Preclinical evaluation of semi-automated laser ablation for pulmonary vein isolation: A comparative study.

INTRODUCTION: Visually-guided laser balloon ablation (VGLA) currently requires careful manual rotation of the laser to create overlapping lesions. A novel semi-automated VGLA may reduce ablation times and lesion gaps. We aimed to compare semi-automated (SA) VGLA to that of manual (MN) VGLA. METHODS: Acute: Nine swine underwent right superior pulmonary vein isolation (PVI) using either SA (n = 3, 13-18 W), MN (n = 3, 8.5-12 W), or radiofrequency (RF, n = 3, 25-40 W) and were killed acutely. Chronic: 16 swine, underwent PVI using either SA (n = 8, 15 W) or MN (n = 8, 10 W), and were survived for 1 month before being killed. All hearts were then submitted for pathological evaluation. RESULTS: Acute: PVI was successful in all 9/9 swine with lesion counts significantly lower in the SA arm (5.3 ± 5.9, 33.7 ± 10.0, and 28.0 ± 4.4 in SA, MN, and RF arms; p = .007 for SA and MN). At necropsy, circumferentiality and transmurality were 98% and 94% in SA, 98% and 80% in MN, and 100% and 100% in RF arms. A single steam pop was noted on sectioning in the SA arm swine and occurred in the high dose (18 W) strategy. Chronic: PVI was acutely successful in 16/16 swine with no difference in PVI durability rates (62.5% vs. 75.0%), lesion transmurality (95.8 ± 17.4% vs.91.9 ± 25.9%), and circumferentiality (95.8 ± 6.6% vs. 94.8 ± 6.3%) between SA and MN arms. Catheter use time and lesion counts were lower in the SA arm compared to the MN arm (11.5 ± 12.7 vs. 21.8 ± 3.8 min, p = .046 and 4.8 ± 3.83 vs. 35.4 ± 4.4, p < .001). CONCLUSION: Motor-assisted semi-automated laser balloon ablation can improve upon procedural efficiency by reducing ablation time.

Routine assessment of cardiotoxicity in patients undergoing long-term immune checkpoint inhibitor therapy.

The indications for immune checkpoint inhibitors (ICIs) are expanding in cancer drug therapy, and while cardiac events associated with ICIs are often fatal, there are few reports regarding cardiac complications associated with long-term ICI therapy. We aimed to study cardiac complications in patients undergoing long-term ICI therapy. From the database of our local cardio-oncology unit, we enrolled patients with cancer undergoing ICI therapy for more than 6 months and for whom cardiologists continuously performed routine follow-ups. We defined the primary endpoint as discontinuation of ICI due to cardiac events. We also analyzed changes in cardiac biomarkers and echocardiographic parameters. We retrospectively analyzed 55 consecutive patients (43 males, mean age: 65 ± 11 years) treated with ICI therapy in our hospital between January 2017 and June 2021. None of the patients discontinued ICI therapy due to cardiac events more than 6 months after treatment was initiated. Among the participants, we observed four patients with elevated serum troponin I levels, seven patients with decreased global longitudinal strain values, and two patients with elevated plasma brain natriuretic peptide levels. No patient required drug intervention for these cardiac events; furthermore, there were no cases of clinically diagnosed myocarditis. In the present study, there were no cardiac events causing ICI discontinuation in patients undergo ICI therapy for more than 6 months.

Explainable Artificial Intelligence Model for Diagnosis of Atrial Fibrillation Using Holter Electrocardiogram Waveforms.

