How close are the phrenic nerves to cardiac structures? Implications for cardiac interventionalists

Combined approach of high-power and very high-power, short-duration ablation in superior vena cava isolation

INTRODUCTION

The effectiveness and safety of 50 W, high-power, short-duration (HPSD) ablation in superior vena cava isolation (SVCI) for patients with atrial fibrillation (AF) have been reported. However, the acute outcomes of SVCI combined with 90 W/4 s, very high-power, short-duration (vHPSD) ablation remain unknown. In this study, we aimed to investigate a novel approach that combines 50 W-HPSD and 90 W/4 s-vHPSD ablation in SVCI and to elucidate the characteristics, outcomes, and safety of this approach by comparing SVCI with conventional ablation index (AI)-guided middle-power, middle-duration (MPMD) ablation.

METHODS

Overall, 126 patients who underwent AF ablation with SVCI using the QDOT MICROTM catheter were retrospectively reviewed; one group underwent SVCI with a combined approach of HPSD and vHPSD ablation (50 W/90 W group, n = 73) and another group underwent AI-guided MPMD ablation (30-40 W group, n = 53). This study compared the procedural details, radiofrequency (RF) ablation profiles, and complications. The RF settings used in the 50 W/90 W group were 50 W/7 s for the lateral segment close to the phrenic nerve and 90 W/4 s for the nonlateral segment.

RESULTS

The 50 W/90 W group required a significantly shorter procedural time (3.2 vs. 5.9 min, p < .001), shorter RF duration (42.0 vs. 162.0 s, p < .001), and lower RF energy (2834 vs. 5480 J, p < .001) than the 30-40 W group. Procedural success, first-pass SVCI, number of RF applications, and SVC reconnection after isoproterenol loading were comparable between the groups. The maximum tip-electrode temperature of the multi-thermocouple system was significantly higher in the 50 W/90 W group than in the 30-40 W group (50.0°C vs. 47.0°C, p < .001). No complications, such as phrenic nerve injury or bleeding requiring transfusion, were observed in either group.

CONCLUSIONS

The combined approach of 50 W/7 s-HPSD and 90 W/4 s-vHPSD ablation resulted in successful and safe SVCI with shorter procedural time, shorter RF duration, and lower RF energy.

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.

Pentaspline Pulsed Field Ablation Catheter Versus Cryoballoon for Atrial Fibrillation Ablation: Results From a Prospective Comparative Study

BACKGROUND

Cryoballoon ablation is currently the gold standard technique for single-shot pulmonary vein isolation (PVI). Pulsed field ablation (PFA) has recently emerged as an interesting nonthermal alternative energy for PVI. The purpose of our study was to evaluate the safety and long-term efficacy of PVI using the pentaspline PFA catheter in comparison to cryoballoon ablation.

METHODS AND RESULTS

Between January 2021 and December 2022, we included all consecutive patients of our center in whom a first PVI-only procedure was performed using PFA or cryoballoon. The choice of the energy was based on patients' preference between general anesthesia (PFA) and local anesthesia (cryoballoon). The primary end point was freedom from documented atrial arrhythmia recurrence after a 3-month blanking period. A total of 301 patients (paroxysmal atrial fibrillation in 220 patients) underwent a first PVI procedure performed using PFA (n=151) or cryoballoon (n=150). Complete short-term PVI was obtained in 144 of 150 patients (96%) in the cryoballoon group and in all patients of the PFA group (P=0.01). Procedure duration was significantly longer in the cryoballoon group. Transient and persistent phrenic nerve injuries were observed in the cryoballoon group only (13/150 and 2/150, respectively). One-year freedom from atrial arrhythmia was significantly higher in the PFA group compared with the cryoballoon group (87.9% versus 77.7%; adjusted hazard ratio, 0.53 [95% CI, 0.30-0.96]; P=0.037).

CONCLUSIONS

This prospective, comparative, real-life study suggested that PFA could overcome safety limitations of cryoballoon with optimal effectiveness. Randomized controlled studies are required to further investigate the potential superiority of PFA over cryoballoon.

Phrenic nerve injury after atrial fibrillation ablation: different recovery courses among cryoballoon, laser balloon, and radiofrequency ablation

BACKGROUND

Phrenic nerve injury (PNI) is one of the common complications in atrial fibrillation (AF) ablation, which often recovers spontaneously. However, the course of its recovery has not been examined fully, especially in regard to the different ablation methods. We sought to compare the recovery course of PNI in cryoballoon, laser balloon, and radiofrequency ablation.

METHODS

This multicenter retrospective study analyzed 355 patients who suffered from PNI during AF ablation. PNI occurred during cryoballoon ablation (CB group) and laser balloon ablation (LB group) for a pulmonary vein isolation in 288 and 20 patients, and radiofrequency ablation for a superior vena cava (SVC) isolation (RF-SVC group) in 47 patients, respectively RESULTS: There was a significant difference in the estimated probability of PNI recovery after the procedure between the methods (p = 0.01). PNI recovered significantly earlier in the CB group, especially within 24 h and 3 months post-procedure (the percentage of the recovery within 24 h and 3 months: 49.7% and 71.5% in the CB group, 15.0% and 22.2% in the LB group, and 23.4% and 41.9% in the RF-SVC group, respectively). Persistent PNI after 12 months was observed in only seven patients in the CB group, one in the LB group, and four in the RF-SVC group, respectively.

CONCLUSION

PNI rarely persists over 12 months after AF ablation; however, there is a difference in the timing of its recovery. PNI recovers quicker with cryoballoon ablation than with laser balloon ablation or radiofrequency ablation of the SVC.

Contrast-enhanced computed tomography in the venous rather than the arterial phase is essential for the evaluation of the right phrenic nerve

BACKGROUND

Preprocedural detection of the running course of the right pericardiophrenic bundles (PBs) is considered to be useful in preventing phrenic nerve (PN) injury during catheter ablation for atrial fibrillation (AF). However, previous studies using the arterial phase of contrast-enhanced computed tomography (CT) reported a relatively low right PBs detection rate.

