Isthmus Anatomy Research Articles

Slowly conducting anatomic isthmuses of tetralogy of Fallot: An opportunity for “prophylactic” ventricular tachycardia ablation

Slowly conducting anatomic isthmuses of tetralogy of Fallot: An opportunity for “prophylactic” ventricular tachycardia ablation

Three-dimensional cardiac magnetic resonance allows the identification of slow-conducting anatomical isthmuses in tetralogy of Fallot.

Patients with repaired tetralogy of Fallot remain at risk of life-threatening ventricular tachycardia related to slow-conducting anatomical isthmuses (SCAIs). Preventive ablation of SCAI identified by invasive electroanatomical mapping is increasingly performed. This study aimed to non-invasively identify SCAI using 3D late gadolinium enhancement cardiac magnetic resonance (3D-LGE-CMR). Consecutive tetralogy of Fallot patients who underwent right ventricular electroanatomical mapping (RV-EAM) and 3D-LGE-CMR were included. High signal intensity threshold for abnormal myocardium was determined based on direct comparison of bipolar voltages and signal intensity by co-registration of RV-EAM with 3D-LGE-CMR. The diagnostic performance of 3D-LGE-CMR to non-invasively identify SCAI was determined, validated in a second cohort, and compared with the discriminative ability of proposed risk scores. The derivation cohort consisted of 48 (34 ± 16 years) and the validation cohort of 53 patients (36 ± 18 years). In the derivation cohort, 78 of 107 anatomical isthmuses (AIs) identified by EAM were normal-conducting AI, 22 were SCAI, and 7 blocked AI. High signal intensity threshold was 42% of the maximal signal intensity. The sensitivity and specificity of 3D-LGE-CMR for identifying SCAI or blocked AI were 100% and 90%, respectively. In the validation cohort, 85 of 124 AIs were normal-conducting AI, 36 were SCAI, and 3 blocked AI. The sensitivity and specificity of 3D-LGE-CMR were 95% and 91%, respectively. All risk scores showed an at best modest performance to identify SCAI (area under the curve ≤ .68). 3D late gadolinium enhancement cardiac magnetic resonance can identify SCAI with excellent accuracy and may refine non-invasive risk stratification and patient selection for invasive EAM in tetralogy of Fallot.

Long-term outcomes of ventricular tachycardia ablation in repaired tetralogy of Fallot: Systematic review and meta-analysis.

Ventricular tachycardia (VT) remains a risk in repaired Tetralogy of Fallot (rTOF); however, long-term benefits of VT ablation have not been established. This study compares the outcomes of rTOF patients with and without VT ablation. We searched multiple databases examining the outcomes of rTOF patients who had undergone VT ablation compared to those without ablation. Primary outcomes were VT recurrence, sudden cardiac death (SCD), and all-cause mortality. Subgroup analysis was conducted based on the type of ablation (catheter and surgical). Slow-conducting anatomical isthmus (SCAI)-based catheter ablation (CA) was also analyzed separately. The secondary outcome was the risk factors for the pre-ablation history of VT. Fifteen cohort studies with 1459 patients were included, 21.4% exhibited VTs. SCAI was found in 30.4% of the population, with 3.7% of non-inducible VT. Factors significantly associated with VT before ablation included a history of ventriculostomy, QRS duration ≥180 ms, fragmented QRS, moderate to severe pulmonary regurgitation, high premature ventricular contractions burden, late gadolinium enhancement, and SCAI. Ablation was only beneficial in reducing VTs recurrence in SCAI-based CA (risk ratio (RR) 0.11; 95% CI 0.03 to 0.33. p < 0.001; I2 = 0%) with no recurrence in patients with preventive ablation (mean follow-up time 91.14 ± 77.81 months). The outcomes of VT ablation indicated a favorable trend concerning SCD and all-cause mortality (RR 0.49 and 0.44, respectively); however, they were statistically insignificant. SCAI-based CA has significant advantages in reducing VT recurrence in rTOF patients. Risk stratification plays a key role in determining the decision to perform ablation.

Ventricular septal defect characteristics influence presence and properties of septal anatomical isthmuses in patients with repaired tetralogy of Fallot

Abstract Background In repaired tetralogy of Fallot (rTOF), the septal anatomical isthmuses (AI), 3, between the ventricular septal defect (VSD) and pulmonary annulus, and 4, between the VSD and tricuspid annulus, are important ventricular tachycardia (VT) substrates when slow conducting. Patients with rTOF can have different VSD characteristics which may influence presence and properties of septal AIs. Methods This study included all consecutive patients with rTOF who underwent electroanatomical mapping (EAM) between 2005 and March 2023 for ventricular arrhythmias, risk stratification, or before pulmonary valve replacement and had a surgical report of initial repair available. Results In 130 of 154 (84%) patients a surgical report was available (35% female, median age at EAM 38 years [IQR 20-49]), with provided VSD details in 90 (69%). The majority of patients had an outlet perimembranous VSD (n=77, 86%), 7 (8%) a doubly-committed juxta-arterial (DC-JA) VSD, and 4 (4%) a muscular outlet VSD. All patients with a DC-JA VSD had a blocked/absent AI 3. Among patients with a DC-JA VSD with a muscular posteroinferior rim, 50% had AI 4, which was not observed in patients with a fibrous posteroinferior rim. In patients with a muscular VSD, AI 4 was present in 25%. In contrast, in patients with an outlet perimembranous VSD, an AI 4 or a blocked/absent AI 3 were rare findings (1% and 4%, respectively). Conclusions VSD characteristics influence presence and properties of septal AIs. In patients with DC-JA VSD septal VT substrates seem to be rare. Detailed surgical information is desirable for patient management.

