Left Ventricular Summit Research Articles

Practical Approaches to Catheter Ablation of Idiopathic Ventricular Arrhythmias

In this review, we provide a practical approach to the catheter ablation of idiopathic focal ventricular arrhythmias (VAs) by summarizing the electrocardiographic (ECG) characteristics, mapping strategies, and ablation techniques for each of the major types of idiopathic VAs. We identify special considerations to be taken when treating specific forms of idiopathic VAs with catheter ablation that can increase success rates and reduce complications. Insights on ECG morphologies of VAs have led to novel criteria that can aid in accurate identification and localization of VA sites of origin. Advancements in mapping catheters and software as well as the use of intracardiac echocardiography have allowed for more precise mapping and ablation of arrhythmias arising from complex cardiac structures. Idiopathic VAs occurring in patients without overt structural heart disease can be categorized into four groups on the basis of anatomic location: (1) outflow tract VAs (which include the right ventricular outflow tract, left ventricular outflow tract, and left ventricular summit; (2) fascicular VAs; (3) papillary muscle VAs; and (4) annular VAs. Knowledge of the ECG characteristics of idiopathic VAs and the three-dimensional anatomy surrounding their sites of origin can guide pre-procedure planning, prioritization of cardiac regions for mapping, and approach for ablation.

Catheter ablation of ventricular arrhythmias in left ventricular noncompaction cardiomyopathy

There are limited data on ventricular arrhythmias (VAs) associated with left ventricular noncompaction (LVNC) cardiomyopathy. This study aims to analyze the clinical and electrocardiographic characteristics of VAs in a group of patients with LVNC. Forty-two nonrelated patients with LVNC and VAs were included that were evaluated at the Inherited Cardiac Disease Unit of the University Hospital Virgen Arrixaca (Murcia-Spain) (ERN Guard-Heart Centre, European Reference Network for Rare and Low Prevalence Complex Diseases of the Heart). Thirteen patients (30.9%) had isolated LVNC, 27 (64.3%) had LVNC associated with dilated cardiomyopathy, and 2 (4.8%) had LVNC associated with hypertrophic cardiomyopathy. Among isolated LVNC individuals, 9 (69.2%) had premature ventricular complexes (PVCs)/nonsustained ventricular tachycardias (VTs), and 4 (30.8%) VTs (1 VT degenerating in ventricular fibrillation). In the dilated cardiomyopathy group, 11 (40.7%) patients had PVCs, 14 (51.9%) VTs, and 2 (7.4%) ventricular fibrillation. In the hypertrophic cardiomyopathy group, one patient had PVCs and the other VTs. Endocardial mapping and ablation were performed in 19 patients (45.2%): 7 ventricular outflow tracts (4 right ventricular outflow tract, 1 left coronary cusp, and 2 right coronary cusp), 2 in the left ventricular summit, 5 related to Purkinje potentials at the mid inferoseptal area, and 5 associated with endocardial scar localized in the basal anterolateral and inferolateral segments. Epicardial ablation was performed in 3 cases. The substrate of VAs in LVNC cardiomyopathy is heterogeneous, with origin in ventricular outflow tracts, Purkinje system related, and resembling scar patterns in nonischemic cardiomyopathy.

Mapping the Left Ventricular Summit for Ablation Success.

Mapping the Left Ventricular Summit for Ablation Success.

Utility of a novel 3F coronary sinus catheter during simultaneous ablation of the left anterolateral accessory pathway and left ventricular summit premature ventricular contractions.

Utility of a novel 3F coronary sinus catheter during simultaneous ablation of the left anterolateral accessory pathway and left ventricular summit premature ventricular contractions.

Left coronary cusp ablation to eliminate epicardial substrates – a novel strategy for left ventricular summit ventricular tachycardia ablation

