Electroanatomical Voltage Mapping Research Articles

Optimal cutoff value of bipolar low-voltage in electroanatomic voltage mapping during atrial fibrillation rhythm.

Electroanatomic voltage mapping (EAVM) of the left atrium (LA) with multielectrodes is usually acquired during sinus rhythm (SR), and the feasibility of EAVM during atrial fibrillation (AF) rhythm is unclear. We performed EAVM of LA during both SR and AF rhythm in 44 patients undergoing catheter ablation for AF and validated the optimal cutoff value of low-voltage area (LVA) during AF rhythm for detecting LVA defined as bipolar voltages ≤0.5mV during SR. In each session, mean 829 and 552 points were acquired by multielectrodes during SR and AF rhythm, respectively. Mean proportion of LVA was 4.9% among LA surface area of 276.2 cm2 . Differences of LVA proportions between SR and AF rhythm were 5.8% (P<0.001), 4.2% (P<0.001), 2.7% (P<0.001), 1.2% (P=0.01), and -0.5% (P=0.17) at the cutoff value of 0.4, 0.35, 0.3, 0.25, and 0.2mV during AF rhythm, respectively. There was a good correlation between LVA proportions during SR and AF rhythm with cutoff value of 0.2mV (R=0.88, P<0.001) and 37 patients (84.1%) had the discrepancy of LVA proportions within 3%. Furthermore, there was no significant difference between LVA proportions at each segment of LA. The discrepancy was relatively large in patients with large LA dimension and LVA during SR. EAVM during AF rhythm was feasible and the optimal cutoff value of LVAwas 0.2mV for detecting LVA ≤ 0.5mV during SR. However, the evidence is restricted to patients with relatively small LVA.

Atrial Fibrosis: Translational Considerations for the Management of AF Patients.

Fibrosis plays a fundamental role in the initiation and maintenance of AF, mainly due to enhanced automaticity and anisotropy-related re-entry. The identification and quantification of atrial fibrosis is achieved either preprocedurally by late gadolinium enhancement MRI or intraprocedurally using electroanatomic voltage mapping. The presence and extent of left atrial fibrosis among AF patients may influence relevant decision making regarding the need for anticoagulation, the adoption of rate versus rhythm control and mainly the type of ablation strategy that will be followed during interventional treatment. Several types of individualised substrate modifications targeting atrial fibrotic areas have been proposed, although their impact on patient outcome needs to be further investigated in adequately powered prospective randomised controlled clinical trials.

Premature ventricular contractions of the right ventricular outflow tract: Upward displacement of the ECG unmasks ST elevation in V1 associated with the presence of low voltage areas

Introduction and AimsFrequent premature ventricular contractions (PVCs) originating from the right ventricular outflow tract (RVOT) are usually considered a benign entity and the ECG is typically normal. The aim of this study was to assess whether upward displacement of the ECG to the second intercostal space (ICS) would reveal any abnormal pattern. MethodsA total of 18 consecutive patients with apparently normal hearts were studied, mean age 44±16 years, 12 women, who underwent catheter ablation of the RVOT due to frequent PVCs. A 12-lead ECG was performed in the standard position and repeated in a higher position, at the level of the second ICS. Three-dimensional bipolar electroanatomical voltage mapping (EVM) was performed in all patients and low voltage areas (LVAs) were defined as areas with amplitude <1.5 mV. ResultsThe ECG in the second ICS was normal in eleven patients but in seven (39%) it revealed a pattern of ST-segment elevation in V1. EVM revealed the presence of LVAs in six patients (33%) which included the earliest activation site (EAS) in five. The ST elevation was associated with the presence of LVAs (p<0.0001) and with the LVAs at the EAS (p=0.002). ConclusionIn this group of patients with apparently normal hearts and with frequent PVCs of the RVOT, upward displacement of the ECG revealed the presence of ST elevation in more than one third of patients, and the ST elevation was associated with the presence of LVAs in the RVOT.

Hybrid Ablation of Ventricular Tachycardia: a Single-Centre Experience.

