Nonischemic Ventricular Tachycardia Research Articles

Patient-specific quantification of cardiorespiratory motion for cardiac stereotactic radioablation treatment planning

BackgroundCardiac radioablation is a new treatment for patients with refractory ventricular tachycardia (VT). The target for cardiac radioablation is subject to cardiorespiratory motion, the heart’s movement with breathing and cardiac contraction. Data regarding the magnitude of target cardiorespiratory motion are limited, but highly important for treatment planning. ObjectivesTo assess cardiorespiratory motion amplitude by using ablation catheter geometrical data. MethodsElectroanatomic mapping data of patients undergoing catheter ablation for VT at three academic centers were exported. The spatial position of the ablation catheter as a function of time while in contact with endocardium was analyzed and used to quantify cardiorespiratory motion. ResultsForty-four patients with ischemic and non-ischemic cardiomyopathy and VT contributed 1,364 ablation lesions to the analysis. Average cardiac and respiratory excursion were 1.62 ±1.21mm and 12.12 ±4.10mm, respectively. Respiratory motion was on average 7.5 times greater than cardiac motion. Cardiorespiratory motion was greatest along the cranio-caudal axis (9.66 ±4.00mm). Regional variations with respect to respiratory and cardiac motion were observed: basal segments had smaller displacements vs. midventricular and apical segments. Patient characteristics (previous cardiac surgery, height, weight, body mass index and LV ejection fraction) had a statistically significant, albeit clinically moderate impact on cardiorespiratory motion. ConclusionsCardiorespiratory motion is primarily determined by respiratory displacement and is modulated by the location of the target and the patient’s biometric characteristics. The patient-specific quantification of cardiorespiratory motion may allow to decrease treatment volume and reduce radiation exposure of surrounding organs at risk while delivering the therapeutic dose to the target.

Surpoint algorithm for improved guidance of ablation for ventricular tachycardia (SURFIRE-VT): a propensity-matched study

Abstract Background Ablation Index (AI) is a novel multiparametric radiofrequency (RF) ablation lesion quality metric, which incorporates contact force, time, and power in a weighted formula. AI guided strategies have been shown to be clinically effective for catheter ablation of atrial arrhythmias. The utility of AI to guide ablation of ventricular tachycardia (VT) in patients with structural heart disease is not known. Objectives To assess RF ablation and procedural characteristics, safety, and long-term clinical outcomes in patients undergoing VT ablation using either an AI guided strategy (maximum AI target value 550) or conventional approach using traditional parameters at a large tertiary medical center. Methods Consecutive patients (n=91) undergoing initial VT ablation for both ischemic (ICM) and non-ischemic (NICM) VT at single tertiary medical center between 2017 and 2022 were examined. Patients were 1:1 propensity matched for baseline characteristics, co-morbid conditions, and antiarrhythmic use depending on whether the ablation was guided by AI or traditional lesion quality parameters. Baseline categorical variables were compared using chi square test or Fisher exact test, and continuous measures were evaluated using Wilcoxon rank sum test. Linear regression was used to assess the impact of the use of AI on ablation characteristics and Cox proportional hazard model was used evaluate clinical outcomes. Results After propensity matching, baseline characteristics were well balanced between AI (n=37) and non-AI (n=37) groups (Table 1). Patients undergoing an AI guided strategy had shorter average procedure duration (-30.9 minutes, 95% CI [-60.4, -1.4], p=0.04) and average time per lesion (-13.7 seconds, 95% CI [-17.9, -9.5], p <0.001), as well as a trend toward significantly lower total RF ablation duration (357 seconds, 95% CI [-776, 61.9] p=0.09) and fewer steam pops (-0.19, 95% CI [-0.40, 0.02] p = 0.08). Lesion sets were similar between AI and non-AI groups (Scar homogenization: 41% vs 27%; p=0.22, Linear: 23% vs 73%; p=0.31, elimination LPs/LAVAs: 50% vs 43%; p=0.25, Scar dechanneling: 19% vs 8%; p=0.19, Core isolation: 5% vs 11%; p=0.4) as was use of epicardial mapping and ablation (11% vs 14%; p=0.73) Inducibility of VT (70% vs 67%; p=0.8) and termination of clinical VT during ablation (11% vs 16%; p=0.17) were also similar between AI and non-AI groups. When compared to a traditional strategy, patients undergoing an AI strategy had similar hazard for VT recurrence (0.97, 95% CI [0.42 – 2.2], p=0.93) and appropriate device therapy (0.79, 95% CI [0.32 – 1.95] p=0.61). Conclusions Compared to a strategy guided by traditional lesion parameters, use of AI of 550 for VT ablation in patients with structural heart disease resulted in shorter procedure time and average time of RF delivery per lesion with similar intermediate term clinical outcomes.Table 1Figure 1

Short-term and long-term effects of noninvasive cardiac radioablation for ventricular tachycardia: A single-center case series.

