possibly based on body surface area, should be considered.…”

Interaction of Left Ventricular Size and Sex on Outcome of Cardiac Resynchronization Therapy Among Patients With a Narrow QRS Duration in the EchoCRT Trial

“…It is prolonged most obviously by HPS delay (eg, LBBB) but also by increased LV dimension, which increases “path length.”2 LV size itself may increase with cardiomyopathy and larger body size. These correlations have been observed in healthy subjects and in patients with cardiomyopathy and LBBB 10, 11, 12, 13, 14. Among patients with normal QRSd with normal LV function, Stewart et al found that each 10 ms increase in QRSd was associated with a 9.2% increase in LVEDV 13.…”