Atrial tachycardias following circumferential pulmonary vein ablation: observations during catheter ablation

Circumferential pulmonary vein ablation performing linear lesions around the ostia of the pulmonary veins has been shown to be effective for the treatment of atrial fibrillation. During the follow-up period, persistent atrial tachycardia may occur as a proarrhythmic complication. Only little information is available about the underlying mechanism. In our study, atrial tachycardia following circumferential pulmonary vein ablation was identified in 13 out of 84 consecutive patients (15.5%), as a transient appearance in four and with recurrences for more than 3 months in nine patients (10.7%). Electrophysiological study and ablation was performed in eight cases, revealing common atrial flutter in two, a focal origin secondary to conduction recovery from the pulmonary vein to the left atrium in two and macro reentrant left atrial flutter in four patients. The electrophysiological characteristics demonstrated by electroanatomic activation mapping (CARTO™) and consecutive ablation therapy with a 100% success rate are described and discussed with regard to the literature.     

T1 Mapping and Extracellular Volume Fraction in Dilated Cardiomyopathy: A Prognosis Study

ObjectivesThe aim of this study is to examine the prognostic value of T1 mapping and the extracellular volume (ECV) fraction in patients with dilated cardiomyopathy (DCM).BackgroundPatients with DCM with functional left ventricular remodeling have poorer prognoses. Noninvasive assessment of myocardial fibrosis using T1 mapping and the ECV fraction may improve risk stratification of patients with DCM; however, this has not yet been systematically evaluated.MethodsA total of 659 consecutive patients with DCM (498 men; 45 ± 15 years) who underwent cardiac magnetic resonance with T1 mapping and late gadolinium enhancement (LGE) imaging with a 1.5-T magnetic resonance scanner were enrolled in this study. Primary endpoints were cardiac-related death and heart transplantation. Secondary endpoints were hospitalization for heart failure, ventricular arrhythmias, and implantable cardioverter-defibrillator or cardiac resynchronization therapy implantation. Survival estimates were calculated by Kaplan-Meier curves with the log-rank test.ResultsDuring a mean follow-up of 66.3 ± 20.9 months, 122 and 205 patients with DCM reached the primary and secondary endpoints, respectively. The presence of LGE had an association with both of the primary and secondary endpoints observed in the patients with DCM (both P < 0.001). The maximum native T1 (HR: 1.04; 95% CI: 1.02-1.09) and maximum ECV fraction (HR: 1.14; 95% CI: 1.08-1.21) had associations with the primary endpoints in the patients with positive LGE (both P < 0.001), whereas the mean native T1 (HR: 1.13; 95% CI: 1.10-1.36) and mean ECV fraction (HR: 1.32; 95% CI: 1.12-1.53) had the best associations in the patients with negative LGE (all P < 0.001).ConclusionsT1 mapping and the ECV fraction had prognostic value in patients with DCM and were particularly important in patients with DCM without LGE. Using a combination of T1 mapping, ECV fraction, and LGE provided optimal risk stratification for patients with DCM.     

Reproducibility of Computerized Measurements of QT Interval from Multiple Leads at Rest and During Exercise

Background: Accurate measurement of the QT interval is important for diagnosing long QT syndrome (LQTS), and in research on determinants of ventricular repolarization time. We tested automatic analysis of QT intervals from multiple ECG leads on chest. Methods: Eleven healthy volunteers and 10 genotyped LQTS patients were tested at rest and during exercise with a bicycle ergometer twice 1–31 months apart. Electrocardiograms were recorded with the body surface potential mapping system, and 12 precordial channels were selected for analysis. Averaged QT peak and QT end intervals were determined with an automated algorithm, and the difference QT end minus QT peak (Tp‐e) was calculated. Repeatability was assessed by coefficient of variation (CV) between measurements. Results: Within one test at rest the QT end intervals were highly repeatable with CV 0.6%. In repeated tests CV was 4.4% for QT end interval and 3.5% when the QT interval was corrected for heart rate. In exercise test at specified heart rates, mean CV was 3.0% for QT end and 2.9% for QT peak interval. The CV of Tp‐e interval was 10.2% at rest, and 9.3% in exercise test. Reproducibility was comparable between healthy subjects and LQTS patients. Conclusions: The BSPM system with automated analysis produced accurate and highly repeatable QT interval measurements. Reproducibility was adequate also over prolonged time periods both at rest and in exercise stress test. The method can be applied in studying duration of ventricular repolarization time in different physiologic and pharmacologic interventions.     

