Ischemic Ventricular Tachycardia Research Articles

3D-targeted, ECG-imaging aided stereotactic radioablation for VT storm: a case report

Abstract Background Stereotactic arrhythmia radioablation (STAR) is a promising non-invasive therapy for patients with ventricular tachycardia (VT). Accurate identification of the arrhythmogenic volume, or clinical target volume (CTV), on the radiotherapy 4D planning computed tomography (CT) scan is key for STAR efficacy and safety. This case report illustrates our workflow of electro-structural image integration for CTV delineation. Case summary A 72-year-old man with ischemic cardiomyopathy and VT storm, despite two (endocardial and epicardial) catheter-based ablations, was consented for STAR. A 3D electro-structural arrhythmia model was generated from co-registered electroanatomic voltage and activation maps, ECG-imaging and the cardiac CT angiography scan (in ADAS 3D), pinpointing the VT isthmus and inferoapical VT exit. At this location, an area with short recovery times was found with ECG-imaging. A multidisciplinary team delineated the CTV on the transmural ventricular myocardium, which was fused with the 4D planning CT scan using a DICOM RT file. The CTV was 63% smaller compared to using the conventional 17-AHA segmental approach (11 vs 24 cm3). A single fraction of 25 Gy was delivered to the internal target volume. After an 8-week blanking period, no VT recurrences or radiation-related side-effects were noted. Eight months later, the patient died from end-stage heart failure. Discussion We report a novel workflow for 3D-targeted and ECG-imaging aided CTV delineation for STAR, resulting in a smaller irradiated volume compared to segmental approaches. Acute and intermediate outcome and safety were favourable. Non-invasive ECG-imaging at baseline and during induced VT holds promise for STAR guidance.

Unsupervised machine learning defines subgroups in ischemic heart disease patients presenting with ventricular tachycardia

Abstract Background Ventricular tachycardia (VT) in ischemic heart disease (IHD) is the leading cause of sudden cardiac death (SCD). Despite the well-defined recommendations, tailoring therapies individually is often a challenge owing to the great heterogeneity in this population. We hypothesized that unsupervised machine learning can uncover hidden patterns to identify patient subgroups with similar characteristics. Aims To use unsupervised machine learning methods on a database of patients with ischemic VT, to discover subgroups with similar characteristics and compare the survival of the identified groups. Methods We collected the data of 566 patients with IHD hospitalized for sustained monomorphic VT, excluding those with acute coronary syndrome. The 17 recorded features included medical history and echocardiography. All-cause mortality was registered with one-year follow-up. We performed dimension reduction using T-distributed Stochastic Neighbor Embedding (TSNE) to produce 3 dimensions of the data. Then, we applied spectral clustering to create three groups within the population. Each group was compared to the rest of the population for each variable. Finally, we compared the survival across the three groups using Kaplan-Meyer analysis, univariate Cox-regression, and Log-rank test. Results We identified three groups with distinct characteristics. Group 1 represented the healthiest population; patients had no previous VT hospitalizations, and none of HD instability, LBBB, SCD, diabetes, VT storm or ICD shocks; additionally, they always had a single VT episode at presentation. They showed better left ventricular ejection fraction (LVEF) (38% vs. 33%, p<0.001) and TAPSE (20 mm vs. 18 mm, p=0.01), less severe mitral and tricuspid regurgitation (MR, TR), smaller left ventricular end-systolic diameter, and longer DT. Conversely, patients in Group 2 (n=349) had more previous VT hospitalizations (30% vs. 18%, p=0,003), more often had diabetes (46% vs. 18%, p<0.001), left bundle branch block (23% vs. 13%, p=0.006), and more often presented with HD instability (47% vs. 28%, p<0.001). Group 3 contained all seriously ill patients with VT storm or incessant VT, more commonly presenting with ICD shocks (34% vs. 21%, p=0.004), SCD (24% vs. 15%, p=0.004), hemodynamic instability (50% vs. 37%, p=0.01). This group had the poorest LVEF (30% vs. 35%, <0.001) and TAPSE (17 mm vs. 19 mm p=0.001), more severe MR and TR, and the shortest DT (140 ms vs. 173 ms p<0.001). Finally, we compared survival across the three groups. Significantly better survival was found in Group 1 (HR: 0.52 CI [0.28 - 0.98]) and Group 2 (HR: 0.61 CI [0.42 - 0.88]), while Group 3 had higher mortality (HR: 2.7 CI [1.83 - 3.97]). Conclusions Using spectral clustering we identified three groups in our cohort of ischemic VT patients. This method delineates the group of ischemic VT patients with the highest risk of mortality who might need more aggressive treatment and closer follow-up.

