PO-04-228 DIFFERENTIATION OF HIGH FREQUENCY NEAR FIELD VS. FAR-FIELD POTENTIALS IN LOW VOLTAGE ZONES DURING SINUS RHYTHM IMPROVES DISCRIMINATION OF LOCAL SITES OF TERMINATION DURING VT

Abstract

Ventricular tachycardia (VT) in patients with structural heart disease (SHD) is often poorly tolerated or presents with several inducible morphologies. These factors support mapping the arrhythmic substrate during sinus rhythm (SR). However, poor discrimination between near-field (NF) and far-field (FF) electrogram (EGM) components in low voltage (LV) areas is the main limitation. The peak frequency (PF) associated with bipolar EGMs may distinguish NF from FF EGMs (Panel D). To evaluate if PF combined with voltage mapping during SR enhances discrimination of the region of VT termination by radiofrequency application (RFa). Bipolar activation and voltage maps were generated with a 16-pole grid catheter (HD Grid) during SR (Panel B). PF maps were retrospectively computed (Panel C). The maps were only analysed if acute termination was achieved by focal RFa within a boundary diameter<1.5cm (panel A). The mapped surface area (SA) was sub-regioned into the termination (T-ZONE) and non-termination (NT-ZONE) zones. The T-ZONE surface was centered about the termination site and was allowed to extend to a rectangular kernel >0.5cm and <1.5cm across perpendicular axes, with the NT-ZONE encompassing the remainder mapped SA. Sensitivity (SE) and specificity (SP) of discrimination of the T-ZONE vs. NT-ZONE were measured according to the %SA covered at different LV thresholds (0.1-1.0mV in increments of 0.1mV - Panel F). LV high PF (LVHF) areas at different PF cutoffs from 150Hz (LVHF150) to 300Hz (LVHF300) were also assessed. 15 patients with SHD and sustained monomorphic VT were enrolled. Four (60-74 years, all male, 3 ischemic) of them had 5 VT’s terminated by 1.4±0.9 focal RF lesions. All termination sites were located in a LVHF region mapped during SR (Panels B,C,E). The T-ZONE occupied 0.41±0.33cm2/92.75±13.31cm2 global SA, and consisted of 15±10 EGM points/1432±337 global points. T-ZONE voltage during SR (0.50±0.32mV) was significantly lower vs. global voltage (2.01±0.69mV, P<0.001), while T-ZONE PF was higher (324±51Hz) vs. global (270±37Hz, P<0.001). ROC discrimination of the T-ZONE yielded AUC’s of 0.79-LV alone, 0.87-LVHF150, 0.91-LVHF200 (Delta +12.2% vs LV alone, Panel F), 0.85-LVHF250 and 0.77-LVHF300. At a 0.7mV cutoff, LVHF200 yielded a balanced SE/SP of 0.89/0.87 vs. LV alone (0.90/0.63). Assessment of regions with LV and high PF during SR improves specificity for discrimination of sites of VT termination compared to LV alone.