METHODS

This study included 63 patients with AF who underwent catheter ablation and preoperative contrast-enhanced CT imaging of the venous and arterial phases (66.7 ± 10.2 years; 44 male). The venous phase of contrast-enhanced CT significantly improved the detection rate of PBs compared to the arterial phase (96.8% vs. 60.3%, p < .001), and PBs were detected in the venous phase only in 23 (36.7%) patients. No significant differences were observed between the right PBs detection rate using non-contrast CT versus the arterial phase of contrast-enhanced CT (p = .37). Patients without visualization of the right PBs during the arterial phase had a higher frequency of chronic heart failure (p = .0083), lower left ventricular ejection fraction (p = .021), and a higher CHADS2 score (p = .048) than those with visualization. In five patients whose right PBs could only be detected during the venous phase of contrast-enhanced CT, the reconstructed running course of the right PBs corresponded with the PN generated by electrical high-output pacing.

CONCLUSION

Contrast-enhanced CT images of the venous phase, rather than the arterial phase, are useful in detecting the right PBs, especially in patients with heart failure or reduced left ventricular ejection fraction.

Conservative rehabilitation therapy for respiratory dysfunction due to phrenic nerve sacrifice during resection of massive mediastinal tumor: A case series study

RATIONALE

Cases of respiratory dysfunction due to phrenic nerve sacrifice during resection of massive mediastinal tumor have rarely been studied in detail. Diaphragmatic dysfunction in such cases can lead to potentially fatal respiratory and circulatory disturbances. Therefore, timely diagnosis and intervention are important. Conservative rehabilitation therapy is the first choice for respiratory dysfunction due to diaphragmatic dysfunction.

PATIENT CONCERNS, DIAGNOSES AND INTERVENTIONS

We present 3 patients with respiratory dysfunction due to phrenic nerve sacrifice during resection of massive mediastinal tumor. The diagnostic methods and therapeutic procedures for diaphragmatic dysfunction for each patient are described in detail. This study highlights the role of ventilator support combined with physical therapy in the treatment of respiratory dysfunction in such cases. The diagnosis of diaphragmatic dysfunction as well as the risk assessment of phrenic nerve involvement are also discussed. The modalities of ventilator support, including modes and parameters, are listed.

OUTCOMES AND LESSONS

This study provides experiences of diagnosis and treatment of respiratory dysfunction due to phrenic nerve sacrifice during resection of massive mediastinal tumor. Timely diagnosis of diaphragmatic dysfunction primarily relies on clinical manifestations and radiography. Conservative rehabilitation therapy can improve or restore diaphragmatic function in majority of patients, and avert or delay the need for surgical intervention. Preoperative assessment of the risk of phrenic nerve involvement is important in such cases.

Optimal prevention method of phrenic nerve injury in superior vena cava isolation: efficacy of high-power, short-duration radiofrequency energy application on the risk points

BACKGROUND OR PURPOSE

Superior vena cava isolation (SVCI) is widely performed adjunctively to atrial fibrillation (AF) ablation. Right phrenic nerve injury (PNI) is a complication of this procedure. The purpose of the study is to determine the optimal PNI prevention method in SVCI.

METHODS

A total of 1656 patients who underwent SVCI between 2009 and 2022 were retrospectively examined. PNI was diagnosed based on the diaphragm position and movement in the upright position on chest radiographs before and after SVCI.

RESULTS

With the introduction of various PN monitoring systems over the years, the incidence of SVCI-associated PNI has decreased. However, complete PNI avoidance has not been achieved. PNI incidence according to fluoroscopy-guided PN monitoring, high-output pace-guided, compound motor action potential-guided, and 3-dimensional electro-anatomical mapping (EAM) systems was 8.1% (38/467), 2.7% (13/476), 2.4% (4/130), and 2.8% (11/389), respectively. However, a high-power, short-duration (50 W/7 s) radiofrequency (RF) energy application only on PNI risk points tagged by a 3-dimensional EAM system completely avoids PNI (0%; 0 /160 since April 2021). PNI showed no symptoms and recovered within an average of 188 days post-SVCI, except for a few patients who required > 1 year.

CONCLUSIONS

Although PNI incidence decreased annually with the introduction of various monitoring systems, these monitoring systems did not prevent PNI completely. Most notably, the delivery of a high-power, short-duration RF energy only on risk points tagged by EAM prevented PNI completely. PNI recovered in all patients. The application of higher-power, shorter-duration RF energy on risk points tagged by EAM appears to be an optimal PNI prevention maneuver.

Phrenic Relocation by Endoscopy, Intentional Pneumothorax Using Carbon Dioxide, and Single Lung Ventilation (PHRENICS) Technique

Strategies to prevent right phrenic nerve (PN) injury during catheter ablation can be difficult to employ, ineffective, and risky. A novel PN-sparing technique involving single lung ventilation followed by "intentional pneumothorax" was prospectively evaluated in patients with multidrug refractory periphrenic atrial tachycardia (AT). This hybrid technique, termed PHRENICS (Phrenic Relocation by Endoscopy & Intentional Pneumothorax using Carbon Dioxide & Single Lung Ventilation), resulted in effective PN relocation away from the target site in all cases, allowing successful catheter ablation of AT without procedural complication or arrhythmia recurrence. The PHRENICS hybrid ablation technique can effectively mobilize the PN, avoiding unnecessary invasion of the pericardium, and can expand the safety of catheter ablation for periphrenic AT.

Conservative rehabilitation therapy for respiratory dysfunction due to phrenic nerve sacrifice during resection of massive mediastinal tumor.. [DOI: 10.21203/rs.3.rs-2423006/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Background: Cases of respiratory dysfunction due to phrenic nerve sacrifice during resection of massive mediastinal tumor have rarely been studied in detail. Diaphragmatic dysfunction in such cases can lead to potentially fatal respiratory and circulatory disturbances. Therefore, timely diagnosis and intervention are important. Conservative rehabilitation therapy is the first choice for respiratory dysfunction due to diaphragmatic dysfunction. Case presentation: We present three patients with respiratory dysfunction due to phrenic nerve sacrifice during resection of massive mediastinal tumor. The diagnostic methods and therapeutic procedures for diaphragmatic dysfunction for each patient are described in detail. This study highlights the role of ventilator support combined with physical therapy in the treatment of respiratory dysfunction in such cases. The diagnosis of diaphragmatic dysfunction as well as the risk assessment of phrenic nerve involvement are also discussed. The modalities of ventilator support, including modes and parameters, are listed. Conclusions: This study provides experiences of diagnosis and treatment of respiratory dysfunction due to phrenic nerve sacrifice during resection of massive mediastinal tumor. Timely diagnosis of diaphragmatic dysfunction primarily relies on clinical manifestations and radiography. Conservative rehabilitation therapy can improve or restore diaphragmatic function in majority of patients, and avert or delay the need for surgical intervention. Preoperative assessment of the risk of phrenic nerve involvement is important in such cases.