Systematic right ventricular electrophysiologic evaluation in patients with repaired tetralogy of Fallot before pulmonary valve replacement

Abstract Introduction Adults with repaired tetralogy of Fallot (rToF) are prone to develop ventricular tachycardia (VT) in adulthood, due to reentry related to slowly conducting anatomical isthmuses (SCAI). Pulmonary valve replacement (PVR) in patients without history of VT, may lead to obliteration of unrecognized SCAI with subsequent catheter ablation failure; electrophysiologic study is thus recommended before PVR. A systematic evaluation of the topology of SCAI in this population is, however, scant. Methods Consecutive rToF patients undergoing PVR with native right ventricular outflow tract were studied with pre-PVR EPS. Electroanatomical mapping with systematic evaluation of all possible anatomical isthmuses (AI) with pacemapping, activation mapping in sinus/paced rhythm and bipolar voltage mapping was performed (AI1: anterior scar/patch to tricuspid annulus; AI2: anterior scar to pulmonary annulus; AI3: pulmonary annulus to ventricular septal defect – VSD- patch; AI4: VSD to tricuspid annulus). Conduction velocity (CV) across all documented AI was calculated (ratio between the distance among the nearest point with bipolar voltage &amp;gt;1.5 mV and their difference in activation timing). Ventricular programmed stimulation was performed at 2 sites (apex and outflow tract) with drive train ad 600/400 ms, up to three extrastimuli until refractoriness or induction, during baseline and isoproterenol infusion. Radiofrequency catheter ablation (RFCA) was performed in all patients with inducible VT and/or SCAI, aiming at conduction block across the SCAI validated with differential pacing. Results Between May 2023 and November 2023, 10 patients with rToF and 1 double outlet right ventricle were studied (73% males, age 46±10 years; 54% with a previous shunt, 46% with a previous transannular patch, 27% pulmonary valvotomy and infundibular boring; median age at surgery 4 years, interquartile range 3-6). EPS was positive for inducible VT in 4 patients (mean cycle length 297 ms, 3 with left bundle branch morphology and 1 right bundle branch morphology, all inferior axis) and polymorphic VT in 1. AI1 was present in 5 patients, AI2 in 5, AI3 in 7, AI 4 in 2. At least 1 SCAI was present in 7 patients (64%), 2 SCAI in 3 patients (43% of patients with SCAI; in every patient SCAI3+SCAI2 in 2 and SCAI 4 in 1 patient). There were no SCAI1; there were 3 SCAI 2 (mean CV 0.43 m/s), 4 SCAI 3 (mean CV 0.3 m/s), 1 SCAI 4 (CV 0.4 m/s). RFCA was performed in 8 patients; acute success was achieved in all patients, achieving bidirectional conduction block across treated SCAI and non-inducibility of VT. Conclusions SCAI are often present in rToF candidate to PVR and without clinical history of spontaneous VT, involving prevalently SCAI3 and SCAI2. Inducible VT is not sufficient as a marker of arrhythmic risk and SCAI should be better sought for. RFCA of SCAI with bidirectional conduction block is acutely highly efficacious.

Multidetector Computed Tomography Assessment of Anatomical Ventricular Tachycardia Isthmuses in Repaired Tetralogy of Fallot

BackgroundTetralogy of Fallot (TOF) is associated with risk for sustained monomorphic ventricular tachycardia (VT). Preemptive electrophysiology study before transcatheter pulmonary valve placement is increasing, but the value of MDCT for anatomical VT isthmus assessment is unknown. ObjectivesThe purpose of this study was to determine the impact of multidetector computed tomography (MDCT) in the evaluation of sustained monomorphic VT for repaired TOF. MethodsConsecutive pre–transcatheter pulmonary valve MDCT studies were identified, and anatomical isthmus dimensions were measured. For a subset of patients with preemptive electrophysiology study, MDCT features were compared with electroanatomical maps. ResultsA total of 61 repaired TOFs with MDCT were identified (mean 35 ± 14 years, 58% men) with MDCT electroanatomical map pairs in 35 (57%). Calcification corresponding to patch material was present in 46 (75%) and was used to measure anatomical VT isthmuses. MDCT wall thickness correlated positively with number of ablation lesions and varied with functional isthmus properties (blocked isthmus 2.6 mm [Q1, Q3: 2.1, 4.0 mm], slow conduction 4.8 mm [Q1, Q3: 3.3, 6.0 mm], and normal conduction 5.6 mm [Q1, Q3: 3.9, 8.3 mm]; P < 0.001). A large conal branch was present in 6 (10%) and a major coronary anomaly was discovered in 3 (5%). Median ablation lesion distance was closer to the right vs the left coronary artery (10 mm vs 15 mm; P = 0.01) with lesion-to-coronary distance <5 mm in 3 patients. ConclusionsMDCT identifies anatomical structures relevant to catheter ablation for repaired TOF. Wall thickness at commonly targeted anatomical VT isthmuses is associated with functional isthmus properties and increased thermal energy delivery.

