Effect of a Bigger Cryoballoon on the Total Antral Lesion Size: Evaluation of POLARx FIT (BETTER-FIT)

The investigators will prospectively evaluate the extent of antral lesion created by the 31 mm balloon size of a novel cryoballoon catheter (POLARx FIT). In 20 patients with paroxysmal atrial fibrillation, the investigators will perform pre- and post-ablation high-definition 3D maps to quantify the extent of lesion created by the 31 mm POLARx FIT cryoballoon.

Rationale: The next generation POLARx cryoablation balloon (CB) catheter will have the option of to deliver cryotherapy with the current balloon size of 28 mm or a new, larger 31 mm size by changing the inner balloon pressure (POLARx FIT, Boston Scientific). Currently, there is no data on the extension of left atrial (LA) lesion formation with the 31 mm balloon size of the POLARx FIT cryoablation balloon catheter. The hypothesis is that a larger CB size results in a wide antral circumferential lesion. Objective: The primary objective is to evaluate the antral lesion size using ultrahigh-density (UHDx) mapping pre- and post-cryoablation with the 31 mm balloon size CB. Secondary objectives are the proportion of pulmonary veins (PVs) where a 31 mm CB could be positioned to achieve a grade 4 occlusion and the single shot success rate with the 31 mm balloon size CB. Study design: Single-center, single-arm, prospective study with pre- and post-PVI UHDx mapping. Study population: Twenty adult patients with paroxysmal AF who are scheduled to undergo pulmonary vein isolation (PVI) with a CB. Intervention: Patients will undergo pre- and post-ablation UHDx mapping (Orion catheter and Rhythmia 3D-mapping system, Boston Scientific) during the index procedure. Main study parameters/endpoints: The primary endpoint is the extent of the antral lesion size. Secondary endpoints are the proportion of PVs with grade 4 occlusion with the 31 mm balloon size CB, the single shot success rate of the 31 mm balloon size CB, difference in rate of achieving grade 4 occlusion in comparison to the standard (28 mm) size. Nature and extent of the burden and risks associated with participation, benefit, and group relatedness: A UHDx mapping will be acquired before and after complete PVI. The procedures will be performed under deep sedation, which is standard practice for CB procedures in our institution. The risk of additional mapping is limited. LA mapping is a standard diagnostic method for patients undergoing PVI with radiofrequency ("standard-of-care"). In the current study, UHDx mapping will now be used in patients undergoing PVI with CB. The most important complication of additional intracardiac mapping is cardiac tamponade, but this risk is low (<0.5%).

This study will have only a single arm. Patients will undergo pulmonary vein isolation using the 31 mm balloon size of POLARx FIT. High-definition 3D maps will be constructed before and after cryoablation to assess the antral lesion size.

In the pre- and post-ablation UHDx-map, bipolar voltage will be assess using a scar-cutoff <0.3 mV. The following spatial measurements will be made: (1) the surface areas of the posterior left- and right-sided PV antral isolation, (2) the LAPW surface area with voltage pre- and post-ablation, and (3) the distance between the ipsilateral, antral levels of isolation at superior, middle and inferior latitudes of the LAPW. The surface area of each PV ostium and the area of the circular antral ablation lesion was measured around each ipsilateral PV pair. Low-voltage areas will be quantified using a bipolar voltage <0.3 mV. The scale on the maps will be set from 0.1 to 0.3 mV. The purple region represents unablated tissue with a bipolar voltage >0.3 mV. The scar-border zone will be represented by bipolar voltages between 0.1-0.3 mV. The PV ostium is located by the steep angle between the LA wall and the tubular aspect of the PV.

In this study the investigators will evaluate the rate of grade 4 occlusion (i.e., contrast stasis) of the 28 mm and 31 mm balloon size POLARx FIT cryoablation catheter. Therefore, cine acquisitions of contrast vein occlusions will be analyzed. Occlusion will be categorized by using a previously described scale (1-rapid outflow of contrast medium from the PV to 4-complete contrast retention with no observable leak). Two experienced observers blinded to vein outcome will assess recorded venograms.

PV isolation will be determined using conventional criteria: entry- and exit-block as assessed with the circular mapping catheter (POLARMAP).

Inclusion Criteria: History of symptomatic paroxysmal AF Subjects who are indicated for a PVI according to the 2020 ESC guidelines for the diagnosis and management of AF Subjects who are willing and capable of providing informed consent Subjects who are willing and capable of participating in all testing associated with this clinical investigation Subjects whose age is 18 years or above Exclusion Criteria: Any known contraindication to an AF ablation or anticoagulation History of previous left atrial ablation or surgical treatment of AF, atrial flutter, or atrial tachycardia AF secondary to electrolyte imbalance, thyroid disease, or any other reversible or non-cardiac cause Significant structural heart disease as evidenced by: Left ventricular ejection fraction <45% based on most recent transthoracic echocardiogram (TTE) performed <6 months prior to enrollment LA diameter >55 mm based on most recent TTE performed <6 months prior to enrollment Previous cardiac surgery Previous cardiac valvular surgical or percutaneous procedure Interatrial baffle, closure device, patch, or occluder Unstable angina or ongoing myocardial ischemia Moderate or severe valvular heart disease on most recent TTE performed <6 months prior to enrolment Congenital heart disease Left atrial thrombus History of blood clotting or bleeding disease Stroke or transient ischemic attack <3 months prior to enrollment Active systemic infection Common ostium PV >24 mm defined by CT-scan Pregnant, lactating, or women of childbearing potential who are, or plan to become, pregnant during the time of the study Subjects who are currently enrolled in another investigational study or registry that would directly interfere with the current study