Multidetector Computed Tomography Assessment of Anatomical Ventricular Tachycardia Isthmuses in Repaired Tetralogy of Fallot.

BACKGROUND: Tetralogy of Fallot (TOF) is associated with risk for sustained monomorphic ventricular tachycardia (VT). Preemptive electrophysiology study before transcatheter pulmonary valve placement is increasing, but the value of MDCT for anatomical VT isthmus assessment is unknown. OBJECTIVES: The purpose of this study was to determine the impact of multidetector computed tomography (MDCT) in the evaluation of sustained monomorphic VT for repaired TOF. METHODS: Consecutive pre-transcatheter pulmonary valve MDCT studies were identified, and anatomical isthmus dimensions were measured. For a subset of patients with preemptive electrophysiology study, MDCT features were compared with electroanatomical maps. RESULTS: A total of 61 repaired TOFs with MDCT were identified (mean 35 ± 14 years, 58% men) with MDCT electroanatomical map pairs in 35 (57%). Calcification corresponding to patch material was present in 46 (75%) and was used to measure anatomical VT isthmuses. MDCT wall thickness correlated positively with number of ablation lesions and varied with functional isthmus properties (blocked isthmus 2.6 mm [Q1, Q3: 2.1, 4.0 mm], slow conduction 4.8 mm [Q1, Q3: 3.3, 6.0 mm], and normal conduction 5.6 mm [Q1, Q3: 3.9, 8.3 mm]; P < 0.001). A large conal branch was present in 6 (10%) and a major coronary anomaly was discovered in 3 (5%). Median ablation lesion distance was closer to the right vs the left coronary artery (10 mm vs 15 mm; P = 0.01) with lesion-to-coronary distance <5 mm in 3 patients. CONCLUSIONS: MDCT identifies anatomical structures relevant to catheter ablation for repaired TOF. Wall thickness at commonly targeted anatomical VT isthmuses is associated with functional isthmus properties and increased thermal energy delivery.

Detailed Assessment of Low-Voltage Zones Localization by Cardiac MRI in Patients With Implantable Devices.

OBJECTIVES: The purpose of this study was to assess the performance and limitations of low-voltage zones (LVZ) localization by optimized late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR) scar imaging in patients with cardiac implantable electronic devices (CIEDs). BACKGROUND: Scar evaluation by LGE-CMR can assist ventricular tachycardia (VT) ablation, but challenges with electroanatomical maps coregistration and presence of imaging artefacts from CIED limit accuracy. METHODS: A total of 10 patients underwent VT ablation and preprocedural LGE-CMR using wideband imaging. Scar was segmented from CMR pixel signal intensity maps using commercial software (ADAS-VT, Galgo Medical) with bespoke tools and compared with detailed electroanatomical maps (CARTO). Coregistration of EP and imaging-derived scar was performed using the aorta as a fiducial marker, and the impact of coregistration was determined by assessing intraobserver/interobserver variability and using computer simulations. Spatial smoothing was applied to assess correlation at different spatial resolutions and to reduce noise. RESULTS: Pixel signal intensity maps localized low-voltage zones (V <1.5 mV) with area under the receiver-operating characteristic curve: 0.82 (interquartile range [IQR]: 0.76-0.83), sensitivity 74% (IQR: 71%-77%), and specificity 78% (IQR: 73%-83%) and correlated with bipolar voltage (r = -0.57 [IQR: -0.68 to -0.42]) across patients. In simulations, small random shifts and rotations worsened LVZ localization in at least some cases. The use of the full aortic geometry ensured high reproducibility of LVZ localization (r >0.86 for area under the receiver-operating characteristic curve). Spatial smoothing improved localization of LVZ. Results for LVZ with V <0.5 mV were similar. CONCLUSIONS: In patients with CIEDs, novel wideband CMR sequences and personalized coregistration strategies can localize LVZ with good accuracy and may assist VT ablation procedures.

Assessment of an ECG-Based System for Localizing Ventricular Arrhythmias in Patients With Structural Heart Disease.