Automated isochronal late activation mapping for substrate characterization in patients with repaired tetralogy of Fallot.

Slow conduction (SC) anatomical isthmuses (AIs) are the dominant substrate for monomorphic ventricular tachycardia (VT) in patients with repaired tetralogy of Fallot (rTF). This study aimed to evaluate the utility of automated propagational analysis for the identification of SC-AI in patients with rTF. Consecutive rTF patients undergoing VT substrate characterization were included. Automated isochronal late activation maps (ILAM) were obtained with multielectrode HD Grid Catheter. Identified deceleration zones (DZs) were compared with both SC-AI defined by conduction velocity (CV) (<0.5 m/s) and isthmuses of induced VT for mechanistic correlation. Fourteen patients were included (age 48; p25-75 35-52 years; 57% male), 2 with spontaneous VT and 12 for risk stratification. Nine VTs were inducible in seven patients. Procedure time was 140 (p25-75 133-180) min and mapping time 29.5 (p25-75 20-37.7) min, using a median of 2167 points. All the patients had at least one AI by substrate mapping, identifying a total of 27 (11 SC-AIs). Isochronal late activation maps detected 10 DZs mostly in the AI between ventricular septal defect and pulmonary valve (80%). Five patients had no DZs. A significant negative correlation between number of isochrones/cm and CV was observed (rho -0.87; P < 0.001). Deceleration zones correctly identified SC-AI (90% sensitivity; 100% specificity; 0.94 accuracy) and was related to VT inducibility (P = 0.006). Deceleration zones co-localized to the critical isthmus of induced VTs in 88% of cases. No complications were observed. Deceleration zones displayed by ILAM during sinus rhythm accurately identify SC-AIs in rTF patients allowing a safe and short-time VT substrate characterization procedure.

The R'' wave in V1 and the terminal QRS vector in aVF combine to a novel 12-lead ECG algorithm to identify slow conducting anatomical isthmus 3 in patients with tetralogy of Fallot

Abstract Background Patients with repaired tetralogy of Fallot (rTOF) have an increased risk for ventricular tachycardia (VT), with slow conducting anatomical isthmus (SCAI) 3 as the dominant VT substrate. Right bundle branch block (RBBB) is common in these patients. SCAI 3 can lead to additional activation delay affecting the terminal RV activation.(1) We hypothesize that these alterations can be detected by sinus rhythm (SR) 12-lead ECG. Purpose To develop a novel algorithm to non-invasively identify SCAI 3 with the SR 12-lead ECG in rTOF patients with RBBB. Methods Consecutive rTOF patients aged ≥16 years old with RBBB who underwent electroanatomical mapping (EAM) at our institution between 2017-2022, and 2010-2016, comprised the derivation, and validation cohort, respectively. 12-lead ECGs in SR were analyzed for presence of R’’ wave in V1 (any positive deflection after R’ in V1) and for duration of a negative terminal QRS portion (NTP) in aVF (ms between QRS complex traversing the isoelectric line from positive to negative vector until QRS offset) (Figure, A). Results Forty-six rTOF patients (aged 40±15 years, 70% male) comprised the derivation cohort. Patients were repaired at a median age of 3.3 [IQR 1.2-6.6] years via a ventricular incision in 21 (55%). Mean QRS duration was 165±23ms and 12 (26%) had a QRS duration of ≥180ms. SCAI 3 was detected in 31 (67%) patients and 15 (33%) had a normal conducting AI 3. Monomorphic sustained VT was inducible in 16 (35%). Among patients with SCAI 3, 17 (55%), and 16 (52%), had an R’’ in V1, and NTP ≥80ms in aVF, respectively, compared to only 1 (7%), and 1 (7%) patients with normal conducting AIs. Of the 24 patients with an R’’ in V1 and/or NTP ≥80ms in aVF, 22 (92%) had a SCAI 3. In univariable analysis an R’’ in V1 had an odds ratio (OR) of 17.0 (p=0.010), a NTP ≥80ms in aVF had an OR of 14.9 (p=0.014), and QRS duration had an OR of 1.04 (per ms, p=0.030) in identifying SCAI 3. After correction for QRS duration, R’’ in V1 and NTP ≥80ms in aVF both remained independently predictive of SCAI 3 (OR 15.4, p=0.017, and OR 10.0, p=0.042, respectively). Combining R’’ in V1 and NTP ≥80ms in aVF into a diagnostic algorithm (Figure, B) yielded a sensitivity of 71% and specificity of 87% in detecting SCAI 3. In the validation cohort (n=34, age 44±14 years, 19 (56%) with SCAI 3 and 15 (44%) with normal conducting AI 3) the diagnostic algorithm had a sensitivity of 84% and specificity of 80% for a SCAI. Conclusion A diagnostic algorithm including R’’ in V1 and NTP ≥80ms in aVF had excellent sensitivity and specificity in detecting SCAI 3 in rTOF patients with RBBB in SR. These ECGs characteristics likely represent a delayed terminal RV activation directed towards the lateral RVOT caused by slow infundibular conduction. Whether this algorithm can contribute to non-invasive risk stratification for VT in a general rTOF population requires additional studies.Diagnostic algorithm to identify SCAI 3

