Noninvasive Assessment of Complexity of Atrial Fibrillation: Correlation With Contact Mapping and Impact of Ablation.

BACKGROUND: It is difficult to noninvasively phenotype atrial fibrillation (AF) in a way that reflects clinical end points such as response to therapy. We set out to map electrical patterns of disorganization and regions of reentrant activity in AF from the body surface using electrocardiographic imaging, calibrated to panoramic intracardiac recordings and referenced to AF termination by ablation. METHODS: Bi-atrial intracardiac electrograms of 47 patients with AF at ablation (30 persistent, 29 male, 63±9 years) were recorded with 64-pole basket catheters and simultaneous 57-lead body surface ECGs. Atrial epicardial electrical activity was reconstructed and organized sites were invasively and noninvasively tracked in 3-dimension using phase singularity. In a subset of 17 patients, sites of AF organization were targeted for ablation. RESULTS: Body surface mapping showed greater AF organization near intracardially detected drivers than elsewhere, both in phase singularity density (2.3±2.1 versus 1.9±1.6; P=0.02) and number of drivers (3.2±2.3 versus 2.7±1.7; P=0.02). Complexity, defined as the number of stable AF reentrant sites, was concordant between noninvasive and invasive methods (r2=0.5; CC=0.71). In the subset receiving targeted ablation, AF complexity showed lower values in those in whom AF terminated than those in whom AF did not terminate (P<0.01). CONCLUSIONS: AF complexity tracked noninvasively correlates well with organized and disorganized regions detected by panoramic intracardiac mapping and correlates with the acute outcome by ablation. This approach may assist in bedside monitoring of therapy or in improving the efficacy of ongoing ablation procedures.

Phase singularity detection through phase map interpolation: Theory, advantages and limitations.

BACKGROUND: During a cardiac arrhythmia, reentrant waves rotate around critical points called phase singularities (PS). PS detection is relevant to the quantitative description of the dynamics and to the identification of potential targets for ablation. Phase interpolation techniques have been proposed to increase the accuracy of PS localization. Our aim is to provide a theoretical basis and a comparative analysis of these methods. METHOD: Different electrode configurations representing mapping systems or catheter multi-electrode arrays were considered: triangular mesh, regular square grid and circular arrays. Linear, spline and inverse squared distance interpolation were used to create a continuous map from discrete measurements of phase. Synthetic phase maps with a PS and background noise were generated. Monte-Carlo simulations were run over millions of realizations to estimate PS locations and calculate the false negative and false positive rates as a function of noise variance. RESULTS: Linear interpolation is shown to be exactly equivalent to the standard discrete approach without interpolation. Spline interpolation had lower false negative rate at the expense of a higher false positive rate in the presence of noise. Inverse squared distance interpolation reduced false positives and was more robust to noise but was more likely to fail to detect a PS. Phase interpolation decreased PS localization error down to 0.17 interelectrode distance. The error was largest when the PS was near an electrode. CONCLUSION: Phase interpolation methods offer additional flexibility to find the adequate trade-off between reducing false positives and false negatives.

Assessment of a conduction-repolarisation metric to predict Arrhythmogenesis in right ventricular disorders.

BACKGROUND: The re-entry vulnerability index (RVI) is a recently proposed activation-repolarization metric designed to quantify tissue susceptibility to re-entry. This study aimed to test feasibility of an RVI-based algorithm to predict the earliest endocardial activation site of ventricular tachycardia (VT) during electrophysiological studies and occurrence of haemodynamically significant ventricular arrhythmias in follow-up. METHODS: Patients with Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) (n = 11), Brugada Syndrome (BrS) (n = 13) and focal RV outflow tract VT (n = 9) underwent programmed stimulation with unipolar electrograms recorded from a non-contact array in the RV. RESULTS: Lowest values of RVI co-localised with VT earliest activation site in ARVC/BrS but not in focal VT. The distance between region of lowest RVI and site of VT earliest site (Dmin) was lower in ARVC/BrS than in focal VT (6.8 ±â€¯6.7 mm vs 26.9 ±â€¯13.3 mm, p = 0.005). ARVC/BrS patients with inducible VT had lower Global-RVI (RVIG) than those who were non-inducible (-54.9 ±â€¯13.0 ms vs -35.9 ±â€¯8.6 ms, p = 0.005) or those with focal VT (-30.6 ±â€¯11.5 ms, p = 0.001). Patients were followed up for 112 ±â€¯19 months. Those with clinical VT events had lower Global-RVI than both ARVC and BrS patients without VT (-54.5 ±â€¯13.5 ms vs -36.2 ±â€¯8.8 ms, p = 0.007) and focal VT patients (-30.6 ±â€¯11.5 ms, p = 0.002). CONCLUSIONS: RVI reliably identifies the earliest RV endocardial activation site of VT in BrS and ARVC but not focal ventricular arrhythmias and predicts the incidence of haemodynamically significant arrhythmias. Therefore, RVI may be of value in predicting VT exit sites and hence targeting of re-entrant arrhythmias.