Noninvasive cardiac radioablation is reported to be effective and safe for the treatment of ventricular tachycardia (VT). This study aimed to analyze the acute and long-term effects of VT radioablation. Patients with intractable VT or premature ventricular contraction (PVC)-induced cardiomyopathy were included in this study and treated using a single-fraction 25-Gy dose of cardiac radioablation. To quantitatively analyze the acute response after treatment, continuous electrocardiography monitoring was performed from 24 hours before to 48 hours after irradiation and at the 1-month follow-up. Long-term clinical safety and efficacy were assessed 1-year follow-up. From 2019 to 2020, 6 patients were treated with radioablation for ischemic VT (n = 3), nonischemic VT (n = 2), or PVC-induced cardiomyopathy (n = 1). In the short-term assessment, the total burden of ventricular beats decreased by 49% within 24 hours after radioablation and further decreased by 70% at 1 month. The VT component decreased earlier and more dramatically than the PVC component (decreased by 91% and 57% at 1 month, respectively). In the long-term assessment, 5 patients showed complete (n = 3) or partial (n = 2) remission of ventricular arrhythmias. One patient showed recurrence at 10 months, which was successfully suppressed with medical treatment. The posttreatment PVC coupling interval was prolonged (+38 ms at 1 month). Ischemic VT burden decreased more markedly than nonischemic VT burden after radioablation. In this small case series of 6 patients, without a comparison group, cardiac radioablation appeared to decrease the intractable VT burden. A therapeutic effect was apparent within 1-2 days after treatment but was variable by etiology of cardiomyopathy.

CE-521-01 STELLATE GANGLION INSTRUMENTATION FOR RECORDING AND STIMULATION IN PATIENTS WITH VENTRICULAR ARRHYTHMIAS. PRELIMINARY EXPERIENCE

Stellate Ganglion (SG) blockade is used for controlling ventricular arrhythmias (VA). In animal models, SG instrumentation with electrode catheters can allow stimulation and recording cardiac sympathetic activity. Studies on direct modulation and recording of the sympathetic nervous system in human are lacking. To assess the feasibility of SG stimulation (SGS) and recording in humans undergoing VA ablation Patients (n=11) undergoing ablation procedures for VAs underwent bilateral SG recording and stimulation. Under ultrasound guidance, a 2F octapolar catheter was advanced in the SG at the C7 level. Signals were recorded at 30 kHz and filtered at 0.5-2kHz bandpass. Nerve activities were defined as a 3-fold increase in the amplitude over baseline. Stimulation was performed up to 80 mA output (50 Hz, 2 ms pulse width) for 20-30 s. Eleven patients (age 63 ± 12.7 years; 82.7% men) with ischemic ventricular tachycardia (VT) (4, 36%), nonischemic VT (5, 45%), and PVCs (2, 18.2%) were included. Stimulation catheter placement was successful without complications in all patients. SGS caused significant increase in the systolic blood pressure (Fig A-B). More after right than left SGS. SGS induced PVCs in 2 patients and VF in 1. We were able to record SG firings preceding VF in a patient with primary VF in the context of ischemic cardiomyopathy (Fig C-E), and left SG firing preceding the arrhythmia after SD stimulation (Fig F-G) in a patient with PVCs induced VF. SG recording and stimulation are feasible in humans. SGS leads to blood pressure increases, more pronounced after right SGS. SG firing can precede VA onset in humans. Technical refinements are needed to improve reliability of SG recordings.

Etiology, clinical profile, and 1-year outcome of patients presenting with nonischemic ventricular tachycardia: An observational study

Etiology, clinical profile, and 1-year outcome of patients presenting with nonischemic ventricular tachycardia: An observational study

Substrate Characterization and Outcome of Catheter Ablation of Ventricular Tachycardia in Patients With Nonischemic Cardiomyopathy and Isolated Epicardial Scar.

