Catheter Ablation Procedures Research Articles

Spectral characterisation of ventricular intracardiac potentials in human post-ischaemic bipolar electrograms

Abnormal ventricular potentials (AVPs) are frequently referred to as high-frequency deflections in intracardiac electrograms (EGMs). However, no scientific study performed a deep spectral characterisation of AVPs and physiological potentials in real bipolar intracardiac recordings across the entire frequency range imposed by their sampling frequency. In this work, the power contributions of post-ischaemic physiological potentials and AVPs, along with some spectral features, were evaluated in the frequency domain and then statistically compared to highlight specific spectral signatures for these signals. To this end, 450 bipolar EGMs from seven patients affected by post-ischaemic ventricular tachycardia were retrospectively annotated by an experienced cardiologist. Given the high variability of the morphologies observed, three different sub-classes of AVPs and two sub-categories of post-ischaemic physiological potentials were considered. All signals were acquired by the CARTO® 3 system during substrate-guided catheter ablation procedures. Our findings indicated that the main frequency contributions of physiological and pathological post-ischaemic EGMs are found below 320 Hz. Statistical analyses showed that, when biases due to the signal amplitude influence are eliminated, not only physiological potentials show greater contributions below 20 Hz whereas AVPs demonstrate higher spectral contributions above ~ 40 Hz, but several finer differences may be observed between the different AVP types.

Impact of Left Atrial Appendage Closure Combined with Catheter Ablation on Endocrine and Mechanical Cardiac Function in Patients with Atrial Fibrillation.

Background The combined procedure of left atrial appendage closure (LAAC) and catheter ablation (CA) is a safe and feasible therapy to treat patients with atrial fibrillation (AF). However, the effect of the combined procedure on cardiac function remains unclear. This study aimed to investigate the changes in endocrine and mechanical function of the heart following the combined procedure. Methods This retrospective study included 62 consecutive patients who underwent the combined procedure of AF ablation and WATCHMAN LAAC and 62 sex and age-matched patients who only received AF ablation. During follow-up, patients were examined for brain natriuretic peptide (BNP) levels to represent endocrine cardiac function. Mechanical cardiac function was assessed during echocardiographic examination by means of the LA ejection fraction, LA strain (Ƹ), and LA strain rate (SR). Results (1) The BNP levels decreased acutely after the procedure, rose at day 3 postoperation, but trended downwards at 3 months postoperation in both groups. No significant difference was observed between the two groups. (2) LA ejection fraction, LA Ƹ, and SR exhibited a continuous upward trend over a 3-month follow-up in both groups. There was no significant difference in LA ejection fractions, SRe (the parameter of LA conduit function), and SRa (the parameter of LA booster pump function) between the two groups. However, the Ƹ and SRs (the parameters of LA reservoir function) improved in patients treated with CA alone. Conclusions The combined procedure of LAAC and CA significantly improved the endocrine and mechanical function of the heart. Compared to simple CA, based on CA with LAAC intervention, it does not significantly change LA endocrine function but may lead to a decline in the LA reservoir function.

Reduced Radiation Exposure Protocol during Computer Tomography of the Left Atrium Prior to Catheter Ablation in Patients with Atrial Fibrillation.