Use of impedance-based catheter tip-to-tissue contact assessment (electroanatomic coupling index, ECI) in typical right atrial flutter ablation.

PURPOSE: The electrical coupling index (ECI) (Abbott, USA) is a marker of tissue contact and ablation depth developed particularly for atrial fibrillation treatment. We sought to evaluate if these measures can be also a marker of lesion efficacy during cavotricuspid isthmus (CTI) ablation for typical right atrial flutter. METHODS: We assessed the ECI values in patients undergoing typical right atrial flutter point-by-point ablation guided by the Ensite Velocity Contact™ (St. Jude Medical, now Abbott St. Paul, MN, USA) electroanatomic mapping system. ECI values were collected before, during (at the plateau), and after radiofrequency (RF) delivery. The physician was blinded to ECI and judged ablation efficacy according to standard parameters (impedance drop, local potential reduction, and/or split in two separate potentials). Patients were followed up at 3 and 12 months. RESULTS: Fifteen consecutive patients (11 males, mean age 69.2 ± 10.6 years) with a history of typical right atrial flutter were included in this study. A total of 158 RF applications were assessed (mean 10.5 ± 6.6 per patient, range 6-28). The absolute and percentage ECI variations (pre-/post-ablation) were significantly greater when applications were effective (p < 0.001). A 12% drop in the ECI after ablation was identified by the ROC curve as the best cutoff value to discriminate between effective and ineffective ablation (sensitivity 94%, specificity 100%). Acute success was achieved in all patients with no complications and no recurrences during follow-up. CONCLUSION: The ECI appeared a reliable index to guide CTI ablation. A 12% drop of ECI during radiofrequency energy delivery was highly accurate in identifying effective lesion.

Assessment of the equivalent dipole layer source model in the reconstruction of cardiac activation times on the basis of BSPMs produced by an anisotropic model of the heart.

Promising results have been reported in noninvasive estimation of cardiac activation times (AT) using the equivalent dipole layer (EDL) source model in combination with the boundary element method (BEM). However, the assumption of equal anisotropy ratios in the heart that underlies the EDL model does not reflect reality. In the present study, we quantify the errors of the nonlinear AT imaging based on the EDL approximation. Nine different excitation patterns (sinus rhythm and eight ectopic beats) were simulated with the monodomain model. Based on the bidomain theory, the body surface potential maps (BSPMs) were calculated for a realistic finite element volume conductor with an anisotropic heart model. For the forward calculations, three cases of bidomain conductivity tensors in the heart were considered: isotropic, equal, and unequal anisotropy ratios in the intra- and extracellular spaces. In all inverse reconstructions, the EDL model with BEM was employed: AT were estimated by solving the nonlinear optimization problem with the initial guess provided by the fastest route algorithm. Expectedly, the case of unequal anisotropy ratios resulted in larger localization errors for almost all considered activation patterns. For the sinus rhythm, all sites of early activation were correctly estimated with an optimal regularization parameter being used. For the ectopic beats, all but one foci were correctly classified to have either endo- or epicardial origin with an average localization error of 20.4 mm for unequal anisotropy ratio. The obtained results confirm validation studies and suggest that cardiac anisotropy might be neglected in clinical applications of the considered EDL-based inverse procedure.

Assessment of body surface potential mapping in diabetic patients with recognized depression.