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.

“Ischemia in Upstream Neighborhood” After Plaque Modification with Intravascular Lithotripsy

Coronary artery calcification impacts outcomes after percutaneous coronary interventions owing to stent under expansion causing increased risk of stent thrombosis and restenosis. Therefore, adequate calcium modification before stent placement is the key to get desired outcomes in the patients with coronary artery calcification. Many devices are available for calcium modification, which includes orbital or rotational atherectomy, cutting balloon, scoring balloon, and intravascular lithotripsy. All these techniques have inherent risks of complications, such as coronary dissection, perforation, and slow or no reflow. We report a case of intravascular lithotripsy in calcified proximal left circumflex artery (LCX) lesion in a 63-year-old female leading to the left anterior descending artery (LAD) with no flow and ischemic ventricular tachycardia requiring DC cardioversion. Intravascular ultrasound from LAD revealed subintimal hematoma from ostium to mid LAD with intimal flap continuation into ostio-proximal LCX. The intimal flap in LAD has not showed any entry or exit tears which might increase the possibility of intramural hematoma shift to adjacent areas and branches leading to no reflow. Hence, cutting balloon fenestration of the intimal flap, followed by left main coronary artery bifurcation stenting was done to get a good result with flowing distal branches.

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

Time for a new destination: foregoing surgical sympathectomy after successful stellate ganglion block in patients with refractory ventricular tachycardia

Abstract Background Electrical storm (ES) is defined as >3 episodes of sustained ventricular arrhythmias in 24 hours and is associated with increased mortality. ES portends a poor prognosis with limited effective treatment options. Stellate ganglion block (STGB) can be used in patients with ES for temporary control of VT. When STGB is successful, patients can be referred for surgical sympathectomy for longer term management. We postulated that STGB can be used as a bridge to other treatments for refractory VT. Purpose To evaluate the efficacy of STGB as a bridge to interventions other than surgical sympathectomy in patients with refractory VT. Additionally, we assessed STGB as an adjunctive therapy to medical optimization when the cause for ES is temporary (e.g., QT prolonging medications, acute ischemia) foregoing the need for long term interventions. Methods This is a single center retrospective study. We enrolled 12 consecutive patients admitted from July 2018 to September 2022 for ES that received a STGB. The primary clinical outcome was cessation of VT for 24 hours beginning 1 hour after STGB was performed. Secondary clinical outcome of the study was freedom from VT until discharge after STGB. Primary safety outcomes were major procedural complications or death within 48 hours after STGB. Results Sixty-seven percent of the patients were male, with a mean age of 58 years and an average left ventricular ejection fraction of 32%. Two-thirds of the patients had ischemic VT of which half were status post CABG and the other half were status post PCI. In the first 24 hours after STGB, 91% of patients were without recurrent VT. Fifty percent of patients did not have recurrent VT from 24 hours after SGB was performed until discharge. Three patients were referred for catheter ablation. No patients received surgical sympathectomy. There were no major complications or deaths within 48 hours of STGB. Conclusion STGB is a safe and effective procedure that can be utilized as a bridge to VT interventions other than surgical sympathectomy. For patients with ES, STGB is also effective at temporarily suppressing VT allowing time for medical optimization and the withdrawal of provoking agents which perpetuate ES. Further research is necessary to determine optimal timing and patient selection for STGB when used as a bridge for alternative VT therapies.Clinical Impact of VT after STGBElectrical Storm Characteristics

An unusual complication after the mitral valve replacement: Ischemic ventricular tachycardia due to the anomalous origin of circumflex artery injury.

