Recordings of diaphragmatic electromyograms during cryoballoon ablation for atrial fibrillation accurately predict phrenic nerve injury

Value of high-output pace-mapping of the right phrenic nerve for enabling safe radiofrequency ablation of atrial fibrillation: insights from three-dimensional computed tomography segmentation

AIMS

Right phrenic nerve (RPN) injury is a disabling but uncommon complication of atrial fibrillation (AF) radiofrequency ablation. Pace-mapping is widely used to infer RPN's course, for limiting the risk of palsy by avoiding ablation at capture sites. However, information is lacking regarding the distance between the endocardial sites of capture and the actual anatomic RPN location. We aimed at determining the distance between endocardial sites of capture and anatomic CT location of the RPN, depending on the capture threshold.

METHODS AND RESULTS

In consecutive patients undergoing AF radiofrequency ablation, we defined the course of the RPN on the electroanatomical map with high-output pacing at up to 50 mA/2 ms, and assessed RPN capture threshold (RPN-t). The true anatomic course of the RPN was delineated and segmented using CT scan, then merged with the electroanatomical map. The distance between pacing sites and the RPN was assessed. In 45 patients, 1033 pacing sites were analysed. Distances from pacing sites to RPN ranged from 7.5 ± 3.0 mm (min 1) when RPN-t was ≤10 mA to 19.2 ± 6.5 mm (min 9.4) in cases of non-capture at 50 mA. A distance to the phrenic nerve > 10 mm was predicted by RPN-t with a ROC curve area of 0.846 [0.821-0.870] (P < 0.001), with Se = 80.8% and Sp = 77.5% if RPN-t > 20 mA, Se = 68.0% and Sp = 91.6% if RPN-t > 30 mA, and Se = 42.4% and Sp = 97.6% if non-capture at 50 mA.

CONCLUSION

These data emphasize the utility of high-output pace-mapping of the RPN. Non-capture at 50 mA/2 ms demonstrated very high specificity for predicting a distance to the RPN > 10 mm, ensuring safe radiofrequency delivery.

Interest of thoracic ultrasound after cardiac surgery or interventional cardiology

Thoracic ultrasound has attracted much interest in detecting pleural effusion or pulmonary consolidation after cardiac surgery. In 2016, Trovato reported, in the World Journal of Cardiology, the interest of using, in addition to echocardiography, thoracic ultrasound. In this editorial, we highlight the value of assessing diaphragm function after cardiac surgery and interventional cardiology procedures. Various factors are able to impair diaphragm function after such interventions. Diaphragm motion may be decreased by chest pain secondary to sternotomy, pleural effusion or impaired muscle function. Hemidiaphragmatic paralysis may be secondary to phrenic nerve damage complicating cardiac surgery or atrial fibrillation ablation. Diagnosis may be delayed. Indeed, respiratory troubles induced by diaphragm dysfunction are frequently attributed to pre-existing heart disease or pulmonary complications secondary to surgery. In addition, elevated hemidiaphragm secondary to diaphragm dysfunction is sometimes not observed on chest X-ray performed in supine position in the intensive care unit. Analysis of diaphragm function by ultrasound during the recovery period appears essential. Both hemidiaphragms can be studied by two complementary ultrasound methods. The mobility of each hemidiaphragms is measured by M-mode ultrasonography. In addition, recording the percentage of inspiratory thickening provides important information about the quality of muscle function. These two approaches make it possible to detect hemidiaphragm paralysis or dysfunction. Such a diagnosis is important because persistent diaphragm dysfunction after cardiac surgery has been shown to be associated with adverse respiratory outcome. Early respiratory physiotherapy is able to improve respiratory function through strengthening of the inspiratory muscles i.e. diaphragm and accessory inspiratory muscles.

Adverse events in cryoballoon ablation for pulmonary vein isolation: Insight from the Food and Drug Administration Manufacturer and User Facility Device Experience

Background

Real-world clinical data on the adverse events related to the use of cryoballoon catheter for pulmonary vein isolation remains limited.

Objective

To report and describe the adverse events related to the use of Artic Front cryoballoon catheters (Arctic Front, Arctic Front Advance, and Arctic Front Advance Pro) reported in the Food and Drug Administration's (FDA) Manufacturers and User Defined Experience (MAUDE) database.

Methods

We reviewed all the adverse events reported to the FDA MAUDE database over a 10.7-year study period from January 01, 2011 to September 31, 2021. All events were independently reviewed by two physicians.

Results

During the study period, a total of 320 procedural-related adverse events reported in the MAUDE database were identified. The most common adverse event was transient or persistent phrenic nerve palsy (PNP), accounting for 48% of all events. This was followed by cardiac perforation (15%), pulmonary vein stenosis (8%), transient ischemic attack or stroke (6%), vascular injury (4%), transient or persistent ST-elevation myocardial infarction (3%), hemoptysis (2%), pericarditis (2%), and esophageal ulcer or fistula (1%). There were six reported intra-procedural death events as a result of cardiac perforation.

Conclusion

The two most common procedural adverse events associated with cryoballoon ablation were PNP and cardiac perforation. All cases of procedural mortality were due to cardiac perforation.

