Mapping and ablation
This prospective observational study included consecutive patients undergoing VA ablation guided by CARTO PRIME and the novel AMA at our center between February 2020 and June 2021. All patients signed a written informed consent. Prior to ablation, all patients received transthoracic echocardiography to rule out LV-thrombus formation. Transesophageal echocardiography (TEE) was performed in patients with elevated risk for left atrial (LA) or LA appendage (LAA) thrombus. The ICD/CRT devices were interrogated prior to ablation and VA therapies have been deactivation during the ablation procedure.
Catheter ablation was performed under general anesthesia. Two diagnostic catheters were introduced via the femoral veins and positioned in the coronary sinus (6 Fr, Webster®, Biosense Webster, Inc., Diamond Bar, CA, USA) and the right ventricle (RV) (5 Fr, Webster®, Biosense Webster, Inc., Diamond Bar, CA, USA). For an antegrade approach, venous access was obtained via the right femoral vein. A single transseptal puncture was performed under fluoroscopic guidance using a modified Brockenbrough technique and an 8.5-Fr transseptal sheath (ViziGo, large curve, Biosense Webster, Inc., Diamond Bar, CA, USA) and an additional retrograde access to the LV was obtained via the right femoral artery.
Endo- and epicardial mapping was performed using a 3D-mapping system (CARTO PRIME®, Biosense Webster, Inc., Diamond Bar, CA, USA) and a multipolar mapping catheter (PentaRay®, Biosense Webster, Inc., Diamond Bar, CA, USA). Ultra-high density electroanatomical reconstruction of the RV and LV was conducted aiming for > 1000 mapping points. A low-voltage area suggestive for endocardial myocardial scar was defined as endocardial bipolar voltage of 0.1–1.5 mV. A low-voltage area suggestive for epicardial myocardial scar was defined as epicardial bipolar voltage of 0.1–1.5 mV and endocardial unipolar voltage of 5–8 mV. Tissue Proximity Indication applied in all cases of LV and RV mapping.
The amount of LA low voltage (from uni- and bipolar mapping) was measured using the area measurement tool. For the epicardial approach, access was gained via a subxiphoid anterior puncture using a micropuncture needle followed by the introduction of a guidewire. Afterwards a steerable sheath (Agilis Epi, St. Jude Medical) was inserted into the epicardial space. Prior to ablation, the course of the left-sided phrenic nerve was constituted using pacemapping.
Following bipolar voltage mapping, the AMA algorithm was utilized to reveal zones of decelerated conduction velocity vectors (CVV) based on manual thresholding enabling the dynamic view function. The novel AMA has been previously described in detail [
1‐
4]. The threshold caliper for conduction velocity vector (Coherent®—visualization setup) was adjusted until the first slow conduction velocity vector (the bold arrows) appeared inside the electroanatomical map. Afterwards, the information from AMA was superimposed onto the endocardial reconstructions and compared with the presence of abnormal uni- and bipolar voltage suggestive for ventricular scar tissue or fibrosis. In case that slow CVV zones were located in a close relationship to areas suggestive for scarred myocardial tissue, we classified this as a match.
Radiofrequency current (RFC) was delivered in the power-controlled mode with a maximum power of 40 W, a maximum temperature of 43 °C, and a flow rate of 30 mL/min using an open-irrigated tip-ablation catheter (ThermoCool SmartTouch SF®, Biosense Webster, Inc., Diamond Bar, CA, USA). LV and RV ultra-high-density mapping was conducted as described above followed by programmed ventricular stimulation when the patient was not in sustained VT at the beginning of the procedure. When VA was sustained and hemodynamically tolerated, activation map was conducted, and critical isthmus sites were identified using entrainment mapping. If no sustained VA was inducible, comprehensive substrate ablation was performed targeting all low-voltage areas, as well as abnormal electrograms such as local abnormal ventricular activity (LAVA) and late potentials (LP). After ablation, pericardial effusion was ruled out and patients were monitored at our intensive care unit (ICU) for more than 24 h. The ICD/CRT device was reactivated before hospital discharge.