The substrate for ventricular tachycardia (VT) in left ventricular (LV) nonischemic cardiomyopathy may be epicardial. We assessed the prevalence, location, endocardial electrograms, and VT ablation outcomes in LV nonischemic cardiomyopathy with isolated epicardial substrate. Forty-seven of 531 (9%) patients with LV nonischemic cardiomyopathy and VT demonstrated normal endocardial (>1.5 mV)/abnormal epicardial bipolar low-voltage area (LVA, <1.0 mV and signal abnormality). Abnormal endocardial unipolar LVA (≤8.3 mV) and endocardial bipolar split electrograms and predictors of ablation success were assessed. Epicardial bipolar LVA (27.3 cm2 [interquartile range, 15.8-50.0]) localized to basal (40), mid (8), and apical (3) LV with basal inferolateral LV most common (28/47, 60%). Of 44 endocardial maps available, 40 (91%) had endocardial unipolar LVA (24.5 cm2 [interquartile range, 9.4-68.5]) and 29 (67%) had characteristic normal amplitude endocardial split electrograms opposite the epicardial LVA. At mean of 34 months, the VT-free survival was 55% after one and 72% after multiple procedures. Greater endocardial unipolar LVA than epicardial bipolar LVA (hazard ratio, 10.66 [CI, 2.63-43.12], P=0.001) and number of inducible VTs (hazard ratio, 1.96 [CI, 1.27-3.00], P=0.002) were associated with VT recurrence. In patients with LV nonischemic cardiomyopathy and VT, the substrate may be confined to epicardial and commonly basal inferolateral. LV endocardial unipolar LVA and normal amplitude bipolar split electrograms identify epicardial LVA. Ablation targeting epicardial VT and substrate achieves good long-term VT-free survival. Greater endocardial unipolar than epicardial bipolar LVA and more inducible VTs predict VT recurrence.

Early Antiarrhythmic Efficacy of Noninvasive Cardiac Radioablation for Ventricular Tachycardia

<h3>Purpose/Objective(s)</h3> Noninvasive cardiac radioablation has been reported to be effective and relatively safe for ventricular tachycardia (VT) in preclinical and clinical studies. However, previous studies implementing cardiac radioablation set a 6-12 weeks of "blanking period" and focused on long-term effects rather than reporting the early changes. In this prospective trial, we focused on the early antiarrhythmic effects within one month after cardiac radioablation. Especially, we tried to seek the differences in response according to the cause of VT. <h3>Materials/Methods</h3> From September 2019 to December 2020, 6 patients (3 ischemic VTs and 3 non-ischemic VTs) were included in this trial and treated with stereotactic body radiotherapy (SBRT) with a single fraction of 25 Gy for intractable VT. A synthesis of imaging studies, 12-lead ECG, and electrophysiological mapping were used to localize the treatment target. The internal target volume was delineated on either maximal intensity projection of 4D-CT or deep inspiration breath hold CT. A 24-hour Holter monitoring was performed for all patients one month before and after SBRT and except for one patient, it was performed from 24 hours before SBRT to 48 hours after SBRT to measure the early response after SBRT. <h3>Results</h3> The number of total ventricular beats decreased by 58% and 60% within 24 hours and 48 hours after SBRT, respectively. It further decreased to 29% of pre-SBRT number of total ventricular beats at one month after SBRT. The decrease of total ventricular beats could be attributed to the decrease of VT burden rather than that of premature ventricular contractions (PVCs) because the burden of VT decreased earlier and more dramatically than that of PVC. After cardiac radioablation, the duration of the longest VT run was shortened. This indicated that cardiac radioablation decreases the VT burden by shortening the durations of VTs. Notably, the cardiac radioablation was more effective for ischemic VTs than non-ischemic VTs in that the VT burden decreased more markedly after SBRT. The electrophysiologic characteristics of VT/PVC were changed after treatment. During one month after SBRT, there was no severe acute toxicity. <h3>Conclusion</h3> In six patients with intractable VT, the noninvasive cardiac radioablation with a dose of 25 Gy was effective even in 1-month follow-up. The decrease of VT burden through shortening of VTs already began within 24 hours after the procedure and continued to decrease until one month after the radioablation. The treatment effect was more remarkable in ischemic than non-ischemic VT patients.

