Diaphragmatic Compound Motor Action Potentials Research Articles

Novel automated “score mapping” of diaphragmatic compound motor action potential for the early detection of phrenic nerve injury during cryoablation

The proximity of phrenic nerve to right sided pulmonary veins (PV) make it susceptible to injury during cryoballoon ablation (CBA) for atrial fibrillation (AF). Monitoring of diaphragmatic compound motor action potentials (CMAP) obtained from lead aVF or modified surface ECG leads placed along the diaphragm have been used for early detection of phrenic nerve injury (PNI). 1 Schaerli N. Badertscher P. Spies F. et al. A Simplified Method to Detect Phrenic Nerve Injury During Cryoballoon Ablation of Atrial Fibrillation Using Lead aVF of the Surface ECG. Circ Arrhythm Electrophysiol. 2021 Aug; 14e009986https://doi.org/10.1161/CIRCEP.121.009986 Crossref Scopus (0) Google Scholar Thirty percent drop in CMAP amplitude has been shown in studies as the threshold for prevention of PNI. 2 Miyazaki S. Hachiya H. Taniguchi H. et al. Prospective Evaluation of Bilateral Diaphragmatic Electromyograms During Cryoballoon Ablation of Atrial Fibrillation. JCE. 2015; 26: 622-628 Google Scholar However, CMAP signals may be susceptible to respiratory variations, catheter movement, inadequate baseline amplitude making it difficult to monitor the change in CMAP. 3 Sharma P.S. Padala S.K. Thompson J.J. Gunda S. Koneru J.N. Ellenbogen K.A. Factors Influencing Diaphragmatic Compound Motor Action Potentials During Cryoballoon Ablation for Atrial Fibrillation. JCE. 2016; 7: 1384-1389 Google Scholar Score-map of the CMAP using template matching with 3D electroanatomic mapping system can be used to automate the monitoring of CMAP. The aims of this study were to assess the relationship of change in CMAP amplitude with change in score-map and then use the automated score-map prospectively for early detection of PNI during CBA.

When does phrenic nerve injury recover after cryoballoon ablation? Data from Japanese multicenter registry

Abstract Funding Acknowledgements Type of funding sources: None. Background Although phrenic nerve injury (PNI) is most frequently encountered complication in cryoballoon ablation, it recovered in most cases. However, the duration of persisting PNI has not been fully investigated yet. Purpose This study sought to confirm the clinical course of PNI after the procedure in cases in which reduction of diaphragmatic compound motor action potential (CMAP)was confirmed during cryoballoon ablation of right-sided pulmonary veins (PVs). Methods We retrospectively analyzed a total of 237 patients who experienced right PNI confirmed by the CMAP amplitude reduction during cryoballoon ablation in 4 Japanese centers. Cryoballooon ablation of right-sided PVs were performed under CMAP monitoring in all cases, and once CMAP amplitude reduction was observed, freezing was immediately interrupted with a double stop technique. The recovery of PNI was confirmed by chest X-ray, and transient PNI was defined as one recovering before the discharge. Results Among 237 patients, PNI occurred during cryoballoon ablation of right superior PV and right inferior PV in 166 and 71 patients, respectively. The mean freezing time to PNI was 126.9±45.6 seconds and the mean balloon temperature when PNI occurred was -50.2±7.5°C. After PNI was confirmed, additional cryoballoon ablation of the same PV or the other ipsilateral PV was performed under CMAP monitoring in 29 and 97 patients, respectively. Transient PNI accounted for 53.2% of patients with PNI (126 out of 237 patients). Among the remaining 111 patients, the PNI recovery was confirmed within 3 months, 6 months or 12 months after the procedure in 42(37.8%), 55 (49.5%), 74 (66.7%) patients, respectively. When we excluded 32 patients who did not undergo sufficient follow-up of chest X-ray, only 5 patients (2.4%) still suffered from PNI at 12 months after the ablation, and the PNI recovery was confirmed after more than 12 months in 3 out of them. When we compared patients who suffered from PNI at 6 months after the procedure with those who did not, there was no significant difference in nadir balloon temperature (-50.4±6.9°C; for PNI recovery [-] vs -50.0±7.8°C; for PNI recovery [+], p=0.75). When freezing time was less than 60 seconds, PNI recovered within 6 months after ablation in all cases, although 23.2% of the patients in whom freezing time was 60 seconds or more still suffered from PNI at 6 months after the procedure (p=0.045). Conclusion The right-sided PNI confirmed by the CMAP amplitude reduction during cryoballoon ablation recovers within a couple of days in half of cases, and it rarely persists more than 12 months after the procedure. When freezing was interrupted less than 60 seconds, it is highly expected that PNI recovers within 6 months.