An unusual complication after the mitral valve replacement: Ischemic ventricular tachycardia due to the anomalous origin of circumflex artery injury.

Effects of Mesenchymal Stem Cell Injection into Healed Myocardial Infarction Scar Border Zone on the Risk of Ventricular Tachycardia.

The scar border zone is a main source of reentry responsible for ischemic ventricular tachycardia (VT). We evaluated the effects of mesenchymal stem cell (MSC) injection into the scar border zone on arrhythmic risks in a post-myocardial infarction (MI) animal model. Rabbit MI models were generated by left descending coronary artery ligation. Surviving rabbits after 4 weeks underwent left thoracotomy and autologous MSCs or phosphate-buffered saline (PBS) was administered to scar border zones in two rabbits in each group. Another rabbit without MI underwent a sham procedure (control). An implantable loop recorder (ILR) was implanted in the left chest wall in all animals. Four weeks after cell injections, ventricular fibrillation was induced in 1/2 rabbit in the PBS group by electrophysiologic study, and no ventricular arrhythmia was induced in the MSC group or control. Spontaneous VT was not detected during ILR analysis in any animal for 4 weeks. Histologic examination showed restoration of connexin 43 (Cx43) expression in the MSC group, which was higher than in the PBS group and comparable to the control. In conclusion, MSC injections into the MI scar border zone did not increase the risk of VT and were associated with favorable Cx43 expression and arrangement.

How much endocardial scar homogenization is required for successful ablation of ischemic ventricular tachycardia?

How much endocardial scar homogenization is required for successful ablation of ischemic ventricular tachycardia?

Bayesian analysis of the Substrate Ablation vs. Antiarrhythmic Drug Therapy for Symptomatic Ventricular Tachycardia trial.

Bayesian analyses can provide additional insights into the results of clinical trials, aiding in the decision-making process. We analysed the Substrate Ablation vs. Antiarrhythmic Drug Therapy for Symptomatic Ventricular Tachycardia (SURVIVE-VT) trial using Bayesian survival models. The SURVIVE-VT trial randomized patients with ischaemic cardiomyopathy and monomorphic ventricular tachycardia (VT) to catheter ablation or antiarrhythmic drugs (AAD) as a first-line strategy. The primary outcome was a composite of cardiovascular death, appropriate implantable cardioverter-defibrillator shocks, unplanned heart failure hospitalizations, or severe treatment-related complications. We used informative, skeptical, and non-informative priors with different probabilities of large effects to compute the posterior distributions using Markov Chain Monte Carlo methods. We calculated the probabilities of hazard ratios (HR) being <1, <0.9, and <0.75, as well as 2-year survival estimates. Of the 144 randomized patients, 71 underwent catheter ablation and 73 received AAD. Regardless of the prior, catheter ablation had a >98% probability of reducing the primary outcome (HR < 1) and a >96% probability of achieving a reduction of >10% (HR < 0.9). The probability of a >25% (HR < 0.75) reduction of treatment-related complications was >90%. Catheter ablation had a high probability (>93%) of reducing incessant/slow undetected VT/electric storm, unplanned hospitalizations for ventricular arrhythmias, and overall cardiovascular admissions > 25%, with absolute differences of 15.2%, 21.2%, and 20.2%, respectively. In patients with ischaemic cardiomyopathy and VT, catheter ablation as a first-line therapy resulted in a high probability of reducing several clinical outcomes compared to AAD. Our study highlights the value of Bayesian analysis in clinical trials and its potential for guiding treatment decisions. ClinicalTrials.gov identifier: NCT03734562.