The long-term results of endocardial and percutaneous epicardial catheter ablation of ventricular tachycardia (VT) in patients with structural heart disease are disappointing. Arrhythmia recurrence after ablation and VTs with an epicardial substrate remain a clinical challenge. The purpose of this manuscript is to elaborate on feasibility and potential advantages of a surgical hybrid ablation (i.e., combined endocardial and surgical epicardial ablation) based on our initial experience consisting of five cases. Endocardial electro-anatomical voltage and activation maps were created (Carto, Biosense Webster, California, USA), and endocardial radiofrequency (RF) applications were applied at exit sites, low voltage areas and isthmi. Next, after surgical access, epicardial voltage and activation maps were produced in combination with visual assessment of the epicardial substrate. Epicardial low voltage areas, isthmi and exit sites were identified and ablated using RF energy. After the procedure, VT was non-inducible in 80% of the cases (4/5, in one case no induction was performed). No peri-procedural complications occurred. After a mean follow-up of 18 months, one patient remained in sinus rhythm without, and 2 with use of antiarrhythmic drugs. One patient needed a redo procedure after 21 months, and in one patient the amiodarone dose was raised because of 2 sustained VTs. After this additional treatment, both kept sinus rhythm. Hybrid VT ablation is a safe and effective patient tailored procedure that comprises the major advantage of combining direct anatomical visualization and enhanced catheter stability with high-density 3D mapping. As a consequence, this procedure should be considered as a valid treatment option in complex VT management.

Electroanatomical voltage mapping and what to consider abnormal in non-ischaemic cardiomyopathy: when one size does not fit all.

Electroanatomical voltage mapping and what to consider abnormal in non-ischaemic cardiomyopathy: when one size does not fit all.

Whole human heart histology to validate electroanatomical voltage mapping in patients with non-ischaemic cardiomyopathy and ventricular tachycardia.

Electroanatomical voltage mapping (EAVM) is an important diagnostic tool for fibrosis identification and risk stratification in non-ischaemic cardiomyopathy (NICM); currently, distinct cut-offs are applied. We aimed to evaluate the performance of EAVM to detect fibrosis by integration with whole heart histology and to identify the fibrosis pattern in NICM patients with ventricular tachycardias (VTs). Eight patients with NICM and VT underwent EAVM prior to death or heart transplantation. EAVM data was projected onto slices of the entire heart. Pattern, architecture, and amount of fibrosis were assessed in transmural biopsies corresponding to EAVM sites. Fibrosis pattern in NICM biopsies (n = 507) was highly variable and not limited to mid-wall/sub-epicardium. Fibrosis architecture was rarely compact, but typically patchy and/or diffuse. In NICM, biopsies without abnormal fibrosis unipolar voltage (UV) and bipolar voltage (BV) showed a linear association with wall thickness (WT). The amount of viable myocardium showed a linear association with both UV and BV. Accordingly, any cut-off to delineate fibrosis performed poorly. An equation was generated calculating the amount of fibrosis at any location, given WT and UV or BV. Considering the linear relationships between WT, amount of fibrosis and both UV and BV, the search for any distinct voltage cut-off to identify fibrosis in NICM is futile. The amount of fibrosis can be calculated, if WT and voltages are known. Fibrosis pattern and architecture are different from ischaemic cardiomyopathy and findings on ischaemic substrates may not be applicable to NICM.

Identification and electrophysiological characterization of early left atrial structural remodeling as a predictor for atrial fibrillation recurrence after pulmonary vein isolation.

Voltage-guided substrate ablation following pulmonary vein isolation (PVI) improves atrial fibrillation (AF) ablation outcomes. However, by setting an upper voltage cutoff of 0.5 mV during sinus rhythm (SR) to guided substrate ablation using electroanatomic voltage mapping (EAVM), mildly affected low-voltage area (maLVA) may be undetected. We sought to determine the optimal bipolar voltage cutoff to identify maLVA, its electrogram complexity, and the implication on ablation outcome. Left atrial (LA) EAVMs were obtained in patients without AF and structural heart disease (control) to devise a voltage cutoff to identify maLVA. Subsequently, we investigated 100 patients without low-voltage area (LVA) of < 0.5 mV who underwent PVI alone. In our 6 control cohorts, 95% of LA regional bipolar voltage was > 1.17 mV. maLVA, defined as <1.1 mV, was present in 43% of AF patients, associated with higher prevalence of abnormal electrograms (44.1% vs. 4.4%, P < 0.001). During a median of 2.4 years, patients with maLVA had higher recurrence rate (Log-rank P < 0.001), and maLVA was an independent predictor for recurrence in a multivariate analysis (hazard ratio [HR] 3.944; 95% confidence interval [CI] 1.292-12.042; P = 0.016). A control-derived LA voltage cutoff of <1.1 mV for EAVM in SR reveals maLVA, harboring abnormal electrograms, as an independent predictor for recurrences after PVI alone in patients without LVA (< 0.5 mV). Adjunctive maLVA-guided substrate ablation targeting mildly remodeled and potentially arrhythmogenic LA substrate may further improve the long-term outcome of AF ablation.