Background We have previously developed an intraprocedural automatic arrhythmia-origin localization (AAOL) system to identify idiopathic ventricular arrhythmia origins in real time using a 3-lead ECG. The objective was to assess the localization accuracy of ventricular tachycardia (VT) exit and premature ventricular contraction (PVC) origin sites in patients with structural heart disease using the AAOL system. Methods and Results In retrospective and prospective case series studies, a total of 42 patients who underwent VT/PVC ablation in the setting of structural heart disease were recruited at 2 different centers. The AAOL system combines 120-ms QRS integrals of 3 leads (III, V2, V6) with pace mapping to predict VT exit/PVC origin site and projects that site onto the patient-specific electroanatomic mapping surface. VT exit/PVC origin sites were clinically identified by activation mapping and/or pace mapping. The localization error of the VT exit/PVC origin site was assessed by the distance between the clinically identified site and the estimated site. In the retrospective study of 19 patients with structural heart disease, the AAOL system achieved a mean localization accuracy of 6.5±2.6 mm for 25 induced VTs. In the prospective study with 23 patients, mean localization accuracy was 5.9±2.6 mm for 26 VT exit and PVC origin sites. There was no difference in mean localization error in epicardial sites compared with endocardial sites using the AAOL system (6.0 versus 5.8 mm, P=0.895). Conclusions The AAOL system achieved accurate localization of VT exit/PVC origin sites in patients with structural heart disease; its performance is superior to current systems, and thus, it promises to have potential clinical utility.

Time-efficient three-dimensional transmural scar assessment provides relevant substrate characterization for ventricular tachycardia features and long-term recurrences in ischemic cardiomyopathy.

Delayed gadolinium-enhanced cardiac magnetic resonance (LGE-CMR) imaging requires novel and time-efficient approaches to characterize the myocardial substrate associated with ventricular arrhythmia in patients with ischemic cardiomyopathy. Using a translational approach in pigs and patients with established myocardial infarction, we tested and validated a novel 3D methodology to assess ventricular scar using custom transmural criteria and a semiautomatic approach to obtain transmural scar maps in ventricular models reconstructed from both 3D-acquired and 3D-upsampled-2D-acquired LGE-CMR images. The results showed that 3D-upsampled models from 2D LGE-CMR images provided a time-efficient alternative to 3D-acquired sequences to assess the myocardial substrate associated with ischemic cardiomyopathy. Scar assessment from 2D-LGE-CMR sequences using 3D-upsampled models was superior to conventional 2D assessment to identify scar sizes associated with the cycle length of spontaneous ventricular tachycardia episodes and long-term ventricular tachycardia recurrences after catheter ablation. This novel methodology may represent an efficient approach in clinical practice after manual or automatic segmentation of myocardial borders in a small number of conventional 2D LGE-CMR slices and automatic scar detection.

Assessment of ventricular tachyarrhythmia in patients with hypertrophic cardiomyopathy with machine learning-based texture analysis of late gadolinium enhancement cardiac MRI.

OBJECTIVE: To assess the diagnostic value of machine learning-based texture feature analysis of late gadolinium enhancement images on cardiac magnetic resonance imaging (MRI) for assessing the presence of ventricular tachyarrhythmia (VT) in patients with hypertrophic cardiomyopathy. MATERIALS AND METHODS: This retrospective study included 64 patients with hypertrophic cardiomyopathy who underwent cardiac MRI and 24-hour Holter monitoring within 1 year before cardiac MRI. There were 42 men and 22 women with a mean age of 48.13±13.06 (SD) years (range: 20-70 years). Quantitative textural features were extracted via manually placed regions of interest in areas with high and intermediate signal intensity on late gadolinium-chelate enhanced images. Feature selection and dimension reduction were performed. The diagnostic performances of machine learning classifiers including support vector machines, Naive Bayes, k-nearest-neighbors, and random forest for predicting the presence of VT were assessed using the results of 24-hour Holter monitoring as the reference test. All machine learning models were assessed with and without the application of the synthetic minority over-sampling technique (SMOTE). RESULTS: Of the 64 patients with hypertrophic cardiomyopathy, 21/64 (32.8%) had VT. Of eight machine learning models investigated, k-nearest-neighbors with SMOTE exhibited the best diagnostic accuracy for the presence or absence of VT. k-nearest-neighbors with SMOTE correctly identified 40/42 (95.2%) VT-positive patients and 40/43 (93.0%) VT-negative patients, yielding 95.2% sensitivity (95% CI: 82.5%-99.1%), 93.0% specificity (95% CI: 79.8%-98.1%) and 94.1% accuracy (95% CI: 88.8%-98%). CONCLUSION: Machine learning-based texture analysis of late gadolinium-chelate enhancement-positive areas is a promising tool for the classification of hypertrophic cardiomyopathy patients with and without VT.