PCV66 BASELINE CHARACTERISTICS AMONG VENTRICULAR TACHYCARDIA ABLATION PATIENTS: A MULTI-HOSPITAL DATABASE ANALYSIS

Ablation is an effective treatment approach among patients with ventricular tachycardia (VT). Using a nationally representative hospital database, this study examined the baseline characteristics of patients undergoing VT ablation in the United States (US). A cross-sectional study design was used. Patients (aged ≥18 years) with a primary diagnosis of VT who underwent catheter ablation (first procedure) in an inpatient or outpatient setting between 2011-2018 were identified using the Premier Healthcare database. Demographic and clinical characteristics of patients and hospital characteristics were examined. Patients were classified into ischemic VT and non-ischemic VT for the assessment of baseline characteristics. A total of 11,390 patients met the study criteria, with 4,703 having ischemic VT and 6,687 having non-ischemic VT. A third of patients were aged ≥70 years (48% for ischemic VT and 22% for non-ischemic VT), with 70% being male (88% for ischemic VT and 57% for non-ischemic VT), and 78% being white (83% for ischemic VT and 78% for non-ischemic VT). Almost 60% of ablation occurred in an inpatient setting (74% for ischemic VT and 49% for non-ischemic VT). In terms of hospital characteristics, 54% of VT ablations occurred in hospitals with bed size 500+, and 58% were classified as teaching hospital. Almost 45% of patients had CHADS2VASc score of ≥3 (67% for ischemic VT and 31% for non-ischemic VT). As per comorbidity status, 61% of patients had hypertension (77% for ischemic VT and 49% for non-ischemic VT), 23% had diabetes (33% for ischemic VT and 16% for non-ischemic VT), and 48% had heart failure (72% for ischemic VT and 31% for non-ischemic VT). Variation in demographic and clinical characteristics was observed among ischemic VT and non-ischemic VT patients, with the former group having considerable comorbidity burden.

10-YEAR TRENDS IN CATHETER ABLATION OF ISCHEMIC AND NON-ISCHEMIC VENTRICULAR TACHYCARDIA

Catheter ablation for ventricular tachycardia (VT) is now commonplace for patients with both ischemic and non-ischemic VT substrates. We sought to describe 10-year trends in patient characteristics, procedure-related complications and in-hospital mortality in patients undergoing VT ablation,

Highlights from the Circulation Family of Journals

Highlights from the <i>Circulation</i> Family of Journals

Long-Term Outcome After Catheter Ablation of Ventricular Tachycardia in Patients With Nonischemic Dilated Cardiomyopathy.

Catheter ablation (CA) of ventricular tachycardia (VT) in patients with nonischemic dilated cardiomyopathy can be challenging because of the complexity of underlying substrates. We sought to determine the long-term outcomes of endocardial and adjuvant epicardial CA in nonischemic dilated cardiomyopathy. We examined 282 consecutive patients (aged 59±15 years, 80% males) with nonischemic dilated cardiomyopathy who underwent CA. Ablation was guided by activation/entrainment mapping for tolerated VT and pacemapping/targeting of abnormal electrograms for unmappable VT. Adjuvant epicardial ablation was performed for recurrent VT or persistent inducibility after endocardial-only ablation. Epicardial ablation was performed in 90 (32%) patients. Before ablation, patients failed a median of 2 antiarrhythmic drugs), including amiodarone, in 166 (59%) patients. The median follow-up after the last procedure was 48 (19-67) months. Overall, VT-free survival was 69% at 60-month follow-up. Transplant-free survival was 76% and 68% at 60- and 120-month follow-up, respectively. Among the 58 (21%) patients with VT recurrence, CA still resulted in a significant reduction of VT burden, with 31 (53%) patients having only isolated (1-3) VT episodes in 12 (4-35) months after the procedure. At the last follow-up, 128 (45%) patients were only on β-blockers or no treatment, 41 (15%) were on sotalol or class I antiarrhythmic drugs, and 62 (22%) were on amiodarone. In patients with nonischemic dilated cardiomyopathy and VT, endocardial and adjuvant epicardial CA is effective in achieving long-term VT freedom in 69% of cases, with a substantial improvement in VT burden in many of the remaining patients.

