Asymptomatic pulmonary vein stenosis after cryoballoon catheter ablation of paroxysmal atrial fibrillation

Anatomical targets and expected outcomes of catheter-based ablation of atrial fibrillation in 2020

Anatomical-based approaches, targeting either pulmonary vein isolation (PVI) or additional extra PV regions, represent the most commonly used ablation treatments in symptomatic patients with atrial fibrillation (AF) recurrences despite antiarrhythmic drug therapy. PVI remains the main anatomical target during catheter-based AF ablation, with the aid of new technological advances as contact force monitoring to increase safety and effective radiofrequency (RF) lesions. Nowadays, cryoballoon ablation has also achieved the same level of scientific evidence in patients with paroxysmal AF undergoing PVI. In parallel, electrical isolation of extra PV targets has progressively increased, which is associated with a steady increase in complex cases undergoing ablation. Several atrial regions as the left atrial posterior wall, the vein of Marshall, the left atrial appendage, or the coronary sinus have been described in different series as locations potentially involved in AF initiation and maintenance. Targeting these regions may be challenging using conventional point-by-point RF delivery, which has opened new opportunities for coadjuvant alternatives as balloon ablation or selective ethanol injection. Although more extensive ablation may increase intraprocedural AF termination and freedom from arrhythmias during the follow-up, some of the targets to achieve such outcomes are not exempt of potential severe complications. Here, we review and discuss current anatomical approaches and the main ablation technologies to target atrial regions associated with AF initiation and maintenance.

Catheter Ablation of Atrial Fibrillation: State of the Art and Future Perspectives

PURPOSE OF REVIEW

Atrial fibrillation (AF), the most common sustained arrhythmia, is associated with high rates of morbidity and mortality. Maintenance of stable sinus rhythm (SR) is the intended treatment target in symptomatic patients, and catheter ablation aimed at isolating the pulmonary veins provides the most effective treatment option, supported by encouraging clinical outcome data. A variety of energy sources and devices have been developed and evaluated. In this review, we summarize the current state of the art of catheter ablation of AF and describe future perspectives.

RECENT FINDINGS

Catheter ablation is a well-established treatment option for patients with symptomatic AF and is more successful at maintaining SR than antiarrhythmic drugs. Antral pulmonary vein isolation (PVI) as a stand-alone ablation strategy results in beneficial clinical outcomes and is therefore recommended as first-line strategy for both paroxysmal and persistent AF. While radiofrequency-based PVI in conjunction with a three-dimensional mapping system was for many years considered to be the "gold standard", the cryoballoon has emerged as the most commonly used alternative AF ablation tool, especially in patients with paroxysmal AF. Patients with persistent or long-standing persistent AF and with arrhythmia recurrence after previous PVI may benefit from additional ablation strategies, such as substrate modification of various forms or left atrial appendage isolation. New technologies and techniques, such as identification of the AF sources and magnetic resonance imaging-guided substrate modification, are on the way to further improve the success rates of catheter ablation for selected patients and might help to further reduce arrhythmia recurrence.

CONCLUSIONS

Pulmonary vein isolation is the treatment of choice for symptomatic patients with paroxysmal and persistent drug-refractory AF. The reconnection of previously isolated pulmonary veins remains the major cause of AF recurrence. Novel ablation tools, such as balloon technologies or alternative energy sources, might help to overcome this limitation. Patients with non-paroxysmal AF and with AF recurrence might benefit from alternative ablation strategies. However, further studies are warranted to further improve our knowledge of the underlying mechanisms of AF and to obtain long-term clinical outcomes on new ablation techniques.

Management of arrhythmia recurrence in patients with pulmonary vein stenosis following atrial fibrillation ablation

AIMS

Arrhythmia recurrence is a common clinical problem in patients with pulmonary vein stenosis (PVS) following catheter ablation of atrial fibrillation. The study sought to analyse the management of arrhythmia recurrence in patients with PVS.