3D mapping of phrenic nerve course for radiofrequency pulmonary vein isolation

INTRODUCTION

Phrenic nerve (PN) injury is a rare but severe complication of radiofrequency (RF) pulmonary vein isolation (PVI). The objective of this study was to characterize the typical intracardiac course of the PN with a three-dimensional electroanatomic mapping system, to quantify the need for modification of the ablation trajectory to avoid delivering an ablation lesion on sites with PN capture, and to identify very circumscribed areas of common PNC on the routine ablation trajectory of a RF-PVI, allowing fast and effective PN screening for everyday usage.

METHODS

We enrolled 137 consecutive patients (63 ± 9 years, 64% men) undergoing PVI. A detailed high output (20 mA) pace-mapping protocol was performed in the right (RA) and left atrium (LA) and adjacent vasculature.

RESULTS

The right PN was most commonly captured in the superior vena cava at a lateral (50%) or posterolateral (23%) position before descending along the RA either straight (29%) or with a posterolateral bend (20%). In the LA, beginning deep within the right superior pulmonary vein (RSPV), the right PN is most frequently detectable anterolateral (31%), then descends to the lateral proximal RSPV (23%), and further towards the lateral antral region (15%) onto the medial LA wall (12%). To avoid delivering an ablation lesion on sites with PN capture, modification of ablation trajectory was necessary in 23% of cases, most commonly in the lateral RSPV antrum (81%). No PN injury occurred.

CONCLUSION

PN mapping frequently reveals the close proximity of the PN to the ablation trajectory during PVI, particularly in the lateral RSPV antrum. Routine PN pacing should be considered during RF PVI procedures.

Catheter ablation for atrial fibrillation in patients with persistent left superior vena cava: Case series and systematic review

Introduction

Persistent left superior vena cava (PLSVC) is the most common form of thoracic venous abnormality. Catheter ablation (CA) for atrial fibrillation (AF) can be complicated by the existence of PLSVC, which could act as an important arrhythmogenic mechanism in AF.

Methods and results

We reported a case series of patients with PLSVC who underwent CA for AF at our center between 2018 and 2021. A systematic search was also performed on PubMed, EMBASE, and Web of Science for research reporting CA for AF in patients with PLSVC. Sixteen patients with PLSVC were identified at our center. Ablation targeting PLSVC was performed in 5 patients in the index procedures and in four patients receiving redo procedures. One patient experienced acute procedure failure. After a median follow-up period of 15 months, only 6 (37.5%) patients remained free from AF/atrial tachycardia (AT) after a single procedure. In the systematic review, 11 studies with 167 patients were identified. Based on the included studies, the estimated prevalence of PLSVC in patients undergoing CA for AF was 0.7%. Ablation targeting PLSVC was performed in 121 (74.7%) patients. Major complications in patients with PLSVC receiving AF ablation procedure included four cases of cardiac tamponades (2%), three cases of cardiac effusion (1.5%), one case of ischemic stroke, and three cases of phrenic nerve injury (1.5%) (one left phrenic nerve and two right phrenic nerve). Pooled analysis revealed that after a median follow-up period of 15.6 months (IQR 12.0–74.0 months), the long-term AF/AT-free rate was 70.6% (95% CI 62.8–78.4%, I² = 0.0%) (Central illustration). Different ablation strategies for PLSVC were summarized and discussed in the systematic review.

Conclusion

In patients with PLSVC, recurrence of atrial arrhythmia after CA for AF is relatively common. Ablation aiming for PLSVC isolation is necessitated in most patients. The overall risk of procedural complications was within an acceptable range.

Sinus Tachycardia: a Multidisciplinary Expert Focused Review

Sinus tachycardia (ST) is ubiquitous, but its presence outside of normal physiological triggers in otherwise healthy individuals remains a commonly encountered phenomenon in medical practice. In many cases, ST can be readily explained by a current medical condition that precipitates an increase in the sinus rate, but ST at rest without physiological triggers may also represent a spectrum of normal. In other cases, ST may not have an easily explainable cause but may represent serious underlying pathology and can be associated with intolerable symptoms. The classification of ST, consideration of possible etiologies, as well as the decisions of when and how to intervene can be difficult. ST can be classified as secondary to a specific, usually treatable, medical condition (eg, pulmonary embolism, anemia, infection, or hyperthyroidism) or be related to several incompletely defined conditions (eg, inappropriate ST, postural tachycardia syndrome, mast cell disorder, or post-COVID syndrome). While cardiologists and cardiac electrophysiologists often evaluate patients with symptoms associated with persistent or paroxysmal ST, an optimal approach remains uncertain. Due to the many possible conditions associated with ST, and an overlap in medical specialists who see these patients, the inclusion of experts in different fields is essential for a more comprehensive understanding. This article is unique in that it was composed by international experts in Neurology, Psychology, Autonomic Medicine, Allergy and Immunology, Exercise Physiology, Pulmonology and Critical Care Medicine, Endocrinology, Cardiology, and Cardiac Electrophysiology in the hope that it will facilitate a more complete understanding and thereby result in the better care of patients with ST.

Diaphragmatic CMAP Monitoring During Cryoballoon Procedures: Surface vs. Hepatic Recording Comparison and Limitations of This Approach

Background

Compound motor action potential (CMAP) monitoring is a common method used to prevent right phrenic nerve palsy during cryoballoon ablation for atrial fibrillation.

Objective

We compared recordings simultaneously obtained with surface and hepatic electrodes.

Methods

We included 114 consecutive patients (mean age 61.7 ± 10.9 years) admitted to our department for cryoballoon ablation. CMAP was monitored simultaneously with a hepatic catheter and a modified lead I ECG, whilst right phrenic nerve was paced before (stage 1) and during (stage 2) the right-sided freezes. If phrenic threat was detected with hepatic recordings (CMAP amplitude drop >30%) the application was discontinued with forced deflation.