Abstract Background Catheter ablation of LV summit VT can be challenging due to possible subepicardial or intramural site of origin and its close proximity to the major coronary vessels. Objective Local electrograms monitoring inside LV summit communicating vein potentially defines arrhythmogenic substrates and facilitates ablation from the adjacent anatomical structures. Results We experienced two cases of LV summit VT with epicardial local abnormal ventricular activities (Epi-LAVA) recorded from distal bipolar electrode of the 2F microcatheter in communicating vein close to the superior portion of LV summit. During sinus rhythm, Epi-LAVA displayed isolated late fractionated potentials in the first case but had initial fractionated potentials fused with terminal portion of far-field ventricular signals and late isolated potentials exhibiting 2:1 conduction in the second case. Epi-LAVA represented earliest ventricular signals during VT in both cases. Pace mapping at Epi-LAVA sites yielded single QRS morphology with excellent pacemap score and induced VT. Our strategy was to perform ablation at the facing site of Epi-LAVA aiming to eliminate the potentials transmurally. Radiofrequency (RF) energy was applied above and under the left coronary cusp opposite to Epi-LAVA sites using 3.5-mm tip open-irrigation catheter with a power of 30–35 W for 60 seconds under real-time intracardiac echocardiograhic guidance. VT was slowed and terminated in 1 second. Repeat ablation delayed and completely abolished Epi-LAVA followed by noninducibility of VT. Anatomical proximity of the left coronary cusp semilunar insertion and subepicardial or intramural site of origin possibly dictates successful ablation. Epi-LAVA from coronary vein mapping serve as a new landmark of the ablation target with a measurable procedural endpoint. Conclusion Elimination of epicardial substrates with RF energy application at the left coronary cusp can be a novel strategy for LV summit VT ablation. Funding Acknowledgement Type of funding source: None

Left ventricular summit arrhythmias with an abrupt V3 transition: Anatomy of the aortic interleaflet triangle vantage point

While early precordial electrocardiographic (ECG) characteristics are useful to differentiate left-sided from the right-sided outflow tract ventricular arrhythmia (OTVA), few patterns predict an origin from the septal margin of the left ventricular (LV) summit. The purpose of this study was to report mapping and ablation characteristics of a new ECG pattern with left bundle branch morphology and an abrupt R-wave transition in lead V3 (ATV3). Over a 3-year period, 78 consecutive patients (mean age 57±15 years; 35% female) with OTVA were referred for mapping and ablation. Twenty patients (26%) exhibited an ATV3 pattern, of whom 65% failed prior ablation. Ninety-two percent of patients with ATV3 that underwent simultaneous epicardial and endocardial mapping demonstrated an intramural or epicardial site of origin. Eighty percent of OTVA with ATV3 was eliminated by ablation from the vantage point of the interleaflet triangle below the right-left coronary junction. The ATV3 pattern showed higher sensitivity, specificity, predictive value, and accuracy than validated ECG criteria (notch or "w" pattern in lead V1, qrS pattern in leads V1 through V3, and pattern break V2) for predicting successful ablation in the region of the anterior LV ostium. At 12±11 months, freedom from ventricular arrhythmia recurrence was 89% and 82% in the ATV3 and control groups, respectively. ATV3 is a simple and distinct ECG pattern indicative of a site of origin from the septal margin of the LV summit. The right-left aortic interleaflet triangle vantage point was effective to eliminate OTVA with ATV3 that overwhelmingly exhibited the earliest activation from the epicardium or mid-myocardium. Test characteristics for ATV3 were superior to ECG patterns validated for the anterior LV ostium.

Electrocardiographic localization of ventricular arrhythmias successfully ablated from the distal great cardiac vein.

Idiopathic ventricular arrhythmias (IVAs) from the left ventricular (LV) summit may be successfully ablated from the distal great cardiac vein (dGCV). Using a 12-lead electrocardiogram (ECG) to localize IVAs that can be ablated from the dGCV is valuable for ablation planning. To determine if a "w" wave, a notch in the Q wave in lead I, and other ECG features can identify IVAs that can be successfully ablated from the dGCV. We reviewed outflow tract premature ventricular contraction (PVC) ablations performed at two centers between September 2010 and June 2018. Successful PVC ablations, in which the PVCs were mapped from the right ventricular outflow tract, coronary cusps, commissures, endocardial LV, and the coronary venous system including the dGCV were included. ECG characteristics were compared between patients with successful ablations in the dGCV and non-dGCV sites. Of the 120 patients (age 56.8 ± 13.8 years, 45% female) that met the inclusion criteria, the dGCV was the successful ablation site in 18 patients (15%). Multivariate analysis with binary logistic regression showed that a "w" in lead I in combination with an early precordial pattern break and a maximum deflection index (MDI) ≥ 0.5 had sensitivity and specificity for a successful ablation in the dGCV of 94.4% and 96.1%, respectively. Combining a "w" wave in lead I with an early precordial pattern break and an MDI ≥ 0.5 is highly sensitive and specific for identifying the dGCV as a successful ablation site for PVCs.