AB-453068-1 NOVEL ‘SCORE-MAPPING’ OF DIAPHRAGMATIC COMPOUND MOTOR ACTION POTENTIAL FOR EARLY DETECTION OF PHRENIC NERVE INJURY DURING CRYOABLATION

The proximity of the phrenic nerve to right-sided pulmonary veins makes it susceptible to injury during cryoballoon ablation (CBA) for atrial fibrillation (AF). Although there are no specific preprocedural predictors for phrenic nerve injury (PNI), monitoring of diaphragmatic compound motor action potentials (CMAP) has been used for the early detection of PNI. A 30% drop in CMAP amplitude has been shown in animal and clinical studies as the threshold for the prevention of PNI The aims of this study were to assess the relationship of change in CMAP amplitude with change in score map and then use the automated score map prospectively for early detection of PNI during CBA In the first half of the study, we paced the phrenic nerve at 10,8,6,4,2 milliamperes or till loss of capture in 20 pts. The relationship between the change in amplitude of CMAP with a corresponding change in the score map was studied by linear regression. 30% drop in CMAP amplitude was associated with a score map of 89%(R2 0.77). In the second half of the study, we used a score map threshold of 90% and studied 84 pts. Ablation was stopped if the score map of CMAP dipped below 90% consistently for >4 beats to take respiratory variation into account A total of 174 cryo applications were done for the right-sided veins in 84 pts. A consistent score-map >98% was obtained in all pts before the beginning of the CBA. Ablation had to be stopped in 13 pts due to a drop in the score map or CMAP amplitude or decreased diaphragm contraction. 5 pts had transient PNI. Change in score map was noticeable before change in CMAP amplitude or decrease in diaphragm contraction. In 8 pts drop in the score map was attributed to catheter movement which was noted by the change in catheter position on the 3D mapping system. Score-map of CMAP returned to >98% with catheter adjustment or within 5 minutes of ablation termination along with improvement of CMAP amplitude in all cases. No pts were noted to have persistent PNI at the end of the procedure Beat-to-beat changes in CMAP amplitude can be noted with respiratory variation or catheter movement making it difficult to monitor the change in amplitude. By using an automated score rather than continuously measuring CMAP amplitude, score mapping can make monitoring changes in CMAP amplitude easier. This descriptive study demonstrates that a 90 % score-map threshold correlates with a 30% drop in CMAP amplitude and can be safely and reliably used for the early detection of PNI

Diaphragmatic paralysis associated with IgLON5 autoimmunity (P5-5.022)

