Conduction slowing area during sinus rhythm harbors ventricular tachycardia isthmus.

INTRODUCTION: The voltage map during sinus rhythm (SR) is a cornerstone of substrate mapping (SM) in scar-related ventricular tachycardia (VT) and frequently used with pace mapping (PM). Where to conduct PM is unclear in cases of an extensive or unidentified substrate. Conduction properties are another aspect incorporated by SM, and conduction slowing has gained interest as being related to successful ablation, although its mechanism has not been elucidated. We aimed to investigate the relationship between SR conduction properties and VT isthmuses. METHODS: Nineteen patients (mean age, 62 years) who underwent VT ablation with voltage mapping and PM were reviewed. Isochronal late activation maps (ILAMs) with eight zones were reconstructed and sequentially named from one to eight according to the SR propagation. Good PM sites were superimposed on ILAMs, and the isthmus was defined using different pacing latencies. ILAM properties harboring isthmuses were investigated. RESULTS: Twenty-eight ILAMs (13 epicardium, 1 right ventricular [RV], and 14 left ventricular [LV] endocardium) were reviewed. Eighteen isthmuses of 24 target VTs were identified, in which the proximal ends were in a later zone than the distal ends (zone 6 vs 4; P < .001), suggesting a reverse isthmus vector to the SR. The conduction velocity of the zone involving the distal isthmus was significantly lower than that of the SR preceding zone (0.40 vs 1.30 m/s; P < .001). SR conduction velocity decelerated by 69.5% (range 59.7%-74.5%) before propagating into the isthmus area. CONCLUSION: Conduction slowing area during SR were related with the exit portion of the VT isthmuses.

Electrophysiologic and anatomic factors predictive of a need for touch-up radiofrequency application for complete pulmonary vein isolation: Comparison between hot balloon- and cryoballoon-based ablation.

INTRODUCTION: Although electrophysiologic and anatomic factors associated with the need for touch-up radiofrequency (RF) applications after cryoballoon ablation (CBA) for atrial fibrillation (AF) have been well described, those associated with the need for such touch-up after hot balloon ablation (HBA) have not. We aimed to identify factors predictive of the need for touch-up applications following HBA. METHODS: Anatomic and electrophysiologic factors predictive of the need for touch-up RF ablation were compared between 46 propensity score-matched pairs of patients who underwent HBA or CBA for AF. RESULTS: Touch-up RF ablation was more frequently required after HBA than after CBA (57% vs 30%, respectively; P = .01), and mostly at the anterior aspect of the left superior pulmonary vein (LSPV) carina after HBA (35%) but at the inferior aspect of the right inferior PV (RIPV) after CBA (71%). Post HBA touch-up was associated with male gender, a CHA 2 DS 2 -VASc score ≤ 2, PV-left atrial bipolar voltage ≥ 1.35 mV, and PV trunk length ≥ 24.0 mm; post CBA touch-up associated with a history of heart failure. CONCLUSION: Following balloon ablation for AF, there may be a need for touch-up applications, especially at the LSPV ridge after HBA but at the RIPV after CBA. It may behoove operators to expect a need for touch-up following HBA when patients are male, have a CHA2 DS 2 -VASc score ≤ 2 points, when PV-LA bipolar voltage is ≥ 1.35 mV, or when the PV trunk is ≥ 24.0 mm or following CBA when there is a history of heart failure.

Impact of low-voltage zones on the left atrial anterior wall on the reduction in the left atrial appendage flow velocity in persistent atrial fibrillation patients.