Applicability of computed tomography preoperative assessment of the LAA in LV summit ablations

PurposeVentricular arrhythmias originating from the left ventricular summit (LVS) may present with challenges for catheter ablation. Recently, the left atrial appendage (LAA) became a new vantage point for mapping and ablating arrhythmias from that region, but data of possible usefulness is limited.MethodsFrom September to December 2019, we retrospectively analyzed 48 consecutive patient hearts (20 male; mean age 57.9y ± 11.56) undergoing diagnostic coronary vessel imaging in 64 dual-source computer tomography angiography (CTA). Distances from the LAA to the LVS, LAA shape type, and coronary arteries in the LVS region were measured. Also, we compared the true LVS area from CTA with a calculated formula derived from LVS definition.ResultsThe mean LVS area calculated from the formula was 291.58 mm2 (± 115.5) while the true area calculated from CT was 263.33 mm2 (± 99.49) (p = 0.44). The mean inaccessible area was 133.42 mm2 (± 72.89), accessible 95.67 mm2 (± 72.77). The mean LAA coverage over LVS was 196.08 mm2—which is approximately 75% of LVS size in general. The most common LAA shape was chicken wing (50%); windsock has the highest accessible area coverage on average (80.23%), followed by chicken wing (59.88%), broccoli (47.72%), and cactus (46.98%). The mean distance from LAA to the surface was 5.14 mm (1.5 to 10 mm) and was not correlated with BMI. LAA has a 98% coverage over the point of transition between the great cardiac vein and anterior interventricular vein.ConclusionAngio-CT assessment of the LAA over the LVS structures may be helpful in decision making before an ablation procedure. LAA appears to be a promising mapping approach in LVS arrhythmias.

Epicardial Ablation of Idiopathic Ventricular Tachycardia.

Ventricular arrhythmias (VAs) occurring in the absence of structural heart disease or ion channelopathies are referred to as idiopathic. They can clinically present with frequent monomorphic premature ventricular contractions, nonsustained ventricular tachycardia (VT), or sustained VT, and generally share a benign prognosis. Approximately 4% to 10% of idiopathic VAs have an epicardial site of origin, represented in most cases by the left ventricular summit and, less frequently, by the cardiac crux. Epicardial foci can be addressed by catheter ablation via the coronary venous system tributaries. In rarer instances, a direct epicardial access from a subxiphoid approach is needed.

Telescopic coronary sinus cannulation for mapping and ethanol ablation of arrhythmia originating from left ventricular summit.

The radiofrequency ablation (RFA) of left ventricular (LV) summit arrhythmia is a challenging procedure due to complexity of the anatomy. Retrograde coronary venous ethanol injection may be successful in selected patients, but there is no uniformly accepted technique for gaining coronary sinus access and the duration of the procedure is relatively long. Patients with LV summit ventricular tachycardia after a failed endocardial RFA scheduled for retrograde ethanol ablation were included. The technique of telescopic coronary sinus catheterization which consisted of an 8F SL0 catheter, a 5F JR/IM catheter and a microcatheter was designed and applied in all patients. The efficacy of the system was validated and the duration of crucial points were measured (coronary sinus intubation and venography, mapping with angioplasty wire and alcohol injection). The transcoronary sinus procedure was performed in 4 (age 17-65 years) without complications (total procedural duration: 100-246 min). The coronary sinus was intubated with an SL0 catheter in 2-5 min, the first contrast injection to venous branches was delivered after 17-29 min, and the time form venous angiography to first alcohol injection was 28-31 min. The total transcoronary procedural duration ranged 66-86 min. The telescopic system was easy to control, allowed rapid electrodes and catheter replacement and no obstacles or complications were noted during mapping and therapy. The telescopic system for retrograde coronary venous ethanol injection consisted of an 8F SL0 catheter, a 5F JR/IM catheter and microcatheter is useful and allows the delivery of therapy, thus, decreasing the duration of the procedure.