Effect of ventricular tachycardia ablation on symptoms and health-related quality of life: data from a single-center registry

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): ALF grants (County Council of Östergotland). Background Ventricular tachycardia (VT) is a significant cause of morbidity and mortality (1). Implantable cardioverter-defibrillators can terminate the arrhythmia and reduce the risk of sudden cardiac death but do not lower the risk of recurrence (2). Thus, the use of VT ablation as a method of prevention of VT recurrence has increased (3). Most articles have focused on the procedure’s efficacy and complications as opposed to data concerning arrhythmia-related symptoms and health-related quality of life (HRQoL). Purpose We sought to examine the effect of VT ablation on patients’ symptoms and HRQoL during a one-year follow-up period. Method Patients referred for catheter ablation of VT to our university hospital between June 2012 and June 2020 were asked to fill in the validated ASTA (Arrhythmia-Specific questionnaire in Tachycardia and Arrhythmia) questionnaire for the assessment of symptoms and HRQoL before and one year after the index procedure. Results One hundred sixty-one patients filled out the ASTA questionnaire before the index procedure and 133 (83 %) at one-year follow-up. Four patients died during follow-up. Of the 133 patients eligible for analysis, 53 had ischemic VT, 45 had non-ischemic VT, and 35 had idiopathic VT. Sixty patients were also followed up in detail concerning arrhythmia recurrence by screening ICD interrogation reports, ECGs, and Holter registrations. Repeated measures analysis of variance showed a significant reduction of symptoms and improvement of HRQoL irrespective of patients’ background disease (ASTA-symptom score: whole population, as well as subpopulations p&amp;lt;0.001, figure 1, ASTA-HRQoL score: whole population as well as subpopulations p&amp;lt;0.001, figure 2) after 1.6 procedures, while 41 % of patients did not report any arrhythmia-related symptoms after one year. Sixty-eight percent of the patients did not suffer any recurrence during the first year after catheter ablation, and the major complication rate was 7%. Conclusions Catheter ablation of VT effectively reduces arrhythmia-related symptoms and improves HRQoL irrespective of patients' background disease during a follow-up period of one year.

Accuracy of a novel ECGi system in localising the critical isthmus exit site in scar-dependant re-entrant ventricular tachycardia

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Vision in ventricular onset (VIVO) is a novel, non-invasive, mapping system designed to locate the site of earliest activation in ventricular arrhythmia. VIVO utilises a mathematical algorithm, cross-sectional imaging data (CT or MRI), 3D images of the electrodes on the patient torso, and a 12-lead electrocardiogram (ECG) to identify the site of earliest ventricular activation.(1) The system has been shown to accurately predict earliest activation of focal premature ventricular contractions (PVCs), but its accuracy in scar dependant re-entrant ventricular tachycardia (VT) has not been investigated.(1-3) Objective To assess the accuracy of VIVO in localising the VT exit site for patients with ischaemic cardiomyopathy (ICM) and scar related re-entrant VT. Methods 5 patients with ICM (age 56 ± 19 yrs, male n = 5) were investigated (table 1). All patients had an implantable cardioverter-defibrillator with standard indications for VT ablation. Invasive electro-anatomical mapping was performed with the Advisor HD Grid multipolar catheter and maps were generated using omnipolar electrograms (EGMs). The VT exit site was identified using activation ± pace-maps and the location defined by the primary operator using the American Heart Association (AHA) 17 segment model of the left ventricle.(4) Using the intra-procedural VT ECG recordings, VIVO maps were constructed post-procedure. The VIVO predicted VT exit site was identified using the AHA 17-segment model by a second operator, blinded to the results of the procedure. A "complete match" was defined as exact segment concordance between the two operators, "partial match" as adjacent segments, and "no match" if neither requirements satisfied. Results Mean left ventricular ejection fraction was 30.5 ± 9.0%. Mean procedure time was 233 ± 31 minutes, with a mean ablation time of 24 ± 18 minutes. A total of 11 re-entrant VTs were mapped. The VT exit site was identified in all cases (10 activation-map; 1 pace-map). A complete match was seen in 91% of VTs and partial match in 9% (table 2). None of the cases demonstrated a "no match" between the invasive and VIVO maps. There were no procedural complications. Conclusion The VIVO mapping system can accurately predict the VT exit site in scar dependant re-entrant VT. Further studies to assess the feasibility of VIVO-guided ablation in scar dependant VT are ongoing.

