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Introduction: Over the past years, mapping and ablation techniques for the treatment of ventricular tachycardia (VT) have evolved rapidly. High Density (HD) substrate mapping is now routine and pre‐procedural imaging is increasingly used. The additional value of these techniques for long‐term VT‐free survival is not clear. Methods: We compared baseline and procedural characteristics, procedural success, safety and outcome of mapping and ablation of ventricular tachycardia in patients with ischemic heart disease between two groups. (1) Low Density (LD) group: VT mapping and ablation with a 4 mm single tip catheter (2) HD group: HD substrate mapping with the Pentaray (Biosense Webster, USA) or HD Grid (Abbott, USA) catheter and ablation with a 4 mm single tip catheter. Results: VT ablation was performed in 133 patients (71 patients in LD group and 62 patients in HD group). The median follow‐up was 5.0 years in LD group and 2.0 years in HD group. One‐, two‐, and five‐year VT recurrence rates were 47%, 56%, and 65% in the LD group versus 39%, 50%, and 55% in the HD group (log‐rank test for VT recurrence p =.70). One‐, two‐, and five‐year ICD shock recurrence rates were 14%, 18%, and 24% in the LD group versus 8%, 15%, and 19% in the HD group (log‐rank test for ICD‐shock p =.79). All‐cause mortality, cardiac (non‐arrhythmic), and arrhythmic death, were similar in both groups. Severe procedural complications (tamponade, stroke, or procedural death) occurred in four patients (5%, 1 vascular, 3 tamponade) in the LD group versus two patients (3%, both tamponade) in the HD group (NS). In univariate and multivariable analysis, only a higher LVEF was significantly associated with VT‐free survival. HD mapping was not significantly associated with VT‐free survival. Anterior infarct location and age were significantly associated with ICD recurrent shock in both univariate and multivariable analyses. Conclusions: In patients with ischemic cardiomyopathy, a HD substrate mapping, and ablation strategy did not lead to higher VT‐free survival and shock‐free survival compared to a single tip mapping and ablation strategy. In this study, only LVF is an independent predictor for VT recurrence. Anterior infarct location and age predict recurrent ICD shocks. [ABSTRACT FROM AUTHOR]

Introduction: The assessment of the ventricular myocardial substrate critically depends on the size of mapping electrodes, their orientation with respect to wavefront propagation, and interelectrode distance. We conducted a dual‐center study to evaluate the impact of microelectrode mapping in patients undergoing catheter ablation (CA) of ventricular tachycardia (VT). Methods: We included 21 consecutive patients (median age, 68 [12], 95% male) with structural heart disease undergoing CA for electrical storm (n = 14) or recurrent VT (n = 7) using the QDOT Micro catheter and a multipolar catheter (PentaRay, n = 9). The associations of peak‐to‐peak maximum standard bipolar (BVc) and minibipolar (PentaRay, BVp) with microbipolar (BVμMax) voltages were respectively tested in sinus rhythm with mixed effect models. Furthermore, we compared the features of standard bipolar (BE) and microbipolar (μBE) electrograms in sinus rhythm at sites of termination with radiofrequency energy. Results: BVμMax was moderately associated with both BVc (β =.85, p <.01) and BVp (β =.56, p <.01). BVμMax was 0.98 (95% CI: 0.93−1.04, p <.01) mV larger than corresponding BVc, and 0.27 (95% CI: 0.16−0.37, p <.01) mV larger than matching BVp in sinus rhythm, with higher percentage differences in low voltage regions, leading to smaller endocardial dense scar (2.3 [2.7] vs. 12.1 [17] cm2, p <.01) and border zone (3.2 [7.4] vs. 4.8 [20.1] cm2, p =.03) regions in microbipolar maps compared to standard bipolar maps. Late potentials areas were nonsignificantly greater in microelectrode maps, compared to standard electrode maps. At sites of VT termination (n = 14), μBE were of higher amplitude (0.9 [0.8] vs. 0.4 [0.2] mV, p <.01), longer duration (117 [66] vs. 74 [38] ms, p <.01), and with greater number of peaks (4 [2] vs. 2 [1], p <.01) in sinus rhythm compared to BE. Conclusion: microelectrode mapping is more sensitive than standard bipolar mapping in the identification of viable myocytes in SR, and may facilitate recognition of targets for CA. [ABSTRACT FROM AUTHOR]