Evaluation of a real-time magnetic resonance imaging-guided electrophysiology system for structural and electrophysiological ventricular tachycardia substrate assessment.

AIMS: Potential advantages of real-time magnetic resonance imaging (MRI)-guided electrophysiology (MR-EP) include contemporaneous three-dimensional substrate assessment at the time of intervention, improved procedural guidance, and ablation lesion assessment. We evaluated a novel real-time MR-EP system to perform endocardial voltage mapping and assessment of delayed conduction in a porcine ischaemia-reperfusion model. METHODS AND RESULTS: Sites of low voltage and slow conduction identified using the system were registered and compared to regions of late gadolinium enhancement (LGE) on MRI. The Sorensen-Dice similarity coefficient (DSC) between LGE scar maps and voltage maps was computed on a nodal basis. A total of 445 electrograms were recorded in sinus rhythm (range: 30-186) using the MR-EP system including 138 electrograms from LGE regions. Pacing captured at 103 sites; 47 (45.6%) sites had a stimulus-to-QRS (S-QRS) delay of ≥40 ms. Using conventional (0.5-1.5 mV) bipolar voltage thresholds, the sensitivity and specificity of voltage mapping using the MR-EP system to identify MR-derived LGE was 57% and 96%, respectively. Voltage mapping had a better predictive ability in detecting LGE compared to S-QRS measurements using this system (area under curve: 0.907 vs. 0.840). Using an electrical threshold of 1.5 mV to define abnormal myocardium, the total DSC, scar DSC, and normal myocardium DSC between voltage maps and LGE scar maps was 79.0 ± 6.0%, 35.0 ± 10.1%, and 90.4 ± 8.6%, respectively. CONCLUSION: Low-voltage zones and regions of delayed conduction determined using a real-time MR-EP system are moderately associated with LGE areas identified on MRI.

Assessment of Remote Myocardium Heterogeneity in Patients with Ventricular Tachycardia Using Texture Analysis of Late Iodine Enhancement (LIE) Cardiac Computed Tomography (cCT) Images.

PURPOSE: Diffuse remodeling of myocardial extra-cellular matrix is largely responsible for left ventricle (LV) dysfunction and arrhythmias. Our hypothesis is that the texture analysis of late iodine enhancement (LIE) cardiac computed tomography (cCT) images may improve characterization of the diffuse extra-cellular matrix changes. Our aim was to extract volumetric extracellular volume (ECV) and LIE texture features of non-scarred (remote) myocardium from cCT of patients with recurrent ventricular tachycardia (rVT), and to compare these radiomic features with LV-function, LV-remodeling, and underlying cardiac disease. PROCEDURES: Forty-eight patients suffering from rVT were prospectively enrolled: 5/48 with idiopathic VT (IVT), 23/48 with post-ischemic dilated cardiomyopathy (ICM), 9/48 with idiopathic dilated cardiomyopathy (IDCM), and 11/48 with scars from a previous healed myocarditis (MYO). All patients underwent echocardiography to assess LV systolic and diastolic function and cCT with pre-contrast, angiographic, and LIE scan to obtain end-diastolic volume (EDV), ECV, and first-order texture parameters of Hounsfield Unit (HU) of remote myocardium in LIE [energy, entropy, HU-mean, HU-median, standard deviation (SD), and mean absolute deviation (MAD)]. RESULTS: Energy, HU mean, and HU median by cCT texture analysis correlated with ECV (rho = 0.5650, rho = 0.5741, rho = 0.5068; p < 0.0005). cCT-derived ECV, HU-mean, HU-median, SD, and MAD correlated directly to EDV by cCT and inversely to ejection fraction by echocardiography (p < 0.05). SD and MAD correlated with diastolic function by echocardiography (rho = 0.3837, p = 0.0071; rho = 0.3330, p = 0.0208). MYO and IVT patients were characterized by significantly lower values of SD and MAD when compared with ICM and IDCM patients, independently of LV-volume systolic and diastolic function. CONCLUSIONS: Texture analysis of LIE may expand cCT capability of myocardial characterization. Myocardial heterogeneity (SD and MAD) was associated with LV dilatation, systolic and diastolic function, and is able to potentially identify the different patterns of structural remodeling characterizing patients with rVT of different etiology.