Sinus rhythm QRS morphology reflects right ventricular activation and anatomical ventricular tachycardia isthmus conduction in repaired tetralogy of Fallot

Patients with repaired tetralogy of Fallot (TOF) are at risk for ventricular tachycardia (VT) related to well-described anatomical isthmuses. The purpose of this study was to explore QRS morphology as an indicator of anatomical isthmus conduction. Patients with repaired TOF and complete right bundle branch block referred for transcatheter pulmonary valve replacement (PVR) or presenting with sustained VT underwent comprehensive 3-dimensional mapping in sinus rhythm. Electrocardiographic characteristics were compared to right ventricular (RV) activation and anatomical isthmus conduction properties. Twenty-two patients (19 pre-pulmonary valve replacement and 3 clinical VT) underwent comprehensive 3-dimensional mapping (median 39 years; interquartile range [IQR] 27-48 years; 12 [55%] male). Septal RV activation (median 40 ms; IQR 34-46 ms) corresponded to the nadir in lead V1 and free wall activation (median 71 ms; IQR 64-81 ms) to the transition point in the upstroke of the R' wave. Patients with isthmus block between the pulmonary annulus and the ventricular septal defect patch and between the ventricular septal defect patch and the tricuspid annulus (when present), were more likely to demonstrate lower amplitude R' waves in lead V1 (5.8 mV vs 9.4 mV; P = .005), QRS fragmentation in lead V1 (15 [94%] vs 2 [13%]; P < .001), and terminal S waves in lead aVF (15 [94%] vs 6 [40%]; P < .001) than those with intact conduction. During catheter ablation, these QRS changes developed during isthmus block. For patients with repaired TOF, the status of septal isthmus conduction was evident from sinus rhythm QRS morphology. Low-amplitude, fragmented R' waves in lead V1 and terminal S waves in the inferior leads were related to septal isthmus conduction abnormalities, providing a mechanistic link between RV activation and common electrocardiographic findings.

The R″ wave in V1 and the negative terminal QRS vector in aVF combine to a novel 12-lead ECG algorithm to identify slow conducting anatomical isthmus 3 in patients with tetralogy of Fallot.

Patients with repaired tetralogy of Fallot (rTOF) have an increased risk of ventricular tachycardia (VT), with slow conducting anatomical isthmus (SCAI) 3 as dominant VT substrate. In patients with right bundle branch block (RBBB), SCAI 3 leads to local activation delay with a shift of terminal RV activation towards the lateral RV outflow tract which may be detected by terminal QRS vector changes on sinus rhythm electrocardiogram (ECG). Consecutive rTOF patients aged ≥16 years with RBBB who underwent electroanatomical mapping at our institution between 2017-2022 and 2010-2016 comprised the derivation and validation cohort, respectively. Forty-six patients were included in the derivation cohort (aged 40±15 years, QRS duration 165±23 ms). Among patients with SCAI 3 (n = 31, 67%), 17 (55%) had an R″ in V1, 18 (58%) had a negative terminal QRS portion (NTP) ≥80 ms in aVF, and 12 (39%) had both ECG characteristics, compared to only 1 (7%), 1 (7%), and 0 patient without SCAI, respectively.Combining R″ in V1 and/or NTP ≥80 ms in aVF into a diagnostic algorithm resulted in a sensitivity of 74% and specificity of 87% in detecting SCAI 3. The inter-observer agreement for the diagnostic algorithm was 0.875. In the validation cohort [n = 33, 18 (55%) with SCAI 3], the diagnostic algorithm had a sensitivity of 83% and specificity of 80% for identifying SCAI 3. A sinus rhythm ECG-based algorithm including R″ in V1 and/or NTP ≥80 ms in aVF can identify rTOF patients with a SCAI 3 and may contribute to non-invasive risk stratification for VT.

Electrophysiological study prior to planned pulmonary valve replacement in patients with repaired tetralogy of Fallot.