Results

The ratio of CMAP/QRS was 4.63 (2.67–9.46) for hepatic and 0.76 (0.55–1.14) for surface (p < 0.0001). Signal coefficients of variation during stage 1 were 3.92% (2.48–6.74) and 4.10% (2.85–5.96) (p = 0.2177), respectively. Uninterpretable signals were more frequent on surface (median 10 vs. 0; p < 0.0001). For the 14 phrenic threats, the CMAP amplitude dropped by 35.61 ± 8.27% on hepatic signal and by 33.42 ± 11.58% concomitantly on surface (p = 0.5417). Our main limitation was to achieve to obtain stable phrenic capture (57%). CMAP monitoring was not reliable because of pacing instability in 15 patients (13.16%). A palsy occurred in 4 patients (3.51%) because cryoapplication was halted too late.

Conclusion

Both methods are feasible with the same signal stability and amplitude drop precocity during phrenic threats. Clarity and legibility are significantly better with hepatic recording (sharper signals, less far-field QRS). The two main limitations were pacing instability and delay between 30% CMAP decrease and cryoapplication discontinuation.

The Terminal Anatomy of Phrenic Nerve: a Deeper Look at Diaphragm Innervation Patterns

BACKGROUND

Traumatic brachial plexus injuries are devastating lesions and neurotization is an usually elected surgical therapy. The phrenic nerve has been harvested as motor fibers donor in brachial plexus neurotization, showing great results in terms of motor reinnervation. Unfortunately, these interventions lack solid evidence regarding long-term safety and possible late respiratory function sequelae, raising crescent concerns after the COVID-19 pandemic onset and possibly resulting in reduced propensity to use this technique. The study of the distal anatomy of the phrenic nerves may lead to a better understanding of their branching patterns, and thus the proposition of surgical approaches that better preserve patient respiratory function.

METHODS

Twenty-one phrenic nerves in ten formalized cadavers were scrutinized. Pre-diaphragmatic branching patterns were inspected through analysis of the distance between the piercing site of the nerve at the diaphragm and the cardiac structures, number of divisions, and length from the point where the main trunk emits its branches to the diaphragm.

RESULTS

The main trunk of the right phrenic nerve reaches the diaphragm near the inferior vena cava and branches into three major divisions. The left phrenic nerve reaches the diaphragm in variable locations near the heart, branching into two to five main trunks. Moreover, we noticed a specimen presenting two ipsilateral parallel phrenic nerves.

CONCLUSION

The right phrenic nerve presented greater consistency concerning insertion site, terminal branching point distance to this muscle, and number of rami than the left phrenic nerve.

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.

A novel approach for effective superior vena cava isolation using the CARTO electroanatomical mapping system

BACKGROUND

Previous studies have demonstrated that some patients have spontaneous right atrium (RA)-superior vena cava (SVC) conduction block, which could be utilized to isolate the SVC effectively by using the Rhythmia mapping system (Boston Scientific). However, employing this approach for SVC isolation using the CARTO electroanatomical mapping system (Biosense Webster) has not yet been clarified. This study aimed to evaluate the safety and efficacy of SVC isolation using the extended early meets late (EEML) tool with the CARTO system.

METHODS

The patients who underwent SVC isolation using the CARTO system were enrolled in this study. The RA-SVC conduction block was visualized with an EEML tool. We prospectively assessed the safety and efficacy of SVC isolation using this system.

RESULTS

We analyzed 54 patients, and all SVCs were successfully isolated with no complications. Altogether, 44 patients (81.5%) had spontaneous RA-SVC conduction block, and the remaining 10 patients (18.5%) did not. The block group required fewer radiofrequency deliveries for the SVC isolation than the nonblock group (10.7 ± 5.0 vs 15.5 ± 4.8, P = .009). The size of the isolated area in the block group was larger than that in the nonblock group (15.2 ± 5.1 cm2 vs 12.4 ± 2.5 cm2, P = .017).

CONCLUSIONS

Approximately 80% of the patients in this study developed a spontaneous RA-SVC conduction block, which might contribute to shortening the time of ablation and avoiding complications.

Epicardial access complications during electrophysiology procedures

INTRODUCTION

Percutaneous epicardial access (EA) was first described more than two decades ago. Since its initial introduction, indications for its utilization in the field of electrophysiology have expanded dramatically.

DISCUSSION

Epicardial mapping and ablation in patients with ventricular tachycardia is routinely performed in tertiary electrophysiology centers around the world. Although limited by lack of randomized controlled trials, epicardial ablation for atrial fibrillation has been suggested as a conjunctive strategy in patients who have failed an initial endocardial catheter ablation attempt, and it is necessary for placement of some left atrial appendage occlusion devices as well. An accurate understanding of the cardiac anatomy is crucial to avoid complications such as inadvertent right ventricular puncture, injury to the coronary arteries, abdominal viscera, phrenic nerves, and esophagus during both EA and catheter ablation.

CONCLUSION

The aim of this review is to provide a comprehensive overview of the cardiac anatomy, technical aspects to optimize the safety of epicardial puncture, recognize and avoid potential complications.

Superior vena cava isolation with 50 W high power, short duration ablation strategy

INTRODUCTION

The optimal ablation strategy is unknown regarding a superior vena cava isolation (SVCI). This study aimed to examine the feasibility and safety and to analyze the lesion characteristics of the SVCI using high-power, short-duration (HPSD) ablation.

METHODS AND RESULTS

A total of 100 patients underwent an index SVCI using HPSD (n = 50, HPSD group) or conventional lower-power and longer-duration (n = 50, LPLD group) ablation, using the Thermocool Smarttouch SF. In the HPSD group, ablation was performed with a power of 50 W for 7 s, and was limited to 4 s at the lateral segment close to the right phrenic nerve. The ablation setting used in the LPLD group was 20-25 W for 20-30 s and was limited to 10-20 W for 15-30 s at the lateral segment when diaphragmatic capture was seen. An electrical SVCI was achieved in all patients. The HPSD group required a significantly shorter procedure time (10.8 ± 3.2 vs. 14.8 ± 6.4 min; p < .01), shorter radiofrequency duration (49 ± 16 vs. 282 ± 124 s; p < .01), fewer lesions (8.3 ± 2.5 vs. 10.4 ± 4.4; p < .01), and lower ablation index (316 ± 38 vs. 356 ± 62; p < .001) than the LPLD group. The incidence of a postprocedural asymptomatic mild diaphragmatic elevation was comparable (2% in the HPSD group vs. 6% in the LPLD group; p = .61).

