Activation pattern of the coronary sinus facilitates the differentiation for ventricular outflow tract arrhythmias.

INTRODUCTION: The accuracy of surface ECG algorithms for predicting the origin of outflow tract ventricular arrhythmias (OT-VAs) might be questioned. Intracardiac electrograms recorded at anatomic landmarks could provide new predictive insights. We aim to evaluate the efficacy of a novel criterion utilizing the activation pattern of the coronary sinus (CS) in localizing OT-VAs, including VAs originating from the right ventricular outflow tract (RVOT), endocardial left ventricular outflow tract (Endo-LVOT), and epicardial left ventricular outflow tract (Epi-LVOT). METHODS: We measured the ventricular activation time of the mitral annulus (MA) from the onset of the earliest QRS complex of VAs to the initial deflection over the isoelectric line at local signals, namely the QRS-MA interval. The activation at 3 and 12 o'clock of the MA was recorded as the QRS-MA3 and QRS-MA12 intervals, respectively. Their predictive values were compared to previous ECG algorithms. RESULTS: A total of 68 patients with OT-VAs were enrolled (51 for development and 17 for validation). From early to late, the ventricular activation sequences at MA12 were as follows: Epi-LVOT, Endo-LVOT, and RVOT. In LBBB morphology OT-VAs, the QRS-MA12 interval was significantly earlier for LVOT origins than RVOT origins. In the combined cohort of development and validation cohort, a cut-off value of ≤10 ms predicted the LVOT origin with a sensitivity of 100% and specificity of 78%. The QRS-MA12 interval ≤ -24 ms additionally predicted epicardial LVOT sites of origin. CONCLUSIONS: The QRS-MA interval could accurately differentiate the OT-VAs localization.

Prevalence and electrocardiographic and electrophysiological characteristics of idiopathic ventricular arrhythmias originating from the septal left ventricular summit.

INTRODUCTION: The left ventricular summit (LVS) is the highest point on the epicardial surface of the left ventricle. A part of the LVS that is located between the left coronary arteries (lateral-LVS) is one of the major sites of idiopathic ventricular arrhythmia (VA) origins. Some idiopathic epicardial VAs can be ablated at endocardial sites adjacent to the epicardial area septal to the lateral-LVS (septal-LVS). This study examined the prevalence and electrocardiographic and electrophysiological characteristics of septal-LVS VAs. METHODS: We studied consecutive patients with idiopathic VAs originating from the LVS (67 patients) and aortic root (93 patients). RESULTS: Based on the ablation results, among 67 LVS VAs, 54 were classified as lateral and 13 as septal-LVS VAs. As compared with the lateral-LVS VAs, the septal-LVS VAs were characterized by a greater prevalence of left bundle branch block with left inferior-axis QRS pattern, later precordial transition, lower R-wave amplitude ratio in leads III to II, lower Q-wave amplitude ratio in leads aVL to aVR, and later local ventricular activation time relative to the QRS onset during VAs (V-QRS) in the great cardiac vein. The electrocardiographic and electrophysiological characteristics of the septal-LVS VAs were similar to those of the aortic root VAs. However, the V-QRS at the successful ablation site was significantly later during the septal-LVS VAs than aortic root VAs (p < .0001). The precordial transition was significantly later during the septal-LVS VAs than aortic root VAs (p < .05). CONCLUSIONS: Septal-LVS VAs are considered a distinct subgroup of idiopathic VAs originating from the left ventricular outflow tract.

Ventricular arrhythmias originating from different portions of the communicating vein of the left ventricular summit: electrocardiographic characteristics and catheter ablation.