Ventricular arrhythmias (VAs) are the most common cause of death in patients with repaired Tetralogy of Fallot (rTOF). However, risk stratifying remains challenging. We examined outcomes following programmed ventricular stimulation (PVS) with or without subsequent ablation in patients with rTOF planned for pulmonary valve replacement (PVR). We included all consecutive patients with rTOF referred to our institution from 2010 to 2018 aged ≥18 years for PVR. Right ventricular (RV) voltage maps were acquired and PVS was performed from two different sites at baseline, and if non-inducible under isoproterenol. Catheter and/or surgical ablation was performed when patients were inducible or when slow conduction was present in anatomical isthmuses (AIs). Postablation PVS was undertaken to guide implantable cardioverter-defibrillator (ICD) implantation. Seventy-seven patients (36.2 ± 14.3 years old, 71% male) were included. Eighteen were inducible. In 28 patients (17 inducible, 11 non-inducible but with slow conduction) ablation was performed. Five had catheter ablation, surgical cryoablation in 9, both techniques in 14. ICDs were implanted in five patients. During a follow-up of 74 ± 40 months, no sudden cardiac death occurred. Three patients experienced sustained VAs, all were inducible during the initial EP study. Two of them had an ICD (low ejection fraction for one and important risk factor for arrhythmia for the second). No VAs were reported in the non-inducible group (p < .001). Preoperative EPS can help identifying patients with rTOF at risk for VAs, providing an opportunity for targeted ablation and may improve decision-making regarding ICD implantation.

Ventricular tachycardia substrates in young patients with repaired tetralogy of fallot

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): We acknowledge the support from the Netherlands Cardiovascular Research lnitiative: An initiative with support of the Dutch Heart Foundation and Hartekind. Background Patients with repaired tetralogy of Fallot (rTOF) have a time-dependent increase in risk of ventricular tachycardia (VT) after the age of 30 years (Y), with slow conducting anatomical isthmus (SCAI) 3, located between the pulmonary annulus and the ventricular septal defect (VSD) patch, as dominant VT substrate (1-4). However, SCAI may be already present before 30Y. Purpose To assess (1) the prevalence of SCAI, (2) the associated factors in SCAI development, and (3) the occurrence of clinical VT, in rTOF patients &amp;lt;30Y. Methods From a database of 146 patients with rTOF or related lesions who underwent electroanatomical mapping (EAM) and programmed electrical stimulation (PES) between 2007 and 2022 for treatment of ventricular arrhythmias (VA), risk stratification or before pulmonary valve replacement (PVR), those aged &amp;lt;30Y at time of procedure were selected and analysed. Results Of 146 rTOF patients, 55 (38%) were &amp;lt;30Y (median 16Y [IQR 14-22]); 33/55 (60%) had TOF, 9/55 (16%) TOF with double outlet right ventricle (DORV), and 13/55 (24%) complex TOF variants, including 8 patients with pulmonary atresia with VSD, 2 patients with absent pulmonary valve, and 3 with other variations. Initial intracardiac surgical repair (median age 0.8Y [IQR 0.4-1.4]) was performed via a ventriculotomy in 10/55 (18%) after palliative shunts in 16/55 (29%). An RV to pulmonary artery (RV-PA) conduit was inserted during initial or early after (&amp;lt;1Y) initial repair in 12/55 (22%). In 14/55 (25%) pulmonary valve replacement (PVR) was performed later in life (median age 10.1Y [IQR 2.7-14.3]). Five of 55 (9%) underwent EAM/PES after a spontaneous VA, 40/55 (73%) before PVR, and 10/55 (18%) for risk stratification. Monomorphic VT was inducible in 8/55 (15%), including 4/5 patients with spontaneous VT, and was proven related to a SCAI 3 in 7/8 (88%). In 16/55 (29%) SCAI 3 could be identified; no other SCAI (1,2,4) was present. Of note, 9/16 (56%) of patients with SCAI 3 had initial RV-PA conduit repair/early PVR, in comparison with only 3/39 (8%) of patients without SCAI. In univariable analysis complex TOF (OR 6.8 [95% CI 1.8-26.4]), ventriculotomy (OR 5.3 [95% CI 1.2-22.3]), any prior PVR (OR 4.8 [95% CI 1.4-16.7]), and initial RV-PA conduit/early PVR (OR 15.4 [95% CI 3.3-71.8]) were significantly associated with SCAI 3. In multivariable analysis initial RV-PA conduit/early PVR remained the only independent predictor of SCAI 3 (OR 13.0 [95% CI 1.2-142.4]). Conclusions A SCAI 3 is present in 29% of rTOF patients &amp;lt;30Y referred for EAM/PES and the dominant VT substrate for spontaneous and inducible VTs. RV-PA conduit placement during initial repair or early PVR (&amp;lt;1Y after repair) is associated with SCAI 3 in young rTOF. Whether the early conduit/valve placement causes scarring at the infundibulum with consecutive slow conduction and/or whether the complex variants contribute to SCAI requires additional studies.