CONCLUSION

The 50-W HPSD ablation strategy allowed for a successful, fast, and safe SVCI with the fewer ablation lesions and the lower ablation index.

Long-term course of phrenic nerve injury after cryoballoon ablation of atrial fibrillation

While phrenic nerve palsy (PNP) due to cryoballoon pulmonary vein isolation (PVI) of atrial fibrillation (AF) was transient in most cases, no studies have reported the results of the long-term follow-up of PNP. This study aimed to summarize details and the results of long-term follow-up of PNP after cryoballoon ablation. A total of 511 consecutive AF patients who underwent cryoballoon ablation was included. During right-side PVI, the diaphragmatic compound motor action potential (CMAP) was reduced in 46 (9.0%) patients and PNP occurred in 29 (5.7%) patients (during right-superior PVI in 20 patients and right-inferior PVI in 9 patients). PNP occurred despite the absence of CMAP reduction in 0.6%. The PV anatomy, freezing parameters and the operator’s proficiency were not predictors of PNP. While PNP during RSPVI persisted more than 4 years in 3 (0.6%) patients, all PNP occurred during RIPVI recovered until one year after the ablation. However, there was no significant difference in the recovery duration from PNP between PNP during RSPVI and RIPVI. PNP occurred during cryoballoon ablation in 5.7%. While most patients recovered from PNP within one year after the ablation, PNP during RSPVI persisted more than 4 years in 0.6% of patients.

Anatomical correlation between left atrium pulmonary vein ablation targets of atrial fibrillation and adjacent bronchi and pulmonary arteries by MSCT

BACKGROUND

The ablation targets of atrial fibrillation (AF) are adjacent to bronchi and pulmonary arteries (PAs). We used computed tomography (CT) to evaluate the anatomical correlation between left atrium (LA)-pulmonary vein (PV) and adjacent structures.

METHODS

Data were collected from 126 consecutive patients using coronary artery CT angiography. The LA roof was divided into three layers and nine points. The minimal spatial distances from the nine points and four PV orifices to the adjacent bronchi and PAs were measured. The distances from the PV orifices to the nearest contact points of the PVs, bronchi, and PAs were measured.

RESULTS

The anterior points of the LA roof were farther to the bronchi than the middle or posterior points. The distances from the nine points to the PAs were shorter than those to the bronchi (5.19 ± 3.33 mm vs 8.62 ± 3.07 mm; P < .001). The bilateral superior PV orifices, especially the right superior PV orifices were closer to the PAs than the inferior PV orifices (left superior PV: 7.59 ± 4.14 mm; right superior PV: 4.43 ± 2.51 mm; left inferior PV: 24.74 ± 5.26 mm; right inferior PV: 22.33 ± 4.75 mm) (P < .001).

CONCLUSIONS

The right superior PV orifices were closer to the bronchi and PAs than other PV orifices. The ablation at the mid-posterior LA roof had a higher possibility to damage bronchi. CT is a feasible method to assess the anatomical adjacency in vivo, which might provide guidance for AF ablation.

Comparison between superior vena cava ablation in addition to pulmonary vein isolation and standard pulmonary vein isolation in patients with paroxysmal atrial fibrillation with the cryoballoon technique

Background

Paroxysmal atrial fibrillation (PAF) can be triggered by non-pulmonary vein foci, like the superior vena cava (SVC). The latter is correlated with improved result in terms of freedom from atrial tachycardias (ATs), when electrical isolation of this vessel utilizing radiofrequency energy (RF) is achieved.

Objectives

Evaluate the clinical impact, in patients with PAF, of the SVC isolation (SVCi) in addition to ordinary pulmonary vein isolation (PVI) by means of the second-generation cryoballoon (CB)

Methods

A total of 100 consecutive patients that underwent CB ablation for PAF were retrospectively selected. Fifty consecutive patients received PVI followed by SVCi by CB application, and the following 50 consecutive patients received standard PVI. All patients were followed 12 months.

Results

The mean time to SVCi was 36.7 ± 29.0 s and temperature at SVC isolation was − 35 (− 18 to − 40) °C. Real-time recording (RTR) during SVCi was observed in 42 (84.0%) patients. At the end of 12 months of follow-up, freedom from ATs was achieved in 36 (72%) patients in the PVI only group and in 45 (90%) patients of the SVC and PV isolation group (Fisher’s exact test p = 0.039, binary logistic regression: p = 0.027, OR = 0.28, 95%CI = 0.09–0.86). In survival analysis, SVC and PV isolation group was also associated with improved freedom from ATs (log-rank test: p = 0.017, Cox regression: p = 0.026, HR = 0.31, 95%CI = 0.11–0.87).

Conclusion

Superior vena cava isolation with the CB in addition to PVI might improve freedom from ATs if compared to PVI alone at 1-year follow-up.

A porcine study of the area of heated tissue during hot-balloon ablation: Implications for the clinical efficacy and safety

INTRODUCTION

Hot-balloon ablation depends solely on thermal conduction, and myocardial tissue is ablated by only conductive heating from the balloon surface. Despite growing clinical evidence of the efficacy and safety of hot-balloon ablation for atrial fibrillation (AF), the actual tissue temperature and the mechanism of heating during such ablation has not been clarified. To determine, by means of a porcine study, the temperatures of tissues targeted during hot-balloon ablation of AF performed with hot-balloon set temperatures of 73°C or 70°C, in accordance with the temperatures now used clinically.

METHODS

After a right thoracotomy, thermocouples with markers were implanted epicardially on the superior vena cava (SVC) and pulmonary veins (PVs) in six pigs. The tissue temperatures during hot-balloon ablation (balloon set temperatures of 73°C and 70°C, 180 s/PV) were recorded, and the maximum tissue temperatures and fluoroscopically measured distance from the balloon surface to the target tissues were assessed.

RESULTS

Sixteen SVC- and 18 PV-targeted energy deliveries were performed. Full-thickness circumferential PV lesions were created with all hot-balloon applications. A significant inverse relation was found between the recorded tissue temperatures and distance (r = -.67; p < .001) from the balloon surface. No tissue temperature exceeded either of the balloon set temperatures. The best distance cutoff value for achieving lethal tissue temperatures more than 50°C was 3.6 mm.

CONCLUSION

The hot-balloon set temperature, energy delivery time, and tissue temperature data obtained in this porcine study supported the clinical efficacy and safety of the hot-balloon ablation as currently practiced in patients with AF.

