Direct pressure monitoring accurately predicts pulmonary vein occlusion during cryoballoon ablation

Incidence of cryoballoon expansion dislodgement during pulmonary vein isolation-An underappreciated frequent cause of incomplete isolation

BACKGROUND

Cryoballoon ablation for atrial fibrillation (AF) requires adequate contact between the pulmonary vein (PV) antrum and cryoballoon. The surge of intraballoon pressure during the initial phase of ablation may change the balloon's shape and compliance, resulting in balloon dislodgement and loss of PV occlusion. Without continuous monitoring, this phenomenon is often undetected but can be associated with incomplete PV isolation (PVI).

METHODS

Primary cryoablation of AF was performed in 15 patients. PV occlusion status pre- and post-freezing were analyzed with intracardiac echocardiography (ICE) and dielectric imaging-based occlusion tool (DIOT) to calculate the incidence of expansion dislodgement of cryoballoon.

RESULTS

A total of 105 cryoablation applications were performed on 57 veins, including three common ostiums of left pulmonary veins. In the evaluation of PV occlusion, both modalities reported consistent results in 86.7% of the assessments. Despite complete PV occlusion before ablation, peri-balloon leak after initiation of freezing was detected by ICE in 5/22 (22.7%) applications and by DIOT in 8/25 (32%) applications.

CONCLUSION

Incidence of expansion dislodgement of the cryoballoon was detected in one-fourth to one-third of cryoablation applications depending on the imaging modality used, which was clinically frequent and significant.

Accuracy of Delta Capnography for the Prediction of Pulmonary Vein Occlusion During Cryoablation for Atrial Fibrillation

The purpose of this study was to quantify the relationship between a drop in end-tidal carbon dioxide (etCO₂) and occlusion of pulmonary veins (PVs) to find a delta etCO₂ (ΔetCO₂) able to predict occlusion during PV isolation (PVI) by cryoballoon. We designed a prospective registry. Paroxysmal atrial fibrillation patients who underwent cryoballoon PVI were included. Capnography was performed. Occlusion was tested by injection. A comparison between ΔetCO₂ and occlusion was performed. Eighteen subjects (138 injections) were included. A drop of >3.5 mmHg predicted occlusion of the PV (sensitivity, 80%; specificity, 86.7%). A ΔetCO₂ of ≥3.5 mmHg during inflation of the cryoballoon in each PV directly correlates with PV balloon occlusion.

Cryoballoon ablation for atrial fibrillation without the use of a contrast medium: a combination of the intracardiac echocardiography and pressure wave monitoring guided approach

In cryoballoon ablation (CBA), a contrast medium is commonly used to confirm balloon occlusion of the pulmonary veins (PVs). However, a contrast medium cannot always be used in patients with renal dysfunction and allergy. The present study aimed to assess the efficacy and safety of CBA without the use of a contrast medium. We retrospectively examined consecutive patients with paroxysmal atrial fibrillation (PAF) who underwent first-time CBA. We compared the procedural results and outcomes in patients for whom a contrast medium was used (contrast group) and those from whom a contrast medium was not used (non-contrast group). In the non-contrast group, we used saline injection on the intracardiac echocardiography and pressure wave monitoring for PV occlusion. Fifty patients (200 PVs) and 22 patients (88 PVs) underwent CBA with and without a contrast medium, respectively. The success rate of PV isolation with CBA alone was 93% and 90% in the non-contrast and contrast groups, respectively (p = 0.40). The fluoroscopy time and nadir temperature were significantly lower in the non-contrast group as compared to that in the contrast group. The recurrence rate 1 year after ablation did not differ between the two groups (18% vs. 18%, p > 0.99). Furthermore, the number of reconnected PVs in patients with recurrence was significantly lower in the non-contrast group than in the contrast group (6% vs. 36%, p = 0.017). In conclusion, CBA using the intracardiac echocardiography and pressure monitoring approach without the use of a contrast medium was safe and efficient.

Acute Safety and Efficacy of Fluoroless Cryoballoon Ablation for Atrial Fibrillation

Pulmonary vein isolation (PVI) is widely used for the ablation of atrial fibrillation, with prior reports suggesting good efficacy. Due to the widespread use of three-dimensional electroanatomic mapping systems and advances in intracardiac echocardiography, fluoroless ablation has been made possible. Fluoroless ablation with a cryoballoon (CB), however, has not been widely performed because of the need to prove occlusion of the vein with contrast dye and fluoroscopy. The objective of this study is to show that CB ablation can be performed safely and effectively without fluoroscopy. A dual-center, case–control study was performed of patients undergoing CB PVI with a fluoroless approach and a control group with traditional fluoroscopic techniques. The absence of color-flow Doppler signals around the periphery of the CB on intracardiac echocardiography and an increase in mean pressure by 5 mmHg, loss of the A-wave, and an increase in the V-wave as measured with continuous-wave pressure monitoring were adopted as indicators of vein occlusion in the absence of fluoroscopy. Temperature at 30 seconds, minimum temperature, time to isolation, procedure length, and complications were evaluated. During the study period of November 15, 2018 to November 15, 2019, a total of 100 patients underwent CB PVI at the participating centers. A total of 50 patients were enrolled in the fluoroless arm [35 men (70%), mean age: 64.9 ± 12 years, mean left atrium size: 44.2 ± 16 mL/m², left ventricular ejection fraction: 61% ± 5%], while 50 patients were enrolled in the control arm with similar characteristics. Four hundred forty-one 441 PVs were evaluated in the study cohort compared to 339 PVs in the control arm. When comparing fluoroless and traditional techniques, the mean temperature at 30 seconds was −31.7°C ± 6°C versus −32.8°C ± 5°C (p = 0.037), the minimum temperature was −47.4°C ± 6°C versus −47.7°C ± 9°C (p = 0.677), the time to isolation was 56.8 ± 28 seconds versus 74.8 ± 45 seconds (p = 0.212), and the procedure time was 102.2 ± 27.3 seconds versus 104.5 ± 16.9 seconds (p = 0.6436). Ultimately, this proof-of-concept study revealed that fluoroless ablation can be performed with success and efficiency outcomes similar to those of a traditional ablation approach. This suggests that the ablation of atrial fibrillation with CB can be performed safely and effectively without the use of fluoroscopy by experienced operators.