The impact of electroanatomical mapping and VT substrate ablation on primary and secondary prevention ICD indication in patients with repaired Tetralogy of Fallot

Abstract Funding Acknowledgements Type of funding sources: None. Background Patients with repaired tetralogy of Fallot (rTOF) remain at risk for monomorphic ventricular tachycardia (MVT) and sudden cardiac death. Primary prevention ICD implantation studies report annualized rates of appropriate ICD therapy of ≈7% mainly for MVT. Slow conducting anatomical isthmus (SCAI) is the dominant MVT substrate, and SCAI transection by ablation has been associated with favorable long-term outcomes. Electroanatomical mapping (EAM) is the gold standard to identify SCAI. The impact of a systematic approach of EAM and ablation of SCAI on patient selection for ICD implantation is unknown. Objective The study aimed to evaluate the long-term arrhythmic outcome of rTOF patients who underwent EAM and ablation for primary and secondary prevention of MVT. Methods Consecutive patients with rTOF who underwent EAM for VT substrate identification between 2005 and 2020 were included. Indication for EAM were (A) spontaneous VT/cardiac arrest or (B) before re-valving or for risk stratification. In patients with SCAI, catheter or surgical transection was attempted. The risk score for VT/SCD proposed by Khairy et. al was calculated. After successful ablation of SCAI, ICD implantation was offered but subject to shared decision making. Patients were followed for VT and all-cause mortality. Results A total of 125 pts (Group A=28; Group B=97) were included (37±17 years, 62% men, QRS 155±32ms, preserved/mildly reduced LV and RV function 96% and 81%, respectively). A SCAI was present in 59 patients (47%) (A=26, B=33). In 45 patients, 67 MVTs were induced (CL 271±54 ms), of which 63 (94%) were related to SCAI. In 44/61 patients (72%) who underwent ablation, procedural success could be achieved (A 16/27, B 28/34). During a median follow-up of 58 (IQR 27-105) months (36 pts with ICDs), 7 patients died (5 heart failure; 2 non-cardiac cause), and 13 had VT (A=9, B=4). In 12/13 pts with VT, SCAI could not be transected (A=8, B=4), and the remaining patient, who had impaired LV/RV function, recurred with a different VT. In patients without SCAI or successful SCAI transection and preserved/mildly reduced function, no VT occurred (figure). According to the risk score, 22, 27, and 48 of group B patients were classified as high (predicted annualized VT 0%), intermediate (3.8%), and low risk (17.5%). Accordingly, 77/125 (62%) (all 28 pts of group A and 49 patients [intermediate or high risk] of group B) would have been considered candidates for ICD. After implementing the EAM-based approach, 39 patients (18 patients in group A and 21 patients in group B) may remain candidates for ICD implantation, indicating a potential 49% reduction in ICD implantation. Conclusion Patients with successful transection of SCAI had excellent long-term outcome. EAM-based risk stratification and (preventive) ablation targeting SCAI may significantly reduce ICD implantation rates for primary and secondary preventions in rTOF.

PO-04-158 INTRACARDIAC ECHOCARDIOGRAPHY GUIDES ANATOMICAL ISTHMUS ABLATION IN PATIENTS WITH VENTRICULAR TACHYCARDIA AND REPAIRED TETRALOGY OF FALLOT

Successful catheter ablation of monomorphic ventricular tachycardia (VT) in patients with repaired Tetralogy of Fallot (TOF) can be achieved by targeting one or more of four common anatomical isthmuses. However, variability in the size and location of surgical patches means careful mapping is required to design ablation lines to block the critical isthmus. Intracardiac echocardiography (ICE) may assist ablation by accurate identification of individual TOF anatomy. To determine whether the routine use of ICE aids linear ablation of VT isthmuses in patients with repaired TOF. Retrospective study of repaired TOF patients undergoing VT ablation at our centre from January 2017 to November 2022. Cases were divided into those which used ICE to assist anatomical mapping versus those which used voltage mapping to identify patches and valve annuli. Once anatomy was defined, we started with a VT stimulation study where haemodynamically stable VTs were mapped. Non-inducible or unstable VTs underwent substrate mapping in sinus rhythm. All cases underwent ablation and had no inducible monomorphic VT as the endpoint. Data are presented as median and [interquartile range]. Twenty-six patients were identified, of which 15 were guided by ICE. The baseline demographic data is presented in the table and a representative figure shows the use of ICE to identify surgical patches. The use of ICE allowed linear ablation of the critical anatomical isthmus in 12/15 patients (80%) compared to 4/11 (36%) without ICE (p=0.023). The remaining patients without linear ablation underwent substrate-based ablation only to sites of local abnormal ventricular activity. There was no significant difference in overall procedure time (ICE: 165 [60] minutes versus no ICE: 145 [50] minutes; p=0.24), nor in fluoroscopy time (ICE: 25 [17] minutes versus no ICE: 31 [16] minutes; p=0.9). Over time, the introduction of ICE was associated with improved workflow. When comparing the first and last five cases using ICE, both median procedure times (from 196 to 160 minutes) and fluoroscopy times (from 35 to 20 minutes) were shorter. Intracardiac echocardiography improves targeted linear ablation of the critical anatomical isthmus for VT in patients with repaired TOF. ICE provides real-time individualised identification of surgical patches and valve anatomy to guide optimal linear lesion sets across isthmuses, with routine use over time showing a trend towards shorter procedural and fluoroscopy times.Tabled 1Baseline demographicsICE (n=15)No ICE (n=11)Age (years)53 [26]41 [23]Male10 (67%)7 (64%)Number of sternotomies2 [1]3 [2]History of syncope5 (33%)1 (9%)QRS width (milliseconds)176 [59]172 [54]Left ventricular ejection fraction (%)50 [25]54 [9]Right ventricular ejection fraction (%)29 [8]27 [7]Implantable cardiac defibrillator7 (47%)5 (45%)History of sustained VT12 (80%)8 (73%)VT ablation15 (100%)11 (100%)Inducible VT at electrophysiology study11 (73%)6 (55%)Linear anatomical isthmus ablation12 (80%)4 (36%)Procedure time (minutes)165 [60]145 [50]Fluoroscopy time (minutes)25 [17]31 [16] Open table in a new tab

