Presence of mechanical dyssynchrony in duchenne muscular dystrophy
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Presence of mechanical dyssynchrony in duchenne muscular dystrophy Kan N Hor1, Janaka P Wansapura2, Hussein R Al-Khalidi3, William M Gottliebson1, Michael D Taylor1, Richard J Czosek1, Sherif F Nagueh4, Nandakishore Akula1, Eugene S Chung5, Woodrow D Benson1, Wojciech Mazur5*
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. Conclusion: 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.
Background In patients with New York Heart Association (NYHA) class III, ambulatory class IV systolic heart failure (HF) and recently class I and II, with electrocardiographic evidence of ventricular dyssynchrony, cardiac resynchronization therapy (CRT) improves quality of life and functional status, reduces heart failure-related hospitalizations, and prolongs survival [1-4]. While current indications are based on QRS duration > 120 ms, HF patients with narrow QRS complexes have been investigated for the presence of mechanical dyssynchrony. In this population, the prevalence of dyssynchrony is * Correspondence: [email protected] 5 The Heart and Vascular Center, The Christ Hospital, Cincinnati, Ohio, USA Full list of author information is available at the end of the article
present though at a lower frequency compared to patients with prolonged QRS. Accordingly, in several small pilot studies [5-8] these pa
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