METHODS AND RESULTS

Retrospective analysis was performed on 29 patients with high-degree PVS. Follow-up contained clinical visits, Holter-electrocardiogram recordings and invasive pulmonary vein (PV) angiography and electrophysiological studies. Arrhythmia recurrence was observed in 18 patients (62%) after PVS formation. Fifteen of 18 patients (83.3%) with and 1 of 11 patients (9.1%) without arrhythmia recurrence had electrical PV reconnection (P = 0.0003). In 14 of 16 patients repeat pulmonary vein isolation (PVI) was conducted (radiofrequency ablation in 12 and cryoballoon ablation in 2 cases). Repeat PVI was successful in all PVs in nine patients and incomplete in five patients (failed attempt in two patients with stent implantation, no attempt in three patients with stenotic PVs). Freedom from arrhythmia recurrence was estimated at 56.3% [95% confidence interval (CI) 36.4-72.0%] after 24 months. At the end of the follow-up, complete PVI was documented in 19 of 23 patients (82.6%) with stable sinus rhythm and in 2 of 6 patients with arrhythmia recurrence (33.3%) (P = 0.0335). The Kaplan-Meier estimate of recurrence-free survival of restenosis after interventional PVS treatment was similar in patients without and with repeat ablation [75.6% (95% CI 57.0-94.3%) and 67.0% (95% CI 43.2-90.7%) after 500 days, P = 0.77].

CONCLUSIONS

Pulmonary vein reconnection is the major driver of arrhythmia recurrence in PVS patients. Repeat PVI is feasible and does not lead to progression of PVS or restenosis if the procedure is carefully performed.

Cryoballoon ablation beyond paroxysmal atrial fibrillation

PURPOSE OF REVIEW

Although radiofrequency-based pulmonary vein isolation (PVI) was considered the 'gold standard' for the treatment of atrial fibrillation for a long time, the cryoballoon has turned out to be a common alternative tool for atrial fibrillation ablation. Most of the data regarding cryoballoon-based ablation relate to patients with paroxysmal atrial fibrillation (PAF). In this review, we summarize recent knowledge on the usage of cryoballoon ablation for other conditions, especially persistent atrial fibrillation.

RECENT FINDINGS

The cryoballoon is an effective ablation tool for PVI. As PVI is the first-line recommended procedural endpoint in atrial fibrillation ablation, it can be recommended not only for the treatment of PAF but also persistent atrial fibrillation and results in satisfying clinical outcomes. Recently, smaller studies and case reports were published reporting on cryoballoon ablation strategies beyond stand-alone PVI. These studies report a wide application spectrum of the cryoballoon and therefore potentially increase clinical success as well as the patient collective amenable to cryoballoon ablation.

SUMMARY

Cryoballoon-based PVI can be recommended not only for patients with PAF but also for patients with persistent atrial fibrillation. Ablation strategies going beyond PVI need further evaluation, but might expand the use of the cryoballoon.

Acute Hemodynamic and Tissue Effects of Cryoballoon Ablation on Pulmonary Vessels: The IVUS-Cryo Study

Background

Cryoballoon‐based pulmonary vein isolation (CB‐PVI) has been widely used for the treatment of atrial fibrillation. Although generally safe and effective, the procedure may be associated with pulmonary vein (PV) stenosis and bronchial or esophageal injury. The mechanisms leading to these complications have not been studied in detail. Our aim was to examine acute effects of cryoballoon on the pulmonary vessel and right heart pressures as well as PV wall morphology.

Methods and Results

In 8 patients (5 men, mean age 55±14 years) undergoing CB‐PVI, pressure in each PV was measured by catheter located inside the PV directly before and after CB‐PVI. The right atrial, right ventricular, and pulmonary artery pressures as well as pulmonary arterial wedge capillary pressure in the pulmonary artery branch corresponding to target PV were also measured. Morphological changes in PVs were assessed using intravascular ultrasonography.

There were no significant differences in PV pressures before and after ablation. The pulmonary arterial wedge capillary pressure significantly increased during cryoapplication (left superior: 20±10 versus 29±8.5 mm Hg, P=0.004; left inferior: 24±10 versus 32±6 mm Hg, P=0.012; right superior: 25±9 versus 35±10 mm Hg, P=0.002; right inferior: 24±10 versus 37±12 mm Hg, P=0.0036). The right atrial and pulmonary artery pressures increased significantly after CB‐PVI (9±6 versus 13±8 mm Hg, P=0.004, and 20±9 versus 24±10 mm Hg, P=0.048, respectively). Intravascular ultrasonography showed acute edema and dissection‐like changes causing relative lumen narrowing in 90% of PVs.