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.

Use of a multi-electrode radiofrequency balloon catheter to achieve pulmonary vein isolation in patients with paroxysmal atrial fibrillation: 12-Month outcomes of the RADIANCE study

BACKGROUND

The RADIANCE first-in-man study evaluated acute (3-month) safety and design concept in terms of utility of a new multi-electrode radiofrequency (RF) balloon catheter (HELIOSTAR, Biosense Webster) to achieve pulmonary vein isolation (PVI). After study conclusion, a subset of patients was followed up to 12 months.

METHODS

Patients with drug refractory paroxysmal atrial fibrillation were enrolled. Neurological assessment, cardiac and cerebral magnetic resonance imagings were performed pre and post procedure. Ablation was delivered at 15 Watts to each PV for 60 seconds (electrodes adjacent to the posterior wall limited to 20 seconds). Adenosine or isoproterenol was administered to confirm PVI. Esophageal endoscopy was performed 48 hours post procedure. Patients were clinically followed up for 12 months.

RESULTS

Thirty-nine patients underwent catheter ablation from four centers. Mean age was 60.7 ± 10.0 years with 23 (57.5%) being male. Confirmation of PVI was performed in all PVs treated (152/152). Confirmation of isolation after one delivery was performed solely on 137 of 152 PVs of which 79.6% (109/137) achieved isolation with a single delivery of RF energy. Acute PV reconnection was seen in 4.6% (7/150) of PVs. Freedom from documented atrial arrhythmia at 12 months in those followed up was 86.4% (32/37). A total of 75.7% (28/37) of patients were free from atrial arrhythmia and off antiarrhythmic medications.

CONCLUSION

The HELIOSTAR RF balloon catheter allows for rapid and safe PVI with majority of PVs only requiring one application.

Phrenic nerve displacement by intrapericardial balloon inflation during epicardial ablation of ventricular tachycardia: Four case reports

BACKGROUND

Phrenic nerve (PN) injury is one of the recognized possible complications following epicardial ablation of ventricular tachycardia (VT). High-output pacing is a widely used maneuver to establish a relationship between the PN and the ablation catheter tip. An absence of PN capture is usually considered an indication that it is safe to ablate, and that successful ablation may be performed at adjacent sites. However, PN capture may impact the procedural outcome. Only a few cases have been reported in the literature that avoid PN injury by using different techniques.

CASE SUMMARY

Three patients with a previous history of myocarditis and one patient with ischemic cardiomyopathy underwent epicardial ablation for drug-refractory VT. Before the procedure, transthoracic echocardiogram, coronary angiogram, and cardiac magnetic resonance imaging were performed on all patients. Under general anesthesia, endo/epicardial three-dimensional anatomical and substrate maps of the left ventricle were accomplished. Before radiofrequency delivery, the course of the PN was identified by provoking diaphragmatic stimulation with high-output pacing from the distal electrode of the ablation catheter. In every case, a scar region with late potentials was mapped along the PN course. After obtaining another epicardial access, a second introducer sheath was placed, and a vascular balloon catheter was inserted into the epicardial space and inflated with saline solution to separate the PN from the epicardium. Once the absence of PN capture had been proven, radiofrequency was applied to aim for complete late potential elimination and avoid VT induction.

CONCLUSION

PN injury can occur as one of the complications following epicardial VT ablation procedures, and may prevent successful ablation of these arrhythmias. PN displacement by using large balloon catheters into the epicardial space seems to be feasible and reproducible, avoid procedure-related morbidity, and improve ablation success when performed in selected centers and by experienced operators.

Impact of persistent left superior vena cava on radiofrequency catheter ablation in patients with atrial fibrillation

AIMS

The impact of persistent left superior vena cava (PLSVC) in atrial fibrillation (AF) patients undergoing radiofrequency catheter ablation (RFCA) is not well known. We performed this analysis to evaluate the electrophysiological characteristics of PLSVC and its role in triggering and maintaining AF.

METHODS AND RESULTS

Patients with AF referred to two tertiary hospitals were screened and patients with PLSVC in pre-RFCA imaging studies were enrolled. Among 3967 patients, PLSVC was present in 36 patients (0.9%). There were four morphological types of PLSVC: type 1, atresia of the right superior vena cava (SVC) (n = 2); type 2A, dual SVCs with an anastomosis between right and left SVCs (n = 15); type 2B, dual SVCs without an anastomosis (n = 16); type 3, PLSVC draining into the left atrium (LA; n = 2); and unclassified in one patient. Thirty-two patients underwent RFCA and electrophysiology study focusing on PLSVC: PLSVC was the trigger of AF in 48.4% of patients and the driver of AF in 46.9% of patients. Cumulatively, PLSVC was a trigger or driver of AF in 22 patients (68.8%). Whether to ablate PLSVC was determined by the results of electrophysiology study, and no significant difference in the late recurrence rate was observed between patients who did and did not have either trigger or driver from PLSVC.

CONCLUSION

Pre-RFCA cardiac imaging revealed PLSVC in 0.9% of AF patients. This study demonstrated that PLSVC has an important role in initiating and maintaining AF in substantial proportion of patients. Electrophysiology study focusing on PLSVC can help to decide whether to ablate PLSVC.

Topographic characteristics of the left atrial medial isthmus

BACKGROUND

The purpose of this study was to provide detailed topography of the left atrial medial isthmus (situated between the right inferior pulmonary vein ostium and the medial part of the mitral annulus).

METHODS

Two hundred human hearts (Caucasian, 22.5% females, 48.7 ± 4.9 years old) were investigated.

RESULTS

The mean length of the medial isthmus was 42.4 ± 8.6 mm. Additionally, the medial isthmus line was divided by the oval fossa into three sections with equal mean lengths (upper: 14.2 ± 7.2 vs middle: 14.1 ± 6.1 vs lower: 14.9 ± 4.6 mm; P > .05). The left upper section of the atrial wall was thinner than the lower section (2.5 ± 1.1 vs 3.4 ± 1.6 mm; P < .0001). This study noted three separate spatial arrangements of the isthmus line. Type I (54.5%) had an oval fossa located outside the isthmus line; type II (32.5%) had an oval fossa crossed by the isthmus line, and type III (13.0%) had an oval fossa rim located tangentially to the isthmus line. In 68.5% of the examined specimens, the isthmus area had a smooth surface. Conversely, the remaining 31.5% had additional structures within its borders such as diverticula, recesses, and tissue bridges.