Right ventricular outflow tract high-density endocardial unipolar voltage mapping in patients with Brugada syndrome: evidence for electroanatomical abnormalities.

Epicardial structural abnormalities at the right ventricular outflow tract (RVOT) may provide the arrhythmia substrate in Brugada syndrome (BrS). Electroanatomical endocardial unipolar voltage mapping is an emerging tool that accurately identifies epicardial abnormalities in different clinical settings. This study investigated whether endocardial unipolar voltage mapping of the RVOT detects electroanatomical abnormalities in patients with BrS. Ten asymptomatic patients (8 males, 34.5 ± 11.2 years) with spontaneous type 1 ECG pattern of BrS and negative late gadolinium enhancement-cardiac magnetic resonance imaging (LGE-c-MRI) underwent high-density endocardial electroanatomical mapping (>800 points). Using a cut-off of 1 mV and 4 mV for normal bipolar and unipolar voltage, respectively, derived from 20 control patients without structural heart disease established by LGE-c-MRI, the extend of low-voltage areas within the RVOT was estimated using a specific calculation software. The mean RVOT area presenting low-voltage bipolar signals in BrS patients was 3.4 ± 1.7 cm2 (range 1.5-7 cm2). A significantly greater area of abnormal unipolar signals was identified (12.6 ± 4.6 cm2 [range 7-22 cm2], P: 0.001). Both bipolar and unipolar electroanatomical abnormalities were mainly located at the free wall of the RVOT. The mean RVOT activation time was significantly prolonged in BrS patients compared to control population (86.4 ± 16.5 vs. 63.4 ± 9.7 ms, P < 0.001). Isochronal mapping demonstrated lines of conduction slowing within the RVOT in 8/10 BrS patients. Wide areas of endocardial unipolar voltage abnormalities that possibly reflect epicardial structural abnormalities are identified at the RVOT of BrS patients.

Long-Term Outcome of Left Atrial Voltage-Guided Substrate Ablation During Atrial Fibrillation: A Novel Adjunctive Ablation Strategy.

Left atrium (LA) low voltage area (LVA) on 3-D electroanatomic bipolar voltage mapping (EAVM), as a surrogate for scar, is associated with poor AF ablation outcome. We evaluated the long-term outcome of an LVA-guided atrial fibrillation (AF) substrate modification strategy as an adjunct to pulmonary vein isolation (PVI). Two hundred and one consecutive patients with AF (82% persistent/Non-PAF, age 65 years), who underwent EAVM during AF prior to PVI, were divided into 2 groups according to the presence or absence of LVA outside the PV antra, defined as bipolar voltage of <0.5 mV. LVA-guided substrate modification was performed after PVI in patients with LVA. LVA was found in 159 patients (79%). Non-PAF (OR 3.851, P = 0.002) and CHA2 DS2 -VASc score (OR 1.815, P < 0.001) were independent predictors for the LVA. After the index procedure, 144 patients (72%) were free from AF at 12 months. With multiple procedures, 148 patients (74%) during a median follow-up of 3.1 years were free from the recurrence. There was no difference in the recurrence (log-rank P = 0.746), and complications (0% vs. 7%, P = 0.125) between the groups. Neither LVA nor Non-PAF was an independent predictor for the recurrence in a multivariate analysis. Patients with LVA had an equally favorable long-term ablation outcome compared to those without. As an adjunct to PVI, voltage-guided substrate modification may be an important ablation strategy in patients with LA structural remodeling.

Voltage combined with pace mapping is simple and effective for ablation of noninducible premature ventricular contractions originating from the right ventricular outflow tract.