Spiral phase velocity mapping of left and right coronary artery blood flow: correction for through-plane motion using selective fat-only excitation

PURPOSE: To develop a method of correcting both right and left coronary artery flow velocities for the through-plane motion of the vessel, in order to allow details in the temporal flow profiles to be viewed. MATERIALS AND METHODS: The methods developed use selective excitation and velocity mapping of the epicardial fat surrounding the artery, either in a separate acquisition (temporal resolution = 22 msec) or interleaved with the water-excitation acquisition (temporal resolution = 44 msec) used to determine coronary blood flow velocities. The two methods were compared in 10 right and 13 left coronary arteries in healthy volunteers. RESULTS: For the right coronary arteries, correction for through-plane motion significantly reduces the mean systolic flow velocity (75.3 mm/second vs. 90.0 mm/second, P < 0.01), while the mean diastolic flow velocity is unchanged (96.8 mm/second vs. 94.5 mm/second, P = ns). The resulting profiles are biphasic, with approximately equal flow in systole and diastole. For the left arteries, correction for through-plane motion reduces the mean systolic flow velocity (25.0 mm/second vs. 72.8 mm/second, P < 0.001), resulting in the expected diastolic predominant flow profiles. For the right arteries, there were no significant differences in the mean systolic and mean diastolic velocities after correction with the separate fat-excitation acquisition, and after correction the poorer temporal resolution combined water excitation/fat excitation acquisition. However, for the left coronary arteries, the combined water excitation/fat excitation acquisition resulted in a slight reduction in the mean diastolic velocity (121.5 mm/second vs. 130.9 mm/second, P < 0.05). CONCLUSION: Selective excitation of the surrounding epicardial fat enables through-plane correction of both left and right coronary flow velocities, enabling the temporal details of flow velocity to be viewed.With a combined WE/FE acquisition, this can be performed without extending the study duration; however, the reduced temporal resolution and temporal mismatch of the excitations results in a blunting of rapidly changing flow profiles. As such, it may be less suitable for the left coronary artery, which has a greater range of through-plane motion than the right, and correction using separate WE and FE acquisitions, or the adjacent myocardium, may be preferable.     

Improved encoding strategy for CPMG-based Bloch-Siegert B(1)(+) mapping

Bloch-Siegert (BS) based B(1)(+) mapping methods use off-resonant pulses to encode quantitative B(1)(+) information into the signal phase. It was recently shown that the principle behind BS-based B(1)(+) mapping can be expanded from spin echo (BS-SE) and gradient-echo (BS-FLASH) based BS B(1)(+) mapping to methods such as Carr, Purcell, Meiboom, Gill (CPMG)-based turbo-spin echo (BS-CPMG-TSE) and multi-spin echo (BS-CPMG-MSE) imaging. If CPMG conditions are preserved, BS-CPMG-TSE allows fast acquisition of the B(1)(+) information and BS-CPMG-MSE enables simultaneous mapping of B(1)(+), M(0), and T(2). To date, however, two separate MRI experiments must be performed to enable the calculation of B(1)(+) maps. This study investigated a modified encoding strategy for CPMG BS-based methods to overcome this limitation. By applying a "bipolar" off-resonant BS pulse before the refocusing pulse train, the needed phase information was able to be encoded into different echo images of one echo train. Thus, this technique allowed simultaneous B(1)(+) and T(2) mapping in a single BS-CPMG-MSE experiment. To allow single-shot B(1)(+) mapping, this method was also applied to turbo-spin echo imaging. Furthermore, the presented modification intrinsically minimizes phase-based image artifacts in BS-CPMG-TSE experiments.     

Initial Experience with the High-Density Mesh Ablation Catheter for Pulmonary Vein Isolation

Background: Pulmonary vein isolation (PVI) is usually performed with multiple point-by-point radiofrequency ablation with a second multielectrode circular mapping catheter to validate isolation. We evaluated a 30-mm high-density mesh electrode (HDMA) for mapping and PVI in patients with recurrent atrial fibrillation (AF).
Methods: In 13 patients (validation group) up to three pulmonary veins (PVs) were targeted with the HDMA. A circular mapping catheter was used to validate PVI. PVI was completed with a CARTO-guided approach (Biosense Webster, Diamond Bar, CA, USA) followed by a voltage remap. In 11 patients (feasibility group) the HDMA catheter was evaluated as a stand-alone mapping and ablation tool.
Results: The diagnostic accuracy of the HDMA catheter to evaluate PVI was 100%. The encircled low-voltage area (<0.15 mV) after HDMA-guided PVI was smaller compared to CARTO-guided PVI. In the feasibility group 76% of the PVs could be isolated. Complete isolation of all PVs was feasible in five patients (45%) with a mean procedure and fluoroscopy time of respectively 180 ± 39 minutes and 40 ± 14 minutes. After 1 year 64% of the patients were free of symptomatic AF.
Conclusions: The HDMA electrode is a reliable mapping tool to validate PVI. The majority of PVs can be isolated, but on a patient basis touch-up ablations are necessary in more than 50% of the cases. Therefore, modifications in catheter design are required. The small area of voltage abatement points to an ostial left atrium-pulmonary vein disconnection. Initial clinical results in a small number of patients are promising.     