Microembolizations in the Arterial Cerebral Circulation in Patients with Atrial Fibrillation Ablation Using the Cryoballoon Technique-Protocol and Methodology of a Prospective Observational Study

There is considerable uncertainty regarding the impact of microembolic signals (MESs) on neuropsychological abilities in patients receiving pulmonary vein isolation and beyond using the cryoballoon technique. We conducted the largest prospective observational study on this topic, providing insights into the gradual unmasking of procedure-related MESs and their impacts on neuropsychological outcomes. MESs were continuously detected periprocedurally using transcranial Doppler ultrasonography. Neuropsychological status was evaluated comprehensively using the CERAD Plus test battery, which consists of 11 neuropsychological subtests. Patients with atrial fibrillation were included in the study with an equal distribution (50:50) of paroxysmal or persistent presentations. Of 167 consecutive eligible patients, 100 were included within the study enrollment period from February 2021 to August 2022. The study, including the documentation of all follow-up visits, ended in November 2022. This paper focuses on describing the study protocol and methodology and presenting the baseline data.

Best Practice Guide for Cryoballoon Ablation in Atrial Fibrillation: The Compilation Experience of More than 1000 Procedures

Nowadays, the cryoballoon (CB) constitutes an established alternative to radio frequency (RF) ablation for pulmonary vein isolation (PVI), which offers the possibility to isolate the PVs with a single application. Since the introduction of the second-generation CB, we prospectively collected our data to optimize the procedure on >1000 consecutive patients who underwent CB PVI performed in our center. It is expected that subsequent guidelines will suggest first-line PVI through CB in patients with paroxysmal AF with a class I indication. Indeed, in the long-term follow-up (36 months) of the EARLY-AF trial, CB had a lower incidence of persistent atrial fibrillation episodes compared to the anti-arrhythmic drugs group. We now review the current best practices in an effort to drive consistent outcomes and minimize complications. PV isolation through CB is the most studied single-shot technique for atrial fibrillation ablation, having shown the potential to alter the natural history of the arrhythmia. Several procedural tips and tricks can improve procedural flow and effectiveness. In the present article we provided not only technical details but measurable biophysical parameters that can reliably guide the operator into achieving the best outcome for his patients.

Clinical outcome of a single procedure cryoballoon ablation for the treatment of atrial fibrillation: A real-world multicenter experience in Portugal

BACKGROUND

Cryoballoon ablation (CBA) for pulmonary vein isolation (PVI) has been growing as an alternative technique, not only in patients with paroxysmal atrial fibrillation (PAF) but also in persistent atrial fibrillation (AF). Cryoballoon ablation has demonstrated encouraging acute and mid-term results. However, data on long-term follow-up of CB-based PVI are scarce.

OBJECTIVE

We sought to examine efficacy, safety, and long-term outcomes of CBA in PAF and persistent AF in four Portuguese centers.

METHODS

All patients that were treated with the cryoballoon catheter according to routine practices with a second-generation 28-mm CB in four centers were included. This was a retrospective, non-randomized analysis. Patients were followed-up for >12 months and freedom from atrial arrhythmias (AA) was evaluated at the end of follow-up.

RESULTS

Four hundred and six patients (57.7±12.4 years, 66% men) participated. AF was paroxysmal in 326 patients (80.2%) and persistent in 80 (19.7%). The mean procedure time duration was 107.7±50.9 min, and the fluoroscopy time was 19.5±9.7 min. Procedural/periprocedural complications occurred in 30 cases (7.3%), being transient phrenic nerve palsy the most frequent incident (2 out of 3 complications). Anatomic variations of the PV were present in 16.1% of cases. At a mean follow-up of 22.0±15.0 months, 310 patients (76.3%) remained in stable sinus rhythm, with at least one AF episode recurrence documented in 98 cases (24.1%). The recurrence rate was 20.5% in the PAF group and 37.8% in the persistent AF group.

CONCLUSION

In this multicenter experience, a single CBA procedure resulted in 75.9% freedom from AF at a 22-month follow-up. This technique was demonstrated to be a safe and effective option in experienced centers for the treatment of PAF and PersAF.

Differences between diaphragmatic compound muscle action potentials recorded from over the sternum and lateral chest wall in healthy subjects

To report normative data for diaphragmatic compound muscle action potentials (DCMAPs) recorded from over the sternum and lateral chest wall (LCW) and highlight factors that may contribute to variations in DCMAP parameters at the two sites. The phrenic nerve of seventy-three healthy subjects was bilaterally stimulated at the posterior border of the sternocleidomastoid muscle. DCMAPs from over the sternum and LCW were recorded (inspiration/expiration). Normative values of sternal and LCW DCMAPs were presented. The mean values of latency of LCW DCMAPs, duration of sternal DCMAPs and area from both recording sites are close to values reported by other studies. The mean values of latency of sternal DCMAPs are higher than that reported by other studies. Significant differences were found between sternal and LCW potentials in the mean latency, amplitude, and area (p < 0.001). The duration did not differ between the two sites. Differences were found between inspiration and expiration, right and left sides, and men and women. Regression analysis showed a relation between latency of sternal and LCW potentials and age. Latency (LCW potentials) and amplitude and area (sternal/LCW potentials) were related to gender. Amplitude (LCW potentials/inspiration) and area (sternal potentials/inspiration) were related to chest circumference (p = 0.023 and 0.013 respectively). Area (sternal potentials/expiration) was related to the BMI (p = 0.019). Our normative values for sternal and LCW DCMAPs are provided. Notable differences in the DCMAPs parameters were detected between the two recording sites, inspiration and expiration, right and left, and men and women. The technique of phrenic nerve should be standardized.