Premature ventricular contractions (PVCs) from the right ventricular outflow tract (RVOT) can resist conventional mapping strategies. Studies regarding optimal mapping and ablation methods for patients with noninducible RVOT-PVCs are limited. We retrospectively evaluated the efficacy and safety of a novel mapping strategy for these cases: voltage mapping combined with pace mapping. METHODS: We retrospectively included symptomatic patients (n = 148; 76 males; age, 44.5 ± 1.4 years) with drug-refractory PVCs originating from the RVOT, who underwent radiofrequency catheter ablation (RFCA), and stratified them as Group 1 and Group 2. Group 1 patients had noninducible RVOT-PVCs, determined after programmed stimulation, burst pacing, and isoproterenol infusion (n = 21; 12 males; age, 39.5 ± 10.8 years). Group 2 patients had inducible PVCs. Group 1 patients were subjected to voltage mapping combined with pace mapping; Group 2 underwent conventional mapping. In all patients prior to RFCA, detailed 3-dimensional electroanatomic voltage maps of the RVOT were obtained during sinus rhythm using the CARTO system. Patients from both groups had similar success and complication rates associated with the RFCA. In Group 2, 89% (113/127) experienced the earliest and the successful ablation points in the voltage transitional zone. During the follow-up (36 ± 8 months), patients from both groups suffered similar rates of PVC relapse (2/21 and 7/127, respectively; P = 0.826). Voltage mapping combined with pace mapping is effective and safe for patients with noninducible RVOT-PVCs determined by conventional methods.

Role of right ventricular three-dimensional electroanatomic voltage mapping for arrhythmic risk stratification of patients with corrected tetralogy of Fallot or other congenital heart disease involving the right ventricular outflow tract

BackgroundThe post-surgical history of repaired congenital heart disease (rCHD), in particular tetralogy of Fallot (TOF), is often complicated by sudden death. Electrical myocardial abnormalities could be a substrate for malignant ventricular arrhythmias. Methods and results146 patients with TOF or other rCHD involving a subpulmonary right ventricle, considered to be at high arrhythmic risk, underwent right ventricular (RV) electroanatomic voltage mapping (EVM). Maps showed endocardial scars (<0.5mV) in all cases, mainly involving the RV outflow tract (n=141, 96.6%). In 28 cases (19.2%), other areas were involved. Total scar extension, expressed as % of total endocardial area, was significantly higher in patients with QRS ≥180ms [4.5% (±2.5) vs 2.8% (±2.4), p=0.014], left and right ventricular systolic dysfunction [4.5% (±3.2) vs 2.8% (±2.3), p=0.016 and 3.5% (±3.0) vs 2.6% (±1.9), p=0.03, respectively], premature ventricular contractions (PVCs) [3.2% (±2.6) vs 2.2% (±1.8), p<0.05], exercise-induced PVCs [3.8% (±2.4) vs 2.6% (±2.2), p=0.01], previous shunt [4.0% (±2.7) vs 2.6% (±2.2), p=0.01] and reintervention [4.2% (±3.2) vs 2.6% (±2.0), p=0.008]. Scar size also showed a positive correlation with duration of post-surgical follow-up (ρ=0.01), age at correction (ρ=0.01) and absolute QRS duration (ρ=0.05). ConclusionsPatients with rCHD involving the right ventricle show electrical scars with variable distribution, not necessarily matching with sites of surgical lesions. Scar extension correlates with some of the risk factors for life-threatening arrhythmias in CHD, such as prolonged QRS. Thus EVM could be considered an additional tool in the assessment of risk stratification in this particular population.

Isolated cardiac sarcoidosis diagnosed by electroanatomic voltage mapping-guided endomyocardial biopsy combined with magnetic resonance imaging and positron emission tomography

Cardiac involvement in sarcoidosis is related to lethal arrhythmias and is considered a serious condition. Because steroid therapy is an effective treatment, early diagnosis of cardiac sarcoidosis (CS) is of paramount importance in respect to improving prognosis. However, the diagnostic yield of histologic examination by endomyocardial biopsy (EMB) in CS is usually low. We report the case of isolated CS histopathologically proven by electroanatomical voltage mapping (EVM)-guided EMB combined with cardiac magnetic resonance imaging (CMR) and 18F-fluorodeoxyglucose positron emission tomography (FDG-PET). A 53-year-old man presented with general fatigue. Electrocardiography showed intermittent complete atrioventricular block and echocardiography showed reduced cardiac function. CMR showed late gadolinium enhancement (LGE) in the areas of myocardium with suspected sarcoidosis. Next, we performed an EVM-guided EMB and found a non-caseating epithelioid granuloma in the right ventricular septum, which showed low voltage on EVM and LGE on CMR. FDG-PET showed accumulation in the same cardiac region. This case shows that EVM-guided EMB combined with diagnostic imaging can be a valuable approach in cases of suspected isolated CS.<Learning objective: To reduce inflammation and prevent ventricular remodeling by early corticosteroid treatment, detecting cardiac sarcoidosis (CS)-affected regions is important. Cardiac magnetic resonance imaging and positron emission tomography help detect such regions. However, histopathological diagnosis of CS by endomyocardial biopsy (EMB) is usually difficult. The present case suggests that electroanatomical voltage mapping-guided EMB combined with diagnostic imaging improves detection of CS-affected regions.>