BACKGROUND: The reduction in the left atrial appendage (LAA) flow velocity is related to the presence of emboli in atrial fibrillation (AF) patients. The LAA is located on the left superior side of the left atrial (LA) anterior wall, and we investigated the relationship between the reduction in the LAA flow velocity (LAAFV) and low voltage zones (LVZs < 0.5 mV) on the LA anterior wall. METHODS: In 146 persistent AF patients, LAAFV measurements, by transesophageal echocardiography, and catheter ablation were performed. LA mapping was performed before ablation during sinus rhythm, and the locations of any anterior-LVZs were documented. RESULTS: Eighty-one patients had a documented LVZ on the LA anterior wall, and those with an LVZ had a significantly lower LAAFV compared to those without (anterior-LVZ(+) vs. anterior-LVZ(-) = 26 ± 11 vs. 34 ± 10 cm/s, p < 0.001), while no significant difference was observed when compared to the other LVZ regions. A low-LAAFV (≦ 20 cm/s) was observed in 36 patients, and the CHADS2-vasc score and existence of an anterior-LVZ were associated with a low-LAAFV. In patients with anterior-LVZs, the distance between the anterior-LVZ and LAA orifice correlated with a low LAAFV (r = 0.534, p < 0.001) as compared to the surface area of the anterior-LVZ (r = - 0.288, p = 0.009). CONCLUSIONS: In persistent AF patients, an LVZ on the LA anterior wall was associated with a low LAAFV. In addition, an anterior-LVZ located near the LAA orifice was further related to a reduction in the LAAFV.

Influence of the left atrial contact areas on fixed low-voltage zones during atrial fibrillation and sinus rhythm in persistent atrial fibrillation.

BACKGROUND: Atrial low-voltage zones (LVZ) are suggested as important factors for maintaining persistent atrial fibrillation (PsAF). The relationship between LVZs and left atrial (LA) contact areas (CoAs) is still unclear. OBJECTIVE: To assess whether CoA regions were involved in atrial substrate properties maintaining PsAF. METHODS: A total of 50 patients with PsAF (36 long-lasting) were analyzed. Three representative CoA detection areas (ascending aorta-anterior-LA, descending aorta-left pulmonary vein antrum, and vertebrae-posterior-LA) were registered on the mapping geometry. Electrograms during AF and sinus rhythm (SR) were acquired, and the fractionated electrograms (CFE; < 80milliseconds) and voltages were analyzed regarding the CoAs. RESULTS: After SR conversion, 76% (38/50) had a significant LVZ (>5% of the total LA surface area). Patients with long-lasting PsAF versus PsAF had larger CoA areas (7.7 ± 3.0 vs. 4.5 ± 2.5cm2 , P < 0.05) and overlapped-LVZs (8.2 [3.2-11.0] vs. 2.1 [0.7-3.7] cm2 , P = 0.0126) between the SR-LVZs (<0.5 mV) and AF-LVZs (<0.2 mV). Overlapped-LVZs were frequently observed in CoA regions (anterior 76.4%; LIPV antrum 78.8%, and vertebrae 39.2%), and those LVZs had smaller unipolar voltages than those distant from the CoA regions (0.64 ± 0.16 vs. 2.5 ± 1.5 mV, P < 0.0001). SR-LVZ targeted ablation, including of CoA regions, rendered AF termination (n = 8, 21%), and 88% of the sites were not located immediately above, but adjacent to, the overlapped-LVZs. Significant AF slowing (6.0 ± 0.6 to 5.6 ± 0.6 Hz; P < 0.05) accompanied by unintentional CFE elimination (9.8-1.8 cm2 ; P < .0001) was achieved in patients without termination. CONCLUSION: Our data suggested that external structures in contact with the LA are involved in the creation of localized diseased myocardium necessary for PsAF maintenance.

Impact of catheter tip-tissue contact on three-dimensional left atrial geometries: Relationship between the external structures and anatomic distortion of 3D fast anatomical mapping and high contact force guided images.

