Automated Peak-Frequency Mapping and Pace Mapping Using ICD-EGMs for Targeted Ablation of Covert VF Triggers

Adrian Zaman (Kiel)1, V. Maslova (Kiel)1, J. Popara (Kiel)1, L. T. Nicholson (Kiel)1, L. Sprenger (Kiel)1, S. Willert (Kiel)1, M. Nonnenmacher (Kiel)2, N. L. Abraham (Eschborn)3, R. Krüger (Eschborn)3, D. Frank (Kiel)1, T. Demming (Kiel)1, E. Lyan (Kiel)1

1Universitätsklinikum Schleswig-Holstein Innere Medizin III mit den Schwerpunkten Kardiologie, Angiologie und internistische Intensivmedizin Kiel, Deutschland; 2Universitätsklinikum Schleswig Holstein Klinik für angeborene Herzfehler und Kinderkardiologie Kiel, Deutschland; 3Abbott Medical GmbH Eschborn, Deutschland


Ventricular fibrillation (VF) is a major cause of sudden cardiac death. The onset of VF is mostly associated with activities from the Purkinje network and structural substrate. Targeted ablation can reduce or even eliminate VF. The mechanism for therapeutic success in VF ablation is not fully understood due to the challenge of understanding the underlying trigger/substrate and hemodynamical instability. Premature ventricular contractions (PVC), as trigger of VF, often arise from the conduction system, especially the Purkinje network, and represent the target in VF ablation. 
Clinical Case:
A 78-year-old man with persistent atrial fibrillation, ischemic cardiomyopathy, severely reduced left ventricular ejection fraction, condition after multiple coronary stenting and CRT-D implantation in 2016 (primary prophylaxis + LBBB). Until last device interrogation no ICD therapies were necessary. Now, numerous VF episodes, some with shocks, were registered despite full dose of metoprolol. All VF episodes were triggered by PVCs with high similarity of ICD-EGMs (figure 1). Finally, he was referred to our center for an EP study/catheter ablation. During admission he presents with mild edema and mild dyspnea (NYHA I). 
The procedure was performed under conscious sedation via transseptal access. During the EP study, no monomorphic PVC occurred and neither VT nor VF was inducible. The electro-anatomical mapping of the left ventricle using the EnSiteX mapping system with the multipolar HD Grid catheter (Abbott Medical) showed absence of low-voltage areas (figure 3A). Automated omnipolar near field annotation using peak-frequency technology algorithm (figure 2) highlighted the area of the conduction system with the Purkinje fibers (PF) potentials. Detailed mapping of the left posterior fascicle (LPF) region revealed conduction system potentials with post-potentials representing retrograde conduction (figure 3B/C, 4A) which can be part of a micro reentry cycle. Low-output pace-mapping from this area produced ICD-EGM morphology with a high degree of similarity to recorded clinical VF-trigger. This prompted the ablation in the region of LPF (figure 4B). At 1-month follow up no VF/VT episode was registered. 6-month FU will be presented at the Jahrestagung. 
Automated near field annotation using peak-frequency technology algorithm is a new tool for the precise visualization of the conduction system, including Purkinje fibers. The regions of retrograde conduction through Purkinje fibers might harbor the trigger of VF and can thus be targeted by catheter ablation. 

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