Sex differences in catheter ablation for ventricular tachycardia in structural heart disease: a single center 10-years experience

Abstract Funding Acknowledgements Type of funding sources: None. Background Women are underrepresented in studies concerning ventricular tachycardia (VT) catheter ablation (CA). Different etiologies and type of structural heart diseases (SHD) are well established in women; nonetheless conflicting results about efficacy and safety of CA in women have been reported. Purpose To evaluate acute and long-term outcome of VT CA in SHD in women compared to men in a high-volume tertiary Center. Methods All consecutive procedures were included from January 2010 to December 2021. Clinical characteristics, VT etiologies and procedure data of female patients were compared to male population. Catheter ablation was performed according to standard protocol in our center. In mappable VTs, the reentry circuit was characterized, and ablation aimed at VT interruption during radiofrequency (RF); otherwise, a substrate modification approach aiming at late potentials abolition or ablation at sites of slow conduction during sinus rhythm was performed. Following ablation, prevention of any VT inducibility and substrate modification was considered ablation endpoint. Acute results, complications, and VT recurrences during follow up were analyzed comparing the two groups. Results Among 1608 overall VT CA procedures, 141 procedures were performed in 117 women. Female were younger, with less comorbidities, less ischemic VT etiology and higher left ventricular ejection fraction (LVEF) as compared to men (Table 1). They were also less likely ICD carriers. No significant differences were found with regards to: epicardial approach (39.7% vs 35.3%, p=0.68); VT inducibility at baseline (57.4% vs 67.6%, p=0.14), VT termination during RF (87.6% vs 77.6%, p=0.51), and prevention of any VT inducibility at the programmed electrical stimulation (PES) after ablation (79.5% vs 78.1%, p=0.7). Major complications occurred in 4.9% of females as compared to 4.3% of male patients. At median follow-up of 25 months, VT recurrences occurred in 24.7% of female population and 27.5% of male group (p=0.42). Cumulative VT-free survival was comparable in both groups (Figure 2). Conclusions Women with SHD have favorable acute and long-term outcome of VT ablation, despite a high prevalence of non-ischemic etiologies. VT recurrence rate and procedure safety is comparable to male patients, suggesting that catheter ablation can be offered as an effective treatment to women with refractory ventricular arrhythmias.

PO-05-100 DETECTION OF THE CRITICAL SUBSTRATE FOR VENTRICULAR TACHYCARDIA ABLATION WITH THE COMBINED IMAGE OF TC-99M SCINTIGRAM AND LATE IODINE ENHANCEMENT CT

Late potentials (LPs) are the important target for ventricular tachycardia(VT) abltion. However, LPs sometimes cannot be observed sufficiently because of intramural localization of VT substrates. Efficacy of CT for prediction of VT substrates even in intramural layer has been reported. On the other hand, Tc-99m scintigram has been reported to determine the viability of myocardium. The uptake of Tc-99m scintigram could quantify the viability of VT substrates and predict the localization of critical VT substrates such as LPs. Moreover, combination of CT and Tc-99m scintigram could show intramural VT substrates. We evaluated the relationship between the localization of LPs and uptake rate of Tc-99m scintigram. Moreover, we evaluated VT substrates with combined image of scintigram and CT. In eight patients (age, 67.5±8.6 years ; left ventricular(LV) ejection fraction, 26.0±8.7%) with ischemic cardiomyopathy and VT, electroanatomical map (EAM) and Tc-99m scintigrafic image of LV were obtained and were divided into twenty segments. LPs were determined as isolated potentials after QRS and were evaluated in EAM. The relationship between LPs and scintigrafic characteristics was evaluated in total of 160 segments. Electrocardiogram gated CT was performed and late iodine enhancement(LIE) was recorded 8 minutes after administration of contrast media. LPs were recorded in 59 segments. According to the Tc-99m uptake rate, cut off value 35% was set for the prediction of the location of LPs with ROC curve. LPs were observed in the lower scintigram perfusion segments with ≤35% uptake rate (n=61) more than the segments with >35% uptake rate (n=99) with statistical significance (78.6% vs 11.1% p<0.0001). With this cutoff value, we performed another VT ablation with intramural substrate. EAM revealed the exit site of VT circuit from endocardium and the existence of intramural substrate (Fig.A). Low Tc-99m uptake area observed around the apical aneurysm and made the borderline between the basal normal voltage area (Fig.B). LIE showed the transmural damaged tissue on the apical aneurysm and the intramural damaged tissue of mid anterior wall(Fig.C). This border zone of Tc-99m uptake and intramural LIE was similar to the exit site of VT circuit. Long cauterization on this area terminated VT. Lower perfusion area of Tc-99m scintigram could be utilized to predict VT substrates in ICM patients and combination of LIE of CT could add the information of the depth of the VT substrate.