OBJECTIVES: Parameters of body surface potential mapping (BSPM) in DM II patients are significantly different comparing with healthy non-diabetic subjects. Hypothesis that these changes are more pronounced in DM II patients with depression was tested in the present study. For this purpose, analysis of the relationship between the Int-QRST (isointegral) maps distribution and the depressive symptoms intensification, as well interrelation between depressive and diabetic symptoms were performed. MATERIAL AND METHODS: BSPM registrations were obtained from the three study groups (aged 37-52 years), namely 40 diabetic patients with clinically documented depression, 30 depressive patient without DM and 90 normal subjects. BSPM recordings were displayed in a form of the Int-QRST maps. Examination with BDI and HbA1c test were also performed in all investigated subjects. RESULTS: Isointegral QRST maps turned out to display abnormal, i.e. non-dipolar distribution. Moreover, extent of Int-QRST maps multipolarity increased in the examined diabetic patients along with DM II duration, BDI scores and HbA1c level. CONCLUSIONS: Non-dipolar distribution of Int-QRST maps, more pronounced in diabetic patients with depression, can be a specific indicator of the increased risk of severe ventricular arrhythmias occurring prior to abnormalities detectable on the standard 12-lead ECG recordings, which is of great importance especially in prevention of life-threatening arrhythmias.

Hibernating substrate of ventricular tachycardia: a three-dimensional metabolic and electro-anatomic assessment.

PURPOSE: Hibernating myocardium (HM) is associated with sudden cardiac death (SCD). Little is known about the electrophysiological properties of HM and the basis of its association with SCD. We aimed to electrophysiologically characterize HM in patients with ventricular tachycardia (VT). METHODS: Endocardial voltage mapping, metabolic 18FDG-positron emission tomography (PET) and perfusion 82Rb, 201Tl, or 99mTc scans were performed in 61 ischemic heart disease patients with VT. Hibernating areas were identified which was followed by three-dimensional PET reconstructions and integration with voltage maps to allow hybrid metabolic-electro-anatomic assessment of the arrhythmogenic substrate. RESULTS: Of 61 patients with ischemic heart disease and refractory VT, 7 were found to have hibernating myocardium (13%). A total of 303 voltage points were obtained within hibernating myocardium (8.2 points per 10 cm2) and displayed abnormal voltage in 48.5 and 78.3% of bipolar and unipolar recordings, respectively, with significant heterogeneity of bipolar (p < 0.0001) and unipolar voltage measurements (p = 0.0004). Hibernating areas in 6 of 7 patients contained all three categories of bipolar voltage-defined scar (<0.5 mV), border zone (0.5-1.5 mV), and normal myocardium (>1.5 mV). The characteristics of local electrograms were also assessed and found abnormal in most recordings (76.6, 10.2% fractionated, 5.3% isolated potentials). Exit sites of clinical VTs were determined in 6 patients, of which 3 were located within hibernating myocardium. CONCLUSIONS: Hibernating myocardium displays abnormal and heterogeneous electrical properties and seems to contribute to the substrate of VT. These observations may underlie the vulnerability to reentry and SCD in patients with hypoperfused yet viable myocardium.

Electrophysiologic Scar Substrate in Relation to VT: Noninvasive High-Resolution Mapping and Risk Assessment with ECGI.