The characterization of benthic habitats is essential for aquatic ecosystem science and management, but is frequently limited by waterbody visibility and depth. Recreation‐grade side‐scan sonar systems are increasingly used to aid scientific inquiries in aquatic environments due to their relative low‐cost, ease of operation, low‐weight, and ease of mounting on a variety of vessels. However, existing procedures and software for post‐processing these data are either limited, closed source, or fail on data from new sonar models, limiting the development of reproducible workflows. Here, we present PING‐Mapper, an open‐source and freely available side‐scan sonar post‐processing toolset for processing and mapping sonar recordings from popular Humminbird instruments. The modular software automatically: (a) decodes sonar recordings from any Humminbird system, (b) exports ping attributes from every sonar channel, (c) uses sonar sensor depth for water column removal, and (d) exports sonogram tiles and georectified mosaics. Sonar channels are processed in parallel for quick decoding and metadata extraction. Major processing wokflows, including georectification and image export, are optimized to scale with computing resources. The software has been extensively tested using data from several rivers of varying character and distribution of depths, but could also be used in estuarine and lacustrine environments. Usage of PING‐Mapper is illustrated in three case studies focused on mapping large woody debris, bathymetric mapping, and visual interpretation and mapping of substrates for selected reaches of the Pearl and Pascagoula river systems in Mississippi. Plain Language Summary: Side‐scan sonar instruments provide a way to survey and visualize the bottom of rivers, lakes, or oceans. Since the early 2000s, companies catering predominantly to anglers have manufactured recreation‐grade side‐scan sonar systems to aid fishermen in locating fish and identifying potential hazards. Scientists seeking to understand and manage aquatic habitats used these systems to create grayscale images of water bottoms because they are inexpensive, easy to operate, and require minimal mounting equipment on the boat. Software has been created by companies to process these data, but the underlying processing workflow and computer code are not publicly available, making it difficult to reproduce and compare results across studies. Other publicly available approaches and software are either outdated, not maintained, or not free. That is why we made PING‐Mapper, a freely available software developed in an increasingly popular programming language called Python. We designed the software to work on any computer to export the data sets quickly and efficiently. The scientific use of exported data sets is demonstrated with three case studies focused on locating and mapping targets (specifically large trees and branches), creating depth maps, and visually discerning the distributions of common substrates, such as sand and cobble. Key Points: We developed an open‐source software for exporting benthic data sets and georeferenced imagery from Humminbird side‐scan sonar systemsSoftware provides an automated and reproducible approach to processing sonar data with minimal interaction from the userThree case studies are presented to highlight use cases of processed benthic data sets [ABSTRACT FROM AUTHOR]

Introduction: An important substrate for atrial fibrillation (AF) is fibrotic atrial myopathy. Identifying low voltage, myopathic regions during AF using traditional bipolar voltage mapping is limited by the directional dependency of wave propagation. Our objective was to evaluate directionally independent unipolar voltage mapping, but with far‐field cancellation, to identify low‐voltage regions during AF. Methods: In 12 patients undergoing pulmonary vein isolation for AF, high‐resolution voltage mapping was performed in the left atrium during sinus rhythm and AF using a roving 20‐pole circular catheter. Bipolar electrograms (EGMs) (Bi) < 0.5 mV in sinus rhythm identified low‐voltage regions. During AF, bipolar voltage and unipolar voltage maps were created, the latter with (uni‐res) and without (uni‐orig) far‐field cancellation using a novel, validated least‐squares algorithm. Results: Uni‐res voltage was ~25% lower than uni‐orig for both low voltage and normal atrial regions. Far‐field EGM had a dominant frequency (DF) of 4.5–6.0 Hz, and its removal resulted in a lower DF for uni‐orig compared with uni‐res (5.1 ± 1.5 vs. 4.8 ± 1.5 Hz; p <.001). Compared with Bi, uni‐res had a significantly greater area under the receiver operator curve (0.80 vs. 0.77; p <.05), specificity (86% vs. 76%; p <.001), and positive predictive value (43% vs. 30%; p <.001) for detecting low‐voltage during AF. Similar improvements in specificity and positive predictive value were evident for uni‐res versus uni‐orig. Conclusion: Far‐field EGM can be reliably removed from uni‐orig using our novel, least‐squares algorithm. Compared with Bi and uni‐orig, uni‐res is more accurate in detecting low‐voltage regions during AF. This approach may improve substrate mapping and ablation during AF, and merits further study. [ABSTRACT FROM AUTHOR]

