Comparison of the relation between left ventricular anatomy and QRS duration in patients with cardiomyopathy with versus without left bundle branch block.
QRS duration (QRSd) is used to diagnose left bundle branch block (LBBB) and is important to determine cardiac resynchronization therapy eligibility. The same QRSd thresholds established decades ago are used for all patients. However, significant interpatient variability of normal QRSd exists, and individualized QRSd thresholds might improve diagnosis and intervention strategies. Previous work reported left ventricular (LV) mass and papillary muscle location predicted QRSd in healthy subjects, but the relation in diseased ventricles is unknown. The aim of the present study was to determine the association between LV anatomy and QRSd in patients with cardiomyopathy. 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. The LV mass, length, internal diameter, LV end-diastolic volume, septal and lateral wall thicknesses, and papillary muscle location were measured. In patients with normal conduction, 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 patients with LBBB, LV length (r = 0.32, p = 0.03), mass (r = 0.39, p = 0.01), diameter (r = 0.34, p = 0.02), and LV end-diastolic volume (r = 0.32, p = 0.04) had positive correlations with QRSd. Contrary to previous studies in healthy subjects, papillary muscle angle (location) was not associated with QRSd in cardiomyopathy patients with normal conduction or LBBB. In conclusion, increasing LV anatomical measurements were associated with increasing QRSd in patients with cardiomyopathy. 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.
Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, United States Food and Drug Administration, Silver Spring, Maryland.
Dulciana D
DD
Chan
Division of Cardiology, Department of Medicine, Johns Hopkins Medical Institutions, Baltimore, Maryland.
Katherine C
KC
Wu
Department of Medicine, University of California San Francisco School of Medicine, San Francisco, California.
Zak
Z
Loring
Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, United States Food and Drug Administration, Silver Spring, Maryland.
Loriano
L
Galeotti
Division of Cardiology, Department of Medicine, Johns Hopkins Medical Institutions, Baltimore, Maryland.
Gary
G
Gerstenblith
Division of Cardiology, Department of Medicine, Johns Hopkins Medical Institutions, Baltimore, Maryland.
Gordon
G
Tomaselli
Division of Cardiology, Department of Medicine, Johns Hopkins Medical Institutions, Baltimore, Maryland.
Robert G
RG
Weiss
Department of Internal Medicine, Duke University Medical Center, Durham, North Carolina.
Galen S
GS
Wagner
Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, United States Food and Drug Administration, Silver Spring, Maryland. Electronic address: david.strauss@fda.hhs.gov.
David G
DG
Strauss
D002036:Bundle of His / Q000473:pathology / Q000503:physiopathology; D002037:Bundle-Branch Block / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology; D009202:Cardiomyopathies / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006339:Heart Rate / Q000502:physiology*; D006352:Heart Ventricles / Q000473:pathology* / Q000503:physiopathology; D006801:Humans; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013318:Stroke Volume; D016277:Ventricular Function, Left / Q000502:physiology*