Clinical feasibility of pulmonary vein orifice pacing for the prediction of phrenic nerve injury during cryoballoon ablation of atrial fibrillation.

INTRODUCTION: Phrenic nerve (PN) injury is a well-known complication of cryoballoon ablation (CBA) for pulmonary vein (PV) isolation in patients with atrial fibrillation. However, it is still insufficient to practically predict phrenic nerve injury (PNI) before freezing. We hypothesized that phrenic nerve capture (PNC) with phrenic nerve orifice pacing (PVOP) might be a surrogate sign of the close proximity of the PN, and that might predict PNI and changes in the compound motor action potential (CMAP) amplitude. METHODS: Seventy patients (60 ± 12 years, male 80%, paroxysmal 56%) underwent PVOP with a 20-electrode ring catheter before the CBA. The clinical outcome was the occurrence of transient and persistent PNI. In addition, the PV position and pacing threshold during PNC with PVOP, and changes in the CMAP amplitude were recorded. We compared these measurements between patients with and without PNC (PNC/non-PNC group) with PVOP. RESULTS: PNC with PVOP occurred in 39 (56%) patients and was localized only to the right superior PV. Transient PNI occurred in seven (10%) patients and permanent in none. The CMAP amplitude decreased significantly more in the PNC group (PNC 33% vs non-PNC 16%, P = .027). PNC group had a higher risk of the composite outcome of transient PNI or ≥30% decrease in the CMAP amplitude (PNC 54% vs non-PNC 13%; P < .001). CONCLUSIONS: This PVOP technique could be feasible and contribute to predicting transient PNI and CMAP amplitude reductions before cryoapplications. Further studies are necessary to elucidate the additional efficacy of PVOP over CMAP monitoring alone.

Diaphragmatic dysfunction.

The diaphragm is the main breathing muscle and contraction of the diaphragm is vital for ventilation so any disease that interferes with diaphragmatic innervation, contractile muscle function, or mechanical coupling to the chest wall can cause diaphragm dysfunction. Diaphragm dysfunction is associated with dyspnoea, intolerance to exercise, sleep disturbances, hypersomnia, with a potential impact on survival. Diagnosis of diaphragm dysfunction is based on static and dynamic imaging tests (especially ultrasound) and pulmonary function and phrenic nerve stimulation tests. Treatment will depend on the symptoms and causes of the disease. The management of diaphragm dysfunction may include observation in asymptomatic patients with unilateral dysfunction, surgery (i.e., plication of the diaphragm), placement of a diaphragmatic pacemaker or invasive and/or non-invasive mechanical ventilation in symptomatic patients with bilateral paralysis of the diaphragm. This type of patient should be treated in experienced centres. This review aims to provide an overview of the problem, with special emphasis on the diseases that cause diaphragmatic dysfunction and the diagnostic and therapeutic procedures most commonly employed in clinical practice. The ultimate goal is to establish a standard of care for diaphragmatic dysfunction.

Diaphragm electromyography guidance for a lung transplant recipient with difficult weaning from mechanical ventilation: A case report.

RATIONALE: Many factors contribute to a complicated postoperative course following difficult weaning off a ventilator after lung transplantation. PATIENT CONCERNS: A female patient underwent a successful surgery but received a size-mismatched lung graft. The graft had been pruned before transplantation. She experienced delayed ventilator weaning 3 days after lung transplantation. DIAGNOSES: A postoperative X-ray revealed a normal mediastinal structure and diaphragm position. Diaphragmatic function was assessed by diaphragm electromyography (EMGdi) via esophageal and surface electrodes. EMGdi showed decreased left compound motor action potentials (CMAPs), prolonged left phrenic nerve conduction time (PNCT), failure to induce right CMAPs and PNCT under bilateral magnetic stimulation, and right phrenic nerve injury. INTERVENTIONS: She was treated with neural nutritional support and prescribed rehabilitation measures such as strengthening limb activities on the bed. OUTCOMES: The patient finally achieved satisfactory outcomes after an early diagnosis and medical interventions. LESSONS: Lung size mismatch before transplantation and phrenic nerve injury during surgery should be avoided wherever possible.