BACKGROUND: Idiopathic ventricular arrhythmias (IVAs) arising from different portions of the communicating vein of the left ventricular summit (summit-CV) are not a rare phenomenon. Whereas its electrocardiographic (ECG) and electrophysiological characteristics are not fully investigated. OBJECTIVE: This study aimed to identify distinct ECG and electrophysiological features of IVAs originating from different portions of summit-CV. METHODS: Nineteen patients confirmed arising from summit-CV were included in this study. RESULTS: The 19 patients were divided into proximal and distal portion groups based on their target sites in summit-CV. In the proximal portion group, 100% (11/11) VAs showed dominant negative (rs or QS) waves in lead I, while in the distal portion group, 87.5% (7/8) showed dominant positive waves (R, Rs or r) (p < 0.000). In lead V1, 100% (11/11) of the proximal portion group showed dominant positive waves (R or Rs), while 62.50% (5/8) of the distal portion group showed positive and negative bidirectional or negative waves (RS or rS) (p < 0.005). RI>4mV, SI<3.5mV, RV1<13mV, SV1>3.5mV, RI/SI>0.83, and RV1/SV1< 2.6 indicated a distal portion of summit-CV with the predictive value of 0.909, 1.000, 0.653, 0.972, 0.903, 0.966, respectively. A more positive wave in lead I and a more negative wave in lead V1 indicated more distal origin in summit-CV. Target sites in proximal and distal summit-CV groups showed similar electrophysiological characteristics during mapping. CONCLUSIONS: There were significant differences in ECG characteristics of VAs at different portions of summit-CV, which could aid pre-procedure planning and facilitate radiofrequency catheter ablation (RFCA) procedures.

Insight from the microelectrodes in case of two different types of premature ventricular contractions originating from left ventricular summit.

Premature ventricular contraction (PVC) is usually eliminated in the earliest activation site based on the conventional electrode of ablation catheter. However, the large size electrode may contain far-field potential. The QDOT MICRO ablation catheter has three micro electrodes with 0.33 mm electrode length, in addition to the conventional electrode with 3.5 mm electrode length. The micro electrodes can reflect only near-field potential. A 78-year-old with symptomatic frequent PVCs underwent catheter ablation. PVC-1 showed good pace-mapping in distal great cardiac vein (GCV). The local bipolar electrograms in the conventional electrode of ablation catheter preceded the PVC-QRS onset by 32 ms in distal GCV and 13 ms in left coronary cusp (LCC), but those in the micro electrodes preceded only by 13 ms both in distal GCV and LCC. PVC-1 was eliminated by radiofrequency (RF) application, not in distal GCV, but in LCC. PVC-2 showed good pace-mapping in LCC. The local bipolar electrograms in both the conventional electrode and the micro electrodes of ablation catheter preceded the PVC-QRS onset by 32 ms in LCC. PVC-2 was eliminated by RF application in LCC. Comparing the local electrograms of micro electrodes and the conventional electrodes may be important for identifying depth of the origin of PVCs.

Venous anatomy of the left ventricular summit region: Insights from high-speed rotational retrograde angiography.

INTRODUCTION: Mapping and ablation through the coronary venous system (CVS) have shown potential for ventricular arrhythmias originating from the left ventricular summit (LVS). Multielectrode catheters and balloons are frequently used for mapping and venous ethanol ablation (VEA). However, there is limited data on the venous size and drainage condition in the LVS region. This study aimed to investigate the morphology, angiographic size, and drainage condition of LV summit veins via high-speed rotational angiography (RA). METHODS: We measured and analyzed the size of the great cardiac vein (GCV), the anterior interventricular vein (AIV), veins near to the LVS, and other main tributaries of CVS in 102 patients undergoing electrophysiology study. RESULTS: Rotational retrograde angiography of LVS was successfully performed in 81 patients. The diameter of GCV at the level of the Vieussens valve and the distal end of GCV (junction of GCV-AIV) was larger in males than females (6.8 ± 1.1 vs. 5.6 ± 1.2 mm, p < .001; 5.2 ± 0.9 vs. 4.6 ± 0.8, p = .002, respectively) while no significant gender differences were observed in other tributaries. The LV summit veins presented downward drainage direction in half of the patients, indicating potential anatomic adjacency with His bundle. Left anterior oblique (LAO) 45° projection might provide the practical and optimal view of the LV summit veins. CONCLUSIONS: The coronary veins of the LVS region present various anatomical morphologies and ostium sizes. We provide a systematic description and angiographic size spectrum of CVS. RA could facilitate assessing the feature of CVS comprehensively.

Insight of electrocardiographic and electrophysiological parameters on the left ventricular function in patients with ventricular arrhythmia from left ventricular summit.