(1) Background: Computer tomography (CT) is an imaging modality used in the pre-planning of radiofrequency catheter ablation (RFA) procedure in patients with cardiac arrhythmias. However, it is associated with a considerable ionizing radiation dose for patients. This study aims to develop and validate low-dose CT scanning protocols of the left atrium (LA) for RFA guidance. (2) Methods: 68 patients scheduled for RFA of atrial fibrillation were sequentially assigned to four groups of ECG-gated scanning protocols, based on the set tube current (TC): Group A (n = 20, TC = 33 mAs), Group B (n = 18, TC = 67 mAs), Group C (n = 10, TC = 135 mAs), and control Group D (n = 20, TC = 600 mAs). We used a 256-row multidetector CT with body weight-dependent tube voltage of 80 kVp (<70 kg), 100 kVp (70–90 kg), and 120 kVp (>90 kg). We evaluated scanning parameters including radiation dose, total scanning procedure time and signal-to-noise ratio (SNR). (3) Results: The average effective radiation dose (ED) was lower in Group A in comparison to Group B, C and D (0.83 (0.76–1.10), 1.55 (1.36–1.67), 2.91 (2.32–2.96) and 9.35 (8.00–10.04) mSv, p < 0.05). The total amount of contrast media was not significantly different between groups. The mean SNR was 6.5 (5.8–7.3), 7.1 (5.7–8.2), 10.8 (10.1–11.3), and 12.2 (9.9–15.7) for Group A, B, C and D, respectively. The comparisons of SNR in group A vs. B and C vs. D were without significant differences. (4) Conclusions: Optimized pre-ablation CT scanning protocols of the LA can reduce an average ED by 88.7%. Three dimensional (3D) models created with the lowest radiation protocol are useful for the integration of electro-anatomic-guided RFA procedures.

Success rate and safety of catheter ablation in preexcitation syndrome: A comparison between adult and pediatric patients.

BackgroundIn contrast to adults, in whom cardiac rhythm disorders are mainly conditioned by coronary artery disease, in children, arrhythmias are most often associated with inherited heart disorders. Catheter ablation (CA) has an important role in the management of cardiac arrhythmias, in adults and children. The aim of the study was to assess and compare the efficacy and safety of CA in children and adults with preexcitation syndrome.MethodsThe study population comprised 43 adults and 43 children diagnosed with a Wolff-Parkinson-White syndrome (WPW). The mean age of the study population was 41 ± 15 years for adults and 14 ± 2.5 years for children. In all patients, an electrophysiological study and CA were performed. Analysis with respect to the procedure duration, fluoroscopy exposure time, location of accessory pathways (AP), immediate success rate and complications were performed.ResultsElectrophysiological study revealed the most frequent presence of left-sided AP (56% in children and 70% in adults). The mean procedure duration was 96 ± 36 min and 106 ± 51 min in children and adults, respectively (p = NS). The mean fluoroscopy duration was 8.5 ± 4.3 min and 5.9 ± 5.8 min in children and adults, respectively p < 0.05. The CA procedure was successful in 40 out of 43 (93%) adults and in 36 out of 43 (83.7%) children (p = NS). In 2 (4%) children minor complications occurred.ConclusionsAblation in children and adults are equally effective with respect to short-term clinical observation.

Impact of Atrial Tachyarrhythmia Recurrence on the Development of Long-Term Adverse Clinical Events Following Catheter Ablation in Patients With Atrial Fibrillation With Systolic Impairment: A Single-Center Observational Study.

BackgroundCatheter ablation can improve long‐term prognosis of patients with atrial fibrillation with systolic impairment. However, atrial tachyarrhythmia (ATA) recurrence increases during long‐term follow‐up. We aimed to investigate the impact of ATA recurrence on the development of long‐term adverse clinical events following catheter ablation for atrial fibrillation and to identify predictors for the development of adverse clinical events.Methods and ResultsThis single‐center observational study included 75 patients with systolic impairment (left ventricular ejection fraction <50%) who underwent the first catheter ablation procedure for atrial fibrillation at our institution (median follow‐up period: 3.5 [range: 2.4–4.7] years). We compared the cumulative incidence of adverse clinical events (all‐cause death, heart failure hospitalization, stroke, or acute myocardial infarction) between the groups with and without ATA recurrence following the first and last procedures. Multivariable analyses were performed to identify predictors for developing adverse clinical events. Twenty‐one patients (28%) developed adverse clinical events at a median of 2.2 (range: 0.64–2.8) years following the first procedure. The proportion of freedom from adverse clinical events following the first procedure was significantly lower in the ATA recurrence group than in the nonrecurrence group (41% [n=40] versus 95% [n=35], P<0.0005); the proportion following the last procedure also showed a similar tendency (35% [n=26] versus 57% [n=49], P<0.0001). ATA recurrence emerged as an independent predictor for adverse clinical events following both procedures after multivariable adjustment.ConclusionsATA recurrence following catheter ablation procedure could predict adverse clinical events in patients with atrial fibrillation with systolic impairment.