Electrical superior vena cava isolation using a novel pace-and-ablate technique under diaphragmatic electromyography monitoring.

BACKGROUND: Diaphragmatic compound motor action potential (CMAP) amplitude monitoring is a standard technique to anticipate phrenic nerve injury during cryoballoon ablation. OBJECTIVE: The purpose of this study was to evaluate the feasibility of a novel superior vena cava isolation (SVCI) technique using simultaneous pacing and ablation through the tip of a single mapping/ablation catheter. METHODS: Fifty-four patients with atrial fibrillation were included. Radiofrequency energy was delivered point by point uniformly for 20 seconds with a power of 20 W until achieving SVCI. Diaphragmatic CMAPs were obtained from modified surface electrodes by high-output pacing from the mapping/ablation catheter throughout the procedure (pace-and-ablate group). Applications were interrupted if CMAP amplitudes significantly decreased without fluoroscopy. The data were compared with those of the 54 patients undergoing conventional SVCI (conventional group). RESULTS: Successful SVCI procedures were achieved in all with a mean of 10.3 ± 2.9 applications. In total, among 559 ablation sites, CMAPs were recorded at 95 (17.0%) with baseline amplitudes of 0.45 ± 0.23 mV. In 10 patients (18.5%), isolation was achieved without any radiofrequency deliveries at CMAP-recorded sites. Among the 95 applications, 6 (6.3%) were interrupted because of CMAP amplitude reductions. At the remaining 88 sites, 20-second radiofrequency applications were delivered without any amplitude decrease (from 0.45 ± 0.21 to 0.46 ± 0.23 mV; P = .885). Phrenic nerve injury occurred in 1 patient in the pace-and-ablate group, which recovered 3 months later, and in 3 conventional group patients, of whom 1 recovered 1 month later (P = .308). The total procedure time tended to be shorter (14.5 ± 6.3 minutes vs 16.7 ± 9.2 minutes; P = .153) and fluoroscopy time significantly shorter (3.9 ± 3.0 minutes vs 6.7 ± 5.7 minutes, P = .002) in the pace-and-ablate group than in the conventional group. CONCLUSION: A novel and simple pace-and-ablate technique under diaphragmatic electromyography monitoring might be feasible for an electrical SVCI.

Intramuscular diaphragmatic stimulation for patients with traumatic high cervical injuries and ventilator dependent respiratory failure: A systematic review of safety and effectiveness.

BACKGROUND: Intramuscular diaphragmatic stimulation using an abdominal laparoscopic approach has been proposed as a safer alternative to traditional phrenic nerve stimulation. It has also been suggested that early implementation of diaphragmatic pacing may prevent diaphragm atrophy and lead to earlier ventilator independence. The aim of this study was therefore to systematically review the safety and effectiveness of intramuscular diaphragmatic stimulators in the treatment of patients with traumatic high cervical injuries resulting in long-term ventilator dependence, with particular emphasis on the affect of timing of insertion of such stimulators. METHODS: The Cochrane database and PubMed were searched between January 2000 and June 2015. Reference lists of selected papers were also reviewed. The inclusion criteria used to select from the pool of eligible studies were: (1) reported on adult patients with traumatic high cervical injury, who were ventilator-dependant, (2) patients underwent intramuscular diaphragmatic stimulation, and (3) commented on safety and/or effectiveness. RESULTS: 12 articles were included in the review. Reported safety issues post insertion of intramuscular electrodes included pneumothorax, infection, and interaction with pre-existing cardiac pacemaker. Only one procedural failure was reported. The percentage of patients reported as independent of ventilatory support post procedure ranged between 40% and 72.2%. The mean delay of insertion ranged from 40 days to 9.7 years; of note the study with the average shortest delay in insertion reported the greatest percentage of fully weaned patients. CONCLUSIONS: Although evidence for intramuscular diaphragmatic stimulation in patients with high cervical injuries and ventilator dependent respiratory failure is currently limited, the technique appears to be safe and effective. Earlier implantation of such devices does not appear to be associated with greater surgical risk, and may be more effective. Further high quality studies are warranted to investigate the impact of delay of insertion on ventilator weaning.