Simultaneous Amplitude Frequency Electrogram Transformation (SAFE-T) Mapping to Identify Ventricular Tachycardia Arrhythmogenic PotentialsinSinus Rhythm.

This study sought to develop a novel automated technique, simultaneous amplitude frequency electrogram transformation (SAFE-T), to identify ventricular tachycardia (VT) isthmuses by analysis of sinus rhythm arrhythmogenic potentials (AP). Substrate ablation is useful for patients with scar-related hemodynamically unstable VT; however, the accuracy of different approaches remains inadequate, varying from targeting late potentials to full scar homogenization. High-density ventricular mapping was performed in 3 groups: 1) 18 normal heart control subjects; 2) 10 ischemic patients; and 3) 8 nonischemic VT patients. In VT patients, isthmus sites were characterized using entrainment responses. Sinus rhythm right ventricle/left ventricle endocardial and epicardial electrograms underwent Hilbert-Huang spectral analysis andwere displayed as 3-dimensional SAFE-T maps. AP and their relation to the VT isthmus sites were studied. AP were defined by a cutoff value of 3.08 Hz mV using normal heart control subjects. Receiver-operating characteristics showed that VT isthmus sites were best identified using SAFE-T mapping (p< 0.001) as compared with bipolar and unipolar scar and late potential mapping with an optimal cutoff value of 3.09 Hz mV, allowing identification of 100% of the 34 mapped VT isthmuses, compared with 68% using late potentials. There was no significant difference between sinus rhythm and paced SAFE-T values. Abnormal SAFE-T areas involved about one-quarter of the scar total area. Automated electrogram analysis using 3-dimensional SAFE-T mapping allows rapid and objective identification of AP that reliably detect VT isthmuses. The results suggest that SAFE-T mapping is good alternative strategy to late potential mapping in identifying VT isthmuses and allows reduced ablation as compared to scar homogenization.

Safety and Feasibility of a Minimally Fluoroscopic Approach for Ventricular Tachycardia Ablation in Patients With Structural Heart Disease: Influence of the Ventricular Tachycardia Substrate.

We sought to evaluate the safety and feasibility of a minimally fluoroscopic approach using the CARTOUNIVU module during scar-related ventricular tachycardia (VT) ablation. Consecutive patients with structural heart disease undergoing VT ablation using the CARTOUNIVU module were prospectively included and classified depending on their VT substrate: (1) ischemic VT (IVT) and (2) nonischemic VT and depending on the presence of an epicardial access. Radiation exposure parameters and major and minor procedure-related complications were registered. A near-zero fluoroscopy exposure was defined as those procedures with an effective dose ≤1 mSv. A total of 44 VT ablation procedures were performed in 41 patients (22 IVT and 19 nonischemic VT). The use of the CARTOUNIVU module resulted in low levels of radiation exposure: median total fluoroscopy time and effective dose of 6.08 (1.51-12.36) minutes and 2.15 (0.58-8.22) mSv, respectively. Patients with IVT had lower radiation exposure than patients with nonischemic VT (total fluoroscopy time, 2.53 [1.22-11.22] versus 8.51 [5.55-17.34] minutes; P=0.016). Epicardial access was associated with significantly higher levels of radiation exposure. Complications occurred in 4.9% patients, none of them being related to the use of the image integration tool. A near-zero fluoroscopy ablation could be performed in 14 of 44 procedures (32%), 43% of IVT procedures, and 50% of procedures with endocardial access only. The use of the CARTOUNIVU module during scar-related VT ablation resulted in low levels of radiation exposure. A near-zero fluoroscopy approach can be achieved in up to half of the procedures, especially in IVT patients with endocardial ablation.

