Abstract 4018: Catheter-based Electromechanical Mapping Accurately Characterizes Segmental Distribution of Left Ventricular Fibrosis in Nonischemic Cardiomyopathy
Background: Endoventricular electromechanical mapping has been used to facilitate regional intramyocardial interventions in ischemic heart disease. However, neither its diagnostic nor therapeutic application has been described in nonischemic cardiomyopathy (NICM). The purpose of this preclinical study was to determine the accuracy of electromechanical mapping for characterizing left ventricular (LV) fibrosis in NICM.
Methods: NICM was induced in twelve sheep ten weeks after repeat doses of intracoronary doxorubicin (3.6 ±0.5 mg/kg), as confirmed by cardiac magnetic resonance. NOGA® XP was used for LV electromechanical mapping in these animals and in six untreated controls. Global and segmental unipolar voltage amplitudes (UV) and linear local shortening ratios (LLS) were validated against quantified fibrosis content, as detected by Masson’s trichrome staining.
Results: Mean LV ejection fraction was 32.6 ±6.0% in NICM animals and 55.5 ±8.8% in controls (P <0.05). Myocardial fibrosis was higher in the NICM group (total content: 7.2 ±1.3% vs 4.0 ±0.2%, P <0.01) and was heterogeneously distributed throughout the LV, with 61% segments displaying 5–10% fibrosis (mainly reactive type) and 17% containing >10% fibrosis (mainly replacement). Reconstructed electromechanical maps revealed multi-segmental reductions in endocardial voltage and mechanical shortening in NICM, with reduced global scores for both UV (7.3 ±1.7 mV vs 10.3 ±2.7 mV in controls, P <0.01) and LLS (12.0 ±2.8% vs 17.7 ±1.6%, P<0.01). Segmental UV and LLS results were inversely related to the degree of fibrosis and were lowest in myocardial segments with >10% fibrosis (P <0.0001). Optimal thresholds for differentiating between segments containing <5% and >10% fibrosis were 7.5 mV for UV (sensitivity 77%, specificity 76%) and 11.5% for LLS (sensitivity 85%, specificity 82%).
Conclusions: Endoventricular, catheter-based mapping with NOGA® XP can identify regional differences in myocardial fibrosis in experimental NICM, with comparable accuracy to its performance in ischemic cardiomyopathy. Given the heterogeneous distribution of fibrosis in NICM, electromechanical mapping has potential utility to direct targeted intramyocardial interventions in this setting.