97-06: Fragmented QRS is Not Associated with Conduction Delay and Ventricular Arrhythmias in Patients with Repaired Tetralogy of Fallot

Introduction: Fragmented QRS complexes (fQRS) on 12-lead ECG may reflect conduction delay due to myocardial scarring and have been associated with ventricular tachyarrhythmia (VT) in patients with ischemic and nonischemic cardiomyopathy. Non-invasive risk stratification for VT in patients with repaired TOF (rTOF) has limited predictive value. This study evaluates the potential electroanatomical substrate underlying fQRS and the value of fQRS for VT risk stratification in rTOF. Methods: Fifty-three rTOF patients (46 ± 16 yrs, 64% male) at risk for VT (n = 42) or with documented VT (n = 11) underwent VT induction and detailed RV electroanatomical voltage and activation mapping (EAM) during SR to evaluate total RV activation time (RVAT) and areas of local conduction delay. Routine 12-lead ECGs prior to EAM were assessed for QRS duration, bundle branch block and fQRS defined as RSR' patterns (>1 R' or notching of R or S wave) in patients with a narrow QRS complex or >2 notches in R or S wave in patients with a wide QRS complex, present in ≥2 contiguous leads. Presence of fQRS, local conduction delay (<0.5m/s) and RVAT were compared between patients with and without spontaneous and/or induced VT. Results: Mean QRSd was 156 ± 33ms; 7 patients had narrow QRS, 46 broad QRS (24 RBBB, 7 RBBB + LAFB, 9 LBBB, 6 other). RVAT was 126 ± 37ms. Localized conduction delay confined to anatomical isthmuses was observed in 23 pts. Twenty-four patients were inducible for 37 VTs, including all with prior documented VT. Thirty-three of 37 VTs could be mapped to a slow conducting anatomical isthmus (SCAI).FQRS was present in 19 (36%) patients (3 narrow, 16 wide QRS complex) and did not differ significantly between patients with and without VT (8/24 versus 11/29 patients respectively, p = 0.728). FQRS was not associated with longer RVAT (131 ± 46ms in patients with fQRS versus 122 ± 32ms without fQRS; p = 0.402) and was not related to the presence of SCAI (SCAI present in 7 patients with fQRS versus 15 patients without fQRS p = 0.857). Conclusion: Fragmented QRS is a frequent finding and not associated with conduction delay and VA in patients with rTOF. It may be due to changes in wavefront propagation as a consequence of the surgical intervention.

Arrhythmogenic anatomical isthmuses identified by electroanatomical mapping are the substrate for ventricular tachycardia in repaired Tetralogy of Fallot.

Aims The majority of ventricular tachycardias (VTs) in repaired tetralogy of Fallot (rTOF) are related to anatomically defined isthmuses. We aimed to identify specific electroanatomical characteristics of anatomical isthmuses (AI) related to VT which may allow for individualized risk stratification and tailored ablation. Methods and results Seventy-four consecutive rTOF patients (40 ± 16 years, 63% male) underwent VT induction and right ventricular electroanatomical voltage and activation mapping during sinus rhythm (SR) to identify the presence and characteristics of AI (isthmus width, length and conduction velocity index [CVi]). Twenty-eight patients were inducible for 41 VTs. All 74 patients had at least one AI. However, AI in patients with VT were longer (22 ± 7 vs. 16 ± 7 mm, P = 0.001), narrower (20 ± 8 vs. 28 ± 11 mm, P < 0.001) and had lower CVi (0.36 ± 0.34 vs. 0.78 ± 0.24 m/s, P < 0.001). Thirty-seven VTs in 24 patients were mapped (pace-, entrainment mapping, and/or VT termination by ablation) to 28 AI. All 28 AI related to VT had a CVi < 0.5 m/s (slow conducting AI (SCAI)). In contrast, 87 of 89 AI of the 46 patients without VT had CVi ≥ 0.5 m/s. Sixty-two patients were discharged without the presence of an SCAI (44 had no SCAI at baseline, 18 underwent ablation of the SCAI) and 10 still had an SCAI (no/failed ablation). During follow-up (50 ± 22 months), no patient without SCAI had any VT, which occurred in 5/10 patients with SCAI ( P < 0.001). Conclusion In rTOF, slow conducting anatomical isthmuses identified by electroanatomical mapping during SR are the dominant substrate for VT allowing individualized risk stratification and preventive ablation.