<h3>Objective:</h3> To describe a rare presentation of IgLON5 IgG mediated neurological disorder <h3>Background:</h3> IgLON5 autoimmunity was previously described with sleep disorder, rhombencephalopathy, vocal cord paresis, progressive-supranuclear-palsy-like syndrome, and recently motor-neuron-disease (MND)-like syndrome. Although diaphragmatic paralysis has been known as a presenting symptom of degenerative (MND) but has never been reported with IgLON5 autoimmunity. <h3>Design/Methods:</h3> Case report <h3>Results:</h3> A 67-year-old man with obstructive sleep apnea and history of vocal cord paralysis 11 years ago, presented with 2-year history of dream enactment behavior, progressive dyspnea and orthopnea. The symptoms became more noticeable and rapidly progressive in the past 10 months. Initially, he felt shortness of breath during the daytime when he bent over. Within a few months, he had to sleep on the recliner with a minimal tilt back at night. Neurological examination demonstrated moderate right facial weakness, mild weakness of interossei muscles of right hand, and triceps. Deep tendon reflexes were marginally brisk without Babinski sign. Sensory examination was normal. Occasional fasciculation was noted in deltoid region. Right upper extremity electromyography was normal. Diaphragmatic ultrasound showed no diaphragmatic expansion during inspiration. Ultrasound-guided electromyography of diaphragm and phrenic nerve conduction study showed no phrenic nerve response on the right, and markedly reduced amplitude of diaphragmatic compound motor action potential on the left side. Brain MRI and cervical spine was essentially unremarkable. Blood work showed normal vitamin B12, creatinine kinase and monoclonal gammopathy screen. Serological evaluation of neural specific antibodies was remarkable for IgLON5-IgG (titer 1:480). The patient was treated with high-dose methylprednisolone and is scheduled to follow up in autoimmune neurology clinic for outcome assessment. <h3>Conclusions:</h3> IgLON5 autoimmunity should be considered in patients with diaphragmatic paralysis, especially ones with sleep disorder, vocal cord paresis, and episodic respiratory disturbances. <b>Disclosure:</b> Dr. Thakolwiboon has nothing to disclose. Dr. Klein has a non-compensated relationship as a Klein with Neurology Journal that is relevant to AAN interests or activities. The institution of Dr. Dubey has received personal compensation in the range of $500-$4,999 for serving as a Consultant for UCB. The institution of Dr. Dubey has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Astellas. The institution of Dr. Dubey has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Argenx. Dr. Dubey has received personal compensation in the range of $0-$499 for serving on a Speakers Bureau for AGRIMS. Dr. Dubey has received personal compensation in the range of $0-$499 for serving on a Speakers Bureau for Advances in Neurology . Dr. Dubey has received personal compensation in the range of $0-$499 for serving on a Speakers Bureau for Moffit Cancer Center . Dr. Dubey has received research support from Department of Defense . Dr. Dubey has received intellectual property interests from a discovery or technology relating to health care. Dr. Dubey has received intellectual property interests from a discovery or technology relating to health care. Dr. Dubey has received intellectual property interests from a discovery or technology relating to health care.

Using the pre-freezing technique results in a wider area of antral isolation during cryoballoon pulmonary vein isolation in patients with atrial fibrillation.

The "pre-freezing" technique was a method in which a fully inflated balloon after the start of freezing was pressed against the pulmonary vein (PV) during cryoballoon ablation and has been applied especially in large-size PVs. Of 556 patients who underwent cryoballoon ablation for atrial fibrillation (AF), the pre-freezing technique was applied to 48 patients. The resulting 2:1 propensity score-matched data set included 120 patients. Using the pre-freezing technique, all left-superior PVs, all left-inferior PVs, and 95% of right-superior PVs were successfully isolated. In most right-inferior PVs, complete sealing using the pre-freezing technique was challenging, and this technique was not applied. Procedure time was similar between the two groups. In the pre-freezing group, the percentage of the left atrial posterior wall isolated was larger (47.6 ± 10.3 vs. 42.8 ± 15.7%, P = 0.006), and the postoperative reduction of diaphragmatic compound motor action potentials tended to occur less frequently (2.5 vs. 12.5%, P = 0.07), and the reduction of the cross-sectional LSPV area was smaller (17.5 ± 12.2 vs. 27.2 ± 19.8%, P = 0.03) than the conventional group. The AF-free rate of the two groups was similar between the two groups (P = 0.15). The pre-freezing technique was a simple method that can isolate a wider surface area during cryoballoon PV isolation. While the postoperative AF recurrence was comparable, the postoperative reduction in the cross-sectional PV area was less than that of the conventional method, which may reduce the risk of PV stenosis.