BACKGROUND: Ischemic cardiomyopathy (ICM) can provide the substrate for ventricular tachycardia (VT). OBJECTIVE: To map noninvasively with high resolution the electrophysiologic (EP) scar substrate, identify its relationship to reentry circuits during VT, and stratify VT risk in ICM patients. METHODS: Noninvasive high-resolution epicardial mapping with electrocardiographic imaging (ECGI) was performed in 32 ICM patients (17 with clinical VT, 15 without VT). Abnormal scar EP substrate was determined based on electrogram (EGM) amplitude (as percentage of maximal peak-to-peak voltage over the entire ventricular epicardium; total scar [TS] < 30%; dense scar [DS] < 15%), fractionation, and presence of late potentials (LPs). Scar burden was defined as the ratio of the scar size to the total epicardial surface area. The VT activation pattern was mapped and correlated with the EP substrate to identify components of the reentry circuit. RESULTS: Patients with VT had higher scar burden (TS: 51.0 ± 9.3% vs 36.5 ± 5.4%, P < 0.05; DS: 29.5 ± 7.3% vs 16.8 ± 6.8%, P < 0.05) with lower normalized unipolar EGM voltage (TS: 0.107 ± 0.027 vs 0.153 ± 0.031, P < 0.05; DS: 0.073 ± 0.023 vs 0.098 ± 0.026, P < 0.05), greater prevalence of fractionated EGMs (TS: 44.1 ± 10.6% vs 26.8 ± 6.3%, P < 0.05; DS: 50.8 ± 10.8% vs 30.9 ± 7.0%, P < 0.05), and LPs (TS: 26.8 ± 10.7% vs 15.8 ± 5.3, P < 0.05). VTs were mapped in eight patients; the reentry circuits were closely related to the EP substrate. CONCLUSIONS: ECGI noninvasively identified scar EP substrate that underlies abnormal conduction in ICM patients. It identified regions within the scar that aligned with critical elements of the reentry circuit during VT. ECGI can potentially be used for VT risk stratification in ICM patients.

Estimation of Purkinje trees from electro-anatomical mapping of the left ventricle using minimal cost geodesics.

The electrical activation of the heart is a complex physiological process that is essential for the understanding of several cardiac dysfunctions, such as ventricular tachycardia (VT). Nowadays, patient-specific activation times on ventricular chambers can be estimated from electro-anatomical maps, providing crucial information to clinicians for guiding cardiac radio-frequency ablation treatment. However, some relevant electrical pathways such as those of the Purkinje system are very difficult to interpret from these maps due to sparsity of data and the limited spatial resolution of the system. We present here a novel method to estimate these fast electrical pathways from the local activations maps (LATs) obtained from electro-anatomical maps. The location of Purkinje-myocardial junctions (PMJs) is estimated considering them as critical points of a distance map defined by the activation maps, and then minimal cost geodesic paths are computed on the ventricular surface between the detected junctions. Experiments to validate the proposed method have been carried out in simplified and realistic simulated data, showing good performance on recovering the main characteristics of simulated Purkinje networks (e.g. PMJs). A feasibility study with real cases of fascicular VT was also performed, showing promising results.

Toward microendoscopy-inspired cardiac optogenetics in vivo: technical overview and perspective.

The ability to perform precise, spatially localized actuation and measurements of electrical activity in the heart is crucial in understanding cardiac electrophysiology and devising new therapeutic solutions for control of cardiac arrhythmias. Current cardiac imaging techniques (i.e. optical mapping) employ voltage- or calcium-sensitive fluorescent dyes to visualize the electrical signal propagation through cardiac syncytium in vitro or in situ with very high-spatiotemporal resolution. The extension of optogenetics into the cardiac field, where cardiac tissue is genetically altered to express light-sensitive ion channels allowing electrical activity to be elicited or suppressed in a precise cell-specific way, has opened the possibility for all-optical interrogation of cardiac electrophysiology. In vivo application of cardiac optogenetics faces multiple challenges and necessitates suitable optical systems employing fiber optics to actuate and sense electrical signals. In this technical perspective, we present a compendium of clinically relevant access routes to different parts of the cardiac electrical conduction system based on currently employed catheter imaging systems and determine the quantitative size constraints for endoscopic cardiac optogenetics. We discuss the relevant technical advancements in microendoscopy, cardiac imaging, and optogenetics and outline the strategies for combining them to create a portable, miniaturized fiber-based system for all-optical interrogation of cardiac electrophysiology in vivo.

Cardiac arrythmias: multimodal assessment integrating body surface ECG mapping into cardiac imaging.

