Case Report:
A 50-year-old male with LMNA cardiomyopathy and NYHA class III and left ventricular ejection fraction (LVEF) of 35% was admitted with electrical storm. His initial presentation was atrial fibrillation in 2007, left bundle branch block and cardia arrest in 2017, following which cardiomyopathy diagnosed and extensive work up including genetic testing revealed that he was haplo-insufficient for LMNA due to a microdeletion of chromosome 1. 7 He underwent placement of a secondary prevention defibrillator/cardiac re-synchronization therapy (CRT-D) following cardiac arrest and recovery. Despite optimal medical therapy and resynchronization therapy, his LVEF continued to decline, and he developed frequent episodes of ventricular tachycardia (VT). One month before admission, he underwent catheter ablation with substrate modification at the peri-aortic area of the left ventricle but continued to have uncontrolled arrhythmia. At that time, Computed tomography of the heart did not suggest myocardial replacement fibrosis, but the images were limited by intracardiac device artifact.
After catheter ablation, arrhythmia was managed with Amiodarone 400mg a day and Metoprolol 200mg a day but continued to have high burden of self-limited but symptomatic slow VT. Three weeks later, he suffered frequent prolonged episodes of slow VT with CL of 460ms below the rate of detection in the device’s slowest therapy zone (420ms). Beside palpitations, he was hemodynamically stable and presented to outpatient clinic. After immediate transferred to the emergency room, a successful manual anti-tachycardia pacing (ATP) converted his rhythm to sinus rhythm. He was referred to the electrophysiology laboratory for mapping and CA of electrical storm.
Procedure description:
The procedure was performed under conscious sedation then changed to general anesthesia during epicardial mapping and ablation. Two catheters were used for the purpose of mapping and ablating: multipolar mapping catheter (PentaRay®) and 3.5-mm tip irrigated catheter (Thermocool SMART-TOUCH; Biosense Webster). Endocardial/epicardial voltage maps were created by using a three-dimensional (3D) electroanatomic mapping system (CARTO, Biosense Webster). Bipolar electrogram amplitude of <1.5 mV was defined as low- voltage zone consistent with scar. Dense scar was defined as voltage ≤0.5 mV. Images integration with the preprocedural contrast-enhanced computer tomography scans and the 3D mapping system images were used to identify and reconstruct LV and coronary arteries anatomy. Catheter ablation sites were chosen based on entrainment, activation, and substrate mapping.
Initially, trans-septal access was utilized to map the left ventricle endocardium then changed to retrograde arterial access for further reach of targeted substrates. During endocardial mapping, extensive low-voltage substrates were noted at the peri-aortic area with extension to the sub-aortic/mitral continuity and the peri-mitral valve areas, with normal endocardial bipolar voltage in the remainder.
Programmed ventricular stimulation from the RV catheter with stimulation at 600/320 millisecond (ms) induced the clinical VT. We were able to induce four VT morphologies during the procedure (Figure 1). Entrainment from the endocardial space at the periaortic area showed concealment and short stimulation to QRS indicating VT exit site. Despite successful concealed entrainment at the peri-aortic area, complete tachycardia CL mapping was not possible during endocardial approach (Figure 2). Earliest sites of activation during clinical VT were noted to be a wide area at the anteroseptal wall. See figure 3. Radiofrequency (RF) ablation lesions were performed at this site.  Extensive RF ablation was performed by targeting all areas of fractionated, late potentials and long stimulus to QRS sites.   In addition, we ablated at the septal aspect of the right ventricle outflow tract (RVOT) opposing the left ventricle outflow tract (LVOT) to bracket the targeted area.
Simultaneous endocardial unipolar voltage mapping indicated possible extensive epicardial scar. See figure 2. After anticoagulation reversal, epicardial access was obtained using the Needle-in-needle technique.8 A Decapolar catheter (Webster®Decanav) was inserted through a long 8 French sheath to the epicardial space and used for mapping and pacing purposes. Low voltage areas were noted anterior to the LVOT with anterior extension toward the apex and at the basal portion of the lateral wall (Figure 2). Ventricular sites with fractionation and late potentials were marked during voltage mapping at the epicardium. Pace mapping was performed to evaluate the best match with the clinical VT.  Coronary artery territory and areas of phrenic capture were marked.  Clinical VT was induced by pacing from the RV catheter. Despite extensive epicardial activation mapping during VT, the full CL was not completely mapped. (Figure 3). Best entrainment from the epicardium was at the LV anterior wall with concealed fusion and long post-pacing interval indicating bystander site. Multiple RF lesions were delivered at the epicardial space that demonstrated good entrainment properties, pace mapping closer to the morphology of clinical VT, earliest pre-systolic site or sites with the long stem to QRS period.  During ablation we utilized RF power of 50 watts, and half normal saline to produce deeper lesions at presumed intra-mural substrate in locations deemed to be safe and > 10mm apart from the marked coronary arteries. 9 Thereafter, attempts to re-induce clinical VT have failed and the target VT was rendered non-inducible. The patient was hemodynamically stable after the procedure and was transferred back to the cardiology floor. After 48 hours of observation, without significant arrhythmia, he was discharged home on Amiodarone. He was hospitalized one month later with frequent ATP and required quinidine treatment which was effective. Both Amiodarone and Quinidine were slowly weaned off later because of side effects. Six months since ablation, he has been free of any significant ventricular arrhythmia or ICD shocks. Because of worsening cardiac function, he is currently undergoing thorough evaluation for cardiac transplantation.