Atrial fibrillation is a clinically important arrhythmia. There are some reports on machine learning models for AF diagnosis using electrocardiogram data. However, few reports have proposed an eXplainable Artificial Intelligence (XAI) model to enable physicians to easily understand the machine learning model's diagnosis results.We developed and validated an XAI-enabled atrial fibrillation diagnosis model based on a convolutional neural network (CNN) algorithm. We used Holter electrocardiogram monitoring data and the gradient-weighted class activation mapping (Grad-CAM) method.Electrocardiogram data recorded from patients between January 4, 2016, and October 31, 2019, totaling 57,273 electrocardiogram waveform slots of 30 seconds each with diagnostic information annotated by cardiologists, were used for training our proposed model. Performance metrics of our AI model for AF diagnosis are as follows: sensitivity, 97.1% (95% CI: 0.969-0.972); specificity, 94.5% (95% CI: 0.943-0.946); accuracy, 95.3% (95% CI: 0.952-0.955); positive predictive value, 89.3% (95% CI: 0.892-0.897); and F-value, 93.1% (95% CI: 0.929-0.933). The area under the receiver operating characteristic curve for AF detection using our model was 0.988 (95% CI: 0.987-0.988). Furthermore, using the XAI method, 94.5 ± 3.5% of the areas identified as regions of interest using our machine learning model were identified as characteristic sites for AF diagnosis by cardiologists.AF was accurately diagnosed and favorably explained with Holter ECG waveforms using our proposed CNN-based XAI model. Our study presents another step toward realizing a viable XAI-based detection model for AF diagnoses for use by physicians.

Feasibility, safety, and durability of porcine atrial ablation using a lattice-tip temperature-controlled radiofrequency ablation catheter.

INTRODUCTION: Pulmonary vein isolation (PVI) using standard radiofrequency (RF) catheters is limited by incomplete contiguity and prolonged procedural times. A novel, 9-mm lattice-tip irrigated RF catheter can create wide lesions rapidly in swine atria. METHODS: In five swine, temperature limited (75°C) irrigated RF for 5 seconds/ablation was selected, to isolate seven pulmonary veins (PVs; five right superior and two inferior commons) and create five right atrial lines. After 4 weeks, repeat mapping and additional ablation to create atrial isthmus lesions were performed. The chronic lesions were submitted for histology. This was compared with right superior PVI data using standard 3.5-mm irrigated tip ablation in six swine. RESULTS: All targeted PVs (seven of seven, 100%) were acutely isolated. Durable isolation was observed in all six of six PVs treated with 5-second applications, but not in one PV inadvertently treated with 4-second applications. For the durably isolated PVs, the mean lesion count/PV and total RF time/PV was 16.3 ± 5.2 applications and 81.3 ± 25.9 seconds for the right superior and 14.5 ± 0.7 applications and 71.1 ± 5.5 seconds for the inferior common PV. Right atrial linear ablation was performed with a lesion count of 12 ± 2.3 applications and RF times of 59.5 ± 12.5 seconds. Cavotricuspid and mitral isthmus linear ablations were transmural along their entire length. All 53 of 53 (100%) sections were transmural on histology. CONCLUSION: Rapid and durable PVI and linear atrial ablation is feasible with this novel 9-mm lattice-tip catheter.

Endocardial ventricular pulsed field ablation: a proof-of-concept preclinical evaluation.

AIMS: Pulsed field ablation (PFA) is a novel, non-thermal modality that selectively ablates myocardium with ultra-short electrical impulses while sparing collateral tissues. In a proof-of-concept study, the safety and feasibility of ventricular PFA were assessed using a prototype steerable, endocardial catheter. METHODS AND RESULTS: Under general anaesthesia, the left and right ventricles of four healthy swine were ablated using the 12-Fr deflectable PFA catheter and a deflectable sheath guided by electroanatomic mapping. Using the study catheter, electrograms were recorded for each site and pre-ablation and post-ablation pacing thresholds (at 2.0 ms pulse width) were recorded in two of four animals. After euthanasia at 35.5 days, the hearts were submitted for histology. The PFA applications (n = 39) resulted in significant electrogram reduction without ventricular arrhythmias. In ablation sites where it was measured, the pacing thresholds increased by >16.8 mA in the right ventricle (3 sites) and >16.1 mA in the left ventricle (7 sites), with non-capture at maximum amplitude (20 mA) observable in 8 of 10 sites. Gross measurements, available for 28 of 30 ablation sites, revealed average lesion dimensions to be 6.5 ± 1.7 mm deep by 22.6 ± 4.1 mm wide, with a maximum depth and width of 9.4 mm and 28.6 mm, respectively. In the PFA lesions, fibrous tissue homogeneously replaced myocytes with a narrow zone of surrounding myocytolysis and no overlying thrombus. When present, nerve fascicles and vasculature were preserved within surrounding fibrosis. CONCLUSION: We demonstrate that endocardial PFA can be focally delivered using this prototype catheter to create homogeneous, myocardium-specific lesions.

