Background
The recent introduction of ablation index (AI) in combination with the CLOSE protocol to guide atrial fibrillation (AF) ablation was an important step towards standardized and efficacious procedures. While the CLOSE protocol stipulates a maximum tolerable interlesion distance (ILDmax) of 6 mm to ensure contiguous lesions, an optimum target ILD, which is not to be confused with ILDmax, has not been defined to date. Of note, in the trial that validated the CLOSE protocol, an interlesion distance well below 6 mm was targeted, as reflected by the median ILD of 4.1 mm.
The recent introduction of ablation index (AI) in combination with the CLOSE protocol to guide atrial fibrillation (AF) ablation was an important step towards standardized and efficacious procedures. While the CLOSE protocol stipulates a maximum tolerable interlesion distance (ILDmax) of 6 mm to ensure contiguous lesions, an optimum target ILD, which is not to be confused with ILDmax, has not been defined to date. Of note, in the trial that validated the CLOSE protocol, an interlesion distance well below 6 mm was targeted, as reflected by the median ILD of 4.1 mm.
Purpose
This randomised study aimed to define the optimum ILD to be targeted in AI-guided AF ablation.
This randomised study aimed to define the optimum ILD to be targeted in AI-guided AF ablation.
Methods
Consecutive patients scheduled for first-time pulmonary vein (PV) isolation (PVI) were randomized to ablation protocols with a target ILD of 5-6 mm vs. 3-4 mm with the primary endpoint of first-pass PVI (German clinical trials register: DRKS00017011):
1. „5-6 mm"-protocol: Target ILD 5.0 – 6.0 mm; target AI: anterior wall ≥550, posterior wall ≥400
2. „3-4 mm"-protocol: Target ILD: 3.0 – 4.0 mm; target AI: anterior wall ≥500, posterior wall ≥375
In line with the CLOSE protocol, the maximally tolerated interlesion distance was 6.0 mm in both protocols.
AI-guided ablation was performed using a Thermocool SmartTouch SF catheter with 30-35 W and the following stability criteria: 3 mm max. distance change, 8 s minimum time, 50% force over time, minimum force 6 g. In the absence of first-pass PVI (i.e. no isolation upon completion of the encirclement of ipsilateral PVs), PVI was accomplished at the investigator’s discretion.
Consecutive patients scheduled for first-time pulmonary vein (PV) isolation (PVI) were randomized to ablation protocols with a target ILD of 5-6 mm vs. 3-4 mm with the primary endpoint of first-pass PVI (German clinical trials register: DRKS00017011):
1. „5-6 mm"-protocol: Target ILD 5.0 – 6.0 mm; target AI: anterior wall ≥550, posterior wall ≥400
2. „3-4 mm"-protocol: Target ILD: 3.0 – 4.0 mm; target AI: anterior wall ≥500, posterior wall ≥375
In line with the CLOSE protocol, the maximally tolerated interlesion distance was 6.0 mm in both protocols.
AI-guided ablation was performed using a Thermocool SmartTouch SF catheter with 30-35 W and the following stability criteria: 3 mm max. distance change, 8 s minimum time, 50% force over time, minimum force 6 g. In the absence of first-pass PVI (i.e. no isolation upon completion of the encirclement of ipsilateral PVs), PVI was accomplished at the investigator’s discretion.
Results
To date 40 consecutive patients have been randomised (19 paroxysmal AF, 21 persistent AF) and 72 ipsilateral PV pairs were encircled according to the study protocol. The majority of patients was ablated under conscious sedation (95%) with a procedure time of 158 ± 28 min. and a fluoroscopy time of 4.5 ± 1.9 min.. Baseline characteristics were evenly distributed among treatment groups. The primary endpoint of first-pass PVI was accomplished in 11 out of 36 PV pairs (31 %) in the „5-6 mm"-group and 34 out of 36 PV pairs (95 %) in the „3-4 mm"-group (Fisher‘s exact test: 0,0000000165) (Fig. 1A). All PVs not isolated at first pass could be isolated with additional ablations. Median ILD was 5.2 mm in the „5-6 mm"-group and 3.5 mm in the „3-4 mm"-group (Fig. 1B). The higher interlesion distance in the „5-6 mm“-group translated into a reduced number of RF lesions required to complete the circle (23 versus 32). According to the reduced ablation index targets in the „3-4 mm“-protocol, median ablation index was lower in the „3-4 mm“-group than in the „5-6 mm“-group (418 versus 450). No complications occured in any of the groups.
To date 40 consecutive patients have been randomised (19 paroxysmal AF, 21 persistent AF) and 72 ipsilateral PV pairs were encircled according to the study protocol. The majority of patients was ablated under conscious sedation (95%) with a procedure time of 158 ± 28 min. and a fluoroscopy time of 4.5 ± 1.9 min.. Baseline characteristics were evenly distributed among treatment groups. The primary endpoint of first-pass PVI was accomplished in 11 out of 36 PV pairs (31 %) in the „5-6 mm"-group and 34 out of 36 PV pairs (95 %) in the „3-4 mm"-group (Fisher‘s exact test: 0,0000000165) (Fig. 1A). All PVs not isolated at first pass could be isolated with additional ablations. Median ILD was 5.2 mm in the „5-6 mm"-group and 3.5 mm in the „3-4 mm"-group (Fig. 1B). The higher interlesion distance in the „5-6 mm“-group translated into a reduced number of RF lesions required to complete the circle (23 versus 32). According to the reduced ablation index targets in the „3-4 mm“-protocol, median ablation index was lower in the „3-4 mm“-group than in the „5-6 mm“-group (418 versus 450). No complications occured in any of the groups.
Conclusions
Here we show that in AI-guided AF ablation, targeting interlesion distances of 3.0 to 4.0 mm is superior to targeting interlesion distances of 5.0 to 6.0 mm with respect to first pass PVI. Moreover, the lower target ILD appears to allow for less extensive ablation at each given point, which may in turn translate into a further reduction of procedural risk. The results underline that target ILD is to be discriminated from ILDmax. While sporadic outliers with an interlesion distance of maximally 6 mm may be tolerable without leading to functional gaps, as reflected by studies using the CLOSE protocol, the median ILD to be targeted should be much lower (around 3-4 mm) in order to create contiguous lesions.
Here we show that in AI-guided AF ablation, targeting interlesion distances of 3.0 to 4.0 mm is superior to targeting interlesion distances of 5.0 to 6.0 mm with respect to first pass PVI. Moreover, the lower target ILD appears to allow for less extensive ablation at each given point, which may in turn translate into a further reduction of procedural risk. The results underline that target ILD is to be discriminated from ILDmax. While sporadic outliers with an interlesion distance of maximally 6 mm may be tolerable without leading to functional gaps, as reflected by studies using the CLOSE protocol, the median ILD to be targeted should be much lower (around 3-4 mm) in order to create contiguous lesions.
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