PO-04-230 IMPROVED VISUALIZATION OF LOW AMPLITUDE LATE POTENTIALS WITH VT SUBSTRATE MAPPING USING A NOVEL EP RECORDING SYSTEM

Accurate identification of low-voltage electrograms (EGMs) suffer from artifacts that often interfere with physiological signals in the <0.1-0.5mV range. For substrate based ablation of ventricular tachycardia (VT), dense scar is defined as regions of myocardium with EGM amplitudes below 0.5 mV. Within these regions, current EP recording systems can fail at identifying low-voltage late potentials that are effective targets of ablation therapy. More recently, new EP amplifiers designed specifically to reduce the impact of interference on the fidelity of signals have been introduced. This study used a novel EP recording system (ECGenius System, CathVision, Copenhagen, DK) to identify low amplitude (<0.5mV) late potentials in regions of scar, and quantify their characteristics in a head-head comparison to a standard recording system (LabSystem Pro, Boston Scientific, MA). We collected recordings in parallel from four patients (30-250 Hz bipolar recording bandwidth) referred to our center for an EP study and ablation for VT. We performed substrate mapping during sinus rhythm with a standard 4mm irrigated ablation catheter (SmartTouch, Biosense Webster, Diamond Bar, CA) and a multi-spline mapping catheter (PentaRay, Biosense Webster). In regions of dense scar (< 0.5 mV, delineated with 3-D electroanatomical mapping) we identified late potentials that were above the baseline noise level of the CathVision system that were otherwise not clearly visible with the LabSystem Pro system. In four patients we identified fourteen sites with late potentials (110 beats) that were only identified with the CathVision System (see figure). The average amplitude of the late signals was 0.079 +/- 0.063 mV, which was above the baseline mean noise of 0.008 mV (range 0.006 to 0.015 mV). In contrast, the baseline mean noise of the LabSystem Pro was 0.060 mV (range 0.040 to 0.090 mV). The mean delay of the late potentials (after the start of the surface ECG QRS) was 377ms (range 198 to 470ms). Improved visualization of low voltage EGMs and late potentials can improve upon substrate-based ablation of ischemic VT. With a novel, and state-of-the art recording amplifier, we demonstrate an improved ability to detect clinically relevant sites for ablation that were not visible with a standard recording system. This technology could improve upon current ablation strategies, and may be particularly useful in the current era of micro-electrodes and relatively smaller recording voltages.

PO-05-082 ANTITACHYCARDIA PACING IS MORE EFFECTIVE WHEN DELIVERED TO THE LEFT BUNDLE BRANCH COMPARED TO THE RIGHT VENTRICLE IN A CANINE ISCHEMIC VENTRICULAR TACHYCARDIA MODEL