Introduction: Stand‐alone substrate ablation has become a standard ventricular tachycardia (VT) ablation strategy. We sought to evaluate the influence of baseline VT inducibility and activation mapping on ablation outcomes in patients with structural heart disease (SHD) undergoing VT ablation. Methods: Single center, observational and retrospective study including consecutive patients with SHD and documented VT undergoing ablation. Baseline VT induction was attempted before ablation in all patients and VT activation mapping performed when possible. Ablation was guided by activation mapping for mappable VTs plus substrate ablation for all patients. Ablation outcomes and complications were evaluated. Results: One hundred and sixty patients were included and were classified in three groups according to baseline VT inducibility:group 1 (non inducible, n = 18), group 2 (1 VT morphology induced, n = 53), and group 3 (>1 VT morphology induced, n = 89). VT activation mapping was possible in 35%. After a median follow‐up of 38.5 months, baseline inducibility of greater than 1 VT morphology was associated with a significant incidence of VT recurrence (42% for group 3 vs. 15.1% for group 2% and 5.6% for group 1, Log‐rank p <.0001) and activation mapping with a lower rate of VT recurrence (24% vs. 36.3%, Log‐rank p =.035). Baseline inducibility of greater than 1 VT morphology (hazards ratio [HR]: 12.05, 95% confidence interval [CI]: 1.60–90.79, p =.016) was an independent predictor of VT recurrence while left ventricular ejection fraction less than 30% (HR: 1.93, 95% CI: 1.13–3.25, p =.014) and advanced heart failure (HR: 4.69, 95% CI: 2.75–8.01, p <.0001) were predictors of mortality or heart transplantation. Complications occurred in 11.2% (5.6% hemodynamic decompensation). Conclusion: Baseline VT inducibility and activation mapping may add significant prognostic information during VT ablation procedures. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Substrate vs. Activation/Entrainment Guided VT Ablation Introduction Substrate-based ablation for scar-related ventricular tachycardia (VT) has gained prominence: however, there is limited data comparing it to ablation guided predominantly by activation and entrainment mapping of inducible and hemodynamically tolerated VTs. We compared the acute procedural efficacy and outcomes of predominantly substrate-based ablation versus ablation guided predominantly by activation and entrainment mapping. Methods and Results Database searches through April 2016 identified 6 eligible studies (enrolling 403 patients, with 1 randomized study) comparing the 2 strategies. The relative risk of VT recurrence at follow-up was assessed as the primary outcome using a random-effects meta-analysis. Secondary endpoints of acute success (based on noninducibility of VT), procedural complications, and mortality were assessed using weighted mean difference with the random effects model. At a median follow-up of 18 months, the relative risk (RR) of VT recurrence was not significantly different with substrate-based versus activation/entrainment guided VT ablation (0.72, 95% confidence interval [CI] 0.44-1.18), P = 0.2). Acute success (RR 1.02, 95% CI 0.95-1.1, P = 0.6), procedural complications (RR 0.8, 95% CI 0.35-1.82, P = 0.5) cardiovascular mortality and total mortality did not differ significantly (RR 0.83, 95% CI 0.38-1.79, P = 0.6 and RR 0.76, 95% CI 0.36-1.59, P = 0.5, respectively). Conclusions This meta-analysis demonstrates similar acute procedural efficacy, and complications, VT recurrence and mortality rates when comparing a predominantly substrate-based ablation strategy to a strategy guided predominantly by activation and entrainment mapping of inducible and hemodynamically tolerated VTs. [ABSTRACT FROM AUTHOR]

