Repeat Mapping and Ablation Strategy
All repeat ablations for patients in this study were performed using RF energy. Femoral site access was obtained, and intravenous heparin was administered to maintain activated clotting times > 350 s. After performing a double transseptal puncture, a Lasso or PentaRay mapping catheter (Biosense Webster, Diamond Bar, California) was positioned in the left atrium. An electroanatomic map of the left atrium was obtained using the CARTO system (Biosense Webster) and superimposed on pre-acquired cardiac CT image.
AFL Cohort : In all AFL patients, simultaneous voltage and activation mapping was performed in patients presenting in AFL. Patients presenting in sinus rhythm underwent a flutter induction protocol consisting of both atrial burst pacing and atrial programmed stimulation until flutter was successfully initiated. Activation mapping of AFL was supplemented with entrainment mapping from putative critical isthmuses to further categorize flutter circuits. Based on the location of critical isthmus identification, flutters were classified as 1) peri-mitral, 2) roof-dependent, and 3) other (including multi-loop circuits, idiosyncratic flutters involving ablation lesion sets, and transitioning flutters with more than one stable circuit). All flutter forms occurring spontaneously or resulting from radiofrequency (RF) delivery during the first repeat ablation were documented. Following conclusion of targeted AFL ablation, PV isolation was assessed and addressed as needed (below).
AFL ablation was performed targeting the critical isthmus with a transecting lesion anchored to either preexisting anatomical structures (i.e., mitral valve annulus) or with iatrogenic scars (e.g., left PV ostia after pulmonary vein isolation (PVI)), generating linear ablation lines. Conduction block across the ablation line was verified by 3D electroanatomical mapping with a multipolar mapping catheter in normal sinus rhythm (NSR). RF ablation was performed until (a) the tachycardia terminated or (b) converted into a second form, identified by a significant change in CS activation or in combination with alteration of surface electrocardiogram (ECG) morphology. Termination of the tachycardia was considered as ablation success if it occurred directly during RF delivery with or without prior prolongation of tachycardia cycle length (TCL) and in the absence of a premature atrial beat (≤90% TCL). Reinduction protocols were performed at the discretion of the operator.
AF Cohort : PVs were assessed for reconnection in all patients, and re-isolation was performed for those showing the electrical reconnection. A 4-mm, open-irrigated, contact force-sensing RF catheter (ThermoCool SmartTouch, Biosense Webster) was used, and re-isolation of the PVs was performed using a real-time automated display of RF application points (Visitag, Biosense Webster) with predefined catheter stability settings. Starting energy delivery parameters were 25 to 35 watts on the posterior LA wall and 35 to 45 watts at other sites. The target contact force was between 5 and 20 g at all sites. Esophageal temperature was monitored, and the RF delivery paused if the esophageal temperature increased by 0.5°C. In patients with recurrent AF, but with durable isolation of the PVs, additional substrate modification was performed in accordance with consensus guidelines.1Additional ablation consisted of lesions involving the roof, floor, posterior wall, mitral isthmus, cavotricuspid isthmus (CTI), superior vena cava (SVC), coronary sinus (CS), and others, including the complex fractionated atrial electrograms (CFAE), were performed at the discretion of the operator. Acute procedural success was defined as electrical isolation of PVs, confirmed by entrance block to individual PVs, and a bidirectional block line when linear ablations were performed.
In the AF cohort, repeat ablation strategies were classified into 1) PVI only, 2) PVI plus additional ablation, and 3) additional ablation only.