Cardiovascular Magnetic Resonance-Guided Radiofrequency Ablation: Where Are We Now?

The possibilities of cardiovascular magnetic resonance (CMR) imaging for myocardial tissue characterization and catheter ablation guidance are accompanied by some fictional concepts. In this review, we present the available facts about CMR-guided catheter ablation procedures as well as promising, however unproven, theoretical concepts. CMR promises to visualize the respective arrhythmogenic substrate and may thereby make it more localizable for electrophysiology (EP)-based ablation. Robust CMR imaging is challenged by motion of the heart resulting from cardiac and respiratory cycles. In contrast to conventional "passive" tracking of the catheter tip by real-time CMR, novel approaches based on "active" tracking are performed by integrating microcoils into the catheter tip that send a receiver signal. Several experimental and clinical studies were already performed based on real-time CMR for catheter ablation of atrial and ventricular arrhythmias. Importantly, successful ablation of the cavotricuspid isthmus was already performed in patients with typical atrial flutter. However, a complete EP procedure with real-time CMR-guided transseptal puncture and subsequent pulmonary vein isolation has not been shown so far in patients with atrial fibrillation. Moreover, real-time CMR-guided EP for ventricular tachycardia ablation was only performed in animal models using a transseptal, retrograde, or epicardial access-but not in humans. Essential improvements within the next few years regarding basic technical requirements, such as higher spatial and temporal resolution of real-time CMR imaging as well as clinically approved cardiac magnetic resonance-conditional defibrillators, are ultimately required-but can also be expected-and will move this field forward.

Radiation Therapy for the Treatment of Cardiac Arrhythmias

A cardiac arrhythmia is an irregular heart rhythm that occurs as a result of malfunction in the electrical signals of the heart. There are several types of arrhythmias. Atrial fibrillation (AF), an arrhythmia of the upper chamber of the heart, is the most common type of sustained arrhythmia, whereas ventricular tachycardia (VT), which originates in the lower chambers of the heart, has a lower rate of incidence than AF but is more difficult to manage.1 Standard treatments for arrhythmias include use of antiarrhythmic drugs which have potential long-term toxicities and the highly invasive catheter ablation procedures with reasonable efficacy but limited in some cases depending on the location and depth of the target.

Outcome and safety of intracardiac echocardiography guided left atrial appendage closure within zero-fluoroscopy atrial fibrillation ablation procedures.

Simultaneous atrial fibrillation (AF) catheter ablation and left atrial appendage closure (LAAC) are sometimes recommended for both rhythm control and stroke prevention. However, the advantages of intracardiac echocardiography (ICE) guidance for this combined procedure have been scarcely reported. We aim to evaluate the clinical outcomes and safety of ICE-guided LAAC within a zero-fluoroscopy catheter ablation procedure. From April 2019 to April 2020, 56 patients with symptomatic AF underwent concomitant catheter ablation and LAAC. ICE with a multi-angled imaging protocol mimicking the TEE echo windows was used to guide LAAC. Successful radiofrequency catheter ablation and LAAC were achieved in all patients. Procedure-related adverse event rate was 3.6%. During the 12-month follow-up, 75.0% of patients became free of arrhythmia recurrences and oral anticoagulants were discontinued in 96.4% of patients. No ischemic stroke occurred despite two cases of device-related thrombosis versus an expected stroke rate of 4.8% based on the CHA2 DS2 -VASc score. The overall major bleeding events rate was 1.8%, which represented a relative reduction of 68% versus an expected bleeding rate of 5.7% based on the HAS-BLED score of the patient cohort. The incidence of iatrogenic atrial septal defect secondary to single transseptal access dropped from 57.9% at 2 months to 4.2% at 12 months TEE follow-up. The combination of catheter ablation and LAAC under ICE guidance was safe and effective in AF patients with high stroke risk. ICE with our novel protocol was technically feasible for comprehensive and systematic assessment of device implantation.