PURPOSE: To demonstrate the feasibility of comprehensive assessment of cardiac arrhythmias by combining body surface electrocardiographic (ECG) mapping (BSM) and imaging. MATERIALS AND METHODS: This study was approved by the institutional review board, and all patients gave written informed consent. Twenty-seven patients referred for electrophysiologic procedures in the context of ventricular tachycardia (VT) (n = 9), Wolff-Parkinson-White (WPW) syndrome (n = 2), atrial fibrillation (AF) (n = 13), or scar-related ventricular fibrillation (VF) (n = 3) were examined. Patients underwent BSM and imaging with multidetector computed tomography (CT) (n = 12) and/or delayed enhanced magnetic resonance (MR) imaging (n = 23). BSM was performed by using a 252-electrode vest that enabled the computation of epicardial electrograms from body surface potentials. The epicardial geometry used for BSM was registered to the epicardial geometry segmented from imaging data by using an automatic algorithm. The output was a three-dimensional cardiac model that integrated cardiac anatomy, myocardial substrate, and epicardial activation. RESULTS: Acquisition, segmentation, and registration were feasible in all patients. In VT, this enabled a noninvasive assessment of the arrhythmia mechanism and its location with respect to the myocardial substrate, coronary vessels, and phrenic nerve. In WPW syndrome, this enabled understanding of complex accessory pathways resistant to previous ablation. In AF and VF, this enabled the noninvasive assessment of arrhythmia mechanisms and the analysis of rotor trajectories with respect to the myocardial substrate. In all patients, models were successfully integrated in navigation systems and used to guide mapping and ablation. CONCLUSION: By combining information on anatomy, substrate, and electrical activation, the fusion of BSM and imaging enables comprehensive noninvasive assessment of cardiac arrhythmias, with potential applications for diagnosis, prognosis, and ablation targeting. Online supplemental material is available for this article.

Accuracy assessment of catheter guidance technology in electrophysiology procedures: a comparison of a new 3D-based fluoroscopy navigation system to current electroanatomic mapping systems.

BACKGROUND: With increasing complexity in electrophysiology (EP) procedures, the use of electroanatomic mapping systems (EAMS) as a supplement to fluoroscopy has become common practice. This is the first study that evaluates spatial and point localization accuracy for 2 current EAMS, CARTO3(®) (Biosense Webster, Diamond Bar, CA, USA) and EnSite Velocity(®) (St. Jude Medical Inc., St. Paul, MN, USA), and for a novel overlay guidance (OG) software (Siemens AG, Forchheim, Germany) in a phantom experiment. METHODS AND RESULTS: A C-arm CT scan was performed on an acrylic phantom containing holes and location markers. Spatial accuracy was assessed for each system using distance measurements involving known markers inside the phantom and properly placed catheters. Anatomical maps of the phantom were acquired by each EAMS, whereas the 3D-based OG software superimposed an overlay image of the phantom, segmented from the C-arm CT data set, onto biplane fluoroscopy. Registration processes and landmark measurements quantitatively assessed the spatial accuracy of each technology with respect to the ground truth phantom. Point localization performance was 0.49 ± 0.25 mm in OG, 0.46 ± 0.17 mm in CARTO3(®) and 0.79 ± 0.83 mm in EnSite(®) . The registration offset between virtual visualization and reality was 1.10 ± 0.52 mm in OG, 1.62 ± 0.77 mm in CARTO3(®) and 2.02 ± 1.21 mm in EnSite(®) . The offset to phantom C-arm CT landmark measurements was 0.30 ± 0.26 mm in OG, 0.24 ± 0.21 mm in CARTO3(®) and 1.32 ± 0.98 mm in EnSite(®) . CONCLUSIONS: Each of the evaluated EP guidance systems showed a high level of accuracy; the observed offsets between the virtual 3D visualization and the real phantom were below a clinically relevant threshold of 3 mm.

Real-time assessment of pulmonary vein disconnection during cryoablation of atrial fibrillation: can it be 'achieved' in almost all cases?