The impact of mechanical oesophageal deviation on posterior wall pulmonary vein reconnection.

AIMS: During atrial fibrillation ablation, oesophageal heating typically prompts reduction or termination of radiofrequency energy delivery. We previously demonstrated oesophageal temperature rises are associated with posterior left atrial pulmonary vein reconnection (PVR) during redo procedures. In this study, we assessed whether mechanical oesophageal deviation (MED) during an index procedure minimizes posterior wall PVRs during redo procedures. METHODS AND RESULTS: Patients in whom we performed a first-ever procedure followed by a clinically driven redo procedure were divided based on both the use of MED for oesophageal protection and the ablation catheter employed (force or non-force sensing) in the first procedure. The PVR sites were compared between MED using a force-sensing catheter (MEDForce), or no MED with a non-force (ControlNoForce) or force (ControlForce) sensing catheter. Despite similar clinical characteristics, the MEDForce redo procedure rate (9.2%, 26/282 patients) was significantly less than the ControlNoForce (17.2%, 126/734 patients; P = 0.002) and ControlForce (17.5%, 20/114 patients; P = 0.024) groups. During the redo procedure, the posterior PVR rate with MEDForce (2%, 1/50 PV pairs) was significantly less than with either ControlNoForce (17.7%, 44/249 PV pairs; P = 0.004) or ControlForce (22.5%, 9/40 PV pairs; P = 0.003), or aggregate Controls (18.3%, 53/289 PV pairs; P = 0.006). However, the anterior PVR rate with MEDForce (8%, 4/50 PV pairs) was not significantly different than Controls (aggregate Controls-3.5%, 10/289 PV pairs, P = 0.136; ControlNoForce-2.4%, 6/249 PV pairs, P = 0.067; ControlForce-10%, 4/40 PV pairs, P = 1.0). CONCLUSION: Oesophageal deviation improves the durability of the posterior wall ablation lesion set during AF ablation.

Transcranial measurement of cerebral microembolic signals during left-sided catheter ablation with the use of different approaches- the potential microembolic risk of a transseptal approach.

Aims: Subclinical brain damage due to microembolization could occur during catheter ablation procedures. We evaluated the microembolic signals (MESs) detected by transcranial Doppler during ablation of supraventricular tachycardias (SVTs) or idiopathic ventricular arrhythmias (VAs) with the use of different approaches. Methods and results: This study included 36 patients (23 men, 49 ± 21 years) who underwent catheter ablation of SVTs (n = 27) or idiopathic VAs (n = 9). Left-sided ablation was performed by either a transaortic (Group 1, n = 11) or transseptal approach (Group 2, n = 9). A sole right-sided ablation was performed in the remaining 16 patients (Group 3). The MESs were counted throughout the procedure, and then analysed offline with a frequency analysis. The mean number of radiofrequency applications, total energy delivery time, total application energy, and total procedure time were 5.8 ± 5.0, 4.3 ± 3.3 min, 6625 ± 4633 J, and 81 ± 40 min, respectively, and there was no significant difference in the parameters between the three groups. The mean total number of MESs was 3.8 ± 3.1 in Group 1, 75 ± 58 in Group 2, and 0.3 ± 0.6 in Group 3 (P = 0.001). Few MESs were detectable during the radiofrequency energy deliveries in all groups. In Group 2, 19 ± 18 MESs were detected during the transseptal puncture period, and subsequently a relatively even distribution of emboli formation was observed. A frequency analysis suggested that 99, 91, and 100% of MESs were gaseous, in Group 1, Group 2, and Group 3, respectively. No neurological impairment was observed in any patients after the procedure. Conclusion: The retrograde aortic approach might potentially have a lower risk of subclinical brain damage than the transseptal approach during left-sided catheter ablation.