JCS/JHRS 2021 guideline focused update on non-pharmacotherapy of cardiac arrhythmias.

JCS/JHRS 2021 guideline focused update on non-pharmacotherapy of cardiac arrhythmias.

Miniseries 2—Septal and paraseptal accessory pathways—Part IV: Inferior paraseptal accessory pathways—lessons from surgical and catheter ablation

Abstract Surgeons and electrophysiologists performing accessory pathway ablation procedures have used the term ‘posteroseptal’ region. This area, however, is neither septal nor posterior, but paraseptal and inferior; paraseptal because it includes the fibro-adipose tissues filling the pyramidal space and not the muscular septum itself and inferior because it is part of the heart adjacent to the diaphragm. It should properly be described, therefore, as being inferior and paraseptal. Pathways in this region can be ablated at three areas, which we term right inferior, mid-inferior, and left inferior paraseptal. The right- and left inferior paraseptal pathways connect the right and left atrial vestibules with the right and left paraseptal segments of the parietal ventricular walls. The mid-inferior paraseptal pathways take a subepicardial course from the myocardial sleeves surrounding the coronary sinus and its tributaries. Our review addresses the evolution of the anatomical concept of the inferior paraseptal region derived from surgical and catheter ablation procedures. We also highlight the limitations of the 12-lead electrocardiogram in identifying, without catheter electrode mapping, which are the pathways that can be ablated without a coronary sinus, or left heart approach.

Different Kinetics of Activated Clotting Time Among Uninterrupted Oral Anticoagulants During Catheter Ablation Procedure.

Activated clotting time (ACT) kinetics under uninterrupted oral anticoagulants (OACs) has not been fully evaluated. The present study is sought to validate ACT kinetics including stability under uninterrupted use of OACs during an ablation procedure in daily clinical practice. We prospectively enrolled consecutive 554 patients with atrial fibrillation who underwent catheter ablation procedure under uninterrupted OACs. We evaluated ACT kinetics at an interval of 15 minutes during the procedure and periprocedural complications among 5 OACs (dabigatran [N = 46], rivaroxaban [N = 125], apixaban [N = 129], edoxaban [N = 184], and warfarin [N = 70]). Compared with the dabigatran group, time to achieve target ACT was significantly longer in the rivaroxaban and apixaban groups, but not in the edoxaban and warfarin groups (8.7 vs 11.7 minutes, P < .001; 13.3 minutes, P < .001; 8.8 minutes, P = .64; 10.3 minutes, P = .19, respectively). Heparin dose to achieve target ACT was comparable except for the warfarin group, whereas, compared with the dabigatran group, time in therapeutic range of ACT within the first hour was comparable in the rivaroxaban and apixaban group but significantly lower in the edoxaban and warfarin groups (73.7 % vs 63.0%, P = .06; 67.0 %, P = .16; 59.2 %, P = .001; 58.2%, P = .004, respectively). In multiple regression analysis, low body weight, rivaroxaban, apixaban, and morning session had significant associations with time and heparin dose to achieve target ACT, and there were positive associations of dabigatran and apixaban with time in therapeutic range of ACT within the first hour. The incidence of periprocedural complications did not significantly differ among the 5 groups. Under uninterrupted OAC use in daily clinical practice, dabigatran showed faster achievement of target ACT and higher stability of ACT than other OACs.

Left Atrium Calcification After Multiple Catheter Ablation Procedures for Atrial Fibrillation.

Left Atrium Calcification After Multiple Catheter Ablation Procedures for Atrial Fibrillation.

High vagal tone predicts pulmonary vein reconnection after cryoballoon ablation for paroxysmal atrial fibrillation.