BACKGROUND: A high catheter tip-tissue contact force (CF) with the myocardium may cause 3-dimensional (3D) map distortion, however, the influence of external structures surrounding the left atrium (LA) on that distortion remains unknown. This study characterized the impact of high CF mapping on the local LA geometry distortion. METHODS: Thirty AF patients underwent 3D-ultrasound merged with CT images (3D-Merge-CT). The LA area in contact with external structures was identified by enhanced CT. Fast-electroanatomical-mapping (FAM) geometries were created by two methods, point-by-point mapping with high (>10g) CFs (high-CF guided-FAM), followed by that with multielectrode-mapping catheters (conventional-FAM). The resulting geometries were compared with the 3D-Merge-CT images. RESULTS: Three representative anatomical contact areas (ascending aorta-vs.-anterior wall, descending aorta-vs.-left pulmonary vein [PV], and vertebrae-vs.-posterior wall) were identified. The PV antrum distorted distance on the 3D-Merge-CT was significantly longer for high-CF guided-FAMs than conventional-FAMs (1.7[0-3.6] vs. 0[0-1.8]mm, P<0.0001). In high-CF maps, the distorted distance significantly differed between regions with and without contact areas in both the PV antrum (0[0-0.17] vs. 1.7[0-3.9]mm, P=0.0201) and LA body region (0[0-1.5] vs. 1.7[0.7-2.2]mm, P<0.005). The catheter tip-tissue CF did not correlate with the distorted distance (r=0.08, P=0.46), and a multivariate analysis revealed that the absence of anatomical contact areas was strongly associated with significant local distortion, independent of the CF. CONCLUSIONS: High-CF guided mapping yields greater 3D-image anatomical distortion than conventional-FAM methods. That distortion was attenuated by regions with anatomical contact areas, suggesting that regional anatomic distortion is involved in the existence of external structures surrounding the LA.

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.

Efficacy of Left Atrial Voltage-Based Catheter Ablation of Persistent Atrial Fibrillation.

BACKGROUND: Low-voltage zones (LVZs) represent fibrotic tissue and are substrates for atrial fibrillation (AF). We hypothesized that LVZ-based substrate modification along with pulmonary vein isolation (PVI) would improve outcomes in persistent AF (PeAF) patients with LVZs, whereas PVI alone would work in patients without LVZs. METHODS AND RESULTS: Voltage mapping of the left atrium (LA) was performed during sinus rhythm in 101 PeAF patients in whom LVZ was defined as an area with bipolar electrograms <0.5 mV. Thirty-nine patients had LVZs and underwent ablation of the entire LVZ area after PVI (LVZabl group). In the remaining 62 patients without LVZs, PVI alone was performed with no further substrate modifications (PVI group). An additional group of 16 consecutive PeAF patients with LVZ did not undergo any substrate modification after PVI and were used as a comparison group (LVZnon-abl group) despite having similar size of LVZs to that in the LVZabl group. After a single session, 28 (72%) patients in the LVZabl group had no recurrence, whereas 49 (79%) patients in the PVI group had no recurrence during 18 ± 7 months of follow-up (log-rank, P = 0.400). In the LVZnon-abl group, only 6 patients (38%) had no recurrence during 32 ± 7 months of follow-up, even after a mean number of sessions of 1.8 (log-rank, P < 0.001, compared with the LVZabl group). CONCLUSIONS: Additional LVZ-based substrate modification after PVI improved the outcome in PeAF patients with LVZs, whereas PVI alone worked in patients without LVZs, even in those with PeAF.

Spatial Relation Between Left Atrial Anatomical Contact Areas and Circular Activation in Persistent Atrial Fibrillation.