Esophagus-Related Complications During Second-Generation Cryoballoon Ablation-Insight from Simultaneous Esophageal Temperature Monitoring from 2 Esophageal Probes.

BACKGROUND: Monitoring luminal esophageal temperatures (LETs) helps predict esophageal thermal lesions (ETLs) after catheter ablation. This study aimed to evaluate esophagus-related complications after second-generation cryoballoon ablation under simultaneous LETs monitoring from 2 esophageal probes. METHODS: Forty consecutive paroxysmal atrial fibrillation patients undergoing second-generation cryoballoon ablation under conscious sedation followed by esophagogastroscopy were prospectively included. Two temperature probes inserted bi-nasally (both non-deflectable in 13, non-deflectable and deflectable in 27 patients) were used for LET monitoring. Pulmonary vein isolation was performed with one 28-mm balloon using single 3-minute freeze techniques. RESULTS: The lowest LETs significantly correlated between different probes; however, deflectable probe showed significantly lower nadir LETs than non-deflectable probes (14.6 ± 9.2 vs. 20.0 ± 10.6 ℃, P<0.0001). Esophagogastroscopy post-ablation demonstrated ETLs and gastroparesis in 8 (20%) and 7 (17.5%) patients (total 13 [32.5%]), respectively. The optimal cutoff for the lowest LET measured on any probe for predicting no ETLs was 12.8 ℃ (sensitivity 78.1%, specificity 100%). When using deflectable and non-deflectable catheters, the optimal cutoff point for the lowest LET for predicting no ETLs was 11.4 ℃ (sensitivity 70.0%, specificity 100%) and 19.4 ℃ (sensitivity 63.6%, specificity 100%), respectively. No ETLs were detected in 12 (30%) patients with the esophagus located between the left atrium and spine. All esophagus-related complications were asymptomatic and had healed on repeat esophagogastroscopy by a mean of 53 ± 25 days after the procedure. CONCLUSIONS: The lowest LET highly depended on the temperature probe location. However, if a different cutoff value was applied, LET monitoring, regardless of the probe type, and anatomical information might help predict ETLs during second-generation cryoballoon ablation.

Prospective Evaluation of Electromyography-Guided Phrenic Nerve Monitoring During Superior Vena Cava Isolation to Anticipate Phrenic Nerve Injury.

BACKGROUND: Right phrenic nerve injury (PNI) is a major concern during superior vena cava (SVC) isolation due to the anatomical close proximity. The functional and histological severity of PNI parallels the degree of the reduction in the compound motor action potential (CMAP) amplitude. This study aimed to evaluate the feasibility of monitoring CMAPs during SVC isolation to anticipate PNI during atrial fibrillation (AF) ablation. METHODS: Thirty-nine paroxysmal AF patients were prospectively enrolled. Radiofrequency energy was delivered point-by-point for 30 seconds with 20 W until eliminating all SVC potentials after the pulmonary vein isolation. Right diaphragmatic CMAPs were obtained from modified surface electrodes by pacing from the right subclavian vein. Radiofrequency applications were applied without fluoroscopy under CMAP monitoring at sites with phrenic nerve capture by high output pacing. RESULTS: Electrical SVC isolation was successfully achieved with a mean of 9.4 ± 3.3 applications in all patients. In 3 (7.5%) patients, the SVC was isolated without radiofrequency delivery at phrenic nerve capture sites. Among a total of 346 applications in the remaining 36 patients, 71 (20.5%) were delivered while monitoring CMAPs. In 1 (1.4%) application, the RF application was interrupted due to a decrease in the CMAP amplitude. However, no PNI was detected on fluoroscopy, and the decreased amplitude recovered spontaneously. The remaining 70 (98.6%) applications exhibited no significant changes in the CMAP amplitude throughout the applications (from 1.01 ± 0.47 to 0.98 ± 0.45 mV, P = 0.383). CONCLUSIONS: Stable right diaphragmatic CMAPs could be obtained, and monitoring CMAPs might be useful for anticipating right PNI during SVC isolation.