Zika virus ( ZIKV), isolated from macaques in Uganda in 1947, was not considered to be a dangerous human pathogen. However, this view has recently changed as ZIKV infections are now associated with serious pathological disorders including microcephaly and Guillain-Barré syndrome. Similar to other viruses in the Flaviviridae family, ZIKV expresses the serine protease NS3 which is responsible for viral protein processing and replication. Herein, we report the expression of an active NS3pro domain fused with the NS2B cofactor ( NS2 BLNNS3pro) in a prokaryotic expression system and profile its specificity for synthesized FRET-type substrate libraries. Our findings pave way for screening potential intracellular substrates of NS3 and for developing specific inhibitors of this ZIKV protease. [ABSTRACT FROM AUTHOR]

Low Voltage-Based Ablation for 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. [ABSTRACT FROM AUTHOR]

Voltage-Guided Ablation for Persistent Afib Background Fibrosis as a substrate for atrial fibrillation (AF) has been shown in numerous preclinical models. Voltage mapping enables in vivo assessment of scar in the left atrium (LA), which can be targeted with catheter ablation. Objective We hypothesized that using the presence or absence of low voltage to guide ablation beyond pulmonary vein antral isolation (PVAI) will improve atrial arrhythmia (AF/AT)-free survival in persistent AF. Methods and Results Single-center retrospective analysis of 2 AF ablation strategies: (1) standard ablation (SA) versus (2) voltage-guided ablation (VGA). PVAI was performed in both groups. With SA, additional lesions beyond PVAI were performed at the discretion of the operator. With VGA, additional lesions to isolate the LA posterior wall were performed if voltage mapping of this region in sinus rhythm showed scar (LA voltage < 0.5 mV). AF-/AT-free endpoint was defined as no sustained AF/AT seen off antiarrhythmic medications after a 2-month postablation blanking period. Seventy-six patients underwent SA and 65 underwent VGA. Patients were well matched for comorbidities, LVEF, and left atrial size. Posterior wall ablation was performed in 57% of patient with SA compared to 42% with VGA. VGA ablation increased 1-year AF-/AT-free survival in patients when compared to SA (80% vs. 57%; P = 0.005). In a multivariate analysis, VGA was the only independent predictor of AF-/AT-free survival (hazard ratio of 0.30; P = 0.002). Conclusions The presence of LA posterior wall scar may be an important ablation target in persistent AF. A prospective randomized trial is needed to confirm these data. [ABSTRACT FROM AUTHOR]

Mapping of Scar-Related VT Background Substrate-based VT ablation is mostly based on maps acquired with ablation catheters. We hypothesized that multipolar mapping catheters are more effective for identification of scar and local abnormal ventricular activity (LAVA). Methods and results Phase1: In a sheep infarction model (2 months postinfarction), substrate mapping and LAVA tagging (CARTO®3) was performed, using a Navistar (NAV) versus a PentaRay (PR) catheter (Biosense Webster). Phase2: Consecutive VT ablation patients from a single center underwent NAV versus PR mapping. Point pairs were defined as a PR and a NAV point located within a 3D-distance of ≤3 mm. Agreement was defined as both points in a pair being manually tagged as normal or LAVA. Four sheep (4 years, 50 ± 4.8 kg) and 9 patients were included (53 ± 14 years, 8 male, 6 ischemic cardiomyopathy). Mapping density was higher within the scar with PR versus NAV (3.2 vs. 0.7 points/cm2, P = 0.001) with larger bipolar scar area (68 ± 55 cm2 vs. 58 ± 48 cm2, P = 0.001). In total, 818 point pairs were analyzed. Using PR, far-field voltages were smaller (PR vs. NAV; bipolar: 1.43 ± 1.84 mV vs. 1.64 ± 2.04 mV, P = 0.001; unipolar; 4.28 ± 3.02 mV vs. 4.59 ± 3.67 mV, P < 0.001). More LAVA were also detected with PR (PR vs. NAV; 126 ± 113 vs. 36 ± 29, P = 0.001). When agreement on LAVA was reached (overall: 72%; both LAVA, 40%; both normal, 82%) higher LAVA voltages were recorded on PR (0.48 ± 0.33 mV vs. 0.31 ± 0.21 mV, P = 0.0001). Conclusion Multipolar mapping catheters with small electrodes provide more accurate and higher density maps, with a higher sensitivity to near-field signals. Agreement between PR and NAV is low. [ABSTRACT FROM AUTHOR]