673Bipolar radiofrequency ablation supported by non-ionic catheter irrigation

Abstract Introduction Bipolar radiofrequency catheter ablation (Bi-RFCA) or irrigation of ablation catheter (AC) using non-ionic coolant, such as dextrose-5 in water (D5W), are novel ways to improve lesion formation in case of arrhythmia refractoriness. Combination of these two methods has not yet been described. Puprose To determine feasibility and effectiveness of Bi-RFCA additionally supported by non-ionic catheter irrigation for treatment of refractory premature ventricular complexes (PVC) or ventricular tachycardia (VT). Methods Consecutive patients after failed extensive Bi-RFCA or D5W-irrigated ablation for symptomatic PVCs or non-sustained VT (nsVT) underwent Bi-RFCA supported with D5W coolant. Results We ultimately enrolled 2 patients (2 males, age 64 ± 12 years) after failed extensive ablations for the left ventricular summit PVCs and nsVT to undergo Bi-RFCA supported with D5W irrigation of both AC and intracardiac return electrode (IRE). Previous pharmacological antiarrhythmic treatment consisting of at least one drug and catheter ablation failed in both patients. Bi-RFCA was delivered between earliest activation sites located in the left/right aortic commissure and the left pulmonic cusp (Figure). Efforts were made to achieve safe distance from coronary arteries, AC, and IRE. Bipolar RFCA (35 ± 7W power, 8 ± 4 applications, 199 ± 166s RF time) led to acute elimination of PVCs in both patients. Baseline impedance oscillated around 250Ω and initial 50-70Ω impedance drop was observed during first 20s of bipolar applications, followed by impedance rise up to 350-450Ω. No steam pop occurred and there were no complications during procedures. All antiarrhythmic drugs were discontinued. Follow-up lasted 8 ± 2 months, there was no nsVT recurrence and 90,4% PVC burden reduction was achieved: from 30000 to 3100 PVC/day in patient #1 and from 39000 to 3500 PVC/day in patient #2. Both patients remained symptom-free. Conclusion Bi-RFCA can be additionally supported using non-ionic D5W coolant. Such approach is feasible and can be safe and effective. More data on impedance imbalance during D5W-supported bipolar RF applications is warranted. Abstract Figure. Fluoroscopic view and 12-lead ECG

A novel ablation strategy of premature ventricular contractions originating from summit guided by CartoUNIVU module.

BackgroundPremature ventricular contractions (PVCs) from left ventricular (LV) summit remain challenging for the risk of coronary artery injury. Computed tomographic or intracardiac echocardiography may be helpful, but both still have many limitations. CartoUNIVU module has rarely been used in PVC ablation.MethodsA total of 22 patients (14 men: mean age 56.4 ± 13.3 years) with an electrocardiogram indication of summit PVCs were included in the two centers study. A novel strategy ablation with the Image Integration Module CartoUNIVUTM module was performed for all the patients with PVCs originating from LV summit area, especially to prevent the coronary artery injury.ResultsThe procedure time was 78.6 ± 22.7 minutes, and the fluoroscopy time was 12.5 ± 3.1 minutes. The distance between the target and nearest coronary artery was 8.0 ± 3.1 mm. Three patients with the distance to the nearest coronary artery <5 mm. During a mean follow‐up of 11.0 ± 1.7 months, 21/22 (95.5%) patients were free from clinical PVC. No coronary artery injury was detected in the all the ablation procedures.ConclusionThe novel strategy ablation with the Image Integration Module CartoUNIVU module is safe and effective for PVCs originating from LV summit area, especially to prevent the coronary artery injury.

Acute and long-term results of bipolar radiofrequency catheter ablation of refractory ventricular arrhythmias of deep intramural origin

Successful bipolar radiofrequency catheter ablation (RFCA) of refractory ventricular arrhythmias (VAs) has been reported. However, the efficacy, safety, and long-term outcomes of bipolar RFCA of VAs are not fully determined. The purpose of this study was to evaluate the effectiveness and safety of bipolar RFCA in treating refractory VAs during long-term follow-up. Eighteen patients who underwent bipolar RFCA for ventricular tachycardia (VT) at 7 institutions were retrospectively investigated. Underlying heart diseases included remote myocardial infarction (n = 3 [17%]) and nonischemic cardiomyopathy (n = 15 [83%]). Although unipolar RFCA was performed in all patients, either it failed to suppress VT or VT recurred. The interventricular septum, left ventricular free wall, and left ventricular summit were targeted for bipolar RFCA. Acute success (VT termination and/or noninducibility) was achieved with bipolar RFCA in 16 patients (89%). Complications during the procedure included complete atrioventricular block (n = 2) and coronary artery stenosis (n = 1). One patient underwent chemical ablation after bipolar RFCA failure. At 12-month follow-up, VT reoccurred in 8 patients (44%). However, in patients with recurrence, VT burden had decreased: only 4 patients underwent re-RFCA, and only 1 of the 4 required chemical ablation. In the remaining 4 patients, re-RFCA was not required, as VT was controlled by medication or an implantable cardioverter-defibrillator. Bipolar RFCA is useful for acute suppression of refractory VT. Although VT recurrence rates during long-term follow-up were relatively high, we observed a significant reduction in VT burden.