Impact of Catheter Contact Force on Superior Vena Cava Mapping and Localization of the Right Phrenic Nerve by High Output Pacing.

BACKGROUND: Right phrenic nerve injury (PNI) is a major concern during superior vena cava (SVC) isolation. Phrenic nerve (PN) localization by high-output pacing is a standard technique for anticipating PNI. This study evaluated the impact of catheter contact force (CF) on SVC mapping and PN localization. METHODS: Twenty-one atrial fibrillation patients undergoing cardiac enhanced computed tomography (CT) were prospectively enrolled. SVC geometries were created at the SVC-right atrium junction level with low (<10 × g) and high (>10 × g) CFs. The PN was localized by high-output pacing (10 V, 2 milliseconds) at the SVC and anterior right superior pulmonary vein (RSPV) with different CFs. RESULTS: The SVC cross-sectional area was significantly greater when created with high (22.1 ± 4.9 × g) compared with low CFs (4.2 ± 1.3 × g) (5.3 ± 1.4 cm2 vs. 2.3 ± 0.7 cm2 , P < 0.0001). High CFs distorted the SVC and anterior RSPV by a mean of 4.8 ± 2.5 and 4.4 ± 1.7 mm, with minimal distortion at the anteroseptal SVC. The PN was more frequently captured with a high compared with low CF at the SVC (95.2% vs. 71.4%, P = 0.038) and RSPV (66.7% vs. 14.3%, P = 0.0005). The PN capture area was also wider with a high compared with low CF at the SVC (9.0 ± 4.1 mm vs. 4.5 ± 2.8 mm, P = 0.001). The PN location was at the anterolateral, lateral, and posterolateral SVC in 3 (14.3%), 13 (61.9%), and 5 (23.8%) patients, respectively, which was identical to that identified on CT. No PNs located >1.98 mm from the RSPV were captured by RSPV pacing. CONCLUSIONS: CF impacted the SVC mapping and PN localization. Cardiac CT identified the PN location, and the distance from the pacing site influenced PN capture.

Cavotricuspid isthmus ablation using a catheter equipped with mini electrodes on the 8 mm tip: a prospective comparison with an 8 mm dumbbell-shaped tip catheter and 8 mm tip cryothermal catheter.

AIMS: The mini electrodes (ME) placed on the tip of the ablation electrode provide more precise local signal. We evaluated whether ME catheter was effective for the ablation of cavotricuspid isthmus (CTI)-dependent atrial flutter. METHODS AND RESULTS: Eighty-five consecutive patients (68 men; 62 ± 10 years) underwent CTI ablation either using a catheter equipped with ME on the 8 mm tip (ME catheter) in 25 patients (Group A), 8 mm dumbbell-shaped (DS) tip catheter (DS catheter) in 30 patients (Group B), or 8 mm tip cryothermal catheter (Cryo catheter) in 30 patients (Group C). In cases of failed isthmus block, the catheter was changed to the other catheter, but patients remained in the original group following intention-to-treat analysis. The endpoint was achieved in all patients after 13 ± 7 applications in Group A, 9 ± 4 applications in Group B, and 5 ± 2 applications in Group C (P < 0.001). The fluoroscopic and procedure times were significantly longer in Group A (9 ± 7 and 28 ± 17 min, P = 0.001, and P = 0.002, respectively) when compared with Groups B (6 ± 4 and 13 ± 6 min) and C (4 ± 3 and 14 ± 7 min). A crossover was performed in 14 (56%) Group A patients, and 3 (10%) Group C patients. The mean power delivered in Group A was significantly lower than in Group B (31.3 ± 9.1 vs. 38.6 ± 7.6 W, P = 0.015). CONCLUSION: The ME catheter was found to be less effective than the Cryo catheter and a DS catheter for the CTI ablation.