Acute Cardiac MRI Assessment of Radiofrequency Ablation Lesions for Pediatric Ventricular Arrhythmia: Feasibility and Clinical Correlation.

BACKGROUND: Arrhythmia ablation with current techniques is not universally successful. Inadequate ablation lesion formation may be responsible for some arrhythmia recurrences. Periprocedural visualization of ablation lesions may identify inadequate lesions and gaps to guide further ablation and reduce risk of arrhythmia recurrence. METHODS: This feasibility study assessed acute postprocedure ablation lesions by MRI, and correlated these findings with clinical outcomes. Ten pediatric patients who underwent ventricular tachycardia ablation were transferred immediately postablation to a 1.5T MRI scanner and late gadolinium enhancement (LGE) imaging was performed to characterize ablation lesions. Immediate and mid-term arrhythmia recurrences were assessed. RESULTS: Patient characteristics include median age 14 years (1-18 years), median weight 52 kg (11-81 kg), normal cardiac anatomy (n = 6), d-transposition of great arteries post arterial switch repair (n = 2), anomalous coronary artery origin post repair (n = 1), and cardiac rhabdomyoma (n = 1). All patients underwent radiofrequency catheter ablation of ventricular arrhythmia with acute procedural success. LGE was identified at the reported ablation site in 9/10 patients, all arrhythmia-free at median 7 months follow-up. LGE was not visible in 1 patient who had recurrence of frequent premature ventricular contractions within 2 hours, confirmed on Holter at 1 and 21 months post procedure. CONCLUSIONS: Ventricular ablation lesion visibility by MRI in the acute post procedure setting is feasible. Lesions identifiable with MRI may correlate with clinical outcomes. Acute MRI identification of gaps or inadequate lesions may provide the unique temporal opportunity for additional ablation therapy to decrease arrhythmia recurrence.

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.

Assessment of ventricular tachycardia scar substrate by intracardiac echocardiography.

BACKGROUND: Intracardiac echocardiography (ICE) is increasingly used to guide complex ablation procedures. This study aimed to assess the scar substrate of ventricular tachycardia (VT) by ICE in patients undergoing VT ablation. METHODS: In 22 patients undergoing VT ablation (10 ischemic, 12 nonischemic), the Biosense CARTOSOUND module (Biosense Webster, Diamond Bar, CA, USA) was used for three-dimensional reconstruction of the ventricles. The characteristics and appearance with ICE imaging of voltage-defined scar zones (bipolar voltage <0.5 mV), border zones (0.5-1.5 mV), and normal myocardium (>1.5 mV) on electroanatomic maps were evaluated. The standard image analysis software Image J (National Institutes of Health, Bethesda, MD, USA) was used to analyze signal intensity (mean pixel signal intensity unit [SIU]) and heterogeneity (standard deviation of signal intensity in analyzed area) on ICE images. RESULTS: A total of 83 myocardial areas were analyzed from two-dimensional ICE images (15 scars, 31 border zones, and 37 normal). Voltage-defined scar zones had increased signal intensities compared to border zones (149 SIU vs 104 SIU, P < 0.0001) and normal myocardium (88 SIU, P < 0.0001). Border zones were more likely to have heterogeneous densities compared to normal myocardium (standard deviation of signal intensity 20 SIU vs 12 SIU, P < 0.0001). In receiver-operator characteristic analyses, signal intensity ≥ 137 SIU differentiated scar from nonscar zones (area under curve 0.91, P < 0.0001). Software-based color enhancement of areas with signal intensity ≥ 137 SIU allowed identification of the VT substrate in all 15 patients with voltage-defined scar zones. CONCLUSIONS: ICE provides important information about the VT anatomical substrate and may have potential to identify areas of scarred myocardium.