Pulmonary vein (PV) isolation is an established treatment for paroxysmal drug-refractory atrial fibrillation (AF). High parasympathetic tone and reconnection of PVs have demonstrated to be possible culprits of AF recurrence after ablation. Our aim was to investigate the association between parasympathetic tone and reconnected PVs in patients with paroxysmal AF. Consecutive patients who underwent a redo catheter ablation procedure for atrial tachyarrhythmia recurrence by means of 3D electroanatomic mapping with documentation of presence or absence of PVs reconnection following an initial procedure of cryoballoon (CB) ablation for symptomatic drug-refractory paroxysmal AF were screened for the study. A total of 92 patients were included, of whom 50 (54.35%) were males. Reconnected PVs were found in 64 (69%) patients. PVs reconnection could be predicted by DC (C-statistic = .770), by SDNNI (C-statistic = .714) and by absolute VLF power (C-statistic = .722), while right-sided PVs reconnection could be better predicted by DC (C-statistic = .848) and by SDNNI (C-statistic = .761). In multivariate binary logistic regression analysis, a DC value ≥6.45 ms and an absolute VLF power value ≥160 ms2 were associated with three times and five times higher odds of PVs reconnection, respectively. On a vein-per-vein analysis, absolute VLF power ≥160 ms2 was associated with three times higher odds, while reaching of -40°C within 60 s was associated with three times lower odds of PVs reconnection. High parasympathetic tonus accurately predicts PVs reconnection. On a vein-per-vein analysis, parasympathetic markers along with biophysical parameters predicted PVs reconnection. On a case-by-case analysis, parasympathetic markers were the only predictors of PVs reconnection, thus being a robust PVs reconnection prediction tool.

RADIATION EXPOSURE IN ACCESSORY PATHWAY ABLATION PROCEDURES IN CARDIAC ELECTROPHYSIOLOGY: A RETROSPECTIVE ANALYSIS

Background. Radiofrequency catheter ablation (CA) has been the treatment of choice in patients with accessory pathway (AP)-mediated tachycardias. Most of these procedures are done under fluoroscopic guidance, leading to significant radiation exposure to the patient and the laboratory personnel. In this analysis, we have looked at the amount of radiation exposure in AP CA procedures performed without the support of a three-dimensional electroanatomic mapping system. We have analyzed changes in exposure indices over the study period and the impact of change in fluoroscopy frame rate (FFR). Objectives. The objectives of this study are to quantify radiation exposure in accessory pathway ablation procedures; to analyze the radiation exposure trend over time; and to evaluate the effect of fluoroscopy frame rate reduction on the radiation exposure indices in these procedures. Methods. All the AP ablation procedures performed at our institute from January 2016 to December 2019 were retrospectively analyzed. The collected data were age, sex, location of APs based on successful site of ablation on fluoroscopy, procedure time, fluoroscopy time, and dose-area product (DAP). Effective dose (ED) was estimated from DAP. The data of procedures performed before January 2018 (“pre” group) were compared with those of the procedures performed after that date (“post” group). Pre-group procedures were performed at an FFR of 7.5 frames per second (fps), and post-group procedures – at an FFR of 3.75 fps. Results. The total number of procedures included in the analysis was 635. The mean age of the patients was 39±14 years, and 401 of them (63%) were males. The most common location of the APs was left lateral (38%). Procedure time and radiation indices showed a significant decrease over the study period (p &lt; 0.001). Post group procedures had significantly shorter procedure time and lower radiation exposure than pre group procedures. Conclusions. A decrease in the FFR was associated with a significant reduction in radiation exposure in AP ablation procedures

Abstract 12036: Decreased Sympathetic Innervation Around the Left Atrium After Multiple Catheter Ablation Procedures for Atrial Fibrillation

