96-21: Detection of Very Low Voltage Critical Signals In Scarred Human Atria with A New Automated Ultra-high Resolution Mapping System

Abstract

Purpose: Critical areas of arrhythmogenesis occur mostly in diseased tissue where voltage is attenuated often below the background noise (BGN). A new 64-poles basket mapping system catheter incorporates very small unidirectional electrodes (0.4 mm2; 2.5 mm center to center interelectrode spacing). We measured BGN on the bipolar electrograms (Eg) channels during mapping of scar-related atrial (A) tachycardias (T) and compared it to Eg in the critical AT isthmus. Method: Patients (n = 16, 69 ± 8 y) with scar-related AT (n = 22) were prospectively studied. Of these, 73% occurred after atrial fibrillation ablation and 27% after a surgical mitral valve repair (adjunct maze in 23%). Both A were mapped for each AT. BGN was measured at pre-specified sites: left A: mid-roof, mid-posterior wall, posterior mitral annulus, inter-A septum, mid-anterior wall, appendage; right A: cavo-tricuspid isthmus, septum, appendage and crista terminalis; see figure) for each map. BGN was also assessed on standard decapolar catheter (2 mm ring electrodes and spacing) and on surface ECG. Scar thresholding was performed whenever necessary in order to visualise the entire circuit. The amplitude of the smallest bipolar Eg of the “isthmus” of macroreentrant AT (targeted for ablation) was also measured. Summary of results: Mean BGN of basket Eg was 0.011 ± 0.003 mV (see figure for each site), lower than the decapolar catheter (0.019 ± 0.023) and surface ECG (0.032 ± 0.023; p < 0.0001). Scar threshold was established at 0.016 ± 0.010 mV (median 0.015). Bipolar Eg amplitude within the critical isthmus was 0.1 ± 0.1 mV. In 9 cases (41%), isthmus bipolar Eg was <0.05 mV and in 6 cases <0.03 mV, but above the adapted scar threshold.