The author discusses the reliability of substrate ablation in treating atrial fibrillation. Topics discussed include the key parts of the cardiovascular system targeted by ablation including pulmonary vein potential and pulmonary vein tachycardia, the evaluated ablation method using an irrigated tip ablation catheter, and the potential of targeting low voltage areas in the atrium of the heart in boosting treatment efficiency of substrate ablation.

ABSTRACT This paper summarizes experiments conducted at the Outdoor Stream Lab to gain insight on the relationships between a channel's spectral characteristics and the river attributes of interest to scientists and managers. Improved understanding of these connections would advance the application of remote sensing to fluvial systems. Motivated by this objective, we examined the following: (i) interactions among local hydraulics, water surface roughness and surface reflectance; and (ii) the influence of periphyton development and streambed disturbance on bottom reflectance. These experiments could thus lead to novel methods for inferring flow velocity and substrate type, respectively, from passive optical image data. Our initial results indicate the following: (i) water surface reflectance can compromise spectrally based depth retrieval by reducing the range of useful wavelengths and weakening correlations between band ratios and depth, implying that removing the surface-reflected component of the total radiance could facilitate bathymetric mapping; (ii) water surface roughness was influenced by local hydraulics and was positively correlated with water surface reflectance, suggesting that observations of surface reflectance could be used to infer flow velocities; (iii) substrate spectral characteristics were influenced by the degree of periphyton development, implying that algal biomass might be estimated from remotely sensed data; and (iv) similarly, bottom reflectance differed significantly for intact versus disturbed substrates, suggesting that areas of streambed disturbance might be identified via remote sensing. Future work will focus on further elucidating connections between surface reflectance, water surface texture and flow velocity, and developing quantitative relationships between bottom reflectance, periphyton abundance and the degree of streambed disturbance. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Background: We investigated the efficacy and safety of strict voltage-based substrate mapping and radiofrequency catheter ablation (SV-substrate-map ablation) in patients with electrical storm. Methods and Results: SV-substrate-map ablation was performed in 15 patients suffering from multiple appropriate shocks (6.0 ± 3.8/day) from implantable cardioverter defibrillators (ICDs). Strict voltage criteria were defined as: non-arrhythmogenic areas, >0.6mV; low voltage areas, >0.1 to ≤0.6 mV; and scar, ≤0.1 mV. Using an electroanatomic mapping system, catheter ablation was performed at every possible arrhythmogenic region inside the low voltage areas. Further, we presented a review of the literature and investigated the published data on substrate-mapping guided ablation for electrical storm. After repeat endocardial ablation procedures in 4 patients and an epicardial approach in one, the targeted ventricular tachycardias (VTs) were successfully ablated, and the electrical storms were completely controlled in all. During a mean follow-up period of 801 ± 409 days, only one VT followed by an appropriate ICD shock was observed. No potential complications occurred during the procedure or follow-up. Our results were comparable or better than that of previous substrate-mapping guided ablation studies. Conclusion: SV-substrate-mapping ablation may be effective and safe for resolving serious clinical situations and prolonging the longevity of ICD devices in patients with electrical storms. [Copyright &y& Elsevier]