Imaging cardiac activation sequence during ventricular tachycardia in a canine model of nonischemic heart failure

Noninvasive cardiac activation imaging of ventricular tachycardia (VT) is important in the clinical diagnosis and treatment of arrhythmias in heart failure (HF) patients. This study investigated the ability of the three-dimensional cardiac electrical imaging (3DCEI) technique for characterizing the activation patterns of spontaneously occurring and norepinephrine (NE)-induced VTs in a newly developed arrhythmogenic canine model of nonischemic HF. HF was induced by aortic insufficiency followed by aortic constriction in three canines. Up to 128 body-surface ECGs were measured simultaneously with bipolar recordings from up to 232 intramural sites in a closed-chest condition. Data analysis was performed on the spontaneously occurring VTs (n=4) and the NE-induced nonsustained VTs (n=8) in HF canines. Both spontaneously occurring and NE-induced nonsustained VTs initiated by a focal mechanism primarily from the subendocardium, but occasionally from the subepicardium of left ventricle. Most focal initiation sites were located at apex, right ventricular outflow tract, and left lateral wall. The NE-induced VTs were longer, more rapid, and had more focal sites than the spontaneously occurring VTs. Good correlation was obtained between imaged activation sequence and direct measurements (averaged correlation coefficient of ∼0.70 over 135 VT beats). The reconstructed initiation sites were ∼10 mm from measured initiation sites, suggesting good localization in such a large animal model with cardiac size similar to a human. Both spontaneously occurring and NE-induced nonsustained VTs had focal initiation in this canine model of nonischemic HF. 3DCEI is feasible to image the activation sequence and help define arrhythmia mechanism of nonischemic HF-associated VTs.

CMR–Based Identification of Critical Isthmus Sites of Ischemic and Nonischemic Ventricular Tachycardia

ObjectivesThis study evaluates whether contrast-enhanced (CE) cardiac magnetic resonance (CMR) can be used to identify critical isthmus sites for ventricular tachycardia (VT) in ischemic and nonischemic heart disease. BackgroundFibrosis interspersed with viable myocytes may cause re-entrant VT. CE-CMR has the ability to accurately delineate fibrosis. MethodsPatients who underwent VT ablation with CE-CMR integration were included. After the procedure, critical isthmus sites (defined as sites with a ≥11 of 12 pacemap, concealed entrainment, or VT termination during ablation) were projected on CMR-derived 3-dimensional (3D) scar reconstructions. The scar transmurality and signal intensity at all critical isthmus, central isthmus, and exit sites were compared to the average of the entire scar. The distance to >75% transmural scar and to the core-border zone (BZ) transition was calculated. The area within 5 mm of both >75% transmural scar and the core-BZ transition was calculated. ResultsIn 44 patients (23 ischemic and 21 nonischemic, left ventricular ejection fraction 44 ± 12%), a total of 110 VTs were induced (cycle length 290 ± 67 ms). Critical isthmus sites were identified for 78 VTs (71%) based on ≥11 of 12 pacemaps (67 VTs), concealed entrainment (10 VTs), and/or termination (30 VTs). The critical isthmus sites, and in particular central isthmus sites, had high scar transmurality and signal intensity compared with the average of the entire scar. Of the pacemap, concealed entrainment, and termination sites, 74%, 100%, and 84% were within 5 mm of >75% transmural scar, and 67%, 100%, and 94% were within 5 mm of the core-BZ transition, respectively. The areas within 5 mm of both >75% transmural scar and the core-BZ transition (median 13% of LV) contained all concealed entrainment sites and 77% of termination sites. ConclusionsBoth in ischemic and nonischemic VT, critical isthmus sites are typically located in close proximity to the CMR-derived core-BZ transition and to >75% transmural scar. These findings suggest that CMR-derived scar characteristics may guide to critical isthmus sites during VT ablation.

Characterization of Trans-septal Activation During Septal Pacing

Background— Identification of intramural basal-septal ventricular tachycardia (VT) substrate is challenging in nonischemic cardiomyopathy. We sought to (1) characterize normal/abnormal trans-septal right ventricular (RV) to left ventricular activation; (2) assess the effect of opposite RV pacing on left ventricular septal bipolar electrograms (EGMs); and (3) establish criteria for the identification of intramural septal VT substrate. Methods and Results— Endocardial activation mapping and local EGM assessment of the left interventricular septum was performed during RV basal septal pacing in 40 patients undergoing VT ablation with no evidence of septal scar (group 1, n=14) and with septal scar (group 2, n=26) defined by low septal unipolar voltage (&lt;8.3 mV) and delayed enhancement on cardiac MRI with/without abnormal bipolar voltage (&lt;1.5 mV) in sinus rhythm. Left ventricular trans-septal activation time was prolonged in Group 2 compared with Group 1 (55.3±33.0 versus 25.7±8.8 ms; P =0.003). In 6 group 2 patients, left ventricular septal breakthrough was displaced to the scar border. During RV pacing, group 2 had fractionated (8.8%), late (2.8%), and split (5.7%) EGMs not seen in group 1. Trans-septal activation &gt;40 ms (sensitivity 60%, specificity 100%; P &lt;0.001) and EGM duration &gt;95 ms during pacing (sensitivity 22%, specificity 91%; P &lt;0.001) identified septal scar (13/26 pts). Conclusions— In patients with nonischemic cardiomyopathy, VT and septal scar, delayed transmural conduction time (&gt;40 ms) and fractionated, late, split, and wide (&gt;95 ms) bipolar EGMs during RV basal pacing identify intramural VT substrate. In select cases, the basal septum appears compartmentalized as the stimulated wavefront is rerouted to the scar border.

