title: QRS prolongation in myotonic muscular dystrophy and diffuse fibrosis on cardiac magnetic resonance.
abstract: Current noninvasive surrogates of cardiac involvement in myotonic muscular dystrophy have low positive predictive value for sudden death. We hypothesized that the cardiac MR signal-to-noise ratio variance (SNRV) is a surrogate of the spatial heterogeneity of myocardial fibrosis and correlates with electrocardiography changes in myotonic muscular dystrophy. The SNRV for contrast enhanced cardiac MR images was calculated over the entire left ventricle in 43 patients with myotonic muscular dystrophy. All patients underwent standard electrocardiography, and a subset of 23 patients underwent signal averaged electrocardiography. After correcting for body mass index, age, and ejection fraction, SNRV was predictive of QRS duration on standard electrocardiography (1.35-msec increased QRS duration/unit increase in SNRV, P < 0.001). SNRV was also predictive of the low-amplitude late-potential duration (1.49-msec increased low-amplitude late-potential duration/unit increase in SNRV, P < 0.001). Ten-fold cross-validation yielded an area under the receiver operating characteristic curve of 0.87 for the predictive value of SNRV for QRS duration greater than 120 msec. The SNRV of the left ventricle is associated with QRS prolongation, likely due to late depolarization of tissue within islands of patchy fibrosis. The association of SNRV with future clinical events warrants further study.
authors.affiliation: Department of Medicine/Cardiology, Johns Hopkins University, Baltimore, Maryland 21287, USA. snazarian@jhmi.edu
authors.forename: Saman
authors.initials: S
authors.lastname: Nazarian
authors.forename: David A
authors.initials: DA
authors.lastname: Bluemke
authors.forename: Kathryn R
authors.initials: KR
authors.lastname: Wagner
authors.forename: Menekhem M
authors.initials: MM
authors.lastname: Zviman
authors.forename: Evrim
authors.initials: E
authors.lastname: Turkbey
authors.forename: Brian S
authors.initials: BS
authors.lastname: Caffo
authors.forename: Monda
authors.initials: M
authors.lastname: Shehata
authors.forename: David
authors.initials: D
authors.lastname: Edwards
authors.forename: Barbara
authors.initials: B
authors.lastname: Butcher
authors.forename: Hugh
authors.initials: H
authors.lastname: Calkins
authors.forename: Ronald D
authors.initials: RD
authors.lastname: Berger
authors.forename: Henry R
authors.initials: HR
authors.lastname: Halperin
authors.forename: Gordon F
authors.initials: GF
authors.lastname: Tomaselli
mesh_terms: D000328:Adult; D016477:Artifacts; D002037:Bundle-Branch Block / Q000401:mortality; D003287:Contrast Media; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006352:Heart Ventricles / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009136:Muscular Dystrophies / Q000000981:diagnostic imaging / Q000503:physiopathology*; D009223:Myotonic Dystrophy / Q000000981:diagnostic imaging / Q000503:physiopathology*; D011237:Predictive Value of Tests; D011859:Radiography
chemical_list: D003287:Contrast Media