The role of a difference between target and actual ablation index values for first-pass point-by-point pulmonary vein isolation: results from a multicenter prospective registry
Authors: Gasimova NZ , Kropotkin EB , Ivanitsky EA , Kolunin GV , Nechepurenko AA , Shavshin DA , Antolic B , Kovalev KS , Mikhaylov EN , Lebedev DS 
Published: May 2021

Abstract

Funding Acknowledgements
Type of funding sources: Other. Main funding source(s): Ministry of Science and Higher Education grant (Russian Federation President Grant)
Background/Introduction. Pulmonary vein electrical isolation (PVI) is a cornerstone of atrial fibrillation (AF) ablation. The Ablation Index (AI) aims to improve the efficacy and safety of radiofrequency (RF) PVI. First-pass isolation (FPI) is an indicator of PVI acute success. Target AI is being calculated for every operator as a mean value (usually, differently for anterior and posterior left atrial (LA) segments) following several "ideal" first-pass PVI procedures. However, adherence to target values, as well as its clinical importance, are unknown.
Purpose. The aim of the present study was to evaluate the difference between the target and actual AI in the real practice.
Methods. This work represents data from the Prospective Multicenter AF Ablation Registry. Data were collected using a web-based system. PVI procedures were performed according to the local practice, and RF ablation settings depended on operators’ preferences. Between January 2019 and December 2020, a total of 446 patients were enrolled from 7 centers, 407 of them underwent first-time AF ablation and were included into the analysis (mean age 61 ± 9 years old; 226 (55%) males; 313 (76%) with paroxysmal AF). FPI was determined as PVI achieved after circular ablation around PVs without additional applications plus persistence of bidirectional block over a 20-minute waiting period. Therefore, patients were divided in two groups: Group 1 (FPI, n = 242) and Group 2 (non-FPI, n = 165).
Results. There was a significant difference between target (the mean target AI for the anterior LA segments was 438 ± 58 and 390 ± 27 for the posterior segments) and actually achieved mean AI (406 ± 33 for anterior segments and 389 ± 34 for posterior segments) with a greater difference for anterior segments (Δ 26 (95% CI [19; 32], p = 0,0001) than for posterior (Δ 4 (95% CI [0,2; 8], p = 0,042). The number of patients with a mean actual AI lower than a target value on the anterior and posterior LA walls was 219 (54%) and 171 (42%), respectively.
In the FPI group higher mean values of target AI were present (FPI 444 ± 52 for anterior and 393 ± 27 for posterior LA segments vs non-FPI 432 ± 51 (p = 0,04) and 387 ± 23 (p = 0,01), respectively). The FPI group was characterized by higher mean actual AIs on anterior segments (FPI 410 ± 36 vs non-FPI 399 ± 25, p = 0,0001). There was no difference between groups in actual AI on the posterior wall (391 ± 27 vs 386 ± 41, p = 0,1).
The non-FPI group was characterized by a higher proportion of subjects with hypertension (87% vs 69%, p = 0,0001) and a lower number of subjects with central obesity (body mass index≥30 in 48% vs 57%, p = 0,04).
Conclusion(s). According to our prospective multicenter data, target AI is not achieved in a significant proportion of patients during PVI. This is associated with acute PV electrical reconduction and the necessity in additional ablations. FPI can be achieved more frequently when a higher mean AI value is achieved.