On-line mapping system for the visualization of the electrical activation of the heart

A simple but still versatile datalogging system based on a VCR (video cassette recorder) has been developed. The VCR allows mass storage of data originating from a maximum of 256 channels as used, for example, in the recording of the time-dependent potential distribution at the surface of the myocardium [1,2]. Incorporated in the system is a display memory allowing on-line simultaneous visualization of the assessed recordings of 16 channels. On an interactive base display parameters (time-window, channel-selection) can be altered without loss of data. A link with a personal computer allows modification of system parameters and storage of data for off-line analysis of the recorded data. The high data rate to and from the VCR (4.3 MHz) fully utilizes the bandwidth available. A normal videotape can, therefore, contain up to 2 Gigabyte of data. Despite this, the use of the tapecounter and the decoding of the time-code inserted into the signal allows quick retrieval of the stored data without needing expensive equipment. The system described brings mass data logging within the reach of a vast number of laboratoria and cardiovascular centers.     

Statistical methods of estimation and inference for functional MR image analysis

Two questions arising In the analysis of functional magnetic resonance imaging (fMRI) data acquired during periodic sensory stimulation are: i) how to measure the experimentally determined effect in fMRI time series; and ii) how to decide whether an apparent effect is significant Our approach is first to fit a time series regression model, including sine and cosine terms at the (fundamental) frequency of experimental stimulation, by pseudogeneralized least squares (PGLS) at each pixel of an image. Sinusoidal modeling takes account of locally variable hemodynamic delay and dispersion, and PGLS fitting corrects for residual or endogenous autocorrelation in fMRI time series, to yield best unbiased estimates of the amplitudes of the sine and cosine terms at fundamental frequency; from these parameters the authors derive estimates of experimentally determined power and its standard error. Randomization testing is then used to create inferential brain activation maps (BAMs) of pixels significantly activated by the experimental stimulus. The methods are illustrated by application to data acquired from normal human subjects during periodic visual and auditory stimulation.     

阴性、阳性精神分裂症患者听觉P300显著性概率地形图研究

目的　探讨阴性、阳性精神分裂症听觉P30 0颅脑区域性改变特征 ,以及抗精神病药物的可能影响。方法　应用显著性概率地形图方法 (t SPM ) ,对 2 2例阴性、2 7例阳性精神分裂症患者与 17例正常人进行对比研究。结果　阴性组与阳性组比较 ,顶区、左枕颞区、左中央前额区显著性差异 (P <0 .0 5 )。与治疗前比较 ,治疗后阴性组前额区、左右中央区、右顶区有显著性差异 (P <0 .0 5 ) ,阳性组左颞顶区有显著性差异 (P <0 .0 5 )。结论　阴性、阳性精神分裂症亚型之间可能有不同的神经生物学基础 ,抗精神病药物可以改善某些大脑皮质机能。     

Spinal Geometry and Paresthesia Coverage in Spinal Cord Stimulation

Objective . To test the following hypotheses, based on computer modeling studies of spinal cord stimulation, by the analysis of data from chronic pain patients: I. the probability-of-paresthesia in a dermatome is highest when the cathode is placed at the corresponding segmental level; II. variation of the rostrocaudal position of the cathode in the lower cervical/high thoracic region results in less variation of the probability-of-paresthesia in a dermatome than stimulation in more caudal regions; III. when stimulating in the midthoracic region, the probability-of-paresthesia in a dermatome is low in comparison to other regions when the cathode is not at the corresponding segmental level. Method . The probability-of-paresthesia in 16 body segments as a function of the rostrocaudal position of the cathode was analyzed from the paresthesia coverage with 3,897 bipolar and unipolar combinations from 106 chronic pain patients. Results . The distributions of the probability-of-paresthesia in the upper and lower limb are in accordance with the hypotheses, but different distributions were found in all trunk areas. Conclusion . The success to be expected from spinal cord stimulation in chronic pain management is inversely related to the thickness of the dorsal cerebrospinal fluid layer at the cathode level. Therefore, preoperative measurement from transverse images can be helpful as a predictor for success.