Introduction: Animal studies show that atrial fibrillation (AF) may emanate from sites of high rate and regularity, with fibrillatory conduction to adjacent areas. We used simultaneous mapping to find evidence for potential drivers in human AF defined as sites with higher rate and regularity than surrounding tissue. Materials and Methods: In 24 patients (age 61 ± 10 years; 12 persistent), we recorded AF simultaneously from 32 left atrial bipolar basket electrodes in addition to pulmonary veins (PV), coronary sinus, and right atrial electrodes. We measured AF cycle length (CL) by Fourier transform and electrogram regularity at each electrode, referenced to patient-specific atrial anatomy. Results: We analyzed 10,298 electrode-periods. Evidence for potential AF drivers was found in 11 patients (five persistent). In persistent AF, these sites lay at the coronary sinus and left atrial roof but not PVs, while in paroxysmal AF six of nine sites lay at PVs (P < 0.05). During ablation, a subset of patients experienced AF CL prolongation or termination with a focal lesion; in each case this lesion mapped to potential driver sites on blinded analysis. Conversely, sequential mapping failed to reveal these sites, possibly due to fluctuations in dominant frequency at driver locations in the context of migratory AF. Conclusions: Simultaneous multisite recordings in human AF reveal evidence for drivers that lie near PVs in paroxysmal but not persistent AF, and were sites where ablation slowed or terminated AF in a subset of patients. The future work should determine if real-time ablation of AF-maintaining regions defined in this fashion eliminates AF. [ABSTRACT FROM AUTHOR]

Objective: To study fluctuations in intracardiac atrial fibrillation (AF) cycle length (CL). Background: Sites of short AF CL may be good ablation targets, and cycle lengthening predicts ablation success. However, the optimum method for measuring AF CL, and its stability, are unclear. We hypothesized that autocorrelation better estimates AF CL than spectral dominant frequency (DF), which is susceptible to double counting, using monophasic action potentials (MAPs) to separate atrial activation from artifact. Methods: In 28 patients with paroxysmal or persistent AF, we analyzed 49 AF epochs using MAPs at the high (HRA) and low (LRA) right atrium. We estimated AF CL over 2 seconds, 10 seconds, and 2 minutes using spectral DF and autocorrelation in MAPs and filtered bipoles. Results: In the HRA, manually measured CL was 167 ± 25 ms. Spectral DF poorly estimated AF CL in bipolar signals (R = 0.31; P = NS), due to double counting, but accurately estimated MAP CL (R = 0.73, P < 0.001). Autocorrelation estimated MAP (R = 0.92; P < 0.001) and bipolar (R = 0.83; P < 0.001) CL, with lower errors than spectral DF (P < 0.0001). Over time, changes in DF consistently preceded reciprocal changes in organization (P < 0.001). Finally, excluding inaccurate spectra, DF and AF organization differed between HRA and LRA over 2 seconds, but correlated over 10 seconds and 2 minutes (P < 0.05). Conclusions: AF CL is better estimated by autocorrelation than spectral DF, particularly for bipoles, and stable when measured for >10 seconds. Notably, changes in AF CL preceded reciprocal changes in organization, yet changes in organization did not precede changes in AF CL. These results may help to interpret AF CL fluctuations. [ABSTRACT FROM AUTHOR]

Substrate Mapping in a Porcine Model of Chronic MI. Introduction: Substrate-based catheter ablation of postmyocardial infarction (post-MI) ventricular tachycardia necessitates electroanatomic definition of the scarred endocardium. We sought to determine whether electrogram criteria during sinus rhythm could identify the location and extent of the myocardial scar by electroanatomic mapping. Methods and Results: A porcine model of healed MI was generated by injecting agarose microspheres into the mid left anterior descending coronary artery. At least 4 weeks post-MI, the animals (n = 24) underwent detailed left ventricular endocardial electroanatomic mapping using a 4-mm-tip catheter (BioSense-Webster, Inc.). Based upon mapping data in normal animals, infarcted tissue was defined as bipolar electrogram amplitude <1.5 mV and electrogram duration ≥50 msec. Radiofrequency ablation lesions (2–10 per animal) were placed to tag the endocardial borders of the electroanatomic mapping-defined scar. The area of the scar defined by abnormal voltage amplitude was 25.9 ± 15.4 cm[sup 2] (range 6.9–60.5). This area correlated well with that defined as scar by the electrogram duration criteria (26.4 ± 16 cm[sup 2]) . Of those points remote from the infarct with falsely low voltage amplitude resulting from presumed poor catheter-tissue contact, 94% were correctly identified as normal when using the electrogram duration criteria. Late potentials were observed predominantly along the borders of the infarcted myocardium. The radiofrequency lesions placed to tag the scar borders were located along the scar periphery during gross pathologic examination. Conclusion: During normal sinus rhythm, both bipolar electrogram voltage amplitude and electrogram duration criteria are able to help differentiate normal from scarred myocardial tissue. Using these criteria, a detailed reconstruction of the endocardial scar can be rendered by electroanatomic mapping of the heart.(J Cardiovasc Electrophysiol, Vol. 14, pp. 524-529, May 2003). [ABSTRACT FROM AUTHOR]