Phrenic nerve protection via packing of gauze into the pericardial space during ablation of cristal atrial tachycardia in a child.

The success of catheter ablation of focal atrial tachycardia is limited by possible collateral damage to the phrenic nerve. Protection of the phrenic nerve is required. Here we present a case of a 9-year-old girl having a history of an unsuccessful catheter ablation of a focal atrial tachycardia near the crista terminalis (because of proximity of the phrenic nerve) who underwent a successful ablation by means of a novel technique for phrenic nerve protection: packing of gauze into the pericardial space. This method is a viable approach for patients with a failed endocardial ablation due to the proximity of the phrenic nerve.

Pulmonary Vein Isolation for Paroxysmal Atrial Fibrillation Using a Circular Multipolar Ablation Catheter: Safety and Efficacy Using Low-Power Settings.

INTRODUCTION: The circular irrigated decapolar nMARQ ablation catheter designed for treating atrial fibrillation (AF) has recently been recalled following two deaths due to esoatrial fistula. Injury to the esophagus has been previously reported in up to 50% of patients using 20-25 W unipolar radiofrequency (RF) energy. Low power of 15 W has been proposed to prevent this complication, but the efficacy of this strategy to avoid AF recurrence is unknown. METHODS AND RESULTS: Consecutive patients with drug-refractory, symptomatic AF were included. Under electroanatomical navigation, the nMARQ catheter was used to isolate all PVs by applying 15 W of unipolar RF simultaneously from up to 10 poles during 40 seconds. Multiple applications were used for each vein, until isolation was achieved. Follow-up was performed after a 2-month blanking period. A total of 50 patients (37 males, age 58 ± 10 years) were included. All PVs were acutely isolated without requiring touch-up by conventional ablation catheters. Pericardial effusion occurred in two patients, of whom one required periocardiocentesis. Right phrenic nerve palsy occurred in another patient, which partially resolved. There were no cases of esophageal fistula or stroke. After a follow-up of 15 ± 4 months, AF recurred in 27/50 (54%) patients. CONCLUSION: The recurrence rate of AF with 15 W unipolar applications is high. Despite use of low power, complications such as pericardial effusion and phrenic nerve palsy may occur.

Clinical experience with a novel electromyographic approach to preventing phrenic nerve injury during cryoballoon ablation in atrial fibrillation.

BACKGROUND: Phrenic nerve palsy remains the most frequent complication associated with cryoballoon-based pulmonary vein (PV) isolation. We sought to characterize our experience using a novel monitoring technique for the prevention of phrenic nerve palsy. METHODS AND RESULTS: Two hundred consecutive cryoballoon-based PV isolation procedures between October 2010 and October 2013 were studied. In addition to standard abdominal palpation during right phrenic nerve pacing from the superior vena cava, all patients underwent diaphragmatic electromyographic monitoring using surface electrodes. Cryoablation was terminated on any perceived reduction in diaphragmatic motion or a 30% decrease in the compound motor action potential (CMAP). During right-sided ablation, a ≥30% reduction in CMAP amplitude occurred in 49 patients (24.5%). Diaphragmatic motion decreased in 30 of 49 patients and was preceded by a 30% reduction in CMAP amplitude in all. In 82% of cases, this reduction in CMAP amplitude occurred during right superior PV isolation. The baseline CMAP amplitude was 946.5±609.2 mV and decreased by 13.8±13.8% at the end of application. This decrease was more marked in the 33 PVs with a reduction in diaphragmatic motion than in those without (40.9±15.3% versus 11.3±10.5%; P<0.001). In 3 cases, phrenic nerve palsy persisted beyond the end of the procedure, with all cases recovering within 6 months. Despite the shortened application all veins were isolated. At repeat procedure the right-sided PVs reconnected less frequently than the left-sided PVs in those with phrenic nerve palsy. CONCLUSIONS: Electromyographic phrenic nerve monitoring using the surface CMAP is reliable, easy to perform, and offers an early warning to impending phrenic nerve injury.