Conclusions

CB‐PVI causes significant rise in pulmonary artery and right atrial pressures as well as PV wall damage. The clinical significance of these findings warrants further investigations.

Pulmonary Vein Stenosis After Second-Generation Cryoballoon Ablation

BACKGROUND

Pulmonary vein stenosis (PVST) can occur after first-generation cryoballoon ablation. This study aimed to evaluate the incidence, severity, and characteristics of PVST after second-generation cryoballoon ablation.

METHODS

In total, 103 patients underwent PV isolation of paroxysmal atrial fibrillation using second-generation cryoballoons with a single big-balloon 3-minute freeze technique. Cardiac enhanced multidetector computed tomography (MDCT) was performed both before and a median of 6.0 (4.0-8.0) months after the procedure in all. PVST was classified as follows: minimal (<25%), mild (25-50%), moderate (50-70%), or severe (>70%).

RESULTS

In total, 406 PVs were analyzed. MDCT demonstrated PV stenosis in 10(2.5%) PVs among 8(7.8%) patients. In detail, minimal and mild PVSTs were observed in 6 and 4 PVs, respectively. PVST occurred in the left superior (LSPV), left inferior, and right superior PVs in 6, 1, and 3 PVs, respectively. No stenosis was observed in 15 PVs with active balloon deflations during freezing. All PVSTs had concentric patterns except for 2 PVs with minimal stenosis. Balloon deformities were observed during freezing of 2 PVs with mild stenosis. When the PVST was defined as a >25% decreased diameter, the incidence was 0.98% (4/406; including 3 LSPVs). PVST did not progress further during the follow-up period.

CONCLUSIONS

Although the incidence of PVST was low, it could occur even if a single big-balloon short freeze technique was applied. The risk of PV stenosis significantly differed among the 4 PVs, and reaching balloon temperatures of -60 °C and active balloon deflations during freezing were not associated with any PV stenosis.

Efficacy, High Procedural Safety And Rapid Optimization Of Cryoballoon Atrial Fibrillation Ablation In The Hands Of A New Operator

BACKGROUND

Cryoballoon (CB) ablation is successful in eliminating atrial fibrillation (AF).

PURPOSE

The purpose of this study was to assess procedural efficacy and safety of CB ablation performed by a newly trained operator.

METHODS

Forty patients with documented paroxysmal AF (58 ± 11 years, 26 male) undergoing CB catheter ablation were prospectively enrolled.

RESULTS

Electrical pulmonary vein (PV) isolation was achieved in all patients (156 PVs). The primary end point (PV isolation using CB only) was reached in 31 patients (92% PV isolation, 144/156 PVs). In the remaining 9 patients (12 PVs), additional single point cryofocal ablations were required to achieve isolation of all veins (LSPV, n = 5; LIPV, n = 3; LCPV, n = 2; RSPV, n = 1; RIPV, n = 1). There was no vascular access complication, pericardial effusion/tamponade, stroke/transient ischemic attack, phrenic nerve palsy, acute PV stenosis, or atrioesophageal fistula. The procedure duration decreased with experience by 30% from 155 min during the first 10 procedures to 108 min (final 10 treatments). Similar effects were observed with fluoroscopy time (-57%; from 28 min to 12 min), dose area product (-66%; from 22 Gy x cm2 to 8 Gy x cm2), CB time in the left atrium (-24%; from 99 min to 75 min), and cryoenergy delivery time (-19%; from 83 min to 67 min), when comparing cases #1-10 to cases #30-40.

CONCLUSIONS

CB ablation of AF is effective and safe in the hands of a new operator. Procedure and fluoroscopy times decrease with user experience.

Pulmonary Hypertension due to Radiofrequency Catheter Ablation (RFCA) for Atrial Fibrillation: The Lungs, the Atrium or the Ventricle?