AIM: Real-time assessment of pulmonary vein (PV) disconnection is possible using an inner circular mapping catheter during cryoablation of atrial fibrillation (AF). However, it has been recently demonstrated that such continuous monitoring may only be possible in <50% of PVs. We hypothesized that a stepwise mapping approach, including pacing manoeuvres, could optimize monitoring of real-time PV disconnection during ablation. METHODS AND RESULTS: Single-centre, prospective observational study (NCT01843465) including 34 consecutive eligible patients (128 PVs) undergoing a first procedure of cryoballoon ablation of AF using the Artic Front Advance(®) 28 mm catheter and a 20 mm diameter Achieve(®) catheter (AC) in all cases. Monitoring of real-time entrance block was possible, when AC was maintained in the standard position (distal to the tip of the Artic Front Advance(®) catheter) in 47 (36.7%) PVs. In an additional 63 cases (49.2%), such monitoring was possible after moving AC to a more proximal position and using different torqueing movements. Finally, using supplemental systematic pacing manoeuvres to test exit block, real-time assessment of PV disconnection was possible in 15 (11.7%) more PVs. Overall, real-time assessment of PV disconnection was possible in 97.7% of cases, after a mean duration of 48.6 ± 33.0 s. CONCLUSION: Our results suggest that optimal use of the AC, with a systematic stepwise mapping approach, may dramatically improve the real-time monitoring of PV disconnection during AF cryoablation.

Assessment of regularization techniques for electrocardiographic imaging.

A widely used approach to solving the inverse problem in electrocardiography involves computing potentials on the epicardium from measured electrocardiograms (ECGs) on the torso surface. The main challenge of solving this electrocardiographic imaging (ECGI) problem lies in its intrinsic ill-posedness. While many regularization techniques have been developed to control wild oscillations of the solution, the choice of proper regularization methods for obtaining clinically acceptable solutions is still a subject of ongoing research. However there has been little rigorous comparison across methods proposed by different groups. This study systematically compared various regularization techniques for solving the ECGI problem under a unified simulation framework, consisting of both 1) progressively more complex idealized source models (from single dipole to triplet of dipoles), and 2) an electrolytic human torso tank containing a live canine heart, with the cardiac source being modeled by potentials measured on a cylindrical cage placed around the heart. We tested 13 different regularization techniques to solve the inverse problem of recovering epicardial potentials, and found that non-quadratic methods (total variation algorithms) and first-order and second-order Tikhonov regularizations outperformed other methodologies and resulted in similar average reconstruction errors.

Risk assessment of ventricular arrhythmia using new parameters based on high resolution body surface potential mapping.

BACKGROUND: The effective screening of myocardial infarction (MI) patients threatened by ventricular tachycardia (VT) is an important issue in clinical practice, especially in the process of implantable cardioverter-defibrillator (ICD) therapy recommendation. This study proposes new parameters describing depolarization and repolarization inhomogeneity in high resolution body surface potential maps (HR BSPM) to identify MI patients threatened by VT. MATERIAL/METHODS: High resolution ECGs were recorded from 64 surface leads. Time-averaged HR BSPMs were used. Several parameters for arrhythmia risk assessment were calculated in 2 groups of MI patients: those with and without documented VT. Additionally, a control group of healthy subjects was studied. To assess the risk of VT, the following parameters were proposed: correlation coefficient between STT and QRST integral maps (STT_QRST_CORR), departure index of absolute value of STT integral map (STT_DI), and departure index of absolute value of T-wave shape index (TSI_DI). These new parameters were compared to known parameters: QRS width, QT interval, QT dispersion, Tpeak-Tend interval, total cosines between QRS complex and T wave, and non-dipolar content of QRST integral maps. RESULTS: STT_DI, TSI_DI, STT_QRST_CORR, QRS width, and QT interval parameters were statistically significant (p ≤ 0.05) in arrhythmia risk assessment. The highest sensitivity was found for the STT_DI parameter (0.77) and the highest specificity for TSI_DI (0.79). CONCLUSIONS: Arrhythmia risk is demonstrated by both abnormal spatial distribution of the repolarization phase and changed relationship between depolarization and repolarization phases, as well as their prolongation. The proposed new parameters might be applied for risk stratification of cardiac arrhythmia.

Catheter ablation of ventricular tachycardias in patients with ischemic cardiomyopathy: validation of voltage mapping criteria for substrate modification by myocardial viability assessment using FDG PET.