Early Recurrence After Pulmonary Vein Isolation of Paroxysmal Atrial Fibrillation With Different Ablation Technologies - Prospective Comparison of Radiofrequency vs. Second-Generation Cryoballoon Ablation.

BACKGROUND: Inflammation plays a prominent role in the etiology of the early recurrence of atrial fibrillation (ERAF). We prospectively compared the proportion of ERAF and time-course patterns of biomarkers between radiofrequency (RF) and cryoballoon (CB) ablation. METHODS AND RESULTS: We enrolled 82 consecutive paroxysmal AF patients undergoing pulmonary vein (PV) isolation, performed with either a 28-mm 2nd-generation CB and 3-min freeze technique or point-by-point RF ablation. Each group had 41 patients. In the RF group, all PVs were successfully isolated with 28.9 ± 6.5 min of RF delivery. In the CB group, a mean of 5.3 ± 1.4 applications/patient was delivered. The proportion of ERAF was similar between the groups. The time-course patterns significantly differed between the groups for high-sensitivity C-reactive protein (hs-CRP) value (P=0.006) and myocardial injury markers (P<0.0001). Greater myocardial injury was observed in the CB than in the RF group (P<0.0001), whereas the peak hs-CRP value was comparable between the groups. The 2-day post-procedure hs-CRP value was the sole factor correlating with ERAF as identified by the multivariable analysis (hazard ratio 1.697; 95% confidence interval, 1.005-2.865; P=0.048) in the RF, but not the CB group. CONCLUSIONS: The proportion of ERAF was comparable after RF and 2nd-generation CB ablation. Despite CB ablation exhibiting greater myocardial injury than RF ablation, the inflammatory responses were comparable between the groups. The inflammatory response extent predicted ERAF post-RF ablation but not post-CB ablation.

Impact of Pulmonary Vein Isolation on Superior Vena Cava Potentials With a Second-Generation Cryoballoon.

BACKGROUND: Radiofrequency ablation of the right superior pulmonary vein (RSPV) can lead to inadvertent superior vena cava (SVC) isolation due to the close anatomical proximity. This study aimed to evaluate the impact of PV isolation on SVC potentials with a second-generation cryoballoon. METHODS: Thirty-one consecutive paroxysmal atrial fibrillation patients who underwent PV isolation exclusively with a 28 mm second-generation cryoballoon and single 3-minute freeze technique were prospectively enrolled. The produced SVC potential conduction delay during the RSPV isolation was prospectively evaluated using circular mapping catheters placed in the SVC throughout the cryoballoon procedure. RESULTS: Stable SVC potentials were recorded in 28 (90.3%) patients. The produced SVC potential conduction delay during the RSPV isolation was a median of 6.0 (0.5-7.6) milliseconds, and >5.0 milliseconds in 16 (57.1%) patients. Among them, the delay had shortened by >5.0 milliseconds in 7 (43.8%) patients within 5 minutes after the RSPV application. The distance between the RSPV ostium and SVC was the sole parameter correlated with the produced delay (R = 0.77, P < 0.0001). For the association between the distance and a produced delay of >5 milliseconds, the area under the curve was 0.896 (95% confidential interval = 0.775-1.000). The optimal cutoff point for the distance predicting the occurrence of the conduction delay (>5 milliseconds) was 2.5 mm (sensitivity 83.3%, specificity 81.2%). CONCLUSIONS: RSPV isolation with a second-generation cryoballoon could produce an SVC potential conduction delay. The anatomical distance between the RSPV and SVC significantly correlated with the impact.