Mapping of the left-sided phrenic nerve course in patients undergoing left atrial catheter ablations.

BACKGROUND: Catheter ablation of atrial fibrillation has been associated with left-sided phrenic nerve palsy. Knowledge of the individual left phrenic nerve course therefore is essential to prevent nerve injury. The aim of this study was to test the feasibility of an intraprocedural pace mapping and reconstruction of the left phrenic nerve course and to characterize which anatomical areas are affected. METHODS: In patients undergoing left atrial catheter ablation, a three-dimensional map of the left atrial anatomical structures was created. The left-sided phrenic nerve course was determined by high-output pace mapping and reconstructed in the map. RESULTS: In this study, 40 patients with atrial fibrillation or atrial tachycardias were included. Left phrenic nerve capture was observed in 23 (57.5%) patients. Phrenic nerve was captured in 22 (55%) patients inside the left atrial appendage, in 22 (55%) in distal parts, in 21 (53%) in medial parts, and in two (5%) in ostial parts of the appendage. In three (7.5%) patients, capture was found in the distal coronary sinus and in one (2.5%) patient in the left atrium near the left atrial appendage ostium. Ablation target was changed due to direct spatial relationship to the phrenic nerve in three (7.5%) patients. No phrenic nerve palsy was observed. CONCLUSIONS: Left-sided phrenic nerve capture was found inside and around the left atrial appendage in the majority of patients and additionally in the distal coronary sinus. Phrenic nerve mapping and reconstruction can easily be performed and should be considered prior catheter ablations in potential affected areas.

Phrenic nerve injury: An underrecognized and potentially preventable complication of pulmonary vein isolation using a wide-area circumferential ablation approach.

INTRODUCTION: Phrenic nerve injury (PNI) is a well-known, although uncommon, complication of pulmonary vein isolation (PVI) using radiofrequency energy. Currently, there is no consensus about how to avoid or minimize this injury. The purpose of this study was to determine how often the phrenic nerve, as identified using a high-output pacing, lies along the ablation trajectory of a wide-area circumferential lesion set. We also sought to determine if PVI can be achieved without phrenic nerve injury by modifying the ablation lesion set so as to avoid those areas where phrenic nerve capture (PNC) is observed. METHODS AND RESULTS: We prospectively enrolled 100 consecutive patients (age 61.7 ± 9.2 years old, 75 men) who underwent RF PVI using a wide-area circumferential ablation approach. A high-output (20 mA at 2 milliseconds) endocardial pacing protocol was performed around the right pulmonary veins and the carina where a usual ablation lesion set would be made. A total of 30% of patients had PNC and required modification of ablation lines. In the group of patients with PNC, the carina was the most common site of capture (85%) followed by anterior right superior pulmonary vein (RSPV) (70%) and anterior right inferior pulmonary vein (RIPV) (30%). A total of 25% of PNC group had capture in all 3 (RSPV, RIPV, and carina) regions. There was no difference in the clinical characteristics between the groups with and without PNC. RF PVI caused no PNI in either group. CONCLUSION: High output pacing around the right pulmonary veins and the carina reveals that the phrenic nerve lies along a wide-area circumferential ablation trajectory in 30% of patients. Modification of ablation lines to avoid these sites may prevent phrenic nerve injury during RF PVI.

Three-dimensional imaging and mapping of the right and left phrenic nerves: relevance to interventional cardiovascular therapy.

