AB-452674-1 HIGH-FREQUENCY ELECTROGRAM CHARACTERISTICS IN REGIONS OF LOW VOLTAGE ACCURATELY DISCRIMINATE SITES OF LEFT ATRIAL TACHYCARDIA TERMINATION

Abstract

Localization of the critical isthmus of conduction of left atrial (LA) macroreentrant tachycardia (LAMRT) circuits within scar tissue is challenging (Panel A). Low voltage (LV) has been used as a marker for the arrhythmic substrate. However, voltage amplitudes due to near-field (NF) vs. far-field (FF) electrogram (EGM) components are not clearly differentiated. The peak frequency (PF) associated with bipolar EGM’s is a novel parameter which may distinguish them (Panel B). To compare the ability of LV vs. LV with high PF (LVHF) to discriminate the LAMRT termination region. Bipolar voltage and activation maps were generated with a 16-pole grid catheter (HD-Grid) during LAMRT (Panels A,B). PF maps were retrospectively computed (Panel C). LAMRT’s were only included if terminated by focal RF lesions (boundary <1.5cm diameter). The LA mapped surface was sub-regioned into the termination (T-ZONE) and non-termination (NT-ZONE) zones. The T-ZONE was centered about the termination site and allowed to extend to a rectangular kernel >0.5cm and <1.5cm across perpendicular axes. The NT-ZONE encompassed the remainder of the mapped surface area (SA). Sensitivity (SE) and specificity (SP) of T-ZONE vs. NT-ZONE discrimination was measured according to the %T-ZONE vs. %NT-ZONE SA occupied at LV thresholds (range 0.1-1.0mV) in 0.1mV increments (Panel E). LVHF at PF cutoffs of 150Hz (LVHF150), 200Hz (LVHF200), 250Hz (LVHF250) and 300Hz (LVHF300) were also assessed for TZONE discrimination (Panel F). 16 consecutive patients with 24 ATs were prospectively enrolled and 13 LAMRT’s were terminated by 2.85±2.82 focal RF lesions. The T-ZONE occupied 0.82±0.30cm2 (41±19 EGM points) vs. 158.6±42.2cm2 (2967±1227 points) for the NT-ZONE. T-ZONE voltage was significantly lower vs. the NT-ZONE (0.12±0.05mV vs. 0.60±0.28mV, P<0.001 respectively). T-ZONE PF was significantly higher than the NT-ZONE PF (345±76Hz vs. 255±34Hz, P<0.001). ROC discrimination of the T-ZONE resulted in AUC’s of 0.69- LV, 0.86- LVHF150, 0.88- LVHF200, 0.86- LVHF250 and 0.78- LVHF300. LVHF200 yielded the best improvement of AUC vs. LV unconstrained by high PF (19.1%)(Panel E). At a 0.2 mV cutoff, LVHF200 yielded a balanced SE/SP of 0.86/0.83 respectively vs. SE/SP of 0.90/0.54 for LV alone. During AT, systematic identification of EGM regions of high frequency within LV can significantly improve the specificity of discrimination of the site of AT termination.