BACKGROUND: Catheter ablation is of growing importance in patients with an ischemic cardiomyopathy and recurrent episodes of ventricular tachyarrhythmias. Most ablation strategies in these patients are based on the detection of areas of scar and border zones to normal myocardium. However, the mapping criteria for identifying these areas have not been validated sufficiently so far. Therefore, we have performed a comparison between electroanatomical bipolar voltage maps obtained during substrate-based VT ablation procedures and [18 F]fluoro-2-deoxyglucose PET studies performed prior to these procedures. METHODS: Seven patients suffering from severe coronary artery disease and repetitive ventricular tachycardias were enrolled in this study. In all patients, there was a history of myocardial infarction and the left ventricular function was severely impaired. A FDG PET was performed at least 1 day prior to the ablation procedure in all patients. Then, a substrate-based VT ablation procedure was performed using the CARTO system (Biosense Webster, Diamond Bar, CA, USA). Finally, the FDG PET images and the bipolar voltage maps were compared in all patients. RESULTS: The ablation procedures could be performed successfully in all patients and 1-5 monomorphic VTs could be eliminated in each patient. There were no major complications. At 1-year follow-up, five out of seven patients (71.4%) remained free from any arrhythmia recurrence. In all patients, there were extensive areas of scar and adjacent low-voltage areas could be identified in the CARTO bipolar voltage maps. In areas commonly defined as "dense scar" (bipolar voltage amplitude <0.5 mV), the mean FDG uptake was 43.1% (SD ±18.2%) indicating predominantly scar tissue. In the so-called low-voltage border zones the mean FDG uptake ranged between 49.5% [(SD ±15.8%); >0.5-1 mV] and 60.1% [(SD ±14.8%); >1-1.5 mV], thereby indicating the presence of predominantly viable myocardium. In areas with a bipolar voltage amplitude >1.5 mV the presence of viable myocardium was confirmed by a mean FDG uptake of approximately 60%. CONCLUSIONS: The results of our study demonstrate that there is a significant amount of viable myocardium in the low-voltage border zones of scars frequently targeted as ablation sites. Therefore, RF current delivery in these areas should be restricted to the minimum assumed to be necessary for successful catheter ablation because extensive RF applications might result in a further deterioration of the left ventricular function. Larger studies are needed to validate our results and to develop more reliable criteria for distinguishing areas of scar from viable myocardium in CARTO bipolar voltage maps.

Noninvasive assessment of the complexity and stationarity of the atrial wavefront patterns during atrial fibrillation.

A novel automated approach to quantitatively evaluate the degree of spatio-temporal organization in the atrial activity (AA) during atrial fibrillation (AF) from surface recordings, obtained from body surface potential maps (BSPM), is presented. AA organization is assessed by measuring the reflection of the spatial complexity and temporal stationarity of the wavefront patterns propagating inside the atria on the surface ECG, by means of principal component analysis (PCA). Complexity and stationarity are quantified through novel parameters describing the structure of the mixing matrices derived by the PCA of the different AA segments across the BSPM recording. A significant inverse correlation between complexity and stationarity is highlighted by this analysis. The discriminatory power of the parameters in identifying different groups in the set of patients under study is also analyzed. The obtained results present analogies with earlier invasive studies in terms of number of significant components necessary to describe 95% of the variance in the AA (four for more organized AF, and eight for more disorganized AF). These findings suggest that automated analysis of AF organization exploiting spatial diversity in surface recordings is indeed possible, potentially leading to an improvement in clinical decision making and AF treatment.

Diagnostic value of body surface potential mapping in assessment of the coronary artery lesion after angina pectoris and without repolarization changes on the electrocardiogram.

BACKGROUND: The body surface potential mapping (BSPM) method is sensitive in detecting minor electrical potential abnormalities, but its diagnostic value is unclear in detection and localization of significant coronary artery lesion (CAL) in patients after angina pectoris and without ischemic electrocardiogram abnormalities at the time of the BSPM record. METHODS AND RESULTS: Characteristic features and quantitative parameters of the isopotential maps during the depolarization were evaluated and compared with the result of coronary angiography in 228 patients (164 males; age, 61.6 +/- 9.5 years). Twenty-three of them had their first angina, but the others had a history of earlier angina, unstable angina, non-ST-elevation infarction. Fifty-nine healthy subjects (32 males; age, 53.3 +/- 12.2 years) served as control. The diagnostic power was high in detection of CAL among patients with previous ischemic events, but it was low in first angina. The accuracy of the CAL localization by multiple regression was different: at 90% specificity level, the sensitivity was near 80% for right/posterior descending CAL and slightly more than 60% for left anterior descending CAL but only 19% for first marginal/first diagonal CAL. CONCLUSIONS: The BSPM changes during the depolarization could well indicate CAL only after previous ischemic events. Sensitivity and specificity of the CAL localization depended on the extension and location of the underlying myocardium damage.