P-MN004. Multiple neurophysiologic biomarkers evaluated the pulmonary function of ALS

Introduction . Declining respiratory-muscle function is the primary cause of death in patients with amyotrophic lateral sclerosis (ALS). Spirometry is the most frequently used to predict hypoventilation and survival in ALS, but their cut off value cannot indicate disease prognosis. Multiple neurophysiological evaluations, which performed using diaphragmatic compound motor-action potential (DCMAP) by phrenic nerve conduction study, diaphragm thickness (DDT) by ultrasonography and new measurement system of thoracic excursion are proposed as new variable biomarkers. Methods . A total of 14 ALS patients diagnosed by El Escorial criteria were enrolled (4 females and 10 males, mean age 71.0 years, mean disease duration 29.2 months, mean body mass index ( BMI ) 19.5 kg/m 2 ). We prospectively evaluated the spirometry, arterial partial pressure of oxgen and carbon dioxide (PaO2 and PaCO2), baseline-to-peak amplitude of DCMAP, and the differences in DDT and thoracic excursion between timed maximal inspiration and maximal expiration (UMIN:000042222). We then analyzed the relationships between neurophysiological biomarkers, the respiratory-function test, and the other quantitative evaluations. Results . All patients completed the examinations with the exception of the respiratory-function test of two patients. The test–retest analysis of neurophysiologic biomarkers showed a high level of reliability. Decrease of DCMAP and DDT was detected in patients who reported no subjective dyspnea. DCMAP and DDT were found to correlate strongly with both PaCO2 and forced vital capacity (FVC); in contrast, thoracic excursion was strongly correlated to PaCO2 but not to FVC. Except for one female patient with high BMI (> 25), correlation with thoracic excursion and FVC was observed. Conclusion . Multiple neurophysiologic evaluations are reliable and reflects respiratory function. DCMAP and DDT are useful for the objective evaluations of respiratory function before the awareness of subjective dyspnea in patients with ALS.

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.

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

PurposePhrenic 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.MethodsWe 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.ResultsThe 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.ConclusionsCMAP 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.

P2625Pathophysiology of diaphragm involvement in systolic heart failure: insights from diaphragm ultrasound and phrenic nerve stimulation studies

Abstract Background Diaphragm ultrasound allows for assessment of both diaphragm excursion and thickness. Cervical and cortical magnetic stimulation (CEMS and COMS) with recording of the diaphragmatic compound motor action potential (CMAP) is diagnostically useful to evaluate the conductive properties of the inspiratory pathway. Systolic heart failure (HF) is characterized by a loss of systolic pump function. Diaphragm weakness in HF has been reported to potentially contribute to exercise intolerance Methods 14 patients with systolic HF (11 men, 3 women; 64±12 years, NYHA 2±0.9, LVEF 36.1±5.6%) and 12 healthy controls matched for age and gender (4 men, 8 women; 56±8 years) underwent spirometric lung function testing and assessment of diaphragm excursion (during tidal breathing, TB, voluntary sniff, VS and deep breathing, DB) and thickness of the right hemidiaphragm by ultrasound. COMS and CEMS of the phrenic nerves with simultaneous bilateral recording of the diaphragm CMAP using surface electrodes was performed in 9 patients. Results Compared to controls, HF patients showed reduced forced vital capacity (75.46±18.05% vs. 107.62±17.13%, p&lt;0.05). Diaphragm excursion amplitude was significantly reduced in HF patients (4.29±1.35 cm vs. 7.34±2.10 cm, p&lt;0.05). Diaphragm contractility was impaired too, as reflected by the diaphragm thickening ratio (DTR; 2.01±0.46 vs. 2.53±0.74, p&lt;0.05). Diaphragm CMAP following COMS and CEMS of the phrenic nerves revealed normal latencies in HF patients compared to controls (COMS Latency; 19.05±2.37 msec vs. 18.97±3.59 msec, p= n. s.). Conclusions Diaphragm involvement in systolic HF is reflected by reduced FVC and impaired ultrasound parameters of diaphragm function. Diaphragmatic pathology is likely to be myopathic because magnetic phrenic nerve conduction studies show no abnormalities. Diaphragm ultrasound may be useful as a diagnostic tool for assessment of diaphragm function in systolic HF. Acknowledgement/Funding This study was supported by Sanofi-Genzyme, Neu-Isenburg, Germany. The funders had no role in study design, data collection and analysis, preparation.