INTRODUCTION: Atrial low-voltage zones (LVZs) may be related to maintenance of atrial fibrillation (AF). The influence of left atrial (LA) contact areas (CoAs) on reentrant or rotor-like sources maintaining AF has not been investigated. METHODS AND RESULTS: Forty patients with persistent AF (PsAF) were analyzed. Three representative CoA regions in the LA (ascending aorta: anterior wall; descending aorta: left inferior pulmonary vein; and vertebrae: posterior wall) were visualized by enhanced CT. Using circular catheters, the LVZs (<0.5 mV) were assessed after restoration of SR, and local activation mapping and frequency domain analyses were performed after induction of AF. Circular activation during AF was visually defined as sites with ≥2 rotations by serial electrograms encompassing >80% of the mean AF cycle length. A pivot was defined as the core of the localized circular activation. Anterior (39/40 patients, 98%), left pulmonary vein antrum (27/40, 68%), and posterior (19/40, 48%) CoAs were identified, and 80% (68/85) of those sites were overlapped by or close (<3 mm) to LVZs. Thirty-six (90%) patients demonstrated circular activation (3.1±1.7 sites/patients) along with significantly higher organized dominant frequencies (6.3 ± 0.5 Hz, regularity-index: 0.26 [0.23-0.41]) within the LA, and the average electrogram amplitude of those pivots was 0.30 mV (0.18-0.52). Of those sites, 55% (66/120) were located at or close to CoA regions. Catheter ablation including of LVZs neighboring CoAs terminated AF in 9 (23%) patients. CONCLUSIONS: External anatomical structures contacting the LA may be related to unique conduction properties in diseased myocardium necessary for PsAF maintenance.

The influence of the external structures in atrial fibrillation patients: Relationship to focal low voltage areas in the left atrium.

INTRODUCTION: Left atrial (LA) low voltage areas (LVAs) are suggested as an important factor for maintaining atrial fibrillation (AF). The relationship between focal LVAs and anatomical contact is still unclear. METHODS: Thirty paroxysmal AF (PAF) and 30 persistent AF (PsAF) patients underwent high density voltage mapping during sinus rhythm before any radiofrequency applications were performed. The relationship between the LVA (<0.5mV) and contact area (CoA) demonstrated by enhanced CT and the distance to near external structures were investigated. RESULTS: The anterior region, posterior wall and left pulmonary vein (LPV) antrum were the three most frequent LVA sites that corresponded to CoA sites, and LVAs mostly overlapped with CoAs (PAF 47/61: 77%, PsAF 63/74: 85%). In the PAF group, patients with posterior-LVAs had a shorter distance to the vertebrae than those without (2.8 ± 1.1 vs. 4.4 ± 1.9 mm; P=0.0086). The distance to the vertebrae was the only predictive factor of the existence of a posterior-LVA and the cut-off value was ≤2.9 mm (P<0.0001). Similarly, an LPV-LVA also had the same results (2.0 ± 0.5 vs. 2.7 ± 0.8mm, P=0.0127) and the cut-off value was ≤2.6mm (P=0.0391). In contrast, the PsAF patients had no difference in the distance when compared to the existence of an LVA. CONCLUSIONS: Anatomical CoAs demonstrated a spatial relationship to the LVAs in AF patients. In PAF patients, the distance to near external structures in the posterior region was a predictive factor for the existence of an LVA and may have had some influence on maintaining AF, while in PsAF patients no relationship was suggested.

Impact of left atrial appendage ridge ablation on the complex fractionated electrograms in persistent atrial fibrillation.