Myocardial Scar Characterization with CT Scar delineation with late gadolinium-enhanced MRI can direct VT substrate mapping and ablation, but imaging is poor and relatively contraindicated in the majority of patients with ICDs. We present a case of scar definition using late iodine-enhanced multidetector CT in a patient with ischemic cardiomyopathy and multiple ICD shocks for VT. CT images were acquired using a novel intracoronary contrast delivery protocol which provided high-resolution subendocardial scar visualization. The segmented scar images were subsequently imported into an electroanatomic mapping platform to guide successful VT ablation. [ABSTRACT FROM AUTHOR]

The authors reflect on the use of ventricular tachycardia substrate mapping in catheter ablation for scar-related ventricular tachycardia (VT). In the article the authors discuss research which has investigated ablation and mapping and offer their opinions on several points raised in the article "Integration of Merged Delayed-Enhanced Magnetic Resonance Imaging and Multi-Detector Computed Tomography for the Guidance of Ventricular Tachycardia Ablation:A Pilot Study" by H. Cochet et al.

A positive endomyocardial biopsy (EMB) is a major diagnostic criterion for arrhythmogenic right ventricular cardiomyopathy (ARVC). Nevertheless, its sensitivity is low due to the focal nature of the disease. Moreover, myocardial samples are usually taken from the uncommonly involved interventricular septum to minimize the risk of perforation. In this report, we describe a novel bioptical approach for ARVC diagnosis guided by the identification of right ventricle (RV) affected regions by means of electroanatomical voltage mapping. [ABSTRACT FROM AUTHOR]

Background Atrial tachycardia ( AT ) is common in patients with adult congenital heart disease and is challenging to map and ablate. We used ultra-high-density mapping to characterize the AT mechanism and investigate whether substrate characteristics are related to ablation outcomes. Methods and Results A total of 50 AT s were mapped with ultra-high-density mapping in 23 procedures. Patients were followed up for up to 12 months. Procedures were classified to group A if there was 1 single AT induced (n=12) and group B if there were ≥2 AT s induced (n=11 procedures). AT mechanism per procedure was macro re-entry (n=10) and localized re-entry (n=2) in group A and multiple focal (n=6) or multiple macro re-entry (n=5) in group B. Procedure duration, low voltage area (0.05-0.5 mV), and low voltage area indexed for volume were higher in group B (159 [147-180] versus 412 [352-420] minutes, P<0.001, 22.6 [12.2-29.8] versus 54.2 [51.1-61.6] cm 2 , P=0.014 and 0.17 [0.12-0.21] versus 0.26 [0.23-0.27] cm 2 /mL, P=0.024 accordingly). Dense scar (<0.05 mV) and atrial volume were similar between groups. Acute success and freedom from arrhythmia recurrence were worse in group B (100% versus 77% P=0.009 and 11.3, CI 9.8-12.7 versus 4.9, CI 2.2-7.6 months, log rank P=0.004). Indexed low voltage area ≥0.24 cm 2 /mL could predict recurrence with 100% sensitivity and 77% specificity (area under the curve 0.923, P=0.007). Conclusions Larger low voltage area but not dense scar is associated with the induction of multiple focal or re-entry AT s, which are subsequently associated with longer procedure duration and worse acute and midterm clinical outcomes.