Quick, safe, and effective maneuver to prevent phrenic nerve injury during cryoballoon ablation of atrial fibrillation.

Phrenic nerve (PN) injury is a typical complication of cryoballoon ablation (CBA) of pulmonary veins. The PN function is monitored by palpating the abdomen during PN pacing, and freezing is prematurely terminated when a reduction in the diaphragm movement is recognized. This study aimed to investigate the efficacy and safety of a "pull-back" maneuver to prevent PN injury. A total of 284 patients were included, and the PN function was monitored by recording the diaphragmatic compound motor action potentials (CMAP) during the cryoballoon applications for pulmonary vein (PV) isolation. When the CMAP amplitude was reduced by more than 30% compared to the control, the "pull-back" maneuver (PBM) was undertaken to prevent PN injury. The average CMAP amplitude significantly decreased from 0.81 ± 0.04 to 0.31 ± 0.21 (p < 0.01) mV during the cryoballoon applications of PVs in 92 PVs. The PBM was employed in all cases, and the average CMAP amplitude recovered to 0.87 ± 0.31mV (p < 0.01) in 79 out of 92 PVs (85.9%), accomplishing the CBA. Cryofreezing had to be prematurely terminated due to failure of the PBM in 13 out of 92 cases (14.1%). The PBM was an effective maneuver to prevent PN injury by creating a distance between the PN and location of the cryoballoon. No adverse events were provoked by this procedure.

Characteristics of Phrenic Nerve Injury During Pulmonary Vein Isolation Using a 28-mm Second-Generation Cryoballoon and Short Freeze Strategy.

BackgroundThe reported incidence of phrenic nerve injury (PNI) varies owing to different definitions, balloon generations, balloon size, freezing regimen, and protective maneuvers. We evaluated the incidence, predictors, and outcome of PNI during cryoballoon pulmonary vein isolation in a large population.Methods and ResultsFive hundred fifty atrial fibrillation patients underwent pulmonary vein isolation using one 28‐mm second‐generation cryoballoon and single 3‐minute freeze strategy under diaphragmatic compound motor action potential (CMAP) monitoring. A total of 34 (6.2%) patients experienced PNI during the right superior and inferior pulmonary vein ablation in 30 and 4 patients, respectively. Applications were interrupted using double‐stop techniques after 136 [104–158] second applications, and a pulmonary vein isolation was already achieved in all but one case. The baseline CMAP amplitude and timing of deflation (CMAP def) were 0.75±0.30 and 0.17±0.17 mV, respectively. Persistent atrial fibrillation, larger right superior pulmonary vein ostia, and deeper balloon positions were associated with higher incidences of PNI. The CMAP def predicted a PNI recovery delay, and the best cutoff value for predicting PNI recovery by the next day was 0.20 mV (sensitivity 57.1%, specificity 100%). Among 6 patients undergoing second procedures 8.5 (6.7–15.0) months later, the right superior pulmonary vein was durable in 3 with >120 second applications. Despite active balloon deflation, no significant pulmonary vein stenosis was observed in 15 right superior pulmonary veins evaluated 6 (5–9) months later. No patients had symptoms, and the PNI recovered 1 day and 1 month postprocedure in 21 and 4 patients, respectively.Conclusions PNI resulting from cryoballoon ablation was reversible. The double‐stop technique is safe, and immediate active deflation following a CMAP decrease appears to be essential for faster PNI recovery.

