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.