Role of Right Ventricular Three-Dimensional Electroanatomic Voltage Mapping for the Arrhythmic Risk Stratification of Patients with Corrected Tetralogy of Fallot or Other Congenital Heart Disease Involving the Right Ventricle Outflow Tract

Introduction: Among adult patients with previous surgical correction for Tetralogy of Fallot (ToF) or other repaired Congenital Heart Disease (rCHD) involving the Righ Ventricular (RV) outflow, ventricular arrhythmias (VA) and sudden cardiac death (SCD) represent a late complication. The impaired hemodynamics that lead to RV dilatation and overload could also modify its electrical properties. 3D Electroanatomic Voltage Mapping (EVM) of the RV could confirm the presence of myocardial electrical abnormalities, allowing to better identify patients at risk of life-threatening arrhythmias.

Changing the Way We “See” Scar: How Multimodality Imaging Fits in the Electrophysiology Laboratory

Substrate characterization is the mainstay of ablation for ventricular tachycardia (VT). Although the use of electroanatomic voltage mapping (EAVM) in the electrophysiology (EP) laboratory has enabled real-time approximation of myocardial scar, it has limitations. This is related to the subjective and tedious nature of voltage mapping and the challenges of defining the transmurality of scar. Various noninvasive methods of scar assessment have emerged, with magnetic resonance imaging (MRI) being the most accurate. Integrated MRI and electroanatomic voltage mapping studies demonstrate good correlation. Nonetheless, MRI has advantages. These include (1) preprocedure identification of epicardial and intramural scar, (2) assessment of ablative lesion formation after unsuccessful ablations, (3) identification of heterogeneous regions of scar, where critical conducting channels are likely to occur, and (4) predictive value in the assessment of sudden cardiac death (SCD). Integration of scar imaging in ventricular tachycardia ablation and risk stratification has great potential to advance the practice of arrhythmia management.

Prediction of atrial fibrillation development and progression: Current perspectives.

Atrial fibrillation (AF) is the most common arrhythmia in clinical practice. Several conventional and novel predictors of AF development and progression (from paroxysmal to persistent and permanent types) have been reported. The most important predictor of AF progression is possibly the arrhythmia itself. The electrical, mechanical and structural remodeling determines the perpetuation of AF and the progression from paroxysmal to persistent and permanent forms. Common clinical scores such as the hypertension, age ≥ 75 years, transient ischemic attack or stroke, chronic obstructive pulmonary disease, and heart failure and the congestive heart failure, hypertension, age ≥ 75 years, diabetes mellitus, stroke/transient ischemic attack, vascular disease, age 65-74 years, sex category scores as well as biomarkers related to inflammation may also add important information on this topic. There is now increasing evidence that even in patients with so-called lone or idiopathic AF, the arrhythmia is the manifestation of a structural atrial disease which has recently been defined and described as fibrotic atrial cardiomyopathy. Fibrosis results from a broad range of factors related to AF inducing pathologies such as cell stretch, neurohumoral activation, and oxidative stress. The extent of fibrosis as detected either by late gadolinium enhancement-magnetic resonance imaging or electroanatomic voltage mapping may guide the therapeutic approach based on the arrhythmia substrate. The knowledge of these risk factors may not only delay arrhythmia progression, but also reduce the arrhythmia burden in patients with first detected AF. The present review highlights on the conventional and novel risk factors of development and progression of AF.

Box Isolation of Fibrotic Areas (BIFA): A Patient-Tailored Substrate Modification Approach for Ablation of Atrial Fibrillation.

