The addition of strict stability criteria does not reduce recurrences after atrial fibrillation ablation using ablation index and can impact on procedure efficiency

Background Ablation Index (AI) is a proprietary lesion quality marker that combines power, contact force and time. Recent studies showed that radiofrequency (RF) pulmonary vein isolation (PVI) using AI can deliver high arrhythmia-free survival rates at mid-term follow-up in patients with paroxysmal atrial fibrillation. Purpose The aim of this multicenter study was to compare the outcome of three different strategies of PVI using AI (group 1 and 2) or VISITAG module with average force and strict criteria of stability as target parameters (group 3). Methods We enrolled 132 consecutive naive patients (97 males, mean age 61,03±9,42) affected by paroxysmal atrial fibrillation who underwent PVI at two high volume centres between January 2017 and February 2019. AI target was set at ≥380 at the posterior wall and ≥500 at the anterior wall. A strict stability criteria (VISITALY criteria: 3 mm for a time of 15 s and a FOT >5 g for 60% of the time) was set for Group 1 procedures (65 patients), whereas Group 2 procedures (67 patients) were carried out with standard stability criteria (VISTAX criteria: 3 mm for a time of 3 s and FOT >3 g for 25% of the time). We then compared those strategies with a historical cohort of 72 patients (40 males, mean age 60,74±8,53) treated at our centres with RF PVI using the VISITAG module with average force and strict stability criteria as target parameters. An interlesion distance ≤6 mm was a target parameter for all procedures. Recurrence was defined as any AF, atrial tachycardia (AT) or atrial flutter (AFL) during the 12 months after ablation, excluding a blanking period of 90 days. Results There were no significant differences in terms of age (Group 1 59,2±8,97; Group 2 62,81±9,58; Group 3 60,74±8,53 years) and left atrial area (Group 1 24,16±20,46; Group 2 22,55±12,32; Group 3 20,74±3,84 cm2). Group 1 showed a slightly higher number of males (Group 1 78,46%; Group 2 68,66%; Group 3 55,56%; p=0,004). Procedure duration was significantly lower in Group 2 compared to Groups 1 and 3 (176,67±50,88 vs 224,05±47,21 min, p<0,001; 176,67±50,88 vs 203,96±52,38 min p=0,02). Fluoroscopy time was significantly higher in Group 1 compared with Group 2 (11,85±4,38 vs 10,39±6,4 min; p=0,014). There was a slight trend to have a higher freedom from AF/AT/AFL at 12 months in group 2 compared to the others (Group 1 86,15% vs Group 2 91,04% vs Group 3 84,72%; p=0,2). Conclusion A strategy of PVI using AI with standard stability criteria performed the best in terms of procedure efficiency, with a significant benefit in terms of procedure duration, delivering a 12 months arrhythmia-free survival rate comparable with other strategies. Combination of AI with strict stability criteria provided no benefit, at a cost of a higher fluoroscopy time and longer procedure duration. Funding Acknowledgement Type of funding source: None

Strict stability with respect to initial time difference for Caputo fractional differential equations by Lyapunov functions

The strict stability properties are generalized to nonlinear Caputo fractional differential equations in the case when both initial points and initial times are changeable. Using Lyapunov functions, some criteria for strict stability, eventually strict stability and strict practical stability are obtained. A brief overview of different types of derivatives in the literature related to the application of Lyapunov functions to Caputo fractional equations are given, and their advantages and disadvantages are discussed with several examples. The Caputo fractional Dini derivative with respect to to initial time difference is used to obtain some sufficient conditions.

Caputo fractional differential equations with non-instantaneous impulses and strict stability by Lyapunov functions

In this paper the statement of initial value problems for fractional differential equations with noninstantaneous impulses is given. These equations are adequate models for phenomena that are characterized by impulsive actions starting at arbitrary fixed points and remaining active on finite time intervals. Strict stability properties of fractional differential equations with non-instantaneous impulses by the Lyapunov approach is studied. An appropriate definition (based on the Caputo fractional Dini derivative of a function) for the derivative of Lyapunov functions among the Caputo fractional differential equations with non-instantaneous impulses is presented. Comparison results using this definition and scalar fractional differential equations with non-instantaneous impulses are presented and sufficient conditions for strict stability and uniform strict stability are given. Examples are given to illustrate the theory.