Peak frequency mapping to differentiate near-field from far-field electrograms for ventricular tachycardia ablation: initial results

FUNDING ACKNOWLEDGEMENTS: Type of funding sources: Private company. Main funding source(s): Abbott Laboratories BACKGROUND: Ablation of ventricular tachycardia (VT) in patients with structural heart disease is challenging. Localization of the critical isthmus of conduction may be difficult because is commonly located within low voltage (LV) areas where far-field (FF) and near-field (NF) electrograms (EGMs) may be present and merged. The peak frequency (PF) associated with bipolar EGMs is a novel parameter which may serve to distinguish NF from FF EGM components. The potential value of PF to identify the critical isthmus of conduction in this setting has never been evaluated. PURPOSE: To compare the ability of LV vs. LVHF to discriminate the VT termination region METHODS: Bipolar voltage and activation maps were generated with a 16-pole grid catheter (Advisor HD Grid) during VT. Peak frequency maps were retrospectively computed. VTs were included if acute termination could be achieved through application of a focal RF lesions set restricted to a boundary <1.5cm diameter. The ventricular LV mapped surface was sub-regioned into the termination (T-ZONE) and non-termination (NT-ZONE) zones. The T-ZONE surface was centered about the site of termination and was allowed to extend to a rectangular kernel >0.5cm and <1.5cm across perpendicular axes, with the NT-ZONE encompassing the remainder of the mapped surface area (SA). Sensitivity (SE) and specificity (SP) of discrimination of the T-ZONE vs. NT-ZONE was measured according to the %T-ZONE vs. %NT-ZONE SA occupied at LV thresholds ranging from 0.1-1.0mV in increments of 0.1mV (Panel E). In addition to LV, LVHF at peak frequency cutoffs of 200Hz (LVHF200), 250Hz (LVHF250), 300Hz (LVHF300) and 400Hz (LVHF400) were also assessed for T-ZONE discrimination. RESULTS: 8 patients with sustained monomorphic VT and structural heart disease (ischemic and non-ischemic) were enrolled. All of them had VT terminated with limited ablation by focal ablation at a discrete region. All areas of VT termination were located in a LV and high PF zone (figure 1). The best area under the curve to identify them was using the 250 Hz cuttoff (AUC 0.91) which was also better that using omnipolar optimized voltage alone (AUC 0.84) (Figure 2). CONCLUSION: PF mapping apparently identifies slow conduction isthmus and provides complementary information to bipolar voltage mapping which can be displayed with emphasis on the electranatomical map. [Figure: see text] [Figure: see text]