The pitfalls of unipolar voltage mapping of the right ventricle

Funding Acknowledgements Type of funding sources: Other. Main funding source(s): The department of cardiology from Leiden University Medical Center receives unrestricted grants from Edwards Lifesciences, Biotronik, Medtronik, Boston Scientific and BioSense Webster. MS was supported by the Research Fellowship of the European Society of Cardiology 2017/2018. Background The current golden standard to accurately delineate scar potentially related to ventricular tachycardia relies on electroanatomical voltage mapping. Endocardial unipolar voltage (UV) mapping is increasingly used to detect intramural or subepicardial non-ischemic scars. 3D mapping systems determine and display the largest peak-to-peak amplitude of the electrogram within the window-of interest usually set from the QRS onset, but cannot not identify far-field electrograms or artifacts. Purpose To evaluate the influence of manual adjustment of the window-of-interest on the amplitude of endocardial and epicardial right ventricular (RV) unipolar electrograms. Methods Patients who underwent ablation of a RV scar-related VT with combined endo- and epicardial RV mapping were included. Endo- and epicardial points were reviewed with special interest towards the unipolar signal. In case a far-field, ST-segment elevation/depression or artifact was present, the window-of-interest was adjusted and the corresponding unipolar amplitude was collected. Results Thirty-three patients were included (age 50 ± 14years and 79% male). The underlying aetiology was definite arrhythmogenic right ventricular cardiomyopathy (ARVC; n = 17), athlete’s right ventricular outflow tract scar in (n = 9), cardiac sarcoidosis in (n = 3), scar of unknown origin (n = 2), borderline ARVC (n = 1) or myocarditis (n = 1). In total, 4225 endocardial points and 1960 epicardial points were re-analyzed. In 2987 (71%) endocardial points and 689 (65%) epicardial points the window-of-interest needed to be adjusted. Reason for this adjustment was ‘inclusion of far-field’ in 1380 (33%) endocardial- and 700 (36%) epicardial points; ‘inclusion of ST-segment elevation/depression’ in 1246 (29%) endocardial- and 316 (16%) epicardial points; RV-pacing artefact in 266 (6%) endocardial- and 116 (6%) epicardial points; and miscellaneous (e.g. unstable baseline or ablation point with artifact) in 95 (2%) endocardial- and 139 (7%) epicardial points (Figure). The median difference between the ‘automatically generated’ UV and the ‘adjusted’ UV was 0.81mV (IQR: 0.40-1.39) for the endocardial points and 0.54mV (IQR: 0.27-0.98) for the epicardial points. In 320 (8%) endocardial points the UV was changed from >5.5mV to <5.5mV, in 412 (10%) points from >4.4 to <4.4mV and in 396 (9%) points from >3.8mV to <3.8mV. Conclusion In the majority of endocardial and epicardial points the window-of-interest for unipolar voltage mapping needs to be adjusted to exclude far-field signal or ST-segment elevation/depression contributing to the automatically determined amplitude. Unadjusted unipolar voltage mapping underestimates low UV regions. RV-pacing generates a large unipolar far-field signal, which can obscure the local unipolar near-field signal. Accordingly, RV UV mapping during RV pacing should be used with caution. Abstract Figure. The pitfalls of UV mapping of the RV