Anatomic approach with bipolar ablation between the left pulmonic cusp and left ventricular outflow tract for left ventricular summit arrhythmias

Radiofrequency catheter ablation (RFCA) of ventricular arrhythmias (VAs) arising from the inaccessible basal region of the left ventricular summit (LVS) is challenging due to proximity to coronary vessels, epicardial fat, and poor radiofrequency (RF) delivery within the distal coronary venous system. The purpose of this study was to describe the outcomes of an anatomic approach to inaccessible LVS-VAs using bipolar radiofrequency (Bi-RFCA) delivered from the anatomically adjacent left pulmonic cusp (LPC) to the opposite left ventricular outflow tract (LVOT). Patients from 3 centers who had undergone Bi-RFCA for inaccessible LVS-VAs refractory to conventional RFCA using an anatomic approach targeting the adjacent LPC (reversed U approach) with catheter tip pointing inferiorly within the LPC and LVOT were reviewed. Seven patients (age 59 ± 12 years; 3 women) underwent Bi-RF from the LPC to the LVOT for LVS-VAs after ≥1 failed conventional RFCA. Bi-RFCA (power 36 ± 7 W; duration 333 ± 107 seconds) resulted in VA suppression in 5 of 7 patients. In 2 cases, Bi-RFCA was successfully performed using dextrose 5% in water. No complications occurred. After mean follow-up of 14 ± 6 months, no recurrent VT was documented in 2 of 2 patients with baseline VT. Mean 84% reduction in premature ventricular contraction (PVC) burden (31% ± 13% vs 4% ± 5% PVCs per day; P = .0027) was documented in the other patients. In patients with LVS-VAs arising from the inaccessible region and refractory to conventional RFCA, an anatomic approach using Bi-RFCA from the LPC and opposite LVOT is an effective alternative approach.

Modern mapping and ablation techniques to treat ventricular arrhythmias from the left ventricular summit and interventricular septum

Managing arrhythmias from the left ventricular summit and interventricular septum is a major challenge for the clinical electrophysiologist requiring intimate knowledge of cardiac anatomy, advanced training and expertise. Novel mapping and ablation strategies are needed to treat arrhythmias originating from these regions given the current suboptimal long-term success rates with standard techniques. Herein, we describe innovative approaches to improve acute and long-term clinical outcomes such as mapping and ablation using the septal coronary venous system and the septal coronary arteries, alcohol ablation, coil embolization, and ablation of all early sites among others.

Outcomes of catheter ablation of ventricular arrhythmia originating from the left ventricular summit: A multicenter study

Catheter ablation has been considered an effective strategy for the treatment of ventricular arrhythmias (VAs) originating from the left ventricular summit (LVS). However, the inherent complexity of the anatomy of the LVS may result in failed ablation or recurrence of VA. The purpose of this multicenter study was investigate the procedural outcomes of ablation of LVS VA. A total of 238 patients (54.6% men; mean age 53.2 ±15.0 years) undergoing catheter ablation of LVS VA were included. Baseline characteristics, procedural parameters, and clinical outcomes were analyzed. Acute procedural success was achieved in 199 patients (83.6%). Initial epicardial ablation via the coronary venous system (93.8% [91/97]) or percutaneous transpericardial approach (6.2% [6/97]) achieved successful ablation in 40 of 97 patients (41.2%), and VA was eliminated by initial approaches from the aortic sinus of Valsalva or subvalvular endocardium in 68 of 139 patients (48.9%; P = .29). Multisite ablations were performed in the process of acute VA elimination in 105 patients (51.8%), and 7 complications occurred. During median follow-up of 26 (1-87) months, 82.2% of patients with acute success were free from VA recurrences, and the overall long-term success rate was 68.1%. Multisite ablation was the only independent predictor of VA recurrences. Acute elimination of VA originating from the LVS could be achieved in 83.6% of patients, with 82.2% having no VA recurrences. Despite acute elimination of VA with multisite ablation, the incidence of VA recurrence still was high.