INTRODUCTION: Ventricular arrhythmia (VA) commonly originate from the left ventricular summit (LVS) and results in left ventricular (LV) dysfunction in some patients; however, factors related to LV cardiomyopathy have not been well elucidated. Therefore, this study aimed to investigate the risk factors for LV cardiomyopathy and the outcomes of patients with LVS VA. METHODS: Between 2013 and 2018, a total of 139 patients (60.7% men; mean age 53.2 ± 13.9 years old) underwent catheter ablation for LVS VA in two centers. Detailed patient demographics, electrocardiograms, electrophysiological characteristics, and clinical outcomes were analyzed. LV cardiomyopathy was defined as left ventricular ejection fraction (LVEF) <50%. RESULTS: Acute procedural success was achieved in 92.8% of patients. There were 40 patients (28.8%) with LV cardiomyopathy, and the mean LVEF improved from 37.5 ± 9.3% to 48.5 ± 10.2% after ablation (p < .001). After multivariate analysis, the independent factors of LV dysfunction were wider QRS duration (QRSd) of the VA (odds ratio [OR] 1.02; 95% confidence interval [CI]: 1.00-1.04; p = .046) and the absolute earliest activation time discrepancy (AEAD) between epicardium and endocardium (OR 1.05; 95% CI: 1.00-1.09; p = .048). After ablation, the LV function was completely recovered in 20 patients (50%). The factors for LV dysfunction without recovery included wider premature ventricular complex (PVC) QRSd (OR 1.09; 95% CI: 1.02-1.17; p = .012) and poorer LVEF (OR 0.85; 95% CI: 0.74-0.97; p = .020). CONCLUSION: In patients with VA from the LVS, PVC QRSd and AEAD are factors associated with deteriorating LV systolic function. Catheter ablation can reverse LV remodeling. Narrower QRSd and better LVEF are associated with better recovery of LV function after ablation.

Stereotactic body radiation therapy for refractory premature ventricular contractions that originate from the left ventricular summit: A case report.

The case highlights an available method to minimize the target volume and reduce the radiation dose by using a temporary catheter, to reduce the long-term risk of radiotherapy for ventricular arrhythmias.

Left ventricular summit premature ventricular contractions treated by venous ethanol infusion: Scar assessment by magnetic resonance imaging.

Left ventricular (LV) summit premature ventricular contractions (PVCs) are often unresponsive to radiofrequency (RF) ablation. Retrograde venous ethanol infusion (RVEI) can be a valuable alternative in this scenario. A 43-year-old woman without structural heart disease presented with LV summit PVCs unresponsive to RF ablation because of their deep-seated origin. Unipolar pace mapping performed through a wire inserted into a branch of the distal great cardiac vein (GCV) demonstrated 12/12 concordance with the clinical PVCs thus indicating close proximity to PVCs' origin. RVEI abolished the PVCs without complications. Subsequently, magnetic resonance imaging (MRI) evidenced an intramural myocardial scar produced by ethanol ablation. In conclusion, RVEI effectively and safely treated PVC arising from a deep site in the LVS. The scar provoked by chemical damage was well characterized by MRI imaging.

Comparison of radiofrequency ablation from the coronary cusps and endocardial left ventricular outflow tract for left ventricular summit ventricular arrhythmias in a porcine and infrared thermal model.

INTRODUCTION: The coronary cusps (CCs) are utilized as an alternative vantage point for radiofrequency catheter ablation (RFCA) of left ventricular summit ventricular arrhythmias but are sometimes a challenge despite favorable activation timing and pace mapping. METHODS: Ex vivo experiments were performed in 12 intact porcine hearts submerged in a 37°C saline bath. Radiofrequency (RF) applications were delivered with an irrigated contact force sensing catheter oriented 45° to the endocardial left ventricular outflow tract (LVOT) surface and nadir of the CCs using different dosing parameters. Sections were stained in 2% triphenyltetrazolium chloride and lesion dimensions were measured. Thermal infrared imaging analysis was used to compare time-to-lethal tissue temperature and depth/area of lethal isotherms. RESULTS: A total of 60 RF applications were performed under different dosing parameters for (1) 30, 40, and 50 Watts (W) × 30 s and (2) 40 W × 30, 45, and 60 s. Lesion depth was greater with RFCA from LVOT than from the CCs (maximum depth 6.11 vs. 2.68 mm). Longer RF duration led to larger lesion volume in the CC group (40 W × 30 s: 8.1 ± 0.4 vs. 40 W × 60 s: 10.1 ± 0.96 mm; p = .002). One steam pop occurred in both the LVOT (50 W × 30 s) and CC groups (40 W × 60 s). Time-to-reach lethal temperature of 58°C was longer in the CC group than in the LVOT group (4.7 vs. 11.3 s; p = .02) CONCLUSIONS: RFCA from the CC led comparatively to shallower lesion depth than from the LVOT. Longer RF duration led to an increase in lesion volume during ablation from CCs.

