title: Assessment of myocardial fibrosis by endoventricular electromechanical mapping in experimental nonischemic cardiomyopathy.
abstract: Cardiac fibrosis plays an important prognostic role in nonischemic cardiomyopathy (NICM), making it a potential therapeutic target. Although electromechanical mapping has been used to identify myocardial scar and facilitate intramyocardial intervention in the setting of ischemic heart disease, its application has not been described in NICM. We assessed the detection of myocardial fibrosis by endoventricular electromechanical mapping in an experimental model of NICM. The NOGA® XP system was used to perform left ventricular mapping in twelve sheep that had undergone intracoronary doxorubicin dosing to induce NICM and in six healthy control animals. Results for endocardial voltage and mechanical shortening were evaluated against myocardial fibrosis burden, as determined by delayed-enhancement cardiac magnetic resonance and quantitative histomorphometry. Doxorubicin treatment resulted in dilated cardiomyopathy with moderate-severe impairment of left ventricular ejection fraction. Late gadolinium uptake was present in 9/12 doxorubicin animals, while histological fibrosis was approximately doubled compared to controls and was distributed multisegmentally throughout the left ventricle. Cardiomyopathy was associated with widespread reductions in unipolar and bipolar voltage amplitude and endocardial shortening. Each parameter showed an inverse relationship with the burden of fibrosis. Moreover, unipolar voltage and linear local shortening ratio displayed moderate accuracy for identifying myocardial segments with delayed contrast enhancement or increased fibrosis content, with optimal discriminatory thresholds of 7.5 mV and 11.5%, respectively. In this model of NICM, electromechanical mapping shows potential for delineating segmental differences in fibrosis. Pending clinical evaluation, it may therefore have applicability for directing targeted intramyocardial interventions in nonischemic heart disease.
authors.affiliation: Department of Medicine and Physiology, University of Adelaide, North Terrace, Adelaide, SA, 5000, Australia.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Psaltis
authors.forename: Angelo
authors.initials: A
authors.lastname: Carbone
authors.forename: Darryl P
authors.initials: DP
authors.lastname: Leong
authors.forename: Dennis H
authors.initials: DH
authors.lastname: Lau
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Nelson
authors.forename: Tim
authors.initials: T
authors.lastname: Kuchel
authors.forename: Troy
authors.initials: T
authors.lastname: Jantzen
authors.forename: Jim
authors.initials: J
authors.lastname: Manavis
authors.forename: Kerry
authors.initials: K
authors.lastname: Williams
authors.forename: Prashanthan
authors.initials: P
authors.lastname: Sanders
authors.forename: Stan
authors.initials: S
authors.lastname: Gronthos
authors.forename: Andrew C W
authors.initials: AC
authors.lastname: Zannettino
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Worthley
mesh_terms: D000818:Animals; D002311:Cardiomyopathy, Dilated / Q000139:chemically induced / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology; D003287:Contrast Media; D004195:Disease Models, Animal; D004317:Doxorubicin; D022062:Electrophysiologic Techniques, Cardiac; D005355:Fibrosis; D006329:Heart Conduction System / Q000503:physiopathology*; D019028:Magnetic Resonance Imaging, Cine; D009206:Myocardium / Q000473:pathology*; D011237:Predictive Value of Tests; D012756:Sheep; D016277:Ventricular Function, Left; D017725:Ventricular Pressure
chemical_list: D003287:Contrast Media; D004317:Doxorubicin