P861Positioning an ECG electrode to the dorsal side can record higher amplitude of diaphragmatic compound motor action potentials (CMAP) during cryoballoon ablation

P861Positioning an ECG electrode to the dorsal side can record higher amplitude of diaphragmatic compound motor action potentials (CMAP) during cryoballoon ablation

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

Diaphragmatic compound motor action potential (CMAP) amplitude monitoring is a standard technique to anticipate phrenic nerve injury during cryoballoon ablation. 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. 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). 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. A novel and simple pace-and-ablate technique under diaphragmatic electromyography monitoring might be feasible for an electrical SVCI.

Factors Influencing Diaphragmatic Compound Motor Action Potentials During Cryoballoon Ablation for Atrial Fibrillation.

The diaphragmatic compound motor action potentials (CMAPs) have been used to predict and prevent phrenic nerve injury (PNI) during cryoballoon ablation of right pulmonary veins. We sought to assess factors that influence the amplitude of the surface CMAP recordings. We analyzed CMAPs from consecutive patients undergoing cryoballoon ablation for paroxysmal atrial fibrillation. CMAP recordings were obtained using electrocardiography electrodes positioned in the "modified lead I" method while stimulating the right PN, until loss of capture (ascertained by palpation and fluoroscopy of the right hemi-diaphragm). A total of 55 patients (age 63 ± 11 years; 60% men; body mass index [BMI] 31 ± 6) had adequate CMAP recordings and were included for evaluation of CMAP signals. CMAPs demonstrated 2 distinct components, an early higher amplitude signal (pacing artifact) and a later lower amplitude signal (true diaphragmatic CMAP). There was no significant change in the true CMAP recording amplitude with decrease in stimulus strength (P = 0.1). There was no impact of BMI on CMAP amplitude (P = 0.93). There was a significant phasic respiratory variation in CMAP amplitude with a mean decrease in CMAP amplitude of 10.8% (range: 8-12%) with inspiration lasting an average of 2 beats (P < 0.001). A decrease in CMAP amplitude of >30% was noted in 6 cases (11%) and termination of cryoablation prevented PNI. Diaphragmatic CMAP amplitude is not affected by stimulus strength or BMI. There is a significant respirophasic decrease in CMAP signal amplitude with inspiration. It is important to be aware of this variation to avoid premature termination of cryoablation.

Novel method for earlier detection of phrenic nerve injury during cryoballoon applications for electrical isolation of pulmonary veins in patients with atrial fibrillation

Diaphragmatic electrogram recording during cryoballoon ablation (CB-A) of atrial fibrillation is commonly used to predict phrenic nerve palsy (PNP). The purpose of this study was to investigate a novel method for predicting PNP at an earlier stage to prevent sustained PNP. A total of 197 patients undergoing CB-A were enrolled. We attempted to detect PNP using fluoroscopic images of diaphragmatic contractions and by monitoring diaphragmatic compound motor action potentials (CMAPs) provoked by superior vena cava (SVC) and left subclavian vein (LCV) pacing during CB-A for bilateral pulmonary veins (PVs). Pacing of the SVC and LCV was performed at 2 outputs, 1 exceeding the pacing threshold by 10% (MIN) and the other at maximum output (MAX). The time from freezing to the initiation of PNP, values of the CMAP amplitude, and severity of PNP were compared for the 2 outputs. There was a significant difference in the time from freezing to initiation of PNP between MIN and MAX pacing (25.7 ± 5.7 vs 81.3 ± 7.4 seconds, P<.01). CMAP amplitudes also differed significantly (0.71 ± 0.39 vs 1.13 ± 0.42, P<.0001). SVC/LCV pacing with MIN output was able to detect PNP significantly earlier than MAX (27 ± 8 vs 91 ± 12 seconds, P<.01), and the time to PNP recovery was significantly shorter for the MIN output (20.2 ± 8.88 hours vs 4.8 ± 1.6 months, P<.001). Pacing the SVC and LCV with lower output detect PNP significantly earlier than maximal output pacing and leads to recovery from PNP on the order of hours postprocedure rather than months.