Endocardial ablation at the mitral valve vestibule and its surroundings for the treatment of arrhythmias linked to the greater cardiac vasculature.

BACKGROUND: The role of the epicardial vasculature in supraventricular and ventricular arrhythmias was described in clinical studies as well as its treatment by intravascular point ablation or alcohol injection. We report on a case series of patients with different arrhythmias linked to an epicardial site of origin with evidence supporting transmural extensions that were targeted for ablation with successful outcomes. METHODS: The records of patients who has catheter ablation for Supraventricular or Ventricular arrhythmias between 2015 and 2020 was searched for patients with (1) arrhythmias linked to the epicardial vasculature and (2) findings to support an endocardial connection to the epicardial vasculature by activation mapping, pace mapping, or differential pacing, and (3) were successfully ablated via an endocardial approach only. RESULTS: From the data searched, we identified five patients with the following arrhythmias left ventricular summit ectopy, peri-mitral atrial flutter, preexcitation with inducible atrioventricular reentry tachycardia (AVRT), and a concealed left side accessory pathway with inducible AVRT that were linked to the following vessels: Great Cardiac vein, persistent left superior vena cava, left coronary cusp, and left ventricular outflow tract. Endocardial connections were supported by a combination of electro anatomical activation mapping, pace-mapping, and differential pacing. Endocardial ablations performed in all patients were successful without complications. CONCLUSION: This report highlights a subset of patients with arrhythmias linked to the greater cardiac vascular system that can be safely and effectively ablated endocardially, given the limitations and possible complications of epicardial ablation within or in the proximity of the epicardial vasculature.

The use of ivabradine in a patient with idiopathic ventricular arrhythmia originating from the left ventricular summit.

Idiopathic ventricular arrhythmias (VA) are common and treatment options include anti-arrhythmic drugs (AAD) or catheter ablation. Patients presenting with idiopathic VA which is originating from the left ventricular summit (LVS) poses a particular challenge as the success for catheter ablation is low and AAD's may not be used long-term due to side effects. Ivabradine is an inhibitor of funny current (If) in cardiac pacemaker cells by blocking hyperpolarization-activated cyclic nucleotide-gated (HCN). In the present case, we reported the use of ivabradine in treatment of idiopathic VA which was originated from LVS and was resistant to multiple AAD's and catheter ablation.

Late elimination of challenging idiopathic ventricular arrhythmias originating from left ventricular summit by anatomical ablation.

Ablation of premature ventricular complexes (PVCs) originating from left ventricular outflow tract (LVOT)/left ventricular summit (LVS) is challenging with considerable rate of failure. Recently, in a novel approach to ablation of these arrythmias, application of radiofrequency energy to anatomically opposite sites of presumed origin of arrythmia, has been associated with moderate procedure success. Although late elimination of PVCs that are persistent following an ablation procedure has been previously reported, this observation has not been studied sufficiently. In this report, firstly, we present three cases of lately eliminated LVS PVCs, then, we discuss possible mechanism of this observation and conclude that after an initial failed attempt of anatomic ablation, operators may choose a period of watchful waiting before attempting a redo procedure.

Effect of radiofrequency on epicardial myocardium after ablation of ventricular arrhythmias from within coronary sinus.

BACKGROUND: Radiofrequency (RF) ablation of idiopathic ventricular arrhythmias (IVA) from the coronary venous system (CVS) has been increasingly performed, but real effect of ablation lesions from CVS on epicardial myocardium has not been studied. OBJECTIVE: To compare effects of RF delivered inside the distal CVS during ablation of IVAs originating from left ventricular summit (LVS) with IVAs ablated from right ventricular outflow tract (RVOT) using cardiac magnetic resonance imaging (CMRI). METHODS: Twenty consecutive patients with IVAs who underwent acutely successful RF ablation at initial appropriate sites, i.e., distal CVS (Group 1, n = 10) or RVOT (Group 2; n = 10) were enrolled. Detailed contrast-enhanced CMRI of each patient was performed 3 months later. Presence and location of scars, distance of CVS to epicardial ventricular myocardium were measured and analyzed. RESULTS: Group 1 consisted of 10 and Group 2 consisted of 10 patients. Three months after the ablation, only three patients in Group 1 had detectable late gadolinium enhancement (LGE) on CMRI while nine out of 10 patients in Group 2 had evident LGE on CMRI (P: 0.02). The mean distance of distal CVS to epicardial anterobasal myocardium was measured to be 8.8 ± 1.6 mm in Group 1. In three cases that had detectable scar on superior anterobasal LV epicardium, the mean distance was 7.4 ± 1.1 mm. CONCLUSIONS: RF delivery inside the CVS is less likely to produce detectable LGE on CMRI compared to RVOT. This may partially explain less than ideal long-term results after ablation of LVS IVAs from within the great cardiac vein/anterior interventricular vein.