Introduction: Cardiac sympathetic activity is involved in the initiation and maintenance of atrial fibrillation. A novel technique that evaluates the atrial accumulation of 123I-MIBG may be able to assess the atrial sympathetic innervation. The purpose of this study was to visually evaluate the modification of sympathetic innervation caused by multiple catheter ablations. Methods: The total study cohort comprised 32 patients with atrial fibrillation. 21 patients underwent only one ablation using a balloon catheter (cryoballoon in 10 patients; hot balloon in 11 patients) (group 1), while 11 patients underwent multiple radiofrequency catheter ablation procedures (three procedures in 6 patients; four procedures in 5 patients) (group 2). In all patients, the left atrial sympathetic activity was evaluated using MIBG images obtained using a novel solid-state whole-body scanner (VERITON). For local quantitative evaluation, the site with the strongest discrete MIBG accumulation was automatically recognized by the computer and compared in pre- and post-procedural images. Results: In all patients, the total left atrial MIBG accumulation value after ablation (6.64х10 4 ±1.65х10 4 PROPCNTS) was significantly lower than that before ablation (7.74х10 4 ±2.25х10 4 PROPCNTS, p=0.0289). At the site with the strongest discrete MIBG accumulation, the MIBG accumulation after ablation was decreased in 19 patients, unchanged in 9, increased in 3, and shifted in 1. The total left atrial MIBG accumulation value before ablation was significantly lower in group 2 (5.74х10 4 ±1.40х10 4 PROPCNTS) than group 1 (6.67х10 4 ±1.57х10 4 PROPCNTS, p=0.0485). Conclusions: The MIBG accumulation in the left atrium decreased after catheter ablation. Furthermore, preoperative evaluation revealed a significant decrease in MIBG accumulation after multiple ablation procedures. This suggests that multiple catheter ablation of the left atrium modifies the sympathetic innervation.

Abstract 11194: Reducing Arm Muscle Activation by Using an Ablation Catheter Torque Tool: Electromyographic Analysis and User Perception

Background: Cardiac ablation catheters are small in diameter and require significant finger dexterity and grip strength to maintain stability and maneuver safely. We designed a catheter torque tool to reduce the muscle activation required to manipulate cardiac ablation catheters and improve user perception of task workload. Objective: The purpose of this study was to evaluate muscle usage and user perception when completing a simulated ablation task with and without the use of a novel ablation catheter torque tool. Methods: Participants, comprised of cardiology attendings and fellows, were fitted with surface electromyographic (EMG) sensors on 6 key muscle groups in the left hand and forearm. Maximum voluntary contraction (MVC) was collected for equal comparison among participants. A standard ablation catheter was inserted into a pediatric cardiac ablation simulator and subjects navigated the catheter tip to 6 specific electrophysiologic targets including a 1-minute simulated radiofrequency lesion. EMG activity normalized to percentage of MVC was collected throughout the task. The task was repeated 4 times, twice with and twice without the torque tool, in randomized order. A NASA Task Load Index (TLX) survey was completed by the participant at the conclusion each task. Results: Thirteen participants completed the study. Using Wilcoxon’s test, there was a significant difference (P &lt; 0.01) in mean percent of MVC in 4 of the 6 muscle groups when comparing bare catheter versus catheter with torque tool: abductor pollicis, brachioradialis, flexor carpi ulnaris, and extensor carpi radialis. The total expended energy for the abductor pollicis (P &lt; 0.01) and extensor carpi radialis (P = 0.02) were significantly reduced. Perceived physical demand, effort, and frustration were also significantly reduced when using the torque tool (P &lt; 0.01). Conclusions: Use of our novel catheter torque tool reduced the amount of muscle activation necessary to manipulate an ablation catheter during a simulated ablation task. Users’ perceived physical demand, effort, and frustration were less when the tool was used. This tool may improve catheter stability, increase procedure safety, and reduce operator stress and muscle fatigue when performing catheter ablation procedures.

Abstract 12387: Porous Tip Radiofrequency Ablation Catheter Reduced Heart Failure Related Complications and Healthcare Utilization in Paroxysmal Atrial Fibrillation Patients