MP-453092-5 ISOCHRONAL LATE ACTIVATION MAPPING FOR TARGETED ABLATION OF VENTRICULAR TACHYCARDIA IN PATIENTS WITH TETRALOGY OF FALLOT

Patients with tetralogy of Fallot (ToF) have an increased risk of reentrant ventricular arrhythmias (VAs) utilizing slowly conducting anatomic isthmuses (SCAIs). Isochronal late activation mapping (ILAM) is an alternative mapping technique that identifies deceleration zones (DZ) during sinus and paced rhythms. These areas have been shown to be candidate sites for reentrant ventricular arrhythmias. Assess feasibility of ablation targeting DZs identified by ILAM during sinus and paced rhythms among patients with ToF and VAs. Patients ≥25 y/o with ToF and planned surgical or transcatheter pulmonary valve replacement (PVR) underwent ventricular stimulation study prior to PVR (PPVR EPS). Voltage maps and sinus/RV paced ILAM were created with high-density mapping catheters. SCAIs were defined as voltage <1.5 mV and <0.5 m/s between anatomic boundaries. Ablation of candidate DZ (>3 isochrones within 1 cm radius) was performed in all patients with inducible VT/VF. As able, activation mapping of VT was performed and successful ablation sites were compared with DZ locations for mechanistic correlation. Eighteen patients (median age 40.7 years [36-48], 56% female) underwent PPVR EPS. Ten (56%) had inducible VA. High-density mapping was performed with a mean of 5049 points [4580-5523] points in sinus rhythm, and 2518 [1615-3752] with RV pacing). A mean of 2 [1-3] DZ were identified per patient. DZ correlated with traditional SCAIs in 68% of patients. Alternate sites including anterior (20%) and lateral (12%) free-wall were also identified. Patients with inducible VA underwent ablation targeting bidirectional block across SCAIs (successful in 97%) and covering of non-SCAI DZ areas. Seven patients (70%) were non-inducible following ablation. Activation mapping could be performed in two patients with successful termination at DZ in both patients (one SCAI and one anterior RV DZ). No sustained ventricular arrhythmias have been detected at 9 [2-16] months follow-up. Isochronal late activation mapping identifies functional substrates for VT during sinus and paced rhythms and guides targeted ablation in ToF with VA. Regions with isochronal crowding correlated with SCAIs while also identifying alternative sites predictive of ablation success.

Ventricular Tachycardia Ablation in Adult Congenital Heart Disease.

Patients with congenital heart disease (CHD) are at risk for late ventricular tachycardia (VT) and sudden cardiac death. Slow conducting anatomical isthmuses, bordered by unexcitable tissue created by valve annuli, ventricular incisions, and prosthetic material are the dominant substrate for macroreentrant monomorphic VTs in repaired CHD. These well-defined substrates allow for catheter or surgical transection with clear endpoints. This review elaborates on VT substrates in various CHD, and evolving mapping and ablation approaches. Because most research is conducted in patients with repaired tetralogy of Fallot, this malformation will serve as a paradigm.

Subthreshold delayed afterdepolarizations provide an important arrhythmogenic substrate in the border zone of infarcted hearts

Sudden cardiac arrest resulting from myocardial infarction (MI) is most often due to ventricular tachycardia (VT). In the infarcted heart, VT has been shown to originate at the periphery of the scar1. Such tissue is often termed the infarct border zone (BZ) and is comprised of a heterogeneous admixture of fibrosis and surviving cardiomyocytes2. Extended regions of BZ tissue that penetrate through non-conducting necrotic core scar can give rise to anatomical isthmuses which provide slow conducting re-entrant pathways that can help sustain VT circuits3.

Arrhythmias in Repaired Tetralogy of Fallot: A Scientific Statement From the American Heart Association.

Arrhythmia and sudden cardiac death remain common in repaired tetralogy of Fallot and affect even those with excellent anatomic repairs. Atrial arrhythmia often has mechanisms different from those in acquired heart disease. Ventricular arrhythmia remains a major source of mortality in repaired tetralogy of Fallot. Noninvasive risk stratification is important to identify patients who may benefit from ablation or primary prevention implantable cardioverter defibrillators. Multiple noninvasive risk factors are associated with ventricular arrhythmia, but no universally accepted risk stratification algorithm exists. The mechanism of ventricular arrhythmia is usually attributable to a consistent and discrete set of slowly conducting anatomic isthmuses related to both the native anatomy and the consequences of the surgical repair, which interact with ventricular remodeling to provide arrhythmic substrate. This substrate can be identified during electroanatomic mapping and prophylactically ablated in appropriate patients. This scientific statement discusses the mechanisms and treatment of arrhythmia in repaired tetralogy of Fallot.