Using High-density Grid Technology to Map Intramural Left Ventricular Summit Premature Ventricular Complexes with Associated Cardiomyopathy.

Using High-density Grid Technology to Map Intramural Left Ventricular Summit Premature Ventricular Complexes with Associated Cardiomyopathy.

Mapping and Ablation of Arrhythmias from Uncommon Sites (Aortic Cusp, Pulmonary Artery, and Left Ventricular Summit).

Despite advances in our understanding of the relevant anatomy and mapping and catheter ablation techniques of idiopathic outflow tract ventricular arrhythmias, challenging sites for catheter ablation remain the aortic cusps, pulmonary artery, and notably the left ventricular summit. A systematic approach should be used to direct mapping efforts efficiently between endocardial, coronary venous, and epicardial sites. Foci at the left ventricular summit, particularly intraseptal and at the inaccessible epicardial region, remain difficult to reach and when percutaneous techniques fail, surgical ablation remains an option but with risk of late coronary artery stenosis.

Bipolar radiofrequency ablation delivered from coronary veins and adjacent endocardium for treatment of refractory left ventricular summit arrhythmias.

Radiofrequency catheter ablation (RFCA) of premature ventricular complexes (PVC) and ventricular tachycardia (VT) can be an effective method of treatment. However, when arrhythmia originates from the left ventricular summit (LVS), an ablation performed with conventional unipolar energy sources can be challenging and may require alternative approaches. Bipolar RFCA from coronary veins and an adjacent endocardium in cases of refractory PVC/VT has not yet been studied. We retrospectively analysed cases of consecutive patients who underwent bipolar ablation in whom conventional unipolar ablation of LVS PVC/VT and antiarrhythmic drugs failed to abolish arrhythmia. Bipolar RFCA was delivered from the earliest PVC/VT activation located in the coronary venous circulation and opposite LV endocardial sites. A total number of 4 patients (1 female, age 55 ± 10years) underwent bipolar ablation of LVS from coronary veins and an adjacent endocardium. Bipolar RFCA led to acute elimination of PVC/VT in all patients. A mean bipolar RFCA time was 244 ± 15s. There were no complications during procedures and all antiarrhythmic drugs were discontinued. A follow-up lasted 15 ± 4months; there was no VT recurrence and the mean 83 ± 27% PVC burden reduction (24250 ± 1372 vs. 3000 ± 3600 PVC/d; p = 0.0228) was achieved. All patients remained symptom-free. Bipolar RFCA from coronary veins and an opposite endocardium can be used for safe and successful treatment of PVC/VT originating from a deep LV summit.

Eccentric Activation Patterns in the Left Ventricular Outflow Tract during Idiopathic Ventricular Arrhythmias Originating From the Left Ventricular Summit: A Pitfall for Predicting the Sites of Ventricular Arrhythmia Origins.

Idiopathic ventricular arrhythmias (VAs) originating from the left ventricular summit (LVS) can be ablated from the great cardiac vein and remote endocardial sites. The ablation sites are determined by mapping in the great cardiac vein and left ventricular outflow tract. This study investigated whether that mapping could accurately predict the sites of LVS-VA origins. We studied 26 consecutive patients with idiopathic LVS-VA origins that were identified in the basal and apical LVS in 15 and 11 patients, respectively. Radiofrequency catheter ablation of the apical LVS-VAs was successful in the great cardiac vein in 9 patients and in the apical LV outflow tract in 2. That of the basal LVS-VAs was successful in the aortomitral continuity in 9 patients, at the junction of the left and right coronary cusps in 4, and in the left coronary cusp in 2. Three apical LVS-VAs exhibited an eccentric endocardial activation pattern that was from the basal to apical LV outflow tract. In 11 basal LVS-VAs, the activation pattern was eccentric because the ventricular activation within the great cardiac vein in the apical LVS was earlier than that in the basal LV outflow tract. In 2 basal LVS-VAs, the activation pattern was eccentric because a relatively early ventricular activation was recorded at multiple sites away from the successful ablation site. Eccentric activation patterns often occurred during idiopathic LVS-VAs, which could mislead the catheter ablation of those VAs. Understanding such eccentric activation patterns was suggested to be able to improve the outcomes of the catheter ablation of those VAs by the anatomic approach.