Introduction: Efforts to improve the safety of catheter ablation procedures have led to continuous improvements in catheter design. A 56-hole porous tip contact force (CF) catheter was developed to provide more uniform cooling with less fluid delivery than a prior 6-hole irrigated design, a change intended to reduce fluid overload and associated complications related to congestive heart failure (CHF). Hypothesis: We hypothesized that ablations using a 56-hole porous tip CF catheter would lead to reductions in CHF-related complications and healthcare utilization, compared to the prior 6-hole design. Methods: Consecutive de novo paroxysmal atrial fibrillation (PAF) ablations were performed between 2/14 - 3/19 by six operators at a single academic center. The 6-hole design was used through 12/16 with the 56-hole porous tip adopted in 10/16. Patient characteristics, procedural detail, and CHF-related complications or symptomatic presentation through 30 days were collected from electronic health records, as defined in table. Results: The population included 174 patients, age 61.1 ± 10.8 years, 67.8% male, with 25.3% having a history of CHF. Compared to the 6-hole design, the 56-hole catheter significantly reduced composite CHF-related complications within 7 days and CHF-related healthcare utilization within 30 days. In contrast to CHF reductions, non-CHF complications within 7 days were not different. Conclusion: In a real-world setting, a 56-hole porous tip irrigated CF catheter significantly reduced CHF-related complications and healthcare utilization in PAF patients when compared to the prior 6-hole design. This reduction may be related to the significant reduction in fluid delivery during the procedure. See table on next page.

Abstract 11799: The Direction and Magnitude of Cardiac Contractile Motion: Considerations for Stereotactic Radio-Ablation of Ventricular Tachycardia

Introduction: Stereotactic ablative radiotherapy is an emerging therapy for ventricular tachycardia (VT), but it is unknown whether its precision may be limited by cardiac motion from the beating heart. Hypothesis: The magnitude of cardiac contractile motion may vary between patients and across different directions in 3D. Methods: Patients who underwent 4D cardiac computed tomography (4DCT) prior to a catheter ablation procedure for atrial or ventricular arrhythmias at 2 medical centers were studied retrospectively. 4DCT was acquired using cardiac-gated Siemens Force or GE Revolution scanners. The displacement of transvenous right atrial (RA) and right ventricle (RV) ICD lead tips across the cardiac cycle (divided into 10 time phases) were measured in orthogonal 3D views on a maximal-intensity projection CT reconstruction (Fig 1) using imaging analysis software (Horos Project). Displacement was compared using 1-way ANOVA. Results: In 14 patients (age 65±11.7 years), contractile motion along the left-right axis, craniocaudal axis, and anteroposterior axis were significantly different for both the RV (0.7±0.4, 0.4±0.2, 0.4±0.2cm, p=0.017) and RA (0.7±0.5, 0.4±0.2, 1.1±0.7cm, p=0.008). The greatest variability between patients in the displacement of the RV lead tip was along the left-right axis (range 0.16cm to 1.52cm) and of the RA lead tip was along the anteroposterior axis (0.2cm to 2.3cm). Clinical characteristics (i.e. ejection fraction) were not associated with the magnitude of motion. Conclusions: Contractile motion was greatest in the left-right direction in the ventricle (up to 1.52cm), but there was a large variation in motion between patients (ranging up to 1.4cm). The magnitude of contractile motion should be assessed on a patient-specific basis. Further studies are underway to develop optimal strategies to account for contractile motion, such as patient-tailored planned target volume expansions and cardiac-gated radiotherapy delivery.

Abstract 11762: The Proximity of the Stomach to the Inferior Wall of the Heart: Implications for Non-Invasive Radio-Ablation of Ventricular Tachycardia

