4987Ventricular tachycardia critical isthmus detection through pacemapping technique guided by a robotic magnetic navigation system

Abstract

Introduction: Percutaneous ablations of ventricular tachycardia are playing a relevant role in the therapeutic approach of patients with drug refractory ventricular tachycardia (VT). Pacemapping approach is emerging as a prominent tool to detect the VT critical isthmus. Case report description: This case report focuses on a 47 years old woman, with a known congenital double aortic arch, that in 2017 referred to our centre for VT ablation. She had an history of ischemic cardiomyopathy started twelve years before with progressive hypokinetic evolution that led the patient to ICD placement in primary prevention in 2007. Since 2008 the device telemetry recorded sustained episodes of ventricular tachycardia (VT) effectively treated by the device with anti-tachycardia pacing. First shocks from the device were delivered since 2011. During follow up a iatrogenic hyperthyroidism amiodarone induced was effectively medically treated but required amiodarone with-holding. A percutaneous ablation procedure was proposed and accepted by the patient in the beginning of 2017. Considering the peculiar anatomy for a retrograde arterial approach, we proposed a magnetic robotic guided navigation approach with trans-septal access (See Figure Panel 1). At the beginning of the procedure the patient was in sinus rhythm (See Figure Panel 2) at 88 bpm. During programmed ventricular stimulation a sustained well tolerated monomorphic VT was induced, the arrhythmia was then stopped by burst pacing. A bipolar voltage mapping was performed showing a wide area of scar located in all segments of the infero-lateral wall (See Figure Panel 3). The induced VT was used as a template and a serie of pacemapping points were collected with the aim of detecting the entrance and the exit channel of the isthmus. Very good correspondence points with fast conduction properties were found in an area of healthy myocardial tissue directly in front of the scar; while a very bad correspondence points series was found exactly in contact with the first one, in the dense scar area, and was characterized by very low conduction velocities. These two areas were surrounded by an intermediate correspondence zone (See Figure 1, Panel 4, section A, B, C, D). We then re-induced the VT to perform an activation map that confirmed the isthmus localization and its role in VT maintenance, in particular the area with bad correspondence of pacemapping points, slower conduction velocities and totally localized inside the dense scar was the entry channel of the isthmus. The area with higher conduction velocities, good correspondence and localized in the healthy tissue was the exit channel of the critical isthmus. In the middle of these two area we could find the critical isthmus (See Figure Panel 5) Delivery of radiofrequency on this zone during VT restored sinus rhythm. The induction protocol was repeated failing to induce any sustained arrhythmia. No periprocedural complication occurred. Fluoroscopy time was limited to perform the trans-septal access. The patients was then discharged and to current follow up no arrhythmia recurrences were recorded at the telemetry of the ICD device. Conclusion: The present case report underlines the primary role exerted by the pacemapping approach to detect the critical isthmus of VT and we also speculate about the safety and reliability of a robotic magnetic guided navigation system to approach this kind of procedures. (Figure Presented).