CONCLUSION

This study is the first to describe the morphometric and topographical features of the left atrial medial isthmus. Interventions within the medial isthmus line should be performed cautiously, especially when they are transected by the oval fossa (32.5%). Careful navigation of the area is also recommended due to the possibility of existent additional structures. The latter could lead to catheter entrapment during ablation procedures.

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.

An assessment of the distance between the phrenic nerve and major intrathoracic structures

Background

There is a lack of consensus in the literature regarding phrenic nerve proximity to thoracic structures at the level of the diaphragm. This study was undertaken to provide thoracic surgeons data on phrenic nerve location in order to reduce iatrogenic injury during invasive surgery.

Methods

Bilateral thoracic dissection was performed on 43 embalmed human cadavers (25 males; 18 females) and data was obtained from 33 left and 40 right phrenic nerves. The site of phrenic nerve penetration into the diaphragm was identified. Calipers were used to measure the distance from each phrenic nerve to the: inferior vena cava (IVC), descending aorta, esophagus, lateral thoracic wall and anterior thoracic wall.

Results

Mean thoracic diameter of male cadavers was significantly greater than that of female cadavers (P value <0.0001). There was no statistically significant difference between the distances from each phrenic nerve to visceral structures between males and females, except regarding the distance from the right phrenic nerve to the anterior thoracic wall where males exhibited significantly greater distances (P value =0.0234).

Conclusions

This study provides important data on phrenic nerve proximity to intrathoracic structures in an effort to help reduce iatrogenic injury during procedures within the thoracic cavity. Although males had a significantly larger thoracic diameter than females, the only statistically significant difference showed that the right phrenic nerve is deeper in the thoracic cavity in males. As this nerve passes closer to visceral structures it may be more susceptible to damage from pathology in surrounding vessels. This may explain the increased incidence of right phrenic nerve damage due to aortic aneurysm in males reported in the literature.

Anatomic Considerations Relevant to Atrial and Ventricular Arrhythmias

Knowledge of relevant cardiac anatomy is crucial in understanding the pathophysiology and treatment of arrhythmias, and helps avoid potential complications in mapping and ablation. This article explores the anatomy, relevant to electrophysiologists, relating to atrial flutter and atrial fibrillation, ventricular tachycardia relating to the outflow tracts as well as endocardial structure, and also epicardial considerations for mapping and ablation.

Recent advances in cryoballoon ablation for atrial fibrillation

Introduction: Pulmonary vein isolation (PVI), by catheter ablation, represents the current treatment for drug-resistant atrial fibrillation (AF). Nowadays cryoballoon (CB) is a recognized ablation method in patients with atrial fibrillation, mainly due to its ease of use, leading to reproducible and fast procedures. This novel single shot technology literally revolutionized the approach to AF ablation. Areas covered: The historical development of the cryoballoon, ablation techniques and new approaches beyond the ordinary PVI and complications are summarized here. Expert opinion: Although cryoballoon ablation has greatly standardized the approach to PVI a few critical points still need to be clarified scientifically in order to further uniform this procedure in cath labs worldwide. Duration and dosage of the cryoapplication is undoubtedly a topic of great interest.

Right phrenic nerve palsy following transcatheter radiofrequency current atrial fibrillation ablation: Case report

Phrenic nerve palsy (PNP) is a well-known complication of cardiac surgery or jugular/subclavian vein catheterization, presenting with cough, hiccups, dyspnoea/shortness of breath and, in some cases, ventilatory failure. Rarely, PNP is a complication of transcatheter radiofrequency ablation for atrial fibrillation. This report describes the case of a 72-year-old woman with a 2-year history of recurrent paroxysmal atrial fibrillation associated with occasional palpitations and shortness of breath who underwent routine transcatheter radiofrequency ablation. Three days after the procedure, the patient developed shortness of breath and progressive dyspnoea. Motor nerve conduction showed the absence of the right phrenic nerve compound motor action potential compared with the normal left side confirming the diagnosis of a right phrenic nerve palsy. This current case demonstrated the importance of undertaking an electrophysiological evaluation of phrenic nerve conduction after transcatheter radiofrequency ablation in patients presenting with palpitations and shortness of breath even if present a few days after the procedure.

Isolation of the superior vena cava from the right atrial posterior wall: a novel ablation approach

Aims

Superior vena cava (SVC) isolation might be difficult to achieve because of the vicinity of the phrenic nerve (PN) and sinus node. Based on its embryogenesis, we hypothesized the presence of preferential conduction from the right atrial (RA) posterior wall, making it possible to isolate the SVC antrally, sparing its anterior and lateral aspect.

Methods and results

This is a descriptive cohort study of 105 consecutive patients in which SVC isolation was obtained with radiofrequency ablation, starting in the septal aspect of the SVC-RA junction and continued posteriorly and inferiorly targeting sites of early activation until electrical isolation was obtained. Acute SVC isolation was achieved in 103 (98%) patients; the mean distance between the site of SVC isolation and the SVC-RA junction was 19.9 ± 5.3 (range 9.7-33.7) mm. During follow-up, 2 (2%) patients developed symptomatic diaphragmatic paralysis due to transient right PN injury; 13 patients underwent a repeat ablation: SVC reconnection was observed in 5 patients, and re-isolation was easily achieved by targeting the corresponding sites of early activation.

Conclusion

Superior vena cava isolation can be completed by targeting its septal segment and sites of early activation in the posterior SVC-RA junction and RA posterior wall; this is a feasible alternative ablation strategy in patients in which SVC isolation cannot be completed with the standard approach. The risk of sinus node injury or SVC stenosis are eliminated; PN injury is still possible but can easily be prevented with high-output pacing to exclude a true posterior course of the PN.

Super-response to cardiac resynchronization therapy may predict late phrenic nerve stimulation

Aims

Changes in the anatomical relationship between left phrenic nerve and coronary veins may occur due to the reverse remodelling observed in super-responders to cardiac resynchronization therapy (CRT) and might be the underlying mechanism in patients developing late-onset phrenic nerve stimulation (PNS) without evidence of lead dislodgement (LD). In this study, we sought to evaluate the role of super-response (SR) to CRT as a potential predictor of late-onset PNS.

