Near-field detection and peak frequency metric for substrate and activation mapping of ventricular tachycardias in two- and three-dimensional circuits

Abstract

Aims

Successful ventricular arrhythmia (VA) ablation requires identification of functionally critical sites during contact mapping. Estimation of the peak frequency (PF) component of the electrogram (EGM) may improve correct near-field (NF) annotation to identify circuit segments on the mapped surface. In turn, assessment of NF and far-field (FF) EGMs may delineate the three-dimensional path of a ventricular tachycardia (VT) circuit.

Methods and results

A proprietary NF detection algorithm was applied retrospectively to scar-related re-entry VT maps and compared with manually reviewed maps employing first deflection (FD _corr) for VT activation maps and last deflection (LD) for substrate maps. Ventricular tachycardia isthmus location and characteristics mapped with FD _corr vs. NF were compared. Omnipolar low-voltage areas, late activating areas, and deceleration zones (DZ) in LD vs. NF substrate maps were compared. On substrate maps, PF estimation was compared between isthmus and bystander sites. Activation mapping with entrainment and/or VT termination with radiofrequency (RF) ablation confirmed critical sites. Eighteen patients with high-density VT activation and substrate maps (55.6% ischaemic) were included. Near-field detection correctly located critical parts of the circuit in 77.7% of the cases compared with manually reviewed VT maps as reference. In substrate maps, NF detection identified deceleration zones in 88.8% of cases, which overlapped with FD _corr VT isthmus in 72.2% compared with 83.3% overlap of DZ assessed by LD. Applied to substrate maps, PF as a stand-alone feature did not differentiate VT isthmus sites from low-voltage bystander sites. Omnipolar voltage was significantly higher at isthmus sites with longer EGM durations compared with low-voltage bystander sites.

Conclusion

The NF algorithm may enable rapid high-density activation mapping of VT circuits in the NF of the mapped surface. Integrated assessment and combined analysis of NF and FF EGM-components could support characterization of three-dimensional VT circuits with intramural segments. For scar-related substrate mapping, PF as a stand-alone EGM feature did not enable the differentiation of functionally critical sites of the dominant VT from low-voltage bystander sites in this cohort.

Graphical Abstract

Graphical Abstract

Left top: LAT emphasis maps in VT activation mapping—Exemplary VT LAT maps with LAT-on-LAT emphasis in a RV VT and LV VT to highlight diastolic potentials. Left bottom: Example of left ventricular substrate map in a patient with extensive chronic anterior myocardial infarct (left, grey < 0.1 mV, purple > 1.5 mV) with emphasis on high-frequency EGMs (middle, emphasizing EGMs with >250 Hz) and visualization of peak frequency values (right, with nominal thresholds of EnSite X: grey < 200 Hz, white > 250 Hz). Right: Schematic illustration of how integration of NF and FF information may allow to distinguish two- and three-dimensional VT circuits and estimate the three-dimensional path of the VT _CC. Yet, important confounders for using NF and peak frequency in ventricular mapping exist and need to be considered. 2D, two-dimensional; 3D, three-dimensional; EGM, electrogram; ICM, ischaemic cardiomyopathy; FF, far field; LV, left ventricle; NF, near field; RV, right ventricle; VT, ventricular tachycardia.