Electrocardiographic characteristics and mapping approach of ventricular arrhythmias originating from the left ventricular summit.

The left ventricular summit is the most common site of idiopathic epicardial ventricular tachycardia (VT). We report a case of a 48-yr-old lady who presented with VT of RBBB configuration, inferior axis and delayed initial activation. During electrophysiological study, local activation in the distal great cardiac vein (GCV) preceded surface QRS by 56 ms whereas mapping in the aortic sinuses and left ventricular outflow tract endocardially revealed late activation. Ablation in the distal GCV with an irrigated catheter successfully terminated the tachycardia. The 12­lead electrocardiogram is an invaluable tool for predicting the VT focus and planning the mapping strategy.

Approach selection of radiofrequency catheter ablation for ventricular arrhythmias originating from the left ventricular summit: potential relevance of Pseudo Delta wave, Intrinsicoid deflection time, maximal deflection index.

BACKGROUND: Ventricular arrhythmias (VAs) originating from the left ventricular summit is a challenge for radiofrequency catheter ablation (RFCA). The present study aimed to investigate the appropriate RFCA strategy for VAs originating from the left ventricular summit. METHODS: Forty-five consecutive patients with VAs arising from the left ventricular summit were successfully ablated at our cardiac electrophysiology center and reviewed in the study. RESULTS: Thirty-two cases of VAs were eliminated in the left ventricular endocardium by retrograde transaortic (n = 22, 22/45, 48.9%) or antegrade transseptal (n = 10, 10/45, 22.2%) approaches, the other 13 cases were eliminated in the left ventricular epicardium by distal great cardiac vein (DGCV) approach (n = 13, 13/45, 28.9%). Though these VAs were similar in electrocardiographic (ECG) morphology, the pseudo delta waves (PDW), intrinsicoid deflection time (IDT), maximal deflection index (MDI) differed among them, PDW >53 ms, IDT > 74 ms, MDI > 0.45 strongly indicated that ablating left ventricular summit VAs by DGCV approach. During mean follow-up of 19.5 ± 13.2 (range, 3-60) months, 2 (4.4%) patients experienced VAs recurrence. CONCLUSION: This retrospective study showed that VAs of left ventricular summit origin can be effectively cured with RFCA. For these VAs, prolonged PdW, IDT, MDI indicating RFCA by DGCV approach can be attempted firstly.

Pathological autopsy of a patient that underwent a successful ablation of an electrical storm from the left ventricular summit.

A 65-year-old man with non-ischemic cardiomyopathy, underwent an autopsy 2 months after the successful ablation of a sustained left ventricular (LV) summit ventricular tachycardia (VT). The patient died due to interstitial pneumonia from amiodarone use. The earliest activation sites of the VT were documented from both inside the anterior interventricular vein (AIV) and epicardial surface. The diameter of the AIV was 3-4 mm, and the radiofrequency (RF) lesion inside the AIV was a slight lesion due to high impedance with a high temperature. The lesion from the epicardial surface was also superficial and insufficient due to neighboring coronary arteries and the existence of epicardial fat. A successful application was performed from the LV endocardium, and diffuse myocardial fibrosis was observed in the mid-myocardium including inside the RF lesions. The actual relationship between the myocardial fibrosis and LV summit VT remains unclear, but this case showed the difficulty of achieving a successful ablation from the epicardial side, when the focus exists in the mid-myocardium around the LV summit.

Clinical cardiac structural anatomy reconstructed within the cardiac contour using multidetector-row computed tomography: Left ventricular outflow tract.