Atrial fibrillation is the most common heart rhythm disorder in United States, characterised by rapid and irregular beating of both the atria resulting in the similar ventricular response. While rate and rhythm control using pharmacological regimens remain the primary management strategies in these patients, radiofrequency catheter ablation (RFCA) is rapidly rising as an alternative modality of treatment. Increase in the incidence of RFCA has shed light on complications associated with this procedure. Pulmonary hypertension (PH) is one of the long-term complications that has been observed postcatheter ablation. There have been multiple mechanisms which have been proposed to explain these elevated pulmonary pressures. These include the involvement of the lungs due to pulmonary vein stenosis, pulmonary vein occlusion and, rarely, pulmonary embolism. Radiofrequency catheter ablation can also lead to scarring of the atrium which can cause left atrial diastolic dysfunction leading to elevated pulmonary pressures. Recently, it was also proposed that elevated pulmonary pressure was related to the unmasking of left ventricular diastolic dysfunction occurring after this procedure. In this article, we review all the mechanisms that are associated with the development of pulmonary hypertension in patients undergoing RCFA for atrial fibrillation and the approach to diagnosis and management of such patients.

[Complications associated with catheter ablation of atrial fibrillation]

The past years catheter ablation has gained significant importance in the treatment of atrial fibrillation (AF), hence procedure numbers have risen worldwide. Initially, data concerning complications were only available through surveys and single center reports but international classification of diseases (ICD) code-based data have recently been published representing real world conditions. The rate of overall acute complications is 6.3 % and has risen slightly in the past 10 years whereby cardiac complications occurred most frequently, followed by vascular, respiratory and neurological complications. Risk factors for a higher complication rate are advanced age (> 80 years), female gender and less experienced investigators and hospitals.

[Advances in cryoballoon technology: benefits and risks in daily practice]

BACKGROUND

Cryoballoon ablation is nowadays a standard approach for pulmonary vein isolation in symptomatic atrial fibrillation. The second generation cryoballoon was introduced in 2012 and modifications and enhancement to the system promised a higher efficiency.

OBJECTIVES, MATERIALS AND METHODS

A comprehensive overview of advances in cryoballoon ablation is provided and the consequences for daily practice are described based on a PubMed literature search, taking into account own experiences.

RESULTS AND CONCLUSION

Advances in cryoballoon ablation result in a significantly higher efficiency. To maintain the overall safety of the procedure and to avoid phrenic nerve palsy and esophageal lesions, special care needs to be taken by following some safety aspects and cut-off criteria. More data are necessary to clarify if recommendations for cryoenergy titration with the new balloon are reasonable. Ongoing prospective studies comparing cryoballoon and radiofrequency (RF) ablation will give answers to the question which energy source is more favorable, and upcoming studies will evaluate the impact of cryoballoon ablation as a first line treatment option.

Management Of Pulmonary Vein Stenosis Following Catheter Ablation Of Atrial Fibrillation

There is limited literature available regarding PV (pulmonary vein) stenosis management. Starting from its incidence, subsequent follow up using imaging technologies to monitor the success and the way of managing different groups pose varied opinions. However, with newer technological advancements and better understanding of mechanism of the atrial fibrillation ablation, the incidence of PV stenosis secondary to catheter ablation is declining. This paper highlights the current trends and future of management of PV stenosis secondary to catheter ablation for atrial fibrillation.

Cryoballoon ablation of pulmonary veins for paroxysmal atrial fibrillation: first results of the North American Arctic Front (STOP AF) pivotal trial

OBJECTIVES

This study sought to assess the safety and effectiveness of a novel cryoballoon ablation technology designed to achieve single-delivery pulmonary vein (PV) isolation.

BACKGROUND

Standard radiofrequency ablation is effective in eliminating atrial fibrillation (AF) but requires multiple lesion delivery at the risk of significant complications.

METHODS

Patients with documented symptomatic paroxysmal AF and previously failed therapy with ≥ 1 membrane active antiarrhythmic drug underwent 2:1 randomization to either cryoballoon ablation (n = 163) or drug therapy (n = 82). A 90-day blanking period allowed for optimization of antiarrhythmic drug therapy and reablation if necessary. Effectiveness of the cryoablation procedure versus drug therapy was determined at 12 months.

RESULTS

Patients had highly symptomatic AF (78% paroxysmal, 22% early persistent) and experienced failure of at least one antiarrhythmic drug. Cryoablation produced acute isolation of three or more PVs in 98.2% and all four PVs in 97.6% of patients. PVs isolation was achieved with the balloon catheter alone in 83%. At 12 months, treatment success was 69.9% (114 of 163) of cryoblation patients compared with 7.3% of antiarrhythmic drug patients (absolute difference, 62.6% [p < 0.001]). Sixty-five (79%) drug-treated patients crossed over to cryoablation during 12 months of study follow-up due to recurrent, symptomatic AF, constituting drug treatment failure. There were 7 of the resulting 228 cryoablated patients (3.1%) with a >75% reduction in PV area during 12 months of follow-up. Twenty-nine of 259 procedures (11.2%) were associated with phrenic nerve palsy as determined by radiographic screening; 25 of these had resolved by 12 months. Cryoablation patients had significantly improved symptoms at 12 months.

