Whole human heart histology to validate electroanatomical voltage mapping in patients with non-ischaemic cardiomyopathy and ventricular tachycardia

Aims Electroanatomical voltage mapping (EAVM) is an important diagnostic tool for fibrosisidentification and risk stratification in non- ischaemic cardiomyopathy(NICM); currently, distinct cut-offsare applied. We aimed to evaluate the performance of EAVM to detect fibrosisby integration with whole heart histology and to identify the fibrosispattern in NICM patients with ventricular tachycardias (VTs). Methods and results Eight patients with NICM and VT underwent EAVM prior to death or heart transplantation. EAVM data was projected onto slices of the entire heart. Pattern, architecture, and amount of fibrosiswere assessed in transmural biopsies corresponding to EAVM sites. Fibrosispattern in NICM biopsies (n = 507) was highly variable and not limited to mid-wall/sub-epicardium. Fibrosisarchitecture was rarely compact, but typically patchy and/or diffuse. In NICM, biopsies without abnormal fibrosisunipolar voltage (UV) and bipolar voltage (BV) showed a linear association with wall thickness (WT). The amount of viable myocardium showed a linear association with both UV and BV. Accordingly, any cut-offto delineate fibrosisperformed poorly. An equation was generated calculating the amount of fibrosisat any location, given WT and UV or BV. Conclusion Considering the linear relationships between WT, amount of fibrosisand both UV and BV, the search for any distinct voltage cut-offto identify fibrosisin NICM is futile. The amount of fibrosiscan be calculated, if WT and voltages are known. Fibrosispattern and architecture are different from ischaemic cardiomyopathyand findings on ischaemic substrates may not be applicable to NICM.