Prospective Evaluation of Bilateral Diaphragmatic Electromyograms During Cryoballoon Ablation of Atrial Fibrillation.

Left phrenic nerve injury (PNI) can occur during cryoballoon ablation of the left pulmonary veins (PVs). This study aimed to evaluate the feasibility of monitoring the bilateral phrenic nerve function during cryoballoon ablation of atrial fibrillation (AF). Fifty consecutive paroxysmal AF patients undergoing cryoballoon ablation using one 28-mm second-generation balloon were prospectively enrolled. Bilateral diaphragmatic compound motor action potentials (CMAPs) were obtained from modified surface electrodes by pacing from the bilateral subclavian veins, and monitored during 3-minute cryoballoon applications at the ipsilateral PVs. One hundred ninety of 202 PVs were successfully isolated exclusively using 28-mm cryoballoons. CMAPs could be obtained in all except 3 cases with catheter inaccessibility in the left subclavian vein. The left and right CMAP amplitudes were similar at baseline (1.04 ± 0.41 mV vs. 1.01 ± 0.43 mV, P = 0.49). Among 105 left and 132 right PV applications while monitoring CMAPs, 2 (1.9%) and 13 (9.8%) applications were interrupted for a decreased CMAP amplitude (P = 0.01). Among them, CMAPs decreased due to right PNI in 4 applications/patients and to catheter dislodgement in the remaining applications. PNI remained in 1 and recovered in the remaining 3 patients one day after the procedure. Applications without requiring interruptions exhibited no significant CMAP amplitude changes throughout the applications, and the time-course pattern was similar between the bilateral CMAPs (P = 0.292). A stable bilateral diaphragmatic CMAP could be similarly obtained during cryoballoon applications in the vast majority of patients. Monitoring CMAPs might be useful to anticipate not only right but also left PNI during cryoballoon ablation.

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

Cryoballoon ablation has been associated with a significant incidence of phrenic nerve injury (PNI). The purpose of this study was to evaluate whether recordings of diaphragmatic compound motor action potentials (CMAP) on a modified lead I during cryoballoon ablation can predict PNI. Cryoballoon ablation was performed in 109 patients with atrial fibrillation (AF). During ablation of the right-sided pulmonary veins, the phrenic nerve was paced from the superior vena cava. The right and left arm electrodes from a 12-lead ECG were positioned 5 cm above the xiphoid process and 16 cm along the right costal margin. The amplitude of CMAP was recorded on lead I during ablation. Cryoballoon was applied 424 times in 211 right-sided veins. PNI occurred in 7 (6.4%) patients. The average CMAP amplitude did not significantly change in patients without PNI from the initial average CMAP amplitude of 0.34 ± 0.18 mV to 0.32 ± 0.17 mV (P = .58). In patients who developed PNI, there was a significant decrease in the initial average CMAP amplitude during the ablation from 0.33 ± 0.14 mV to 0.09 ± 0.05 mV (P <.001). The maximal percent change in the average CMAP amplitude in patients with PNI was higher (70% ± 10%) than in patients without PNI (7.6% ± 7%; P <.001). In any patient without PNI, the CMAP amplitude did not decrease more than 35% from baseline. Recording of CMAP amplitude on a modified lead I is reliable and could be early and sensitive method for predicting PNI in patients undergoing cryoballoon ablation for AF.