Cryoballoon atrial fibrillation ablation experience in Japan

PURPOSE OF REVIEW

In Japan, cryoballoon ablation has been widely accepted and more than 70 000 patients have undergone pulmonary vein isolation using this novel technology since the introduction. This review focused on the current status of cryoballoon ablation in Japan and clarified the characteristics as compared to Europe and the United States.

RECENT FINDINGS

The number of atrial fibrillation patients undergoing cryoballon ablation has rapidly increased over the last 6 years. Most of the Japanese physicians consider the indication of cryoballoon ablation based on the anatomy of the pulmonary veins and left atrium evaluated on preprocedural computed tomography, and often perform adjunctive radiofrequency ablation after the pulmonary vein isolation. The reported overall efficacy and safety were similar to that in Europe and the United States; however, there are some distinctive complications of the cryoballoon procedure in Japan, such as air embolisms, gastric hypomotility and coronary artery spasms.

SUMMARY

Currently, the cryoballoon pulmonary vein isolation is widely accepted in Japan owing to the low incidence of lethal complications, shorter procedure time and acceptable single procedure atrial fibrillation freedom.

Predicting Phrenic Nerve Palsy in Patients Undergoing Atrial Fibrillation Ablation With the Cryoballoon-Does Sex Matter?

Background: Phrenicus nerve palsy (PNP) is a typical complication during pulmonary vein isolation (PVI) using the cryoballoon with the ominous potential to counteract the clinical benefit of restored sinus rhythm. According to current evidence incidence of PNP is about 5–10% of patients undergoing Cryo-PVI and is more frequent during ablation of the RSPV compared to the RIPV. However, information on patient specific characteristics predicting PNP and long-term outcome of patients suffering from this adverse event is sparse.

Aim of the Study: To evaluate procedural and clinical characteristics of AF patients with PNP during cryoballoon PVI compared to patients without PNP.

Methods and Results: Between 2013 and 2019 we included 632 consecutive AF patients undergoing PVI with the cryoballoon in our study. 84/632 (13.3%) patients experienced a total number of 89 PNP during the ablation procedure. 75/89 (84%) cryothermal induced PNP recovered until the end of the procedure (transient PNP, tPNP), whereas 14/89 (16%) PNP hold beyond the end of the procedure (non-transient PNP, ntPNP). Using multivariate logistic regression, we found that sex and BMI are strong and independent predictors of cryothermal induced non-transient PNP during cryoballoon PVI with an odds ratio of 3.9 (CI: 95%, 1.1–14.8, p = 0.04) for female gender. Interestingly, all patients (14/14, 100%) with a non-transient PNP experienced complete PNP resolution after a mean recovery time of 68 ± 79 days.

Conclusion: Our data indicate for the first time, that female sex and lower BMI are independent predictors for non-transient PNP caused by cryoballoon PVI. Fortunately, during follow up all PNP patients resolved completely with a median recovery time of 35 days.

Management of phrenic nerve injury post-cardiac surgery in the paediatric patient

BACKGROUND

Phrenic nerve injury is a common complication of cardiac and thoracic surgical procedures, with potentially severe effects on the health of a child. This review aims to summarise the available literature on the diagnosis and management of PNI post-cardiac surgery in paediatric patients with CHD.

MAIN BODY

The presence of injury post-surgery can be difficult to detect and may present with non-specific symptoms, emphasising the importance of an effective diagnostic strategy. Chest X-ray is usually the first investigation for a suspected diagnosis of PNI, which is usually confirmed using fluoroscopy, ultrasound scan, or phrenic nerve stimulation (gold standard). Management options include supportive ventilation and/or invasive diaphragmatic plication surgery. While the optimal timing of plication surgery remains controversial, it is now the most widely accepted treatment for PNI in children post-CHD surgery, especially for very young patients who cannot be weaned off supportive ventilation. Further research is needed to determine the optimal timing of surgical intervention for positive outcomes and to explore the benefits of using minimally invasive surgical techniques in children.

CONCLUSION

PNI is a common and serious complication of CHD surgery, therefore, its diagnosis and management in the paediatric population are of major importance. Further research is needed to determine the optimal timing of surgical intervention for positive outcomes and to explore the benefits of using minimally invasive surgical techniques in children.

Tracing the Right Phrenic Nerve - A Systematic Review and Meta-Analysis

Background

The Right phrenic nerve (RPN) is vulnerable to injury during the isolation of the right pulmonary veins (RPV). The study aimed to provide a comprehensive meta-analysis of the overall prevalence of right phrenic nerve injury (RPNI), its course and its association with the superior and inferior pulmonary veins.

Methods

Through December 2017, a database search was performed on PubMed, Science Direct, EMBASE, SciELO, and Web of Science. The references were also extensively searched in the included articles.