AIMS: Phrenic nerves (PNs) can be damaged during interventional cardiovascular therapy because of the nerves' proximity to the heart. This study aimed to analyse the anatomy of the PN by performing three-dimensional (3-D) imaging and pace mapping. METHODS AND RESULTS: Forty consecutive patients with atrial fibrillation referred for catheter ablation were enrolled in this study and underwent preoperative cardiovascular computed tomography (CT). In 10 patients with sinus rhythm during tomography, 3-D images of the right and left pericardiophrenic bundles (PBs), consisting of the ipsilateral PN and accompanying vessels, were reconstructed from the CT data. During the electrophysiological study, PN pace mapping was performed from both atria. The course of the PBs generated by CT imaging and the PN pace map generated by the 3-D mapping system were compared. By electrical pacing, the PNs were captured in 40 individuals (100%) from the superior vena cava and the right atrium, and in 17 patients (43%) from the left atrial appendage. Clear 3-D images of PBs were reconstructed in all cases in which CT-reconstruction was performed. The distance between the locations of the right PB generated by CT imaging and those of the right PN-capture sites in the right-sided heart on the mapping system was 8.7 ± 5.8 mm. CONCLUSIONS: The 3-D routes of the bilateral PNs passing near the heart were verified by pace mapping. The preoperatively reconstructed 3-D course of the PB succeeded in locating the PN, which may facilitate the comprehension of PN anatomy to avoid its injury during interventional cardiovascular therapy.

Outcome of nerve transfers for traumatic complete brachial plexus avulsion: results of 28 patients by DASH and NRS questionnaires.

The objective of this study was to evaluate outcomes of patients who suffered complete brachial plexus avulsion before and after nerve transfers by assessing upper extremity function and pain using the DASH and NRS questionnaires. Patients who underwent nerve transfers improved their DASH and NRS scores compared with before surgery. Although individually there was no correlation with improved scores, the triple combination of rehabilitation exercises, electrical stimulation therapy and neurotrophic drugs postoperatively correlated positively with improved functional outcomes. This study suggested a positive effect of the passage of time and nerve transfers in total brachial plexus avulsions from patients' self assessments.

A prospective study of temporal course of phrenic nerve palsy in children after cardiac surgery.

The aim of the study is to determine the temporal course of phrenic nerve palsy in children after cardiac surgery. Prospective electrophysiological measurement of phrenic nerve latencies and diaphragmatic action potential (DAP) amplitudes before and after operation were recorded in 59 children who underwent open heart surgery for congenital heart disease. In patients with phrenic nerve dysfunction, the procedure was repeated at 1 week and 2 weeks after the operation to determine the temporal course. In the early postoperative period, 12 patients had abnormal left phrenic nerve latencies and/or DAP amplitudes, 11 had abnormal right phrenic nerve latencies and/or DAP amplitudes, and 3 had abnormal bilateral phrenic nerve latencies and/or DAP amplitudes. After 2-week follow-up, only one of these patients had persistent left phrenic nerve palsy. Prolonged phrenic nerve latencies and decreased DAP amplitudes often occur in the early postoperative phase in children who undergo cardiac surgery. This palsy is usually transient, and electrophysiologic studies should be repeated at least up to 1 week after surgery before diaphragmatic plication is considered.

Reinnervation of the paralyzed diaphragm: application of nerve surgery techniques following unilateral phrenic nerve injury.

BACKGROUND: Unilateral phrenic nerve injury often results in symptomatic hemidiaphragm paralysis, and currently few treatment options exist. Reported etiologies include cardiac surgery, neck surgery, chiropractic manipulation, and interscalene nerve blocks. Although diaphragmatic plication has been an option for treatment, the ideal treatment would be restoration of function to the paralyzed hemidiaphragm. The application of peripheral nerve surgery techniques for phrenic nerve injuries has not been adequately evaluated. METHODS: Twelve patients presenting with long-term, symptomatic, unilateral phrenic nerve injuries following surgery, chiropractic manipulation, trauma, or anesthetic blocks underwent a comprehensive evaluation, including radiographic and electrophysiologic assessments. Surgical treatment was offered following a minimum of 6 months of conservative management. Operative planning was based on preoperative and intraoperative testing using one or more established nerve reconstruction techniques (neurolysis, interpositional grafting, or neurotization). RESULTS: Measures of postoperative improvement included pulmonary function testing, fluoroscopic sniff testing, and a standardized quality-of-life survey, from which it was determined that eight of nine patients who could be completely evaluated experienced improvements in diaphragmatic function. CONCLUSIONS: Based on the favorable results in this small series, we suggest expanding nerve reconstruction techniques to phrenic nerve injury treatment and propose an algorithm for treatment of unilateral phrenic nerve injury that may expand the current limitations in therapy.