Novel Electromyographic Monitoring Technique for Prevention of Right Phrenic Nerve Palsy During Cryoballoon Ablation

Right phrenic nerve palsy (PNP) is the most frequent complication of cryoballoon ablation. Diaphragmatic electromyography can predict PNP with a comfortable safety margin. Our goal was to evaluate the feasibility, efficacy, and safety of electromyography-guided PN monitoring using a novel hepatic vein approach for prevention of PNP. This study includes 57 patients (47 males) indicated for cryoballoon ablation for treatment of atrial fibrillation. During right superior pulmonary vein ablation, the PN was paced at 60 beats per minute and diaphragmatic compound motor action potential (CMAP) amplitude was recorded via a quadripolar catheter positioned in a subdiaphragmatic hepatic vein. If a 30% drop in CMAP amplitude was observed, ablation was discontinued with forced deflation. Reliable recording of CMAP before ablation was feasible in 50 of 57 patients (88%). In 7 patients (12%), stable PN pacing could not be achieved. In 44 of 50 patients, CMAP amplitude remained constant during cryoapplication. The mean value of CMAP amplitude was 639.7±240.5 µV; mean variation was 13±4.3%. In 6 of 50 patients (12%) including 5 treated with a 23-mm cryoballoon and 1 with a 28-mm cryoballoon, the 30% reduction cutoff was reached and cryoablation was discontinued. Recovery of CMAP amplitude after discontinuing cryoablation took <60 seconds in all cases. No PNP or complication related to PN monitoring occurred. Recording of diaphragmatic CMAP using a catheter positioned in a subdiaphragmatic hepatic vein seems feasible during cryoballoon ablation. Electromyography-guided PN monitoring seems safe and potentially helpful for prevention of PNP.

Diaphragmatic electromyography during cryoballoon ablation: a novel concept in the prevention of phrenic nerve palsy

Hemidiaphragmatic paralysis is the most frequent complication associated with cryoballoon ablation for atrial fibrillation. To date, no preventive strategy has proved effective. We sought to assess the feasibility of diaphragmatic electromyography during cryoballoon ablation, explore the relationship between altered signals and phrenic nerve palsy, and define characteristic changes that herald hemidiaphragmatic paralysis. Cryoballoon ablation was performed in the right superior pulmonary vein or superior vena cava in 16 mongrel dogs weighing 37.7 ± 2.4 kg, at sites determined by phrenic nerve capture. During ablation, the phrenic nerve was paced at 60 bpm from the superior vena cava while recording diaphragmatic compound motor action potentials (CMAPs) by esophageal decapolar catheters. Diaphragmatic excursion was monitored by fluoroscopy and abdominal palpation. Before ablation, the CMAP amplitude was 592 (interquartile range 504, 566) μV, initial latency 21.5 ± 4.2 ms, peak latency 64.7 ± 21.1 ms, and duration 101.7 ± 13.3 ms. Hemidiaphragmatic paralysis was obtained in all dogs 62 ± 34 seconds into the cryoapplication. The CMAP amplitude decreased exponentially, with no patterned changes in latencies and duration. Discriminatory analyses by receiver-operating curve characteristics identified a 30% reduction in CMAP amplitude as the most predictive cutoff value for hemidiaphragmatic paralysis (c-statistic 0.965; P<.0001). This criterion presaged diaphragmatic paralysis, as detected by abdominal palpation, by 31 ± 23 seconds. Diaphragmatic electromyographic signals could be reliably recorded during cryoballoon ablation. An exponential decrease in CMAP amplitude precedes diaphragmatic paralysis, with a 30% reduction yielding the best discriminatory potential. A promising safety margin was detected, which merits prospective validation.

Phrenic nerve conduction studies.

To refine the technique of phrenic nerve conduction, we first studied electrode positioning and sources of chest wall artifact. Diaphragmatic compound motor action potentials (DCMAPs) were mapped at close intervals over 4 hemithoraces of two subjects, finding optimum recording sites which were then used to quantitate artifacts due to EKG, chest wall EMG, and configurational thoracic changes of respiration. Based on these findings, 20 normal subjects were studied, showing ease of application and good side-to-side agreement for DCMAP latencies; but, in contrast to prior reports, right-to-left correlation for amplitude and waveform was poor, making the unaffected side an unreliable standard in unilateral partial phrenic nerve lesions.