Risk assessment of ventricular arrhythmias in patients with nonischemic dilated cardiomyopathy by strain echocardiography.

BACKGROUND: Indications for prophylactic implantable cardioverter-defibrillator implantation in patients with nonischemic dilated cardiomyopathy (DCM) are based on left ventricular (LV) ejection fraction (LVEF), although LVEF has limited ability to predict arrhythmias. It has recently been shown that strain echocardiography can predict ventricular arrhythmias in patients after myocardial infarction. The aim of this study was to evaluate whether strain echocardiography may help in the risk stratification of ventricular arrhythmias in patients with DCM. METHODS: Ninety-four patients with nonischemic DCM were prospectively included. By speckle-tracking strain echocardiography, global longitudinal strain was calculated as the average of peak longitudinal strain from a 16-segment LV model. The time interval from electrocardiographic peak R to peak negative strain was assessed in each LV segment. Mechanical dispersion was defined as the standard deviation of time to peak negative strain from 16 LV segments. RESULTS: After a median of 22 months of follow-up (range, 1-46 months), 12 patients (13%) had experienced arrhythmic events, defined as sustained ventricular tachycardia or cardiac arrest. LVEF and global longitudinal strain were reduced in patients with DCM with arrhythmic events compared with those without (28 ± 10% vs 38 ± 13%, P = .01, and -6.4 ± 3.3% vs -12.3 ± 5.2%, P < .001, respectively). Global longitudinal strain showed greater area under the curve than LVEF to identify arrhythmic events in receiver operating characteristic curve analyses (P = .05). Patients with arrhythmic events had increased mechanical dispersion (98 ± 43 vs 56 ± 18 ms, P < .001). Mechanical dispersion predicted arrhythmias independently of LVEF (hazard ratio, 1.28; 95% confidence interval, 1.11-1.49; P = .001). CONCLUSIONS: Global longitudinal strain is a promising marker of arrhythmias. Mechanical dispersion predicted arrhythmic events in patients with DCM independently of LVEF. Strain echocardiography may help in the risk stratification of patients with DCM not fulfilling current implantable cardioverter-defibrillator indications.

An atypical assessment of Ebstein's anomaly in an 86-year-old man.

We present the echocardiographic analysis of an 86-year-old man affected by Ebstein's anomaly. In the natural history of this congenital disease only 5% of patients survive beyond the fifth decade. The patient presented severe right atrial dilatation and right heart failure, and he was referred to our institution for supraventricular tachycardia.

[Assessment of the functional state of the right ventricle by radionuclide tomoventriculography].

The aim of this work was to evaluate the potential of radionuclide tomoventriculography (RTVG) for the study of the functional state of right ventricle (RV) in patients with thromboembolism of branches of the pulmonary artery (TEPA) or ventricular arrhythmias. A total of 96 patients were admitted for examination to the clinics of Research Institute of Cardiology, Siberian Division of Russian Academy of Medical Sciences in 2006-2008. They were divided into 3 groups. Group 1 (n = 40) included patients of mean age 62 +/- 11 years with non-massive TEPA, group 2 (n = 15) patients with coronary heart disease NYHA class I-II (50 +/- 9 years), group 3 (n = 4) children and adolescents 13.2 +/- 3.7 years with ventricular extrasystole and/or monomorphic ventricular tachycardia. All patients were examined by ECG-synchronized RTVG. The study showed that this method can be used to efficaciously determine volume characteristics of right ventricle, ejection fraction, relationship between fast and slow filling phases, and intreventricular dyssynchronism. The functional ability of the right side of the heart in patients with minor lesions in the pulmonary vasculature should be regarded as a sign of acute thromboembolism and marked systole-diastolic dysfunction of right ventricle (under similar conditions) as a manifestation of chronic post-thromboembolic hypertension. The number of areas of asynchronous myocardial contractions and the degree of intraventricular dyssynchronism detected by RTVG positively correlate with the degree of contractile dysfunction of right ventricle. Scintiographic signs of intraventricular dyssynchronism suggest predominance of contractile heterogeneity of right ventricle over physiological one.