BACKGROUND: The left atrial appendage (LAA) is a possible key contributor to the maintenance of persistent atrial fibrillation (PsAF). The effect of LAA ostial ablation on global left atrial higher-frequency sources remains unclear. METHODS: Complex fractionated electrograms (CFEs) and dominant frequency (DF) maps acquired with a NavX system in 58 PsAF patients were enrolled and examined before and after LAA posterior ridge ablation, which followed a stepwise linear ablation. RESULTS: High-density left atrial mapping identified continuous CFE sites in 50 % and high-DFs (≥ 8 Hz) in 53 % of patients at the LAA posterior ridge. In 44 patients in whom AF persisted despite pulmonary vein isolation (PVI) and linear ablation, LAA ablation significantly increased the mean CFE cycle length from 98 ± 29 to 108 ± 30 ms (P<0.0001) and decreased DF from 6.1 ± 0.8 to 5.9 ± 0.8 Hz (P<0.005) within the coronary sinus (CS). A multivariate analysis showed single-procedure failures could be predicted by the left atrial volume index and absence of continuous CFEs at the LAA posterior ridge region. The percent decrease in the global left atrial DF after LAA posterior ridge ablation was significantly lower in the patients with than in those without an enlarged left atrium (LA) (>90 mL/m(2)) (median 0 vs 4.8 %; P<0.01) and significantly lower in the patients with than in those without the absence of continuous CFEs in the LAA posterior ridge region (median 0.6 vs 4.8 %; P<0.05). CONCLUSION: These findings suggested that an approach incorporating an LAA posterior ridge ablation was effective in modifying higher-frequency sources in the global LA in PsAF patients, but a lesser effect was documented in patients with electroanatomical remodeling of the LA.

Influence of left atrium anatomical contact area in persistent atrial fibrillation-relationship between low-voltage area and fractionated electrogram.

BACKGROUND: Atrial low-voltage areas are suggested to be related to maintenance of atrial fibrillation (AF). The influence of the left atrium (LA) contact area (CoA) has not been investigated. METHODS AND RESULTS: Twenty-two persistent AF patients underwent high-density mapping during AF and sinus rhythm (SR). Three representative CoA regions in the LA (ascending aorta: anterior wall; descending aorta: left inferior pulmonary vein [LIPV]; and vertebrae: posterior wall) were identified. Electrogram analysis of both high dominant frequency (high-DF; >8 Hz) and complex fractionated atrial electrogram (con-CFAE; <50 ms) regions during SR was done. The anatomical relationship between CoA and both the very low-voltage areas (vLVA; <0.2 mV) and high-frequency sources was determined. Forty-seven vLVA (194.4 cm(2)) and 60 CoA (337.0 cm(2)) were documented, and 32 vLVA directly overlapped CoA. The vLVA were preferentially found in the anterior (45%) and posterior (13%) walls of the LA, and in the LIPV (13%), and corresponded to CoA sites. The mean voltage during SR at high-DF sites was significantly lower than that at con-CFAE sites (0.62 vs.1.54 mV; P<0.0001). Seventy-two percent of high-DF sites overlapped CoA, while 54% of con-CFAE did. Furthermore, 44% of high-DF surface area directly overlapped CoA, while only 19% of con-CFAE did. CONCLUSIONS: Very low-voltage regions had a strong association with CoA. Sites with CoA had a higher incidence of fractionated electrograms both during SR and AF.

Epicardial adipose tissue-based defragmentation approach to persistent atrial fibrillation: its impact on complex fractionated electrograms and ablation outcome.

BACKGROUND: Increased epicardial adipose tissue (EAT) volume is associated with atrial fibrillation (AF). However, the efficacy of EAT-based left atrial (LA) ablation for persistent AF (PsAF) is unclear. OBJECTIVE: The purpose of this study was to assess whether EAT-based LA ablation is effective for PsAF. METHODS: In 60 PsAF patients (group I), 3-dimensional reconstructed computed tomography images depicting EAT were merged with NavX-based dominant-frequency (DF) and complex fractionated electrogram (CFE) maps obtained during AF. Pulmonary vein antrum isolation (PVAI) was followed by map-guided EAT-based ablation. Results were compared to those in a historical control group (group II, case-matched patients who underwent generalized stepwise ablation including linear plus CFE-targeted ablation). RESULTS: In 70% (n = 42) of group I patients, the LA-EAT was located at the pulmonary vein antra; anterior and inferior surfaces, roof, septum, and mitral annulus; and left atrial appendage. EAT was at or near (<3 mm) 71% (390/550) of high-DF (> -8 Hz) sites. In 41 patients with persistent AF despite EAT-targeted ablation, CFE burden decreased significantly (from 96% to 13%, P < .0001), and DF decreased within the coronary sinus (6.9 ± 0.7 Hz vs 5.9 ± 0.7 Hz, P < .0001). Radiofrequency energy duration was significantly less in group I than in group II (25 ± 6 minutes vs 31 ± 12 minutes, P < .05). During 16-month follow-up, freedom from AF on antiarrhythmic drugs was 78% vs 60% (P < .05). CONCLUSION: PVAI plus EAT-based ablation efficiently eliminates high-frequency sources and yields relatively high success. EAT-based LA ablation is a simple, clinically feasible PsAF ablation strategy.