Methods and results

Consecutive patients implanted with a left ventricular (LV) lead in a single centre were retrospectively analysed. Phrenic nerve stimulation was classified as 'early' when it occurred within 3 months of implantation and 'late' for occurrences thereafter. 'Late' PNS was considered related to LD (LD-PNS) when LV threshold differed by > 1 V or impedance >250 Ω from baseline values or in case of radiological displacement. Cases not meeting the former criteria were classified as 'non-LD-PNS'. Super-response was defined as a decrease ≥30% of the left ventricluar end-systolic volume at 1-year echocardiography. At 32 ± 7 months follow-up, PNS occurred in 20 of 139 patients. Late non-LD-PNS incidence was significantly higher in the SR group (8/61; 13.1%) when compared with the non-SR (1/78; 1.3%) (P = 0.010). Super-response remained the only predictor of non-LD-PNS at multivariate analysis (odds ratio: 11.62, 95% confidence interval 1.41-95.68, P = 0.023).

Conclusion

Incidence of late non-LD-PNS is higher among SR to CRT, suggesting a potential role of the changes in the anatomical relationship between left phrenic nerve and coronary veins.

Phrenic Nerve Limitation During Epicardial Catheter Ablation of Ventricular Tachycardia

OBJECTIVES

This study sought to investigate the incidence of phrenic nerve (PN) limitation and the utility of displacing the PN with a balloon.

BACKGROUND

The PN can limit the epicardial ablation of ventricular tachycardia (VT).

METHODS

From 2010 to 2017, 363 patients undergoing VT epicardial ablation at a single center were studied. Before the ablation, we used high output (20-mA) pacing maneuvers to verify the course of the PN. When we observed its capture, we used 1 of 3 different approaches to protect it: 1) non-balloon strategy (nerve-sparing ablation); 2) PN displacement with a small balloon (6 mm × 20 mm); or 3) PN displacement with a large balloon (20 mm × 45 mm).

RESULTS

PN capture occurred in 25 patients (7%) at the target ablation site. The most common cause was myocarditis (12 patients [48%]), and the incidence of the PN limitation was significantly higher in myocarditis than in other causes (19% vs. 4%, respectively; p = 0.0002). PN displacement was attempted in 7 patients by using large balloons and in 6 patients with small balloons, resulting in successful PN displacements and complete late potential (LP) abolition in 6 patients (86%) and 3 patients (50%), respectively. Among the 12 patients in whom the non-balloon strategy was used, only 1 patient (8%) achieved LP abolition (compared with the large balloon group; p = 0.002), whereas 3 patients experienced PN paralysis.

CONCLUSIONS

The PN limited the epicardial ablation in 7% of patients. Because nerve-sparing ablations often resulted in PN injuries, a possible solution could be to displace the PN with a large balloon, leading to a safer procedure and completion of LP abolition.

Partial Recovery of Limb Function Following End-to-Side Screw Anastomosis of Phrenic Nerve in Rats with Brachial Plexus Injury

Background

Brachial plexus injury (BPI), a severe nervous system injury, is a leading cause of functional damages of the affected upper limb. Patients with BPI manifested with motor weakness or paralysis, sensory deficits, and pain. We established a BPI rat model to explore the in vivo effect of end-to-side screw anastomosis (ETSSA) of phrenic nerve on the recovery of limb function after BPI.

Material/Methods

After modeling, rats were treated with end-to-side anastomosis (ETSA) and ETSSA respectively. After 1 and 3 months, the behavioral changes of rats were observed using the Terzis grooming test, and the compound muscle action potential (CMAP) and muscle tension of biceps brachii were detected. The muscle weight recovery rate (MWRR) and cross-sectional area recovery rate (CARR) were calculated. Toluidine blue staining was used to observe the myelinated nerve fibers in the proximal phrenic nerve and distal musculocutaneous nerve of suture. The ratio of regenerated nerve traversing rate (NTR) was counted and motor endplate area of biceps brachii was measured.

Results

The rats treated with ETSA and ETSSA exhibited elevated grading of Terzis grooming test with time. Although both the ETSSA and ETSA can reduce the MWRR, CARR and motor endplate area in BPI rats, ETSSA showed a better influence on the latency delayed rate (LDR) and amplitude recovery rate (ARR) of CMAP, muscular tension recovery rate (MTRR), MWRR, number of regenerated myelinated nerve fibers, NTR, and motor endplate area in BPI rats.

Conclusions

Our study provided evidence that ETSSA can restore the limb function recovery to a greater extent, and accelerate the regeneration of nerve fibers in rats with BPI; the effect of ETSSA was better than that of ETSA.

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.

Anatomy of the atria : A road map to the left atrial appendage

The left atrial appendage (LAA) has received increasing attention in recent years because of thrombi formation in patients with atrial fibrillation, which increases the risk of stroke. In patients who have contraindications for long-term oral anticoagulation therapy, percutaneous procedures are used to occlude the LAA and there are now several devices available for implantation, both endocardially and epicardially. Despite the high-resolution imaging techniques on hand today, limitations remain in providing information about wall thickness and neighboring structures; therefore, in-depth knowledge of the normal atrial anatomy is mandatory when considering such interventions. Here, the anatomy of the right and left atria is reviewed with relevance to interventional procedures required for LAA occlusion. The components of the atria, particularly the LAA as well as the atrial septum, are described with emphasis on their spatial relationships to neighboring cardiac and extracardiac structures. Sound knowledge of the atrial anatomy including endocardial and epicardial aspects is necessary. This will help interventionists take full advantage of imaging techniques when assessing the suitability of the LAA anatomy for closure, selecting the optimal device types and sizes, and guiding the LAA closure procedure, thereby reducing potential complications and increasing procedural success.

Postintervention Dyspnea after Radiofrequency Catheter Ablation: Think of a Phrenic Nerve Injury

Phrenic nerve injury (PNI) is a rare complication of catheter ablation therapy, most commonly observed in cryoablation of the right side pulmonary veins. We present a case of PNI after radiofrequency catheter ablation that developed acute dyspnea 24 hours after the intervention. Dyspnea is the main symptom of PNI, so the diagnosis should always be suspected if it appears after any type of catheter ablation involving the trajectory of the phrenic nerve. There is no specific treatment for PNI. The only maneuver that has been reported to accelerate the recovery of PNI is early stopping of the ablation therapy.