Validation of coronary sinus activation pattern during left atrial appendage pacing for beat-to-beat assessment of mitral isthmus conduction/block.

INTRODUCTION: Mitral isthmus (MI) ablation for treatment of perimitral flutter is often performed during atrial fibrillation (AF) ablation but is technically challenging. Traditional assessment of MI conduction by left atrial activation mapping while pacing from either side of the line is time-consuming, and cannot be performed during ongoing ablation. Analysis of the coronary sinus (CS) activation pattern during left atrial appendage (LAA) pacing has been proposed as a simpler technique for evaluating MI conduction, enabling beat-to-beat assessment of conduction during ablation procedures and prompt identification of conduction block. METHODS: MI conduction was evaluated in 40 patients undergoing MI ablation using both: ((i) endocardial activation mapping and other standard techniques, and (ii) CS activation pattern during LAA pacing (change from distal-to-proximal activation to proximal-to-distal taken to signify the onset of MI block). RESULTS: CS activation sequence was used to assess conduction in 39 of 40 patients (unable to advance CS catheter distally in one case). MI block was achieved in 36 of 39 cases. The mean MI conduction time (LAA to distal CS) was 92.9 +/- 25.9 ms prior to ablation and 178.4 +/- 59.9 ms after MI block was confirmed. The mean step-out in conduction time at point of block was 80.8 +/- 40.6 ms. In all individuals in whom CS activation indicated block, there was concordance with endocardial activation, differential pacing and, where detectable, presence of widely split double potentials. CS lesions were required to achieve block in 24 of 36 (67%) successful cases. Radiofrequency application time and procedure time to achieve MI block were 10.8 +/- 6.0 minutes and 21.1 +/- 15.3 minutes, respectively.

Global electrophysiological and hemodynamic assessment of ventricular pacing employing non-contact mapping.

OBJECTIVE: Right ventricular (RV) pacing has been associated with abnormal cardiac electrical and mechanical dyssynchrony, resulting in impaired global and regional ventricular pump function. This study aimed to characterize the relative effects of pacing site on left ventricular (LV) activation patterns and associated hemodynamic performances. METHODS: Acute pacing was performed in anesthetized swine (n=10) instrumented for RV and LV pressure, noncontact mapping (NCM) of endocardial unipolar electrograms, surface ECG, aortic flow, and sonomicrometry. Bipolar endocardial pacing leads were positioned in the right atrial appendage (RAA), RV apex (RVA), and RV outflow tract (RVOT), while bipolar epicardial leads were positioned on the LV-free wall (LVFW) and LV apex (LVA). RESULTS: LVFW and RVA pacing induced the largest increase in intraventricular electrical dyssynchrony (IVED; 32.2+/-10 ms, 21.7+/-4.1 ms, respectively; both p<0.01), whereas pacing from all sites increased QRS and total endocardial LV activation durations (p<0.01). The largest impairment of LV and RV contractility (dP/dtmax) and relaxation (dP/dtmin) was observed during RVA pacing (p= ns). Synchronous electrical activation patterns were observed on NCM during RVOT and LVA pacing. LVFW pacing was the only site that significantly increased tau values as compared to RAA pacing (approximately 25%), whereas LVA pacing elicited only slight increases (approximately 1%). CONCLUSIONS: In swine with preserved ventricular conduction, in vivo pacing of the RVOT and LVA was associated with preserved, physiologically similar electrical activation sequences and LV function relative to RAA pacing. In contrast, RVA pacing caused widespread electrical dyssynchrony of the LV and prolonged activation durations, thereby impairing associated cardiac performance. Such insights into alternate site cardiac pacing, which employed the combination of high-resolution electrical mapping with real-time hemodynamic assessments, may further increase acute and long-term benefits in patients requiring permanent pacemaker support.