Nonischemic cardiomyopathy substrate and ventricular tachycardia in the setting of coronary artery disease

Patients with coronary artery disease (CAD) may have ventricular tachycardia (VT) from a separate nonischemic process. Catheter ablation in these patients can be misguided by abnormalities of coronary arteries. To identify (1) the prevalence of unanticipated nonischemic VT in patients with known CAD presenting with VT and (2) the substrate and VT characteristics of this unique subset of patients. We examined consecutive patients referred for VT catheter ablation who had a history of myocardial infarction and angiography documented CAD with presumed ischemic VT. Patients with low-voltage zones and/or VT origin inconsistent with CAD distribution were included for further analysis. Of 732 patients, 9 (1.2%) (7 men; median age 74 years; ejection fraction 30%) fulfilled inclusion criteria. Endocardial left ventricular scar inconsistent with CAD distribution was found in 8 patients. In 1 patient, only epicardial left ventricular scar was found. The distribution of low voltage (<1.5 mV) was predominantly around the aortic and mitral valves. Thirty-one VTs were induced in 8 patients. Most VTs had right bundle branch block (68%); of these VTs, 67% had an R/S transition zone later than lead V4 consistent with basal VT origin. Epicardial ablation was necessary in 2 patients. During follow-up (30 [25-39] months), 7 of 9 patients (78%) were free of recurrent VT. A small but important subgroup of patients with CAD and VT has a nonischemic substrate/etiology for VT. The presence of multiple VTs with basal origin suggests a potential nonischemic perivalvular substrate and possible need for epicardial VT ablation.

Abstract 19251: Identification of Conducting Channels by Delayed Enhanced Cardiac Magnetic Resonance Imaging

Objective: Delayed enhanced cardiac magnetic resonance imaging (DE-CMRI) is able to define a heterogeneous zone of fibrotic tissue and surviving myocytes, known as ‘gray zone’ (GZ). Studies suggest that the GZ is related to ventricular tachycardia (VT) slow conducting channels (CC). There are established algorithms for GZ characterization. We evaluated the correlation of DE-CMRI defined CC and VT electroanatomic maps (EAM). Methods: Preprocedural DE-CMRI for scar evaluation and electrophysiology study were done in 14 male patients with ischemic (10) and non-ischemic (4) cardiomyopathy and VT. GZ was assessed on contiguous two-dimensional (2D) short axis DE-CMRI slices and reconstructed three-dimensional (3D) models. The reconstructed scar models were integrated in a clinical mapping system and compared to EAM. GZ were defined based on previously described signal intensity (SI) thresholds; full-width half maximum (FWHM), n-standard deviation (NSD) using 2-3SD thresholds and ‘Roes’ (≥ 35% - 50% of peak SI as GZ, and &gt; 50% of peak SI as core). Results: CMRI and scar detection was possible in all patients including 64% of the patients with ICDs. Software analysis allowed detection and reconstruction of scar core and GZ on all 2D- and 3D-CMRI image series. Scar core and GZ were detected with all 3 algorithms. There was more scar core by NSD (NSD vs. Roes vs FWHM, 27±11g vs. 17±8g vs 17±8g, p &lt; 0.01 ) but more GZ by FWHM (NSD vs. Roes vs. FWHM, 5±2g vs. 8±3g vs 12±7g, p &lt; 0.01 ). CC were detected by CMRI in 50% (NSD), 64% (Roes) and 64% (FWHM) of patients. Compared to 12 CC seen on EAM, there were 17 CC seen by FWHM and Roes and 11 CC by the NSD method. There were 14 successful ablation sites in 12 patients with 2 (14%) located in EAM defined CC compared with 18% (FWHM and Roes) and 9% (NSD) in CMRI defined CC. Above 80% of the ablation sites were located in GZ areas on DE-CMRI for all algorithms (91%, 82% and 91% for NSD, Roes and FWHM). Conclusion: CMRI defined GZ/channels can be detected by established algorithms and compared with EAM. The FWHM has the highest GZ mass and FWHM/Roes visualize more CC. More than 80% of successful ablation sites are located in direct vicinity of the GZ. This may enable a more refined analysis of the MRI scar substrate with important features for the successful ablation sites.