Catheter ablation strategies beyond pulmonary vein isolation (PVI) for treatment of atrial fibrillation (AF) are less well defined. Increasing clinical data indicate that atrial fibrosis is a critical common left atrial (LA) substrate in AF patients (pts). We applied a new substrate modification concept according to the individual fibrotic substrate as estimated from electroanatomic voltage mapping (EAVM) in 41 pts undergoing catheter ablation of AF. First, EAVM during sinus rhythm was done in redo cases of 10 pts with paroxysmal AF despite durable PVI. Confluent low-voltage areas (LVA) were found in all pts and were targeted with circumferential isolation, so-called box isolation of fibrotic areas (BIFA). This strategy led to stable sinus rhythm in 9/10 pts and was transferred prospectively to first procedures of 31 pts with nonparoxysmal AF. In 13 pts (42%), no LVA (<0.5 mV) were identified, and only PVI was performed. In 18 pts (58%), additional BIFA strategies were applied (posterior box in 5, anterior box in 7, posterior plus anterior box in 5, no box in 1 due to diffuse fibrosis). Mean follow-up was 12.5 ± 2.4 months. Single-procedure freedom from AF/atrial tachycardia was achieved in 72.2% of pts and in 83.3% of pts with 1.17 procedures/patient. In approximately 40% of pts with nonparoxysmal AF, no substantial LVA were identified, and PVI alone showed high success rate. In pts with paroxysmal AF despite durable PVI and in approximately 60% of pts with nonparoxysmal AF, individually localized LVA were identified and could be targeted successfully with the BIFA strategy.

Abstract 15592: Role of Electroanatomic Voltage Mapping for Risk Stratification in Patients With Repaired Congenital Heart Disease Involving the Right Ventricle

Introduction: Among adult patients with previous surgical correction for Tetralogy of Fallot or other repaired Congenital Heart Disease (rCHD) involving the RV, ventricular arrhythmias (VA) and sudden cardiac death (SCD) represent a late complication. The imparied haemodynamics that lead to RV dilatation and overload could also alterate its electroanatomic structure. Hypothesis: 3D electroanatomic mapping (EAM) of the RV could confirm the presence of myocardial electrical abnormalities, allowing to better identify patients at risk for life-threatening arrhythmias. Methods: 146 patients (age 19.2 ±7.0) with rCHD involving the RV were selected from a population undergoing routine post-surgical follow-up, according to the presence of VA or severe RV dilatation. These patients underwent 3D EAM of the RV. We tested the correlation between size of scar tissue (areas with voltage &lt; 0.5 mV) and several parameters universally accepted by the literature as risk factors for VA in this particular patient population. Results: In 125 (85.6%) patients, EAM demonstrated areas of low voltage in the antero-lateral RVOT. In 20 of these (16%, 13.7% of the total) the scar extended to the septum. 72 (49.3%) had a peritricuspid scar, and in 20 (13.7%) other areas of the RV were interested. Total low-voltage area, expressed as % of total endocardial area, was significantly higher in patients with history of PVCs [3.2% (±2.6) vs 2.2% (±1.8), p&lt;0.05], complex PVCs at 24h-Holter ECG (Lown class ≥2) [3.4 (±2.5) vs 2.6 (±2.3), p&lt;0.05], exercise-inducible PVCs [3.8 (±2.4) vs 2.6 (±2.2), p=0.01] and history of previous shunt [4.0 (±2.7) vs 2.6 (±2.2), p=0.01]. Scar size was also positively correlated with age (p=0.01), age at correction (p=0.01) and QRS duration on surface ECG (p&lt;0.05). Conclusions: In patients with rCHD involving the RV it is common to observe endocardial low-voltage areas with variable distribution, not always corresponding to the sites of surgical lesion. Morover, the size of the scar tissue area correlates with some of the parameters which have been already identified as risk factors for life-threatening arrhythmias and SCD in adult patients with CHD. We suggest that EAM should become part of the routine tests for the stratification of arrhythmic risk in this population.

The heterogeneous composition of post-infarct ventricular scar is a critical factor compared to local myocardial volume in influencing the accuracy of electroanatomical voltage mapping

The heterogeneous composition of post-infarct ventricular scar is a critical factor compared to local myocardial volume in influencing the accuracy of electroanatomical voltage mapping