CONCLUSIONS

The STOP AF trial demonstrated that cryoballoon ablation is a safe and effective alternative to antiarrhythmic medication for the treatment of patients with symptomatic paroxysmal AF, for whom at least one antiarrhythmic drug has failed, with risks within accepted standards for ablation therapy. (A Clinical Study of the Arctic Front Cryoablation Balloon for the Treatment of Paroxysmal Atrial Fibrillation [Stop AF]; NCT00523978).

[Cardiac computed tomography and ablation of atrial fibrillation]

Both cardiac computed tomography (CT) and interventional electrophysiology (EP) have evolved considerably in recent years. Technical improvements in CT have significantly reduced the radiation dose in cardiac applications. This imaging technology plays an important role in preprocedural planning and guidance of the procedures in many EP centers worldwide. Furthermore, CT is the imaging modality of choice to diagnose relevant complications in ablation of atrial fibrillation, e.g. pulmonary vein stenosis or atrioesophageal fistula. In anatomically driven ablation procedures, such as balloon-based procedures in atrial fibrillation, detailed analysis of the relevant cardiac structures is absolutely crucial not only to reduce radiation exposure and procedure times but also to improve ablation success and to reduce the occurrence of complications. Current software applications enable 3-dimensional reconstruction of cardiac images and the integration into electroanatomical navigation systems. This article reviews the available evidence in this field and highlights recent developments in image guidance for ablation of atrial fibrillation.

Waveform optimization for internal cardioversion of atrial fibrillation

INTRODUCTION

A novel atrial defibrillator was developed at the Royal Victoria Hospital in collaboration with the Nanotechnology and Integrated Bio-Engineering Centre, University of Ulster. This device is powered by an external pulse of radiofrequency energy and designed to cardiovert using low-tilt monophasic waveform (LTMW) and low-tilt biphasic waveform (LTBW), 12 milliseconds pulse width. This study compared the safety and efficacy of LTMW with LTBW for transvenous cardioversion of atrial fibrillation (AF).

METHODS

Patients were anticoagulated with warfarin to maintain International Normalized Ratio between 2 and 3 for 4 weeks prior cardioversion. Warfarin international normalized ratio level was maintained in between 2 and 3 for 4 weeks prior cardioversion. St Jude's defibrillating catheter was positioned in the distal coronary sinus and right atrium and connected to the defibrillator via a junction box. After a test shock using a dummy load, the patient was cardioverted in a step-up progression from 50 to 300 V. Shock success was defined as return of sinus rhythm for 30 seconds or more. If cardioversion was unsuccessful at peak voltage, the patient was crossed over to the other arm of the waveform type and cardioverted at peak voltage.

RESULTS

Thirty patients were randomized equally to LTBW and LTMW (15 each). Seven out of 15 patients (46%) cardioverted to sinus rhythm with LTBW, and 1 (6%) of 15, with LTMW (P = .035). Including crossover patients, 14 patients (46%) converted to sinus rhythm. After crossover, 4 patients were cardioverted with LTBW and 2 with LTMW. Overall mean voltage, current, and energy used for cardioversion were 270.53 ± 35.96 V, 3.68 ± 0.80 A, and 9.12 ± 3.73 J, respectively, and intracardiac impedance was 70.82 ± 13.46 Ω. For patients who were successfully cardioverted, mean voltage, current, energy, and intracardiac impedance were 268.28 ± 42.41 V, 3.52 ± 0.63 A, 8.51 ± 3.16 J, and 73.92 ± 12.01 Ω. There were no major adverse complications during the study. Cardiac markers measured postcardioversion were unremarkable.

CONCLUSION

Low-tilt biphasic waveform was more efficacious for low-energy transvenous cardioversion of AF. A significant proportion of patients were successfully cardioverted to sinus rhythm with low energy. Radiofrequency-powered defibrillation can be safely used for transvenous cardioversion of AF.