Results

Detection of the RPN may vary according to the identification method. It ranges from 100% in postmortem studies, 93% in intraoperative, to 57.88% in computer tomography (CT) imaging. Based on the included studies (n-507), the distance from the right superior pulmonary vein (RSPV) ostium to the RPN was 12.48mm (±6.21). In postmortem studies, the distance was 6.92mm (±3.94); in pre or intraoperative techniques, 13.32mm (±5.96) if noninvasive, 13.97mm (±7.8) if invasive. Distances ranged from 0DC342.6 mm. For the right inferior pulmonary vein (RIPV) (n-125) the mean distance was 16.53mm (±8.92) with distances from 0.4 68mm. The risk of RPNI with distance-included studies was 12.46% (47 RPNI in 377 cases). In the meta-analysis, the distance from the RSPV to the RPN that was associated with an increased risk of RPNI was 7.36mm.

Conclusions

RPNI is a relatively rare complication. A firm understanding of its course, relation to the PV ostium, and detection are vital for preventing future injuries and complications.

Contemporary analysis of phrenic nerve injuries following cryoballoon-based pulmonary vein isolation: A single-centre experience with the systematic use of compound motor action potential monitoring

BACKGROUND

Phrenic nerve injury (PNI) remains one of the most frequent complications during cryoballoon-based pulmonary vein isolation (CB-PVI). Since its introduction in 2013, the use of compound motor action potential (CMAP) for the prevention of PNI during CB-PVI is increasing; however, systematic outcome data are sparse.

METHODS

The CMAP technique was applied in conjunction with abdominal palpation during pacing manoeuvres (10 mV, 2 ms) from the superior vena cava for 388 consecutive patients undergoing CB-PVI between January 2015 and May 2017 at our tertiary arrhythmia centre. Cryoablation was immediately terminated when CMAP amplitude was reduced by 30%.

RESULTS

Reductions in CMAP amplitude were observed in 16 (4%) of 388 patients during isolation of the right veins. Of these, 11 (69%) patients did not manifest a reduction in diaphragmatic excursions. The drop in CMAP amplitude was observed in 10 (63%) patients during ablation of the right superior pulmonary veins (PVs) and in 7 (44%) patients during ablation of the right inferior PVs. Postprocedural persistent PNI was observed in three of four patients for a duration of 6 months, with one of these patients remaining symptomatic at the 24-month follow-up. One of the four patients was lost to long-term follow-up.

CONCLUSIONS

All PNIs occurred during right-sided CB-PVI and were preceded by a reduction in CMAP amplitude. Thus, the standardized use of CMAP surveillance during CB-PVI is easily applicable, reliable and compared with other studies, results in a lower number of PNIs.

Atrial fibrillation ablation in heart failure patients: improved systolic function after cryoballoon pulmonary vein isolation

Aims

Atrial fibrillation (AF) and heart failure (HF) are the most common cardiac diseases and often coexist leading to increased mortality and morbidity compared with AF patients without HF. As shown previously, AF ablation using radio frequency (RF) in HF patients leads to a reduction of AF burden, an increase of left ventricular ejection fraction (LVEF) and consequently to reduced hospitalization and mortality. Previous AF ablation studies on HF patients have been liberal about additional targets beyond pulmonary vein isolation (PVI). Thus, the aim of this study was to assess systematically the impact of a straightforward PVI‐only strategy on LVEF, NYHA functional class, and cardiovascular hospitalization rate in HF patients.

Methods and results

Out of 414 consecutive patients undergoing PVI, only with the cryoballoon 113 patients with reduced LVEF [mean: 38.4 ± 10.8%, reduced ejection fraction (rEF) group] and 301 patients with normal LVEF (>55%) at baseline were identified [normal ejection fraction (nEF) group]. Remarkably, even though freedom from arrhythmia recurrence after 1 year was significantly lower in the rEF group (64.9%) compared with the nEF group (71.2%, P = 0.036), mean LVEF improved from 38.4 ± 10.8% to 52.5 ± 17.2% (P < 0.001) after cryoballoon ablation in the rEF group. Accordingly, HF‐related symptoms as well as hospitalization rate declined significantly in the rEF group during follow‐up compared with baseline.

Conclusions

The results of the present study suggest that catheter ablation restricted to a straightforward PVI‐only strategy using the cryoballoon leads to improved left ventricular ejection fraction as well as improvement of NYHA functional class and increased freedom from cardiovascular rehospitalization.

Positioning an ECG electrode to the dorsal side can record higher amplitude of CMAPs during cryoballoon ablation

PURPOSE

Phrenic nerve injury (PNI) is one of the important complications during cryoballoon (CB) ablation. Recording diaphragmatic compound motor action potentials (CMAPs) during CB ablation can predict PNI. CMAP monitoring may be inaccurate when CMAP amplitudes are low. We examined the effect of positioning an electrocardiography (ECG) electrode at the dorsal side.

METHODS

We retrospectively analyzed the cases of 197 consecutive patients who underwent CB ablation for pulmonary vein isolation (PVI) (April 2016 to December 2018) at our institution. CMAP amplitudes were monitored using two recording methods just before cryoapplication. (a) Conventional method: right-arm ECG electrode positioned 5 cm above the xiphoid on the ventral side; left-arm ECG electrode positioned along the costal margin. (b) Our original method: right-arm electrode positioned 5 cm above the xiphoid on the dorsal side; left-arm electrode positioned along the costal margin.