The left ventricular outflow tract (LVOT) is a common site of idiopathic ventricular arrhythmia. Many electrocardiographic characteristics for predicting the origin of arrhythmia have been reported, and their prediction rates are clinically acceptable. Because these approaches are inductive, based on QRS-wave morphology during the arrhythmia and endocardial or epicardial pacing, three-dimensional anatomical accuracy in identifying the exact site of the catheter position is essential. However, fluoroscopic recognition and definition of the anatomy around the LVOT can vary among operators, and three-dimensional anatomical recognition within the cardiac contour is difficult because of the morphological complexity of the LVOT. Detailed knowledge about the three-dimensional fluoroscopic cardiac structural anatomy could help to reduce the need for contrast medium injection and radiation exposure, and to perform safe interventions. In this article, we present a series of structural images of the LVOT reconstructed in combination with the cardiac contour using multidetector-row computed tomography. We also discuss the clinical implications of these findings based on the accumulated insights of research pioneers.

Shift of exit site during ablation of ventricular tachycardia originating from the vicinity of left ventricular summit.

A 44-year-old man with structurally normal heart underwent catheter ablation of left ventricular summit tachycardia. The initial mapping revealed the origin of tachycardia at the junction of great cardiac vein and anterior interventricular vein. During ablation the exit site shifted to the nearby regions, which was recognized by subtle changes of 12-lead ECG. Mapping and ablating at different exit sites rendered the tachycardia noninducible.

Idiopathic ventricular tachycardia cured by radiofrequency application from the distal great cardiac vein and the left coronary cusp.

A 79 year-old male without structural heart disease suffered from drug refractory ventricular tachycardia (VT). VTs and premature ventricular complexes (PVCs) with the same morphology occurred incessantly with a concordant R pattern in chest leads and a tall R in Lead II, III, and aVF. The origin was expected to be near the left epicardial ventricular outflow tract (LVOT), which was termed the left ventricular summit area. Pace-mapping from the LVOT and the left coronary cusp (LCC) did not match well with the QRS morphology of the PVC. A good match was obtained from the distal great cardiac vein (GCV), and radiofrequency (RF) delivery eliminated the PVC and VT. However, the PVC recurred four times upon cessation of RF delivery. By placing an ablation catheter at the LCC, we obtained pace-mapping showing two different types of QRS morphologies; one was an rS pattern in V1, and the other was an R pattern in V1 with a longer stimulus to QRS interval, which was a nearly perfect match to the PVC. RF application to the LCC permanently eliminated PVCs and VTs. Several VTs from the epicardial LVOT can be cured by RF application from both the distal GCV and the LCC.

Anatomically Based Ablation of Left Ventricular Summit Premature Ventricular Complexes Guided by Intracardiac Echocardiography.

Catheter ablation of premature ventricular contractions (PVCs) arising from the left ventricular summit (LVS) presents technical challenges due to the regional anatomy and frequent intramural site of origin (SOO). Intracardiac echocardiography (ICE) and the CARTOSOUND® (Biosense Webster, Diamond Bar, CA, USA) module allow the operator to directly reconstruct and visualize the dimensions and orientation of the LVS live and present it in relation to neighboring structures. We retrospectively reviewed consecutive cases between January 2021 and December 2022 of patients undergoing PVC ablation for a presumed LVS origin. The LVS was reconstructed by creating a three-dimensional representation of the left ventricular septum, using two-dimensional ICE sections. The earliest site in each chamber was tagged on the reconstructed LVS, and the presumed SOO was localized using a geometrical center point from all sites. Ablation was first delivered to the earliest site, except when the presence of coronary branches precluded radiofrequency delivery within the great cardiac vein. Of 20 patients (8 women, 62.4 ± 7.1 years old) with a presumed LVS origin, 12 had PVC recurrence within the monitoring period after the initial ablation for 192.5 ± 37.2 s at the earliest site. Among them, earliest activation was seen at the sinus of Valsalva (SoV), coronary venous system (CVS), and left ventricular endocardium (LVE) in four, six, and two patients, respectively. Using the reconstructed LVS, the anatomically closest site to the SOO was identified in the SoV, CVS, and LVE in four, two, and six cases, respectively. Throughout the study period (14.5 months; range, 9.3-19.7 months), 17 patients (85%) had complete elimination of PVCs as evaluated by 24-h event monitors at the 12-month visit. In 50% of cases, among patients in whom ablation at the earliest signal was unsuccessful, the site of successful ablation did not correlate with the second earliest signal or had no identifiable signal during initial activation mapping. The reconstructed LVS not only guided activation mapping but also identified sites proximal to the center point that had either a late activation signal, a low-amplitude signal, or no signal at all.