Implantable cardioverter-defibrillators (ICDs) can terminate ventricular tachycardia (VT) with Antitachycardia pacing (ATP) delivered to a right ventricular (RV) pacing lead, thereby avoiding painful and damaging high-energy shocks. However, ATP efficacy is limited for fast VT, and ATP can accelerate VT or convert VT to ventricular fibrillation (VF). Physiological pacing delivered to the left bundle branch (LBB) has emerged as a clinically relevant target to minimize ventricular dyssynchrony and pacing-induced heart failure. ATP efficacy and safety delivered to the LBB are yet to be investigated. Evaluate the therapeutic efficacy and safety of ATP delivered to an LBB lead compared to ATP delivered to a conventional RV lead. In 6 anesthetized dogs, pacing leads from two ICDs (CobaltTM XT DR, Medtronic, Inc) were implanted at the RV apex (6947 Sprint Quattro SecureTM, Medtronic, Inc) and the LBB (3830 SelectSecureTM, Medtronic, Inc). A lateral thoracotomy procedure was performed, and a two-hour lateral anterior descending artery ischemia-reperfusion injury was caused. The thoracotomy was closed and on post-infarct day 4, dogs were anesthetized, and sustained VT episodes were induced by programmed electrical stimulation. ATP (up to 5 trains of 8 pulses at approximately 88% of the VT cycle length) was delivered to either the LBB or RV pacing site in a randomized fashion. The success rate of ATP in terminating the VT episodes and the rate of VT acceleration and degeneration into VF from both pacing locations were evaluated. In our canine ischemic VT model, VT was induced 80 times, with a mean VT cycle length of 178±35 ms. ATP was delivered and tested for each episode. For ATP delivered to the RV, the success rate for terminating VT was 54%. The success rate for terminating VT for ATP delivered to the LBB was 73% (Fig. A, p < 0.05). ATP resulted in VT acceleration for 10% and 5% of ATP attempts delivered to the RV and LV, respectively (Fig. B, p = Not Significant, NS). Degeneration to VF occurred for 5% of all ATP attempts delivered to the RV, and there was no such incident for ATP delivered to the LBB (Fig. B). Higher efficacy and lower incidence of VT acceleration were observed with ATP delivered to LBB compared to ATP delivered to the RV in this canine ischemic VT model. Improved performance of ATP delivered to LBB compared to RV provides additional incentive for expanded use of LBB leads for pacing and therapy delivery.

Optimization of decrementing evoked potential mapping for functional substrate identification in ischaemic ventricular tachycardia ablation.

Optimization of decrementing evoked potential mapping for functional substrate identification in ischaemic ventricular tachycardia ablation.

Using real-world data from health systems to evaluate the safety and effectiveness of a catheter to treat ischemic ventricular tachycardia.

The ThermoCool STSF catheter is used for ablation of ischemic ventricular tachycardia (VT) in routine clinical practice, although outcomes have not been studied and the catheter does not have Food and Drug Administration (FDA) approval for this indication. We used real-world health system data to evaluate its safety and effectiveness for this indication. Among patients undergoing ischemic VT ablation with the ThermoCool STSF catheter pooled across two health systems (Mercy Health and Mayo Clinic), the primary safety composite outcome of death, thromboembolic events, and procedural complications within 7days was compared to a performance goal of 15%, which is twice the expected proportion of the primary composite safety outcome based on prior studies. The exploratory effectiveness outcome of rehospitalization for VT or heart failure or repeat VT ablation at up to 1year was averaged across health systems among patients treated with the ThermoCool STSF vs. ST catheters. Seventy total patients received ablation for ischemic VT using the ThermoCool STSF catheter. The primary safety composite outcome occurred in 3/70 (4.3%; 90% CI, 1.2-10.7%) patients, meeting the pre-specified performance goal, p = 0.0045. At 1year, the effectiveness outcome risk difference (STSF-ST) at Mercy was - 0.4% (90% CI: - 25.2%, 24.3%) and at Mayo Clinic was 12.6% (90% CI: - 13.0%, 38.4%); the average risk difference across both institutions was 5.8% (90% CI: - 12.0, 23.7). The ThermoCool STSF catheter was safe and appeared effective for ischemic VT ablation, supporting continued use of the catheter and informing possible FDA label expansion. Health system data hold promise for real-world safety and effectiveness evaluation of cardiovascular devices.

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.