Introduction: Stereotactic ablative radiotherapy is a promising therapy for ventricular tachycardia (VT), but the formation of gastro-pericardial fistula is a serious complication associated with this procedure. The proximity of the stomach to the heart has not been well characterized. Hypothesis: We hypothesized that the stomach is located in close proximity (&lt;1cm) to the inferior cardiac wall. Methods: Patients who underwent 4D cardiac computed tomography (4DCT) prior to a catheter ablation procedure for atrial or ventricular arrhythmias at 2 medical centers were studied retrospectively. 4DCT was acquired using cardiac-gated Siemens Force or GE Revolution scanners. The closest distance from the stomach or esophagus to the left ventricular (LV) myocardium was measured during both end systole and diastole (Fig 1) using imaging analysis software (Horos Project, Annapolis, MD). Clinical predictors of close proximity were assessed using Student’s t-test, Chi-squared and Pearson’s linear regression. Results: In 42 patients (age 65±11.4 years, VT/PVC ablation in 21/42 patients, 50%), the mean gastric proximity was 7.5±4.2mm during end-systole and 6.1±3.6mm during end-diastole (p=0.12). Smaller gastric proximity was significantly associated with increasing LV diameter (y=-1.376*x +12.55; p=0.03) or a history of coronary artery disease (4.8±2.2mm vs 8.3±4.4mm, p=0.02). The closest proximity of the stomach was found most frequently in the mid-segment (compared to the basal or apical segments of the inferior wall, p&lt;0.0001). Conclusions: In patients with arrhythmias, the stomach is located within a mean of 6mm to the mid-inferior wall of the LV, with closer proximity in patients with dilated hearts. Careful avoidance of the stomach is critical during radio-ablative therapy of VT to avoid complications, particularly in patients with mid-inferior wall targets and dilated hearts. Studies are ongoing to study motion management strategies to improve precision.

Abstract 1122‐000070: Multiple Watershed Strokes Following Catheter Ablation Procedure

Introduction : Cerebral watershed strokes involve the junction of two non‐anastomosing arterial systems, which are hemodynamic zones at risk. Strokes occur in 3% to 9% of patients after cardiac procedures. The mechanism underlying post‐cardiac surgery watershed stroke involves a combination of hypoperfusion and embolization, but the role of hypoperfusion has not been well elucidated. Watershed strokes in the general population are usually secondary to global hypoperfusion, such as during cardiac arrest, but may also be attributable to stenosis of the carotid artery or other major vessel, leading to local hypoperfusion. Atrial fibrillation confers a threefold to fivefold increase in the risk of stroke, causing 15–20% of all thromboembolic events in the United States. Catheter ablation of atrial fibrillation is the treatment of choice, and currently one of the most commonly performed electrophysiology procedures in the United States. Successful catheter ablation in patients with atrial fibrillation is associated with a decrease in systolic blood pressure. One study showed that in patients with hemodynamically significant stenosis, the average decrease in mean blood pressure during TIA attack was 26.4. mm Hg. In addition, carotid artery stenosis is frequently associated with stenosis of the vertebral arteries, carotid siphon, and cerebral arteries. In these patients, cerebral blood flow is directly dependent on perfusion pressure, due to the loss of normal autoregulatory capacity in the cerebral circulation. Methods : Single Case Study Results : 84‐year‐old male patient with a past medical history of hypertension, gastrointestinal hemorrhage, coronary artery disease status post coronary artery bypass graft, prostate cancer, and atrial flutter on Apixaban status post recent catheter ablation performed five days prior to presentation at the hospital. Patient presented to the emergency room with complaints of spotty vision. The remainder of the neurologic exam was unremarkable. Patient’s vision changes started after the cardiac ablation procedure and progressively worsened. At the time of assessment, NIH score was 1 due to left eye hemianopsia. CT scan of the head without contrast was done and was negative for hemorrhage. CTA of the neck showed 60% stenosis of the left carotid artery. MRI of the brain was done and showed infarct zones between the right anterior cerebral artery and right middle cerebral artery, the right middle cerebral artery and right posterior cerebral artery, the left anterior cerebral artery and left middle cerebral artery, and in the area supplied by the right posterior cerebral artery. Interestingly, based on the radiologic features, all of these strokes happened at approximately the same time. Conclusions : This case demonstrates that even in asymptomatic patients with hemodynamically insignificant carotid stenosis, hypotensive episodes can elicit hemodynamically significant changes that may result in ischemic stroke. Current guidelines don’t include radiologic assessment of the carotid arteries before catheter ablation procedure in patients with known atherosclerotic disease. Based on our findings, in patients with known atherosclerotic disease, we recommend radiologic assessment of the carotid arteries prior to catheter ablation. Patient who undergo catheter ablation usually have an echocardiogram done prior to the procedure.