RESULTS

The CMAP amplitude during right phrenic nerve pacing was significantly higher at the dorsal side than the ventral side (0.80 ± 0.31 mV vs 0.66 ± 0.29 mV, P < .01). Similarly, the CMAP amplitude during left phrenic nerve pacing was significantly higher at the dorsal side than the ventral side (0.92 ± 0.39 mV, 0.73 ± 0.37 mV, P < .01). PNI occurred in six patients (3.0%); three patients experienced transient PNI, another three patients experienced persistent PNI, and none developed permanent PNI.

CONCLUSIONS

CMAP amplitudes were significantly high at the dorsal side compared to the ventral side. Monitoring phrenic nerve function using an ECG electrode at the dorsal side is a simple and easy procedure.

Acute Procedural Complications of Cryoballoon Ablation: A Comprehensive Review

Catheter ablation is increasingly performed for treatment of atrial fibrillation (AF). Balloon based procedures have been developed aiming at safer, easier and more effective treatment as compared to point to point ablation. In the present review article, we aimed to discuss acute procedural complications of cryoballoon ablation.

Difficulties in tracheal extubation due to phrenic nerve injury during massive mediastinal tumor resection: A case report

RATIONALE

Massive mediastinal tumors present a major challenge for surgery and anesthesia management due to possible perioperative circulation and respiratory dysfunction.

PATIENT CONCERNS

A 36-year-old female underwent difficulty with tracheal extubation and required mechanical ventilation for 3 months after resection of a massive mediastinal tumor.

DIAGNOSES

Postoperative B-ultrasound examination of diaphragmatic motor weakness and electrophysiological examination indicated respiratory failure due to phrenic nerve injury.

INTERVENTIONS

The patient failed tracheal extubation several times after the operation and finally a tracheotomy was performed. Mechanical ventilation, anti-infective treatment, and systemic supportive treatment were provided.

OUTCOMES

The patient recovered well after tracheotomy and approximately 3 months of ventilation support.

LESSONS

Weaning difficulty caused by phrenic nerve injury seriously affected patient postoperative rehabilitation. To reduce the occurrence of similar problems, intraoperative phrenic nerve electrophysiological monitoring should be conducted.

Impact of atrial rhythm on pulmonary vein signals in cryoballoon ablation - Sinus rhythm predicts real-time observation of pulmonary vein isolation

Purpose

Real-time observation of pulmonary vein (PV) potentials with a spiral mapping catheter has emerged as a key electrogram-based procedural parameter to estimate lesion quality and titrate cryoenergy application during PV isolation (PVI) with the cryoballoon. Whether correct PV electrogram interpretation and thus PVI real-time observation rate depends on atrial rhythm during cryoballoon PVI is unknown. We compared observation rates of time-to PV isolation (TTI) during sinus rhythm (SR group) and during atrial fibrillation (AFib group) in cryoballoon PVI.

Methods

We prospectively included 157 consecutive patients undergoing cryoballoon PVI and compared the incidence of PVI real-time recording of each pulmonary vein during SR and in AFib.

Results

Overall PVI real-time observation rate was 82.1% (491/598 PV) with significantly higher TTI observation rate in the SR group (315/365 PV, 86.3%) compared to the AFib group (176/233 PV, 75.5%; p < 0.001). Per vein analysis demonstrated that only TTI observation rate in the left superior pulmonary vein (LSPV) was significantly higher during SR (85/92, 92.4%) compared to AFib (37/54, 68.5%; p < 0.001). Regression analysis revealed that atrial rhythm is a strong and independent predictor of PVI real-time observation in the LSPV with an odds ratio of 4.98 (95%-CI: 1.86–13.34, p = 0.001) to detect TTI during SR.

Conclusions

Our results demonstrate that correct interpretation of PV electrograms and thus PVI real-time observation is more likely in SR than in AFib. Hence, cardioversion of patients in AFib at the beginning of the procedure should be considered to yield higher PVI real-time observation rates facilitating TTI guided cryoenergy titration.

Cryoballoon ablation of persistent atrial fibrillation: feasibility and safety of left atrial roof ablation with generation of conduction block in addition to antral pulmonary vein isolation

Aims

Although the generation of linear lesions by ablation improves success rates in patients with persistent atrial fibrillation (AF), the procedure has been considered unsuitable for cryoablation balloon catheter technologies. We developed a technique for linear ablations, using second-generation cryoballoon technology.

Methods and results

This was a single-arm, prospective study in 76 patients with persistent AF treated consecutively at our centre. Cryoablation was performed using a 28 mm second-generation cryoballoon. The first cryoenergy application was performed in close proximity to the position during isolation of the left superior pulmonary vein (PV). Sequential overlapping freezes were applied along the left atrial (LA) roof by slight clockwise rotation of the sheath in combination with slight retraction of the sheath and incremental advancement of the cryoballoon, until reaching the original position for right superior PV isolation. The acute endpoint was the creation of a roofline, defined as complete conduction block across the LA roof >120 ms and ascending activation across the posterior LA wall. Acute success in roofline generation was achieved in 88% of patients, applying on average five (median 4-6) freezes with nadir temperature of -40°C (-36 to -44°C). In five patients, conduction block could not be achieved. No phrenic nerve injuries occurred during roofline generation.