Repetitive multiform narrow complex tachycardia

A 73-year-old man presented to the emergency department with palpitations. After experiencing transient exertional palpitations and dyspnea a few months earlier, investigation revealed moderate left ventricular dysfunction and extensive coronary artery disease with evidence of prior inferior infarction. He underwent bypass grafting and remained symptom free with normalization of his ejection fraction until the current presentation. Figure 1 demonstrates his presenting rhythm that did not respond to adenosine but terminated with intravenous diltiazem. What is the most likely mechanism of the tachycardia? Figure 1 shows a regular narrow complex tachycardia with 3 distinct alternating QRS morphologies: (1) right bundle branch block (RBBB), V1 R 120 ms, V4 precordial transition, left superior axis; (2) RBBB, V1 rsRʹ 100 ms, positive precordial concordance, left superior axis; and (3) RBBB, V1 R 100 ms, positive precordial concordance, left superior axis. The RBBB and left superior axis of all 3 morphologies suggest that the ventricles are activated via the left posterior fascicle, or at the very least, there is early engagement of this fascicle. While supraventricular tachycardia with aberrant conduction is theoretically possible, varying ventricular morphologies in this fashion, lack of termination with adenosine, and the relatively narrow QRS duration (<130 ms) would make this less likely. Together with the response to diltiazem, the overall evidence suggests ventricular tachycardia involving the left posterior fascicle. The classic form of idiopathic fascicular ventricular tachycardia involves the left posterior fascicle, in which there is slow antegrade conduction along abnormal Purkinje fibers in the mid-septum (resulting in P1 potentials) and conduction over the left posterior fascicle (resulting in P2 potentials).1Nogami A. Naito S. Tada H. et al.Demonstration of diastolic and presystolic Purkinje potentials as critical potentials in a macroreentry circuit of verapamil-sensitive idiopathic left ventricular tachycardia.J Am Coll Cardiol. 2000; 36: 811-823Crossref PubMed Scopus (218) Google Scholar In any individual patient, variable relationships of the abnormal Purkinje fiber to the left posterior fascicle can result in a more basal or apical site of breakout to the left ventricle; these differences can often be suggested on the surface electrocardiogram by the width of the QRS complex and the precordial transition.2Liu Q. Shehata M. Jiang R. et al.Macroreentrant loop in ventricular tachycardia from the left posterior fascicle: new implications for mapping and ablation.Circ Arrhythm Electrophysiol. 2016; 9e004272Crossref Scopus (7) Google Scholar,3Ma W. Lu F. Shehata M. et al.Catheter ablation of idiopathic left posterior fascicular ventricular tachycardia: predicting the site of origin via mapping and electrocardiography.Circ Arrhythm Electrophysiol. 2017; 10e005240Crossref PubMed Scopus (1) Google Scholar Sung et al4Sung R.K. Kim A.M. Tseng Z.H. et al.Diagnosis and ablation of multiform fascicular tachycardia.J Cardiovasc Electrophysiol. 2013; 24: 297-304Crossref PubMed Scopus (29) Google Scholar described multiform fascicular QRS complexes due to alternate conduction over the left anterior fascicle and the left posterior fascicle from the septal fascicle, but the QRS forms described in the present report are different. Idiopathic fascicular ventricular tachycardia typically occurs in patients with structurally normal hearts, which was not the case in the present report. However, abnormal Purkinje fibers have also been implicated in a minority of patients with ischemic ventricular tachycardia and extension of inferoposterior scar to the left posterior fascicle.5Bogun F. Good E. Reich S. et al.Role of Purkinje fibers in post-infarction ventricular tachycardia.J Am Coll Cardiol. 2006; 48: 2500-2507Crossref PubMed Scopus (121) Google Scholar In this case, it was hypothesized that different QRS morphologies were due to varying sites of left ventricular breakout (Figure 2). The patient underwent electrophysiology study, where multiple episodes of ventricular tachycardia were able to be induced with ventricular extrastimuli similar to those seen on presentation. Ablation of the left posterior fascicle was undertaken, with subsequent noninducibility and no further episodes after 12 months of follow-up.