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.

Real-time three-dimensional echocardiographic assessment of left ventricular systolic dyssynchrony in healthy children.

BACKGROUND: The use of resynchronization therapy for the treatment of left ventricular (LV) systolic dysfunction in children has been expanding. Because QRS duration is not a reliable indicator of the presence or severity of dyssynchrony in every case, additional methods of quantitation of dyssynchrony are needed. The purpose of this study was threefold: (1) to define normal values for LV real-time quantitative three-dimensional echocardiographic (3DE) dyssynchrony indices (DIs), (2) to analyze the feasibility and observer variability of 3DE DIs in a wide range of children, and (3) to determine the effects of age, heart rate, body surface area, and LV end-diastolic volume on these parameters. METHODS: The two specific parameters studied were the standard deviation of the time to minimum systolic volume for the number of segments analyzed and the time difference between the earliest and latest contracting segments. Both parameters were expressed as a percentage of the cardiac cycle length. RESULTS: In 125 normal children aged 1 day to 19 years, adequate dyssynchrony studies were obtained in 102 (81.8%). The mean LV 3DE DIs expressed as the standard deviation of the time to minimum systolic volume for the number of segments analyzed were 1.16 ± 0.58 for 16 segments, 1.01 ± 0.60 for 12 segments, and 0.93 ± 0.68 for 6 segments. The mean LV 3DE DIs expressed as the time difference between the earliest and latest contracting segments were 3.80 ± 1.57 for 16 segments, 2.99 ± 1.42 for 12 segments, and 2.27 ± 1.35 for 6 segments. There were no effects of age, heart rate, body surface area, or LV end-diastolic volume on 3DE DIs. Intraobserver variability was 5.1%, and interobserver variability was 7.6%. CONCLUSION: Three-dimensional echocardiographic DI analysis is reproducible and feasible in most children. Three-dimensional echocardiographic DIs are not affected by growth-related parameters in children but are lower than previously reported adult values.

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.

[Cardiac sympathetic innervation in patients with ventricular arrhythmias: an assessment by 123I-metaiodobenzylguanidine scintigraphy].

The aim of this study was to determine the state of sympathetic innervation in patients with ventricular arrhythmias (VA) using 123I-metaiodobenzylguanidine 123I -MIBG) scintigraphy. Fifty six patients (26 men and 30 women, mean age 37.4+/-11,6) underwent single-photon emission computed tomography (SPECT) imaging and planner scintigraphy after injection of 123I-MIBG (activity 148 MBq). They form three groups. Thirty patients with idiopathic VA (IVA) were included in group I: 14 patients with ventricular extrasystoles (VE) and 16 - with ventricular tachycardias (VT). Group II was formed by 17 patients (with dilated cardiomyopathy, n=7 and chronic myocarditis, n=10), 6 of them had VE and 11 - VT. The control group III was formed by 9 healthy subjects with structurally normal heart without VA. We analyzed early (30 minutes) and delayed (4 hours) images after 123I-MIBG administration. The global sympathetic activity (SA) was assessed by heart/mediastinum ratio and washout rate. Regional SA was assessed by extent and severity of defect. In group I 25 of 30 patients (83.3%) had regional SA abnormalities significantly different from controls (p<0.001). At the same time global uptake of 123I-MIBG in this group was not affected. In group II regional SA abnormalities were revealed in all patients (100%) and global reduction of 123I-MIBG uptake - in 14 patients (82.4%). Regional and global SA abnormalities in group II were different from controls (p<0.0001) and patients with IVA (p<0.001). There was no difference in SA abnormalities between patients with VE and VT. Our results suggest that patients with different VA have abnormalities of sympathetic innervation, including patients with structurally normal heart.