Conclusion

Generation of linear roofline lesions is possible with the second-generation cryoballoon. The technique can be used in combination with PV isolation to treat persistent AF with good acute success rates, short procedure times, and acceptable safety concerns. If validated by further studies, the method would be an appealing alternative to radiofrequency ablation techniques.

Characteristics of dormant pulmonary vein conduction induced by adenosine triphosphate in patients with atrial fibrillation undergoing cryoballoon ablation

BACKGROUND

Adenosine triphosphate (ATP) can provoke acute reconnections after pulmonary vein isolation (PVI). This study aimed to investigate dormant conduction (DC) after ablation with second-generation cryoballoon (CB).

METHODS

Two hundred sixteen patients (148 male; age 64±9 years) with atrial fibrillation (AF) were included. After a successful PVI with the CB, 20mg of ATP was administered. All patients were followed up for 425±56 days.

RESULTS

Seven hundred ninety-five out of 864 (92%) PVs were successfully isolated solely by the CB. DCs were revealed in 8 (3.7%) after ATP injections. AF recurrences occurred in 2 out of 8 patients, while no AF recurrences could be documented in 6 out of 8 patients with DCs after a blanking period of 3 months (25% vs. 75%). In contrast, 29 (13.9%) patients without DCs had AF recurrences, and there was no significant difference between those with and without DCs regarding the recurrence rate of AF (p=0.38). There were no reliable predictors of DCs after the PVI with the CB.

CONCLUSION

The present study demonstrated a low rate of transient PV reconnection after adenosine infusion following successful PVI with the CB. There was no reliable predictor of DCs. Further studies will be needed in order to appreciate the prognostic value of adenosine testing after successful PVI with the CB.

The Impact of Advances in Atrial Fibrillation Ablation Devices on the Incidence and Prevention of Complications

The number of patients with atrial fibrillation currently referred for catheter ablation is increasing. However, the number of trained operators and the capacity of many electrophysiology labs are limited. Accordingly, a steeper learning curve and technical advances for efficient and safe ablation are desirable. During the last decades several catheter-based ablation devices have been developed and adapted to improve not only lesion durability, but also safety profiles, to shorten procedure time and to reduce radiation exposure. The goal of this review is to summarise the reported incidence of complications, considering device-related specific aspects for point-by-point, multi-electrode and balloon-based devices for pulmonary vein isolation. Recent technical and procedural developments aimed at reducing procedural risks and complications rates will be reviewed. In addition, the impact of technical advances on procedural outcome, procedural length and radiation exposure will be discussed.

Cryoballoon Ablation for Atrial Fibrillation: a Comprehensive Review and Practice Guide

The cryoballoon was invented to achieve circumferential pulmonary vein isolation more efficiently to compliment the shortcomings of point-by-point ablation by radiofrequency ablation (RFA). Its efficacy and safety were shown to be comparable to those of RFA, and the clinical outcomes have improved with the second-generation cryoballoon. The basic biophysics, implemental techniques, procedural recommendations, clinical outcomes, and complications of the cryoballoon are presented in this practical and systematic review.

How to Prevent, Detect and Manage Complications Caused by Cryoballoon Ablation of Atrial Fibrillation

Atrial fibrillation is the most common cardiac arrhythmia and the prevalence is increasing every year. Patients who fail to maintain sinus rhythm with use of anti-arrhythmic drug therapy are referred for catheter ablation. Cryoballoon (CB) ablation has emerged as an effective and alternative treatment option to traditional point-by-point radiofrequency ablation, but there can be complications. This article reviews the incidence, presentation, risk factors, management and preventative strategies of three major complications associated with CB ablation: phrenic nerve injury, atrial oesophageal fistula and bronchial injury. Although these complications are rare, electrophysiologists should institute measures to identify high-risk patients, implement best-practice techniques to minimise risks and maintain a high index of suspicion to recognise the complications quickly and implement correct treatment strategies.

Complications of Atrial Fibrillation Cryoablation

Catheter ablation either by using radiofrequency or cryo energy in symptomatic patients with atrial fibrillation (AF) has shown to be effective as compared to anti-arrhythmic drugs. However, all the techniques used during AF ablation are not free of complication. There are several well-known peri-procedural complications in which operators should be informed of the possible risks, cautious during the procedure and able to manage them when occurred. Herein, we aimed to review possible complications of AF cryoablation.

Vagal response in cryoballoon ablation of atrial fibrillation and autonomic nervous system: Utility of epicardial adipose tissue location

Background

Mechanism and effects of vagal response (VR) during cryoballoon ablation procedure on the cardiac autonomic nervous system (ANS) are unclear. The present study aimed to evaluate the relationship between VR during cryoballoon catheter ablation for atrial fibrillation and ANS modulation by evaluating epicardial adipose tissue (EAT) locations and heart rate variability (HRV) analysis.

Methods

Forty-one patients with paroxysmal atrial fibrillation (11 with VR during the procedure and 30 without VR) who underwent second-generation cryoballoon ablation were included. EAT locations and changes in HRV parameters were compared between the VR and non-VR groups, using Holter monitoring before ablation, immediately after ablation and one month after ablation.