Spatial relationship between high-dominant-frequency sites and the linear ablation line in persistent atrial fibrillation: its impact on complex fractionated electrograms.

AIMS: Complex fractionated electrograms (CFEs) and high-dominant-frequency (DF) sites theoretically represent abnormal substrates and targets for atrial fibrillation (AF) ablation. The relationship between the high-DF sites in the left atrium (LA) and commonly used linear ablation line to the distribution of the CFEs in patients with persistent AF is unknown. METHODS AND RESULTS: This study enrolled 62 persistent AF patients who underwent construction of LA CFE and DF maps (>350 points/map). Circumferential pulmonary vein isolation and linear ablation including that at the septum, roof, mitral-annulus, and ridge of the appendage were performed. Multipolar catheter mapping identified sites with high DFs (≥ 8 Hz) in all patients (9.8 ± 4.6/patient). In 47 patients in whom AF persisted despite ablation, there was a significant reduction in the continuous CFE (<50 ms) burden after the linear ablation (62 vs.11%; P < 0.0001), with a decrease in both the DF within the coronary sinus (6.9 ± 0.9 vs. 5.9 ± 0.8 Hz; P < 0.0001) and CFE surface area (42.8 ± 18.8 vs. 12.6 ± 10.5 cm(2); P < 0.0001). Comparing the high-DF sites with the ablated lesions, 64% of the high-DF sites (324 of 507) were on or adjacent to the ablation lines. Residual CFEs were observed in the infero-posterior regions in 83% of the patients. Almost half of the high-DF sites away from the linear ablation line were identified in the inferior (34%) and posterior (14%) LA regions. CONCLUSION: Linear ablation resulted in the localization of the continuous CFE regions and reduced the global LA DF in patients with persistent AF. This may be related to the proximity relationship between the linear ablation lines and high-DF sites except for in the infero-posterior regions.

Characterization of myocardial scars: electrophysiological imaging correlates in a porcine infarct model.

BACKGROUND: Definition of myocardial scars as identified by electroanatomic mapping is integral to catheter ablation of ventricular tachycardia (VT). Myocardial imaging can also identify scars prior to ablation. However, the relationship between imaging and voltage mapping is not well characterized. OBJECTIVE: The purpose of this study was to verify the anatomic location and heterogeneity of scars as obtained by electroanatomic mapping with contrast-enhanced MRI (CeMRI) and histopathology, and to characterize the distribution of late potentials in a chronic porcine infarct model. METHODS: In vivo 3-dimensional cardiac CeMRI was performed in 5 infarcted porcine hearts. High-density electroanatomic mapping was used to generate epicardial and endocardial voltage maps. Scar surface area and position on CeMRI were then correlated with voltage maps. Locations of late potentials were subsequently identified. These were classified according to their duration and fractionation. All hearts underwent histopathological examination after mapping. RESULTS: The total dense scar surface area and location on CeMRI correlated to the total epicardial and endocardial surface scar on electroanatomic maps. Electroanatomic mapping (average of 1,532 ± 480 points per infarcted heart) showed that fractionated late potentials were more common in dense scars (<0.50 mV) as compared with border zone regions (0.51 to 1.5 mV), and were more commonly observed on the epicardium. CONCLUSION: In vivo, CeMRI can identify areas of transmural and nontransmural dense scars. Fractionated late diastolic potentials are more common on the epicardium than the endocardium in dense scar. These findings have implications for catheter ablation of VT and for targeting the delivery of future therapies to scarred regions.