Gaps after linear ablation of persistent atrial fibrillation (Marshall-PLAN): Clinical implication

Beyond pulmonary vein (PV) isolation, anatomic isthmus transection is an adjunctive strategy for persistent atrial fibrillation. Data on the durability of multiple lines of block remain scarce. The purpose of this study was to evaluate the impact of gaps within such a lesion set. We followed 291 consecutive patients who underwent (1) vein of Marshall ethanol infusion, (2) PV isolation, and (3) mitral, cavotricuspid, and dome isthmus transection. Dome transection relied on 2 distinct strategies over time: a single roof line with touch-ups applied in case of gap demonstrated by conventional maneuvers (first leg), and an alternative floor line if the roof line exhibited a gap during high-density mapping with careful electrogram reannotation (second leg). Twelve-month sinus rhythm maintenance was 70% after 1 procedure and 94% after 1 or 2 procedures. Event-free survival after the first procedure was lower in case of residual gaps within the lesion set (log-rank, P = .004). Delayed gaps were found in 94% of a second procedure performed in the 69 patients relapsing despite a complete lesion set with PV gaps increasing the risk of recurrence of atrial fibrillation (67% vs 34%; P = .02) and anatomic isthmus gaps supporting a majority of atrial tachycardias (60%). Between the first leg and the second leg, a significant decrease was found in roof lines considered blocked during the first procedure (99% vs 78%; P < .001) and in delayed dome gaps observed during a second procedure (68% vs 43%; P = .05). Gaps are arrhythmogenic and can be reduced by optimized ablation and assessment of lines of block. Closing these gaps improves sinus rhythm maintenance.

Non-invasive identification of slow conducting anatomical isthmuses in patients with tetralogy of Fallot by 3D late gadolinium enhancement cardiovascular magnetic resonance

Abstract Funding Acknowledgements Type of funding sources: None. Background Patients with repaired tetralogy of Fallot (rTOF) remain at risk of sudden cardiac death due to reentrant sustained monomorphic ventricular tachycardia (SMVT). Slow conducting anatomical isthmuses (SCAI), in particular SCAI3 at the outlet septum, bordered by the pulmonary annulus and the ventricular septal defect patch, are the dominant substrate for SMVT. Electroanatomical mapping (EAM) is the invasive gold standard to identify SCAIs, and transection of SCAI by catheter ablation has been correlated with favorable long-term outcome. Non-invasive identification of SCAI for risk stratification and treatment planning is needed but has not been established yet. Three-dimensional (3D) late gadolinium-enhanced (LGE) cardiovascular magnetic resonance (CMR) facilitates accurate visualization of morphologically complex hearts with high-spatial resolution. Objective The study thought to determine whether 3D LGE-CMR can identify SCAIs. Methods Consecutive patients with rTOF who underwent right ventricular (RV) EAM and 3D LGE-CMR were included. LGE-CMR-derived 3D RV reconstructions were created (ADAS-3D) and merged with 3D RV EAM data. Mapping points were superimposed on the CMR-derived 3D reconstruction allowing for direct comparison of EAM data and local signal intensity (SI). The optimal SI cut-off to identify low bipolar voltage (LBV, BV&amp;lt;1.76mV) was determined by receiver operating characteristic carve. An abnormal AI on LGE-CMR was defined as AI with continuous SI above the obtained cut-off connecting AI borders. Results Forty-eight rTOF patients (34±16 years, 58% male) were included. At EAM, 21 patients had normal AI, and 20 and 7 had a SCAI (&amp;lt;0.5m/s) or blocked AI, which was AI3 in all. Patients with SCAI showed low BV of AI3 (median 0.7 [range 0.25-2.59] mV). In 11 patients, 14 SMVTs could be induced, all related to SCAI3. A total of 9240 points were analyzed, showing a significant correlation between BV and SI (R=0.4, P&amp;lt;0.001). The optimal SI cut-off to identify LBV was 42% of the maximal SI (MSI) (AUC 0.80; sensitivity, 74%; specificity, 78%). Using this cut-off of MSI, a SCAI or blocked AI3 could be correctly identified by LGE-CMR in all 27 patients, and a normal AI3 could be correctly confirmed by LGE-CMR in 14/21 patients with normal EAM findings (Figure). The sensitivity and specificity of 3D LGE-CMR for identifying SCAI or blocked AI3 were 100% and 67%, respectively. Of note, among patients with normal EAM findings, those with abnormal AI3 on LGE-CMR had significantly lower BV of AI3 than those with normal AI3 on LGE-CMR (2.06 [Range, 1.62-2.60] vs. 3.53 [2.22-5.67] mV, P&amp;lt;0.01). Conclusion 3D LGE-CMR can identify SCAI with 100% sensitivity and may identify diseased AI3 even before critical conduction delay occurs. This technique may allow for non-invasive risk stratification of VT and can refine patient selection for invasive EAM.