Results

The total EAT volume surrounding the left atrium (LA) in the VR and non-VR groups was 29.0±18.4 cm³ vs 27.7±19.7 cm³, respectively (p=0.847). The VR group exhibited greater EAT volume overlaying the LA-left superior pulmonary vein (PV) junction (6.1±3.6 cm³ vs 3.6±3.3 cm³, p=0.039) than the non-VR group. HRV parameters similarly changed following ablation in both the groups. EAT volume overlaying LA-right superior PV junction was significantly correlated with the relative changes in root-mean-square successive differences (r=−0.317, p=0.043) and high frequency (r=−0.331, p=0.034), immediately after the ablation.

Conclusions

Changes in HRV parameters following ablation were similarly observed in both the groups. EAT volume on the LA-PV junction is helpful for interpretation of VR occurrence and ANS modulation.

A multicenter study of the need of additional freezing for cryoballoon ablation in patients with atrial fibrillation: The AD-Balloon study

Background

Pulmonary vein isolation (PVI) is a cornerstone of catheter ablation in patients with paroxysmal atrial fibrillation (PAF), and balloon-based ablation has been recently performed worldwide. Ablation using the second-generation cryoballoon (CB2) (Arctic Front Advance^TM, Medtronic, MN, USA) is useful for PVI; however, there is some debate concerning the optimal freezing time and number of cycles after PVI is achieved.

Methods

The AD-Balloon study was designed as a prospective, multicenter, randomized clinical trial to evaluate the optimal strategy (freezing cycles) of CB2 ablation (UMIN Clinical Trials Registry UMIN000020130). The main objective of this study is to investigate the need for an additional freezing cycle after PVI in patients treated with CB2 ablation. Patients will be randomly assigned in a 1:1 ratio to treatment with additional freezing (AD group) or without additional freezing (non-AD group). In the AD group, 3 min of additional freezing time will be applied in all pulmonary veins after PVI is confirmed at the previous freezing cycle. In the non-AD group, no additional freezing will be applied in all pulmonary veins after PVI is confirmed. The primary endpoint of this study is the occurrence of atrial tachyarrhythmias within a 1-year follow-up period. We will enroll 110 consecutive patients with PAF. We will also investigate the usefulness of delayed-enhancement magnetic resonance imaging to assess the ablation lesions caused by CB2 ablation.

Results

The results of this study are currently under investigation.

Conclusion

The AD-Balloon study would assess the need for an additional freezing cycle after PVI is achieved. Our findings may contribute to further improvement of the CB2 ablation procedure.

Comparison of Phrenic Nerve Injury during Atrial Fibrillation Ablation between Different Modalities, Pathophysiology and Management

Atrial fibrillation ablation has emerged as an effective tool in the management of symptomatic atrial fibrillation. Currently, the electrophysiologists are striving to maximize the success while minimizing complications. Phrenic nerve injury (PNI) is one of the concerning complications, especially in cases of cryoballoon ablation. Due to anatomical proximity to atrial tissue, phrenic nerve is particularly susceptible to injury. With evolving monitoring techniques it is now possible to minimize the likelihood of a permanent PNI. However, the challenge remains to detect PNI at the earliest and to avoid further damage to the nerve. In this review, we discuss pertinent anatomical principles, techniques to avoid PNI and management in cases where PNI is encountered.

The Hot and the Cold: Radiofrequency Versus Cryoballoon Ablation for Atrial Fibrillation

Catheter ablation is superior to antiarrhythmic drugs in maintaining sinus rhythm for patients with atrial fibrillation (AF). Pulmonary vein (PV) isolation is the cornerstone of any AF ablation procedure. Conventionally, this is achieved by performing point by point lesions using radiofrequency (RF) energy. However, this is technically challenging, time consuming and is associated with a number of complications. Long-term durability of PV isolation is also a concern. To address these issues, 'one-shot' energy delivery systems and alternative energy sources have been developed. The cryoballoon system has emerged as the most commonly used alternative to point by point RF technology. In this paper, we compare the technology, biophysics and clinical data of cryoballoon to conventional RF ablation for AF. The safety and efficacy of cryoballoon compared to RF ablation is critically reviewed. We conclude by looking at future applications of this technology.

Incidence and Predictors of Complications During Cryoballoon Pulmonary Vein Isolation for Atrial Fibrillation

BACKGROUND

Cryoballoon pulmonary vein isolation (PVI) has emerged as an alternative to radiofrequency PVI for atrial fibrillation (AF). Data are lacking to define the rates and predictors of complications, particularly phrenic nerve injury (PNI).

METHODS AND RESULTS

We evaluated a single-center prospective registry of 450 consecutive patients undergoing cryoballoon PVI between 2011 and 2015. Patients were 59±10 years old, 26% were women, 58% had hypertension, their mean CHA2DS2VASc score was 1.7±1.3, 30% had persistent atrial fibrillation, and 92% received a second-generation 28-mm balloon. Predefined major complications were persistent PNI, pericardial effusion, deep vein thrombosis, arteriovenous fistula, atrioesophageal fistula, bleeding requiring transfusion, stroke, and death. PNI was categorized as persistent if it persisted after discharge from the laboratory. Logistic regression was performed to identify predictors of complications and specifically PNI. We identified a major complication in 10 (2.2%) patients. In 49 (10.8%) patients, at least transient PNI was observed; only 5 persisted beyond the procedure (1.1%). All cases of PNI resolved eventually, with the longest time to resolution being 48 days. We also describe 2 cases of PNI manifesting after the index hospitalization. Regression analysis identified 23-mm balloon use (16.3% versus 5.2%, odds ratio 2.94, P=0.011) and increased age (62.8±7.7 versus 58.7±0.12 years, odds ratio 1.058, P=0.014) as independent significant predictors of PNI. There were no significant predictors of major complications.