Accuracy of combined endocardial and epicardial electroanatomic mapping of a reperfused porcine infarct model: a comparison of electrofield and magnetic systems with histopathologic correlation.

BACKGROUND: Contact mapping of the ventricle with NAVX has not been validated. OBJECTIVE: This study sought to compare the accuracy of infarct mapping between NAVX and CARTO using a histopathologic gold standard. METHODS: A closed-chest porcine infarction model was created by circumflex artery occlusion. After 4 to 12 weeks, 7 subjects underwent high-density endocardial and epicardial mapping using CARTO (Biosense Webster, Diamond Bar, California) and NAVX (St. Jude Medical, St. Paul, Minnesota) mapping systems. After mapping, animals were euthanized and histopathologic examination was used to quantify areas of scar at depths of 1 to 4 mm. RESULTS: Using a single-point acquisition approach with CARTO and a multipoint acquisition approach with the NAVX, endocardial and epicardial maps created using CARTO consisted of 360 ± 121 points performed in 54 ± 23 minutes/361 ± 90 points in 41 ± 13 minutes compared with 697 ± 132 points in 35 ± 8 minutes/1,303 ± 207 points in 30 ± 11 minutes using NAVX. At a 2-mm depth from the endocardial and epicardial surface, the mean scar area quantified by histopathology was 9.5 ± 8.7 cm(2) and 6.2 ± 4.8 cm(2), respectively. Correlation between histopathology and electroanatomic maps was excellent (r = 0.88, CARTO and 0.92, NAVX). Correlation between scar area determined by CARTO and NAVX was good (r = 0.88, P <.0001). CONCLUSION: Balloon occlusion-reperfusion of the circumflex artery creates a localized patchy infarction in the inferolateral wall. Multipolar mapping achieves higher density in a shorter period of time and increases the detection of late potentials. A strong correlation between CARTO and NAVX exists, and both systems demonstrate good correlation with histopathologic quantification of scar.

Distribution of late potentials within infarct scars assessed by ultra high-density mapping.

BACKGROUND: Late potential (LP) electrograms represent areas of slow conduction and are often sites critical to reentrant tachycardia circuits. The distribution of LPs within infarct scar is not known. OBJECTIVE: The purpose of this study was to delineate infarct heterogeneity using ultra high-density mapping and to determine the location of LPs with respect to scar architecture. METHODS: Detailed endocardial (n = 21) and epicardial (n = 8) ultra high-density mapping was performed to delineate the substrate for ventricular tachycardia (VT) in 21 patients with ischemic cardiomyopathy. LP was defined as a low-voltage electrogram (< 1.5 mV) with distinct onset after the QRS. Very late potentials (vLPs) were classified as LPs with onset > 100 ms after the QRS. RESULTS: A mean of 787 ± 391 and 810 ± 375 points in the LV endocardium and epicardium were sampled. Multipolar mapping identified heterogeneous islets (HIs) with relatively preserved electrogram amplitudes (≥ 0.51 mv) within dense scar (8.5 ± 4.9/4.5 ± 2.6 HIs per endocardium/epicardium) in all patients. In maps on which putative VT isthmuses were identified (25/29), 57% of vLP were recorded in or adjacent to HI. An LP-targeted ablation strategy combined with pace mapping achieved acute success in all patients (complete success in 52% and partial success in 48%). After 15 ± 7 months, 65% of patients remained free of VT episodes. CONCLUSION: Ultra high-density mapping with a multipolar catheter facilitates the delineation of heterogeneous scar architecture at higher resolution. Electrograms within and adjacent to HIs have a higher incidence of vLP, and these sites are frequently critical to reentry. These findings have important implications for substrate-based ablation strategies.