Evaluation of diaphragmatic electromyograms in radiofrequency ablation of atrial fibrillation: prospective study comparing different monitoring techniques.

BACKGROUND: The utility of compound motor action potential (CMAP) monitoring for anticipating phrenic nerve injury (PNI) during cryoballoon ablation has been reported. We sought to compare two different CMAP recording techniques and evaluated the feasibility during pulmonary vein antrum isolation (PVAI) and superior vena cava isolation (SVCI) using radiofrequency energy. METHODS AND RESULTS: Forty-two patients undergoing paroxysmal atrial fibrillation ablation were prospectively enrolled. SVCI was performed following PVAI if SVC potentials were observed. CMAPs were recorded 3 times (before and after PVAI, and after SVCI) simultaneously from surface electrodes (CMAPsuf) and a decapolar catheter in the subdiaphragmatic hepatic vein (CMAPabd). The baseline CMAPsuf and CMAPabd were 0.92 ± 0.36 and 0.65 ± 0.43 mV except in one case with catheter inaccessibility. The CMAPsuf did not correlate with the body mass index, or CMAPabd. In 2 and 9 patients, the CMAPsuf and CMAPabd amplitudes were < 0.5 and < 0.3 mV, respectively. The diaphragm to catheter distance was significantly longer in cases with a CMAPabd < 0.3 mV than one > 0.3 mV (39.2 ± 10.8 vs. 21.5 ± 6.6 mm, P < 0.0001). Two cases with a CMAPsuf < 0.5 mV had larger amplitudes on the CMAPabd. In 1 patient, apparent PNI occurred during the SVCI, and the CMAP disappeared after the SVCI in both techniques. The CMAPs did not significantly decrease after the PVAI and SVCI; however, a >30% decrease was observed in 2 patients in both techniques. In both, no PNI was apparent on fluoroscopy or chest X-ray. CONCLUSIONS: Stable evaluable CMAPs were obtained with the CMAPsuf in most patients. Monitoring with the CMAPabd could be an alternative and complementary method.

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

BACKGROUND: 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). METHODS: 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. RESULTS: 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). CONCLUSIONS: 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.

Adenosine Triphosphate Test After Cryothermal Pulmonary Vein Isolation: Creating Contiguous Lesions Is Essential for Eliminating Dormant Conduction.

BACKGROUND: Adenosine triphosphate (ATP) testing reveals dormant pulmonary vein (PV) conduction after electrical PV isolation (PVI). This study aimed to evaluate the incidence of latent PV conduction after cryothermal PVI. METHODS: Fifty-four consecutive paroxysmal atrial fibrillation patients undergoing cryothermal PVI were prospectively enrolled. PVI was performed with one 28-mm second-generation balloon using a 3-minute freeze technique, and touch-up lesions were created by focal cryothermal applications. ATP testing was performed following PVI with a 20-mm circular mapping catheter placed in each PV. RESULTS: Of 217 PVs, 205 (94.5%) were isolated using a cryoballoon, and 12 required additional focal ablation. ATP testing was performed in 46 patients for 173 and 8 PVs, which were isolated by cryoballoons and focal ablation, respectively. No dormant PV conduction was provoked in any PVs, which were isolated by cryoballoons, whereas 4 (50.0%) out of 8 PVs requiring focal ablation had transient ATP-provoked reconnections (0 vs. 50.0%, P < 0.0001) with a median duration of 11.3 (10.7-17.1) seconds. The latent PV conduction site was identical to the residual conduction gap site after cryoballoon ablation in all. All latent conduction was successfully eliminated by 2 (2.0-9.5) additional focal applications. At a mean follow-up of 7.7 ± 1.6 months, 81.5% of the patients were arrhythmia free after a single procedure. CONCLUSIONS: No dormant PV conduction was provoked in PVs, which were isolated by 28-mm second-generation cryoballoons, but was provoked in 50% of PVs, which were isolated by focal cryoablation. These findings suggest that creating contiguous lesions is essential for eliminating dormant conduction in cryothermal ablation.

Ventricular arrhythmias with superior axis originating from the left ventricular septum: electrocardiographic characteristics predicting successful ablation and insights into their mechanism-observations from a small series of patients.

AIMS: This study aimed to evaluate the electrocardiographic characteristics and predictors of successful ablation for ventricular arrhythmias (VAs) with superior axis originating in the ventricular septum. METHODS AND RESULTS: This study included 385 consecutive patients with VAs undergoing radiofrequency ablation (RFA). Of these, 14 patients (3.7%) were identified who had VAs with superior axis that were mapped to and ablated at the left ventricular (LV) septum. These patients were classified into two groups, successful (n = 9, Success-RFA) and failed (n = 5, Fail-RFA) ablation. The QRS duration of the VAs was longer in the Success-RFA than the Fail-RFA [median (25%, 75% quartile), 140 (134, 149) vs. 128 (116, 132) ms; P = 0.007]. In the Success-RFA, the QRS morphology in lead V1 exhibited qR or rSR (r < 0.2 mV) pattern. In the Fail-RFA, QRS in lead V1 demonstrated an initial R-wave of ≥0.2 mV except for one patient who demonstrated a qR pattern. The initial R-wave amplitude of <0.2 mV in lead V1 identified successful ablation cases with 100% sensitivity and 80% specificity. The magnitude of the initial R-wave amplitude in lead V1 could be related to the originating site's depth within the septal tissue, which could also explain the RFA results. CONCLUSION: Four percent of VA patients had superior axis on electrocardiogram and foci that mapped to the LV septum, two-thirds of which were successfully ablated. The initial R-wave amplitude of <0.2 mV in lead V1 identified RFA success with high sensitivity and specificity.

Catheter ablation of atrial tachyarrhythmias causing inappropriate implantable cardioverter-defibrillator shocks.

AIMS: Inappropriate shocks have been an important issue post-implantable cardioverter-defibrillator (ICD) implantation. Moreover, inappropriate ICD shocks are associated with increased mortality. The objective of this study was to evaluate the feasibility of catheter ablation therapy for atrial tachyarrhythmias (ATa) responsible for inappropriate ICD shocks. METHODS AND RESULTS: Among 108 consecutive patients who underwent ICD implantations, 22, 5, and 3 experienced inappropriate ICD shocks due to ATa, sinus tachycardia, and T-wave oversensing, respectively. Among the 22 patients with ATa, 18 patients (55 ± 10 years, 15 men, structural heart disease in 9) underwent catheter ablation of ATa causing inappropriate shocks. The median duration between the ICD implantation and first inappropriate shock was 10.0 (3.0-24.5) months. The ATa were atrial fibrillation (AF), atrial flutter (AFL), and atrioventricular nodal reentrant tachycardia in 14, 2, and 2 patients, respectively. One patient underwent an atrioventricular nodal ablation for persistent AF associated with a venous anomaly. Among 13 patients who underwent pulmonary vein antrum isolation, 10 (76.9%) were free from AF for a median of 21.0 (13-37.3) months after an average of 1.3 ± 0.5 procedures. In four patients with AFL or a supraventricular tachycardia, none had any arrhythmia recurrence for a median of 6.0 (3.3-93.5) months after a cavotricuspid isthmus or slow pathway ablation, respectively. There were no procedural complications. During the median follow-up of 19.0 (9.5-37.3) months after the last procedure, no patients experienced any inappropriate shocks. CONCLUSION: Catheter ablation is a feasible therapeutic option for treating ATa responsible for inappropriate shock(s) in patients with ICD.