Catheter Ablation of Ventricular Tachycardia in Nonischemic Heart Disease

Background— Catheter ablation of ventricular tachycardia (VT) in nonischemic heart diseases can be challenging, and outcomes across different diseases are incompletely defined. The aim of this study was to describe the outcomes after catheter ablation for nonischemic VT in a large cohort and to compare the electrophysiological findings and outcomes according to the type of underlying disease. Methods and Results— Of the 891 consecutive patients undergoing catheter ablation for ventricular arrhythmias, 226 patients (52±14 years; 79% men) with sustained VT due to nonischemic heart disease were included. The primary end point was all-cause death or heart transplantation. Secondary end points were a composite of death, heart transplantation, or readmission because of VT recurrence within 1 year of discharge. Underlying heart diseases were dilated cardiomyopathy in 119 (53%), valvular heart disease in 34 (15%), arrhythmogenic right ventricular cardiomyopathy in 37 (16%), congenital heart disease in 16 (7%), cardiac sarcoidosis in 13 (6%), and hypertrophic cardiomyopathy in 7 (3%) patients. After ablation, inability to induce any VT was achieved in 55%, and another 20% had inducible VTs modified. Major complications occurred in 5%. Arrhythmogenic right ventricular cardiomyopathy had better outcomes than dilated cardiomyopathy for primary ( P =0.002) and secondary end points ( P =0.004). Sarcoidosis had worse outcome than dilated cardiomyopathy for secondary end point ( P =0.002). At 1 year after the last ablation (a mean of 1.4±0.6 procedures, 1–4), freedom from death, heart transplantation, and readmission for VT recurrence were achieved in 173 (77%) patients. Conclusions— In patients with recurrent VT due to nonischemic heart disease, catheter ablation is often useful, although the outcome varies according to the nature of the underlying heart disease.

Sinus rhythm electrocardiogram identification of basal-lateral ischemic versus nonischemic substrate in patients with ventricular tachycardia

Sinus rhythm (SR) electrocardiogram (ECG) features in patients with nonischemic cardiomyopathy (NICM) and ventricular tachycardia (VT) have been described. ECG characteristics that distinguish nonischemic VT substrate from prior myocardial infarction (MI) have yet to be determined. We aimed to identify ECG differences between patients with basal-inferolateral scar due to NICM versus prior MI. SR/atrial-paced ECGs from patients who underwent VT ablation with endocardial/epicardial basal-inferolateral nonischemic scar (n = 25) were compared to patients with inferior/inferolateral MI (n = 30). Surface QRS complexes in each lead were analyzed. Patients with bundle branch block or ventricular pacing were excluded. The best diagnostic algorithm was determined by multivariate analysis then validated prospectively. The NICM group had smaller R amplitude in leads I, II, and III (p ≤ 0.05 for all), greater S amplitude in leads II, III, and V6 (p ≤ 0.001 for all) and S/R ratio in lead V6 (p = 0.001). Inferior Q waves were uncommon in NICM (24 % vs. 87 %, p < 0.001). Lateral QRS fragmentation was uncommon (20 %) but only found in NICM. A three-step algorithm was derived with 100 % sensitivity and 77 % specificity for NICM. In the validation cohort (n = 51), ICM was appropriately excluded in 93 % of the cases of NICM (91 % interobserver agreement) by the algorithm. Lateral lead QRS fragmentation, absence of inferior Q waves, and lead V6 S/R ratio ≥0.25 on the SR ECG distinguishes patients with basal-lateral scar due to NICM from those with prior MI. These findings demonstrate the value of the surface ECG in identifying unique scar-based VT substrate.