title: Presence of mechanical dyssynchrony in Duchenne muscular dystrophy.
abstract: BACKGROUND
  Cardiac dysfunction in boys with Duchenne muscular dystrophy (DMD) is a leading cause of death. Cardiac resynchronization therapy (CRT) has been shown to dramatically decrease mortality in eligible adult population with congestive heart failure. We hypothesized that mechanical dyssynchrony is present in DMD patients and that cardiovascular magnetic resonance (CMR) may predict CRT efficacy.
  
  
  METHODS
  DMD patients (n = 236) were stratified into 4 groups based on age, diagnosis of DMD, left ventricular (LV) ejection fraction (EF), and presence of myocardial fibrosis defined as positive late gadolinum enhancement (LGE) compared to normal controls (n = 77). Dyssynchrony indices were calculated based on timing of CMR derived circumferential strain (ecc). The calculated indices included cross-correlation delay (XCD), uniformity of strain (US), regional vector of variance (RVV), time to maximum strain (TTMS) and standard deviation (SD) of TTMS. Abnormal XCD value was defined as > normal + 2SD. US, RVV, TTMS and SD were calculated for patients with abnormal XCD.
  
  
  RESULTS
  There was overall low prevalence of circumferential dyssynchrony in the entire DMD population; it increased to 17.1% for patients with abnormal EF and to 31.2% in the most advanced stage (abnormal EF with fibrosis). All but one DMD patient with mechanical dyssynchrony exhibited normal QRS duration suggesting absence of electrical dyssynchrony. The calculated US and RVV values (0.91 ± 0.09, 1.34 ± 0.48) indicate disperse rather than clustered dyssynchrony.
  
  
  CONCLUSIONS
  Mechanical dyssynchrony is frequent in boys with end stage DMD-associated cardiac dysfunction. It is associated with normal QRS complex as well as extensive lateral fibrosis. Based on these findings, it is unlikely that this patient population will benefit from CRT.
authors.affiliation: The Heart and Vascular Center, The Christ Hospital, Cincinnati, Ohio, USA.
authors.forename: Kan N
authors.initials: KN
authors.lastname: Hor
authors.forename: Janaka P
authors.initials: JP
authors.lastname: Wansapura
authors.forename: Hussein R
authors.initials: HR
authors.lastname: Al-Khalidi
authors.forename: William M
authors.initials: WM
authors.lastname: Gottliebson
authors.forename: Michael D
authors.initials: MD
authors.lastname: Taylor
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Czosek
authors.forename: Sherif F
authors.initials: SF
authors.lastname: Nagueh
authors.forename: Nandakishore
authors.initials: N
authors.lastname: Akula
authors.forename: Eugene S
authors.initials: ES
authors.lastname: Chung
authors.forename: Woodrow D
authors.initials: WD
authors.lastname: Benson
authors.forename: Wojciech
authors.initials: W
authors.lastname: Mazur
mesh_terms: D000293:Adolescent; D000367:Age Factors; D058406:Cardiac Resynchronization Therapy; D002648:Child; D003287:Contrast Media; D004562:Electrocardiography; D005240:Feasibility Studies; D005355:Fibrosis; D019786:Gadolinium DTPA; D006801:Humans; D019028:Magnetic Resonance Imaging, Cine; D008297:Male; D020388:Muscular Dystrophy, Duchenne / Q000150:complications*; D009206:Myocardium / Q000473:pathology; D009820:Ohio; D018579:Patient Selection; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013318:Stroke Volume; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology / Q000628:therapy; D016277:Ventricular Function, Left; D055815:Young Adult
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA