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.

Usefulness of Global Longitudinal Strain-Guided Management in Preventing Human Epidermal Growth Factor Receptor 2 (HER2) Inhibitor-Induced Myocardial Damage.

Background: Trastuzumab, an anti-human epidermal growth factor receptor 2 (HER2) monoclonal antibody, is a specific first-line treatment for patients with HER2-positive cancers. Cardiac dysfunction is among the most problematic adverse events associated with trastuzumab. Although regular echocardiographic screening is recommended for early detection of cardiac damage, few reports have investigated the validity of echocardiographic screening in chemotherapy. Therefore, the aim of this study was to determine whether a GLS-guided management approach could reduce cardiotoxicity and discontinuation of trastuzumab chemotherapy. Methods and Results: To evaluate the usefulness of global longitudinal strain (GLS)-guided cardioprotective interventions, we retrospectively analyzed 67 patients treated with trastuzumab who underwent structured echocardiographic assessments before and after 1, 3, and 6 courses of trastuzumab administration. If a >15% relative decrease in GLS was identified, cardioprotective agents were administered. Thirty (44.8%) patients had breast cancer; the remaining patients had salivary gland cancer. The median observation period for the intervention group was 304 days from the initial evaluation. Nineteen (28.4%) patients exhibited a >15% relative decrease in GLS, and consequently received cardioprotective agents. The incidence of trastuzumab discontinuation for cardiogenic reasons was significantly lower among patients receiving GLS-guided interventions than among those not receiving the intervention (2.4% vs. 24.0%; P=0.009). The incidence of a subsequent decline in left ventricular ejection fraction was lower among patients receiving the intervention than among those not receiving the intervention (4.8% vs. 24.0%; P=0.04). Conclusions: GLS-guided cardioprotective intervention significantly decreased the incidence of trastuzumab discontinuation.

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.

Longitudinal Strain and Troponin I Elevation in Patients Undergoing Immune Checkpoint Inhibitor Therapy.

Background: Immune checkpoint inhibitors (ICIs) are a central part of cancer therapy; however, cardiac complications, such as myocarditis, have the potential for significant morbidity and mortality. Within this population, the clinical significance of longitudinal strain (LS) remains unknown. Objectives: This study sought to define the changes in LS in ICI-treated patients, and their associations with high-sensitivity troponin I (hsTnI) and myocarditis. Methods: We conducted a retrospective cohort study of patients who received ICIs at our hospital from April 2017 to September 2021. All patients underwent echocardiography and blood sampling at standardized time intervals. We measured the changes in global and regional LS before and after ICI administration. Age- and sex-adjusted Cox regression analysis was used to evaluate the association between LS and elevations in hsTnI and myocarditis. Results: In a cohort of 129 patients with a median follow-up period of 170 (IQR: 62-365) days; 6 and 18 patients had myocarditis and hsTnI elevation, respectively. In an age- and sex-adjusted Cox proportional hazards model, an early relative worsening of ≥10% in the basal and mid LS and ≥15% in global LS was associated with hsTnI elevation. Relative reductions in LS were not significantly associated with myocarditis; however, 4 of the 6 patients with myocarditis had relative reduction of ≥10% in the basal LS. Conclusions: An early worsening in the global and regional LS was associated with increased hsTnI in patients receiving ICIs. Assessment of LS early after ICI administration should be further studied as a strategy for risk stratification of ICI-treated patients.

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.

Preclinical Evaluation of Pulsed Field Ablation: Electrophysiological and Histological Assessment of Thoracic Vein Isolation.

BACKGROUND: Pulsed field ablation (PFA) is a uniquely tissue-selective, nonthermal cardiac ablation modality. Delivery parameters such as the electrical waveform composition and device design are critical to PFA's efficacy and safety, particularly tissue specificity. In a series of preclinical studies, we sought to examine the electrophysiological and histological effects of PFA and compare the safety and feasibility of durable pulmonary vein and superior vena cava (SVC) isolation between radiofrequency ablation and PFA waveforms. METHODS: A femoral venous approach was used to gain right and left atrial access under general anesthesia in healthy swine. Baseline potentials in right superior pulmonary and inferior common vein and in SVC were assessed. Bipolar PFA was performed with monophasic (PFAMono) and biphasic (PFABi) waveforms in 7 and 7 swine sequentially and irrigated radiofrequency ablation in 3 swine. Vein potentials were then assessed acutely, and at ≈10 weeks; histology was obtained. RESULTS: All targeted veins (n=46) were successfully isolated on the first attempt in all cohorts. The PFABi waveform induced significantly less skeletal muscle engagement. Pulmonary vein isolation durability was assessed in 28 veins: including the SVC, durability was significantly higher in the PFABi group (18/18 PFABi, 10/18 PFAMono, 3/6 radiofrequency, P=0.002). Transmurality rates were similar across groups with evidence of nerve damage only with radiofrequency. Pulmonary vein narrowing was noted only in the radiofrequency cohort. The phrenic nerve was spared in all cohorts but at the expense of incomplete SVC encirclement with radiofrequency. CONCLUSIONS: In this chronic porcine study, PFA-based pulmonary vein and SVC isolation were safe and efficacious with demonstrable sparing of nerves and venous tissue. This preclinical study provided the scientific basis for the first-in-human endocardial PFA studies.

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.

Thromboembolic Risks of the Procedural Process in Second-Generation Cryoballoon Ablation Procedures: Analysis From Real-Time Transcranial Doppler Monitoring.

BACKGROUND: Atrial fibrillation ablation is associated with substantial risks of silent cerebral events (SCEs) or silent cerebral lesions. We investigated which procedural processes during cryoballoon procedures carried a risk. METHODS AND RESULTS: Forty paroxysmal atrial fibrillation patients underwent pulmonary vein isolation using second-generation cryoballoons with single 28-mm balloon 3-minute freeze techniques. Microembolic signals (MESs) were monitored by transcranial Doppler throughout all procedures. Brain magnetic resonance imaging was obtained pre- and post-procedure in 34 patients (85.0%). Of 158 pulmonary veins, 152 (96.2%) were isolated using cryoablation, and 6 required touch-up radiofrequency ablation. A mean of 5.0±1.2 cryoballoon applications was applied, and the left atrial dwell time was 76.7±22.4 minutes. The total MES counts/procedures were 522 (426-626). Left atrial access and Flexcath sheath insertion generated 25 (11-44) and 34 (24-53) MESs. Using radiofrequency ablation for transseptal access increased the MES count during transseptal punctures. During cryoapplications, MES counts were greatest during first applications (117 [81-157]), especially after balloon stretch/deflations (43 [21-81]). Pre- and post-pulmonary vein potential mapping with Lasso catheters generated 57 (21-88) and 61 (36-88) MESs. Reinsertion of once withdrawn cryoballoons and subsequent applications produced 205 (156-310) MESs. Touch-up ablation generated 32 (19-62) MESs, whereas electric cardioversion generated no MESs. SCEs and silent cerebral lesions were detected in 11 (32.3%) and 4 (11.7%) patients, respectively. The patients with SCEs were older than those without; however, there were no significant factors associated with SCEs. CONCLUSIONS: A significant number of MESs and SCE/silent cerebral lesion occurrences were observed during second-generation cryoballoon ablation procedures. MESs were recorded during a variety of steps throughout the procedure; however, the majority occurred during phases with a high probability of gaseous emboli.

Temperature-Controlled Radiofrequency Ablation for Pulmonary Vein Isolation in Patients With Atrial Fibrillation.

BACKGROUND: Saline irrigation improved the safety of radiofrequency (RF) ablation, but the thermal feedback for energy titration is absent. OBJECTIVES: To allow temperature-controlled irrigated ablation, a novel irrigated RF catheter was designed with a diamond-embedded tip (for rapid cooling) and 6 surface thermocouples to reflect tissue temperature. High-resolution electrograms (EGMs) from the split-tip electrode allowed rapid lesion assessment. The authors evaluated the preclinical and clinical performance of this catheter for pulmonary vein (PV) isolation. METHODS: Using the DiamondTemp (DT) catheter, pigs (n = 6) underwent discrete atrial ablation in a temperature control mode (60°C/50 W) until there was ∼80% EGM amplitude reduction. In a single-center clinical feasibility study, 35 patients underwent PV isolation with the DT catheter (study group); patients were planned for PV remapping after 3 months, regardless of symptomatology. A control group included 35 patients who underwent PV isolation with a standard force-sensing catheter. RESULTS: Porcine lesion histology revealed transmurality in 51 of 55 lesions (92.7%). In patients, all PVs were successfully isolated; no char or thrombus formation was observed. Compared with the control group, the study cohort had shorter mean RF application duration (26.3 ± 5.2 min vs. 89.2 ± 27.2 min; p < 0.001), shorter mean fluoroscopic time (11.2 ± 8.5 min vs. 19.5 ± 6.8 min; p < 0.001), and lower acute dormant PV reconduction (0 of 35 vs. 5 of 35; p = 0.024). At 3 months, 23 patients underwent remapping: 39 of 46 PV pairs (84.8%) remained durably isolated in 17 of these patients (73.9%). CONCLUSIONS: This first-in-human series demonstrated that temperature-controlled irrigated ablation produced rapid, efficient, and durable PV isolation. (ACT DiamondTemp Temperature-Controlled and Contact Sensing RF Ablation Clinical Trial for Atrial Fibrillation [TRAC-AF]; NCT02821351).

Outcomes of Ventricular Tachycardia Ablation Using Percutaneous Left Ventricular Assist Devices.

BACKGROUND: Although percutaneous left ventricular assist devices (pLVADs) facilitate mapping and ablation of hemodynamically unstable ventricular tachycardia (VT), there is limited data whether clinical outcomes are improved. We sought to retrospectively compare the outcomes of patients undergoing scar-related VT ablation with and without pLVAD support. METHODS AND RESULTS: The study population comprised 194 patients (109 pLVAD and 85 non-pLVAD). The pLVAD group more often had dilated cardiomyopathy (33% versus 13%; P=0.001), New York Heart Association heart failure class ≥III (51% versus 25%; P<0.001), lower left ventricular ejection fractions (26±10% versus 39±16%; P<0.001), and electrical storm (49% versus 34%; P=0.04). Procedure times (422±112 versus 330±92 minutes; P<0.001), postablation VT inducibility (20% versus 7%; P=0.02), and length of subsequent hospitalization (median 6 versus 4 days; P=0.001) were all higher in the pLVAD group. During median follow-up of 215 days, the primary end point (recurrent VT, heart transplantation, or death) occurred in 36% of the pLVAD versus 26% of the non-pLVAD groups (P=0.14). After propensity matching for differences between groups, no differences were seen between groups for both acute procedural outcomes and the primary end point. CONCLUSIONS: In this large single-center scar-related VT ablation experience, despite the worse clinical status of the patients selected for pLVAD support, clinical outcomes were better than expected and were similar to healthier patients not receiving hemodynamic support. Patients with dilated cardiomyopathy presenting with electrical storm, advanced heart failure, and severe left ventricular dysfunction most frequently received hemodynamic support during VT ablation.

Chamber-Specific Radiofrequency Lesion Dimension Estimation Using Novel Catheter-Based Tissue Interface Temperature Sensing: A Preclinical Assessment.

OBJECTIVES: This study sought to compare a novel lesion dimension estimation approach to actual measurements of lesion dimensions on necropsy in porcine atria and ventricles. BACKGROUND: An irrigated-tip, force-sensing radiofrequency catheter with 6 temperature (tip-tissue interface) sensors allows for assessment of lesion dimensions based on estimated tissue temperature. Lesion dimension assessment has not been attempted previously in atrial tissue. METHODS: Ablations were performed using this catheter in all chambers. Irrigated radiofrequency was delivered using 20 to 50 W for durations that ranged from 15 to 90 s with contact force ranging from 5 to 45 g to replicate a wide spectrum of clinical conditions. All swine were then sacrificed and lesions were identified and photographed. Three independent observers made offline measurements, which were then averaged to obtain lesion width and depth for comparison with estimated dimensions based on interface tissue temperature. RESULTS: In 9 swine, 54 atrial and 61 ventricular lesions were assessed. In the atria, the mean difference between the measured and estimated depth and width was 0.9 ± 0.74 mm and 1.2 ± 0.9 mm, respectively. Eighty percent of all lesions had a difference of ≤1.7 mm for depth and ≤1.74 mm for width. In the ventricle, the mean difference between the measured and estimated depth and width was 0.75 ± 0.6 mm and 1.66 ± 1.1 mm, respectively. Eighty percent of all lesions had a difference of ≤1.1 mm ventricular depth and ≤2.6 mm for width. CONCLUSIONS: Estimation of lesion dimensions can be achieved with clinically relevant accuracy using unique temperature signatures. These data have important implications for understanding the adequacy of lesion overlap and assessment of transmurality.

Optimal slow pathway ablation site for slow-fast atrioventricular nodal reentrant tachycardia with 2:1 atrioventricular conduction.

BACKGROUND: The exact circuit responsible for the atrioventricular (AV) nodal reentrant tachycardia (AVNRT) is still unknown. We evaluated the optimal slow pathway ablation area in patients with and without 2:1 AV conduction during the slow-fast AVNRT. METHODS: Among 207 consecutive patients with slow-fast AVNRT who underwent slow pathway ablation, 12 (5.8 %) patients who had 2:1 AV conduction during tachycardia (group A) were included. Fifty-nine patients without 2:1 AV conduction during tachycardia or a lower common pathway (group B) were included as a control group. We measured the fluoroscopic vertical distance on the 45° left anterior oblique view between the optimal slow pathway ablation area and His bundle electrogram (HBE) recording site (height AH) and between the coronary sinus ostium and HBE site (height CH). The horizontal distances (width AH, width CH) on the 30° right anterior view were also measured. RESULTS: The tachycardia cycle length (300 ± 39 vs. 371 ± 71 ms, p = 0.001) and AH interval during tachycardia (259 ± 33 vs. 324 ± 69 ms, p = 0.001) were significantly shorter in group A than in group B. The height AH/height CH was significantly smaller in group A than in group B (0.62 ± 0.15 vs. 0.76 ± 0.27, p = 0.034) whereas height CH was similar between the two groups (22.8 ± 6.4 vs. 23.4 ± 7.5 mm, p = 0.84). The width CA and width CH were similar between the two groups. Slow pathway ablation was successfully achieved in all 71 patients without any complications. The number of applications tended to be greater in group A than in group b; however, the difference did not reach statistical significance (8.8 ± 8.0 vs. 5.2 ± 5.2, p = 0.147). CONCLUSIONS: The optimal slow pathway ablation area was located at a more superior position in group A than in group b.

Creating bidirectional conduction block in the cavotricuspid isthmus by cryothermal ablation with a short freeze time: Insight from the results with a 2-minute freeze cycle.

BACKGROUND: Optimal freeze doses are unknown during cryothermal cavo-tricuspid isthmus (CTI) ablation. This study aimed to evaluate the feasibility of 2-minute freeze doses for CTI ablation. METHODS: Forty-eight consecutive patients undergoing cryothermal CTI ablation following pulmonary vein isolation were enrolled. CTI ablation was performed with 2-minute freeze cycles and 8-mm tip cryocatheters. RESULTS: Bidirectional CTI block was successfully achieved in 45(93.8%) patients with a median of 5.0[4.0-6.0] cryocatheter applications. The total procedure and fluoroscopic times were a median of 16.5[13.0-20.0] and 4.0[2.0-5.0]min, respectively. A crossover to radiofrequency was performed in 3 patients including 1 due to coronary spasms during the cryoapplication. The tip temperature when block was achieved was a median of -81.0[-73.3 - -84.0]°C. Application times from the start of the last application to achieving block were significantly longer in patients with acute conduction resumption than in those without (46.8±4.0 vs. 20.2±8.8s, p<0.0001), and the optimal cutoff point for predicting no acute resumption was 38.5s (sensitivity 100%, specificity 99.5%). Vasospastic angina occurred in 2 patients, during the procedure in 1 and after in another. Durability could be evaluated a median of 6.0[3.0-8.0] months after the procedure in 14 patients, and conduction resumption was observed in 8(57.1%). The majority of gaps were located at the inferior vena cava edge. CONCLUSIONS: Acute CTI block was obtained by 2-minute freeze cycles with short procedure and fluoroscopic times. Care should be taken to avoid coronary spasms during the peri-procedural period. Additional cryoapplications might be required to improve conduction block durability.

Quantitative Analysis of the Isolation Area During the Chronic Phase After a 28-mm Second-Generation Cryoballoon Ablation Demarcated by High-Resolution Electroanatomic Mapping.

BACKGROUND: The post-second-generation cryoballoon (CB) ablation isolation area during the chronic phase has not been described. The aim of this study was to quantitatively evaluate the chronic-phase isolation area after 28-mm second-generation CB ablation and compare it to the estimated conventional radiofrequency circumferential pulmonary vein isolation (CPVI) line. METHODS AND RESULTS: Thirty-two patients with paroxysmal atrial fibrillation underwent pulmonary vein (PV) isolation using second-generation CB. After a median of 6.0 (4.0-9.0) months, the PV isolation area was evaluated using high-resolution mapping (1-mm electrode, 2-mm interelectrode spacing; 527±99 points per map) and pacing techniques in all patients (17 with and 15 without arrhythmia recurrence beyond blanking period) and compared with estimated conventional radiofrequency CPVI area. PV reconnections were observed in 34 of 126 PVs (27.0%) among 21 of 32 patients (65.6%), which were eliminated by a median of 1.0 (1.0-3.0) focal radiofrequency application. The left- and right-sided PV antrum isolation area and nonablated posterior wall areas were 9.8±1.7, 8.1±2.3, and 17.0±6.1 cm(2), respectively. The cryoablated areas were significantly smaller than the estimated conventional radiofrequency CPVI areas in all but the right inferior PV. The difference was highest in the left superior PV. In 2 patients (6.3%), recurrent atrial fibrillation originated from the foci identified at the left superior PV antrum outside the CB isolation area but inside the estimated conventional radiofrequency CPVI line. CONCLUSIONS: Although the PV isolation areas during the chronic phase after the second-generation CB ablation were generally wide, they were significantly smaller than the area encircled by the CPVI line except at the right inferior PV antrum. Recurrent atrial fibrillation could originate from the left superior PV antrum and could be isolated by a CPVI but not by a CB.

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.