Achieving contrast-free ultra-low radiation exposure without compromising safety and acute efficacy through evolving AF cryoballoon ablation procedure techniques

INTRODUCTION

In general, early experience with the first-generation cryoballoon introduced an increase in radiation exposure as compared to traditional radiofrequency ablations for atrial fibrillation (AF). However, through operator vigilance and the incorporation of various techniques and technologies, procedural radiation exposure can be managed to an exceptionally low level while maintaining the safety and efficacy of the cryoballoon procedure.

METHODS AND RESULTS

A retrospective chart review of all consecutive AF ablation procedures performed by a single operator at a single high-volume center with the second-generation cryoballoon (Arctic Front Advance) was performed between 2014 and 2017. Procedural and radiation exposure data were collected and analyzed year-over-year. 307 cases were reviewed with the majority as index procedures (95%) and patients presenting in paroxysmal AF (87%). The observed median absorbed dose was 2.4 mGy (interquartile range (IQR) = 1.0,6.2) and decreased significantly from 6.7 mGy (IQR = 1.6,6.2) in 2014 to 2.0 mGy (IQR = 1.5,4.5) in 2017 (P < 0.001). Median fluoroscopy time was 0.4 min (IQR = 0.25,0.75) and demonstrated reductions from 0.75 min (IQR = 0.40,1.4) in 2014 to 0.20 min (IQR = 0.10,0.40) in 2017 (P < 0.001). No radiopaque contrast agent was used in any procedure. A complication rate of 2% (6 total events) was observed, and no cases resulted in stroke, death, permanent phrenic nerve injury, or pulmonary vein stenosis. In total, 304 of 307 (99%) procedures resulted in complete isolation of all pulmonary veins.

CONCLUSION

Ultra-low radiation doses and contrast-free procedures can be achieved as part of an overall "safety-first" approach during cryoballoon AF ablation without compromising safety or acute efficacy.

"Clinical Impact of the Cryoballoon Temperature and Occlusion Status on the Success of Pulmonary Vein Isolation"

Background

Complete occlusion of the pulmonary veins (PVs) with the cryoballoon (CB) is considered to be the crucial factor for a successful PV isolation (PVI). We investigated whether a complete occlusion was indispensable for a successful CB based PVI of every PV.

Methods and Results

Atrial fibrillation patients (n=123, 97; paroxysmal) undergoing a de novo PVI were enrolled. A total of 477 PVs were analyzed. The occlusion grade (OG) was scored as follows: OG3 (complete occlusion), OG2 (incomplete occlusion with slight leakage), OG1 (poor occlusion with massive leakage). There was no significant difference in the CB temperature (CBT) at all measured time points (from 30 to 120sec after freezing) and nadir CBT between OG2 and OG3 in all PVs except for the right inferior PV (RIPV). The RIPV isolation success rate was significantly lower for the OG2 status than OG3 (97.5 vs. 57.6%; p<0.0001). In contrast, there was not significant difference in the isolation success rate of the other three PVs between OG2 and OG3. In particular, the success rate of the right superior PV (RSPV) isolation was >95% for both OG2 and OG3. Phrenic nerve paralysis (PNP) was provoked during the RSPV isolation in two patients in whom the RSPVs were frozen during OG3.

Conclusion

An OG3 may not always be required for a successful PVI of all PVs except the RIPV. OG2 could have comparable effects as OG3 in terms of a successful RSPV isolation. Not aiming for OG3 for the RSPV may reduce the risk of PNP.

Pressure-Guided cryoablation of pulmonary veins in atrial fibrillation: A fast and effective strategy

BACKGROUND

Cryoballoon ablation of atrial fibrillation (AF) involves successful electrical pulmonary vein isolation (PVI). Pulmonary vein (PV) ostial occlusion with cryoballoon is classically assessed using PV angiography. A pressure-guided technique to assess ostial occlusion has been evaluated in small cohorts with mixed results. We evaluated the efficacy of this pressure-guided PVI technique and its impact on reducing contrast and fluoroscopy time as compared to the traditional approach.

METHODS

We evaluated patients with paroxysmal AF, who underwent cryoballoon PVI. Patients prior to January 20th, 2013 underwent confirmation of PV occlusion by angiography only. Patients ablated after this time had PV occlusion initially determined by pressure monitoring and further confirmed by contrast injection into the PV in most cases (Pressure-guided PVI). Differences in the volume of contrast used and fluoroscopy time were evaluated.

RESULTS

46 patients had pressure-guided PVI and29 patients had occlusion of PV confirmed by angiography alone. Pressure-guided PVI was 99.5% successful in ablating AF, which was non-inferior to traditional method of PV isolation. This technique used an average of 8cc of contrast and 21.5min of fluoroscopy time, which was significantly less than the contrast amount used, and fluoroscopy time with angiographic isolation of PV.

CONCLUSION

Pressure-guided PVI is an effective method for cryoablation of AF. This method not only significantly reduces the volume of contrast used but also decreases the fluoroscopy without compromising the success of PVI.