Atrial tachycardias adjacent to the phrenic nerve: recognition, potential problems, and solutions.

BACKGROUND: Ablation of atrial tachycardias (AT) arising from the crista terminalis region (CT) can be complicated by phrenic nerve (PN) injury. OBJECTIVE: This study sought to describe epicardial protection techniques to prevent PN injury from endocardial ablation of AT. METHODS: Ablation was attempted in 4 patients with focal AT arising from the CT in whom conventional endocardial ablation was limited by PN proximity identified by capture during pacing. RESULTS: Four women ages 20, 28, 30, and 31 years with structurally normal hearts presented with symptomatic ATs failing medical therapy. In the first patient, endocardial cryoablation was performed during superior vena cava (SVC) PN pacing. After acute success, AT recurred. Open surgical ablation was then performed, but AT was noninducible under anesthesia, and an anatomic ablation was performed. AT was abolished, but sinus node dysfunction required pacemaker implantation. In the subsequent 3 patients with AT adjacent to the right PN, protection of the PN was attempted by inserting a peripheral angioplasty balloon (2 patients) or steerable ablation catheter and sheath into the epicardial space between the PN and atrium. Endocardial radiofrequency ablation was successful in all 3 patients without PN injury. CONCLUSION: Epicardial protection of the PN allowing for safe endocardial ablation of CT ATs is a feasible method of managing these challenging cases and seems to be preferable to surgery.

Ablation of atrial fibrillation in humans using a balloon-based ablation system: identification of the site of phrenic nerve damage using pacing maneuvers and CARTO.

Injury of the phrenic nerve during pulmonary vein isolation for the treatment of atrial fibrillation is a well-recognized complication, especially when performing ostial ablations or using balloon-based technologies. This report describes the exact anatomical location of phrenic nerve injury during an attempt of right superior pulmonary vein isolation using a balloon that delivered high intensity focused ultrasound. Electroanatomical three-dimensional CARTO (Biosense Webster, Diamond Bar, CA, USA) mapping of the superior caval vein, the right and left atrium, as well as the right superior pulmonary vein was performed in conjunction with meticulous phrenic nerve pacing maneuvers before and after ablation and showed that the nerve was damaged at the level of the antero-inferior ostium of the right superior pulmonary vein. Diaphragmatic denervation occurred despite using an oversized balloon fluoroscopically placed at the atrial side of the pulmonary vein ostium.

Central hypoventilation and diaphragmatic eventration: diagnosis and management.

Congenital central alveolar hypoventilation syndrome (CCAHS) is a disorder of ventilatory control that occurs without neuromuscular blockade or pulmonary disease. It is characterized by a lack of response to habitual respiratory stimulants, especially hypercapnia. In this article, the management of this syndrome by diaphragmatic pacing is discussed. Paralysis of the phrenic nerve in small children usually results from injury during birth or during a cardiothoracic operation and results in eventration of the hemidiaphragm. Alternatively, eventration of the diaphragm may be a congenital condition. In both cases it may lead to respiratory distress in the newborn. In this article, we review the diagnosis of these conditions and their management, focusing on the surgical indications. We also discuss outcome.

Diaphragmatic paralysis following chiropractic manipulation of the cervical spine.

We present a case of phrenic nerve damage resulting in unilateral diaphragmatic paralysis following chiropractic manipulation of the neck. Related vascular and neurologic complications of spinal manipulation are reviewed.