CONCLUSIONS

In a large contemporary cohort, cryoballoon PVI is associated with low procedural risk, including lower rates of PNI than previously reported. Older age and 23-mm balloon use were associated with PNI. Our low rate of PNI may reflect more sensitive detection methods, including compound motor action potential monitoring and forced double-deflation.

Prevalence and Pre-Procedural Predictors Associated With Right Phrenic Nerve Injury in Electromyography-Guided, Second-Generation Cryoballoon Ablation: Single Large Balloon and Single 3-Minute Freeze Techniques

OBJECTIVES

This study aimed to evaluate the incidence and pre-procedural predictors of right phrenic nerve injury (PNI) in electromyography-guided, second-generation cryoballoon (CB) ablation.

BACKGROUND

Second-generation CBs perform better pulmonary vein isolation (PVI) than first-generation CBs; however, right PNI remains a concern.

METHODS

One hundred consecutive patients with paroxysmal atrial fibrillation who underwent cryoablation were prospectively enrolled. Contrast-enhanced cardiac multidetector computed tomography (MDCT) was obtained pre-procedurally. PVI was performed with one 28-mm second-generation balloon using a 3-min freeze technique under electromyography guidance.

RESULTS

In all, 377 of 392 (96.2%) PVs were isolated using a CB. In 9 (9.0%) patients, right PNI was observed during the ablation of the right superior PV (RSPV). All events occurred during freezing, except for 1 that occurred during thawing. Right peri-cardiophrenic bundles (RPCBs) were identified at the level of the RSPV on MDCT in 97 patients. In the logistic regression analysis, the distance from the RSPV ostium to the RPCBs (hazard ratio: 0.263; 95% confidence interval [CI]: 0.110 to 0.630; p = 0.003) was the sole predictor of PNI. The optimal cutoff point for the distance for predicting right PNI was 12.4 mm (sensitivity 96.6%, specificity 88.9%) with an area under the curve of 0.968 (95% CI: 0.922 to 1.000). The PNI resolved spontaneously within 1 day and 2 months in 6 and 2 patients, respectively, and at 8 months in the remaining patient, with delayed recognition of an electromyography decrease.

CONCLUSIONS

Persistent right PNI is a rare complication during electromyography-guided, second-generation CB ablation. Electromyography should be monitored even during the thawing time. Pre-procedural MDCT might be useful for risk stratification of right PNI.

ECG-Guided Surveillance Technique in Cryoballoon Ablation for Paroxysmal and Persistent Atrial Fibrillation: A Strategy to Prevent From Phrenic Nerve Palsy

AIMS

Phrenic nerve palsy (PNP) is still a cause for concern in Cryoballoon ablation (CBA) procedures. New surveillance techniques, such as invasive registration of the compound motor action potential (CMAP), have been thought to prevent the occurrence of PNP. The present study investigates the impact of CMAP surveillance via an alternative and non-invasive ECG-conduction technique during CBA.

METHODS

PVI with CBA was performed in 166 patients suffering from AF. Diaphragmal contraction was monitored by abdominal hands-on observation in Observation Group I; Observation Group II was treated using additional ECG-conduction, as a means of modified CMAP surveillance method. During the ablation of the right superior and inferior pulmonary veins, the upper extremities lead I was newly adjusted between the inferior sternum and the right chest, thereby recording the maximum CMAP. The CMAP in the above-mentioned ECG leads was continuously observed in a semi-quantitative manner.

RESULTS

PNP was observed in 10 (6%) patients in total. In Observation Group I, 6 out of 61 (9.8%) demonstrated PNP. In Observation Group II a significant decrease of PNP could be demonstrated (p <0,001) and occurred in 4 out of 105 patients (3.8%). While three patients from Observation Group I left the EP lap with an ongoing PNP, none of the patients in Observation Group II had persistent PNP outside of the EP lab.

CONCLUSION

The present study demonstrates that additional ECG-conduction, used as modified CMAP surveillance, is an easy, effective and helpful additional safety measure to prevent PNP in CBA.

[Cryoablation: Clinical applications in cardiac electrophysiology from their biophysical bases]

Cryoablation is an energy alternative to radiofrequency for ablation of various arrhythmias, where its unique biophysical properties offer a greater safety profile. Since its first use for the surgical treatment of different arrhythmias until its conceptualization in the current technical transcatheter, cryoablation has proven not to be only a safe source of energy, but also an effective source in the long-term. While the radiofrequency has been the energy most used for isolation of pulmonary veins in atrial fibrillation ablation, technological advances in cryoballon have managed to simplify the procedure without sacrificing its effectiveness. Cryoablation has been widely used for arrhythmias located in high-risk locations, such as the ablation of the atrioventricular nodal reentrant tachycardia and septal accessory pathways, due to its theoretical null risk of complete AV block. This review intends to give the clinical applications of the cryothermy through a thorough understanding of their biophysical basis.