High-density activation mapping of fractionated electrograms in the atria of patients with paroxysmal atrial fibrillation

BACKGROUND: Areas of complex fractionated atrial electrograms (CFAEs) have been implicated in the atrial substrate of atrial fibrillation (AF). The mechanisms underlying CFAE in humans are not well investigated. OBJECTIVES: The purpose of this study was to investigate the regional activation pattern associated with CFAE using a high-density contact mapping catheter. METHODS: Twenty patients with paroxysmal AF were mapped using a high-density multielectrode catheter. CFAE were mapped at 10 different sites (left atrium [LA]: inferior, posterior, roof, septum, anterior, lateral; right atrium [RA]: anterior, lateral, posterior, septum). Local atrial fibrillation cycle length (AFCL) was measured immediately before and after the occurrence of CFAE, and the longest electrogram duration (CFAEmax) was assessed. RESULTS: Longer electrogram durations were recorded in the LA compared with the RA (CFAEmax 118 +/- 21 ms vs 104 +/- 23 ms, P = .001). AFCL significantly shortened before the occurrence of CFAEmax compared with baseline (LA: 174 +/- 32 ms vs 186 +/- 32 ms, P = .0001; RA: 177 +/- 31 ms vs 188 +/- 31 ms, P = .0001) and returned to baseline afterwards. AFCL shortened by >or=10 ms in 91% of mapped sites. Two different local activation patterns were associated with occurrence of CFAEmax: a nearly simultaneous activation in all spines in 84% indicating passive activation, and a nonsimultaneous activation sequence suggesting local complex activation or reentry. CONCLUSION: Fractionated atrial electrograms during AF demonstrate dynamic changes that are dependent on regional AFCL. Shortening of AFCL precedes the development of CFAE; thus, cycle length is a major determinant of fractionation during AF. High-density mapping in AF may help to differentiate passive activation of CFAE from CFAE associated with an active component of the AF process.     

Radiofrequency ablation of left atrial flutter mediated with double potentials in a seemingly normally structured heart

Background

Left atrial flutter (left AFL) is common in patients who undergo atrial fibrillation ablation and cardiac surgery; however, few reports describe left AFL in detail in a seemingly normally structured heart, and the mechanisms of the occurrence of such arrhythmia are still not clear. We describe left AFL in patients without prior cardiac surgery or catheter ablation and discuss the electrophysiological characteristics that may explain the preferential generation and perpetuation of such tachycardia.

Methods and results

Eleven patients with left AFL, who had no history of cardiac surgery or interventions, underwent electrophysiological studies and 3-dimensional electroanatomic mapping studies. Echocardiography revealed a relatively mild dilation of the left atrium, mild to moderate mitral regurgitation, and a normal left ventricular ejection fraction. The electroanatomic mapping during tachycardia showed a “reentrant” activation pattern in all patients. The mean tachycardia cycle length was 266 ± 17 ms. A single-loop reentrant circuit was identified in 7 patients. A counterclockwise left atrial flutter evolved around the mitral valve annulus in 6 patients. The tachycardia rotated around the left atrial anterior wall in 1 patient. Four patients exhibited a double-loop reentrant circuit with a “figure of 8” pattern reentry. Double potentials as the critical isthmus of the circuit were identified in the left atrial anterior wall near the mitral annulus which displayed a low-voltage area matched with the left atrium–aorta contiguity. The conduction velocity was significantly slower in the double-potential recording area than in the lateral mitral annulus (0.36 ± 0.03 m/s vs 0.74 ± 0.12 m/s; P < 0.05). Successful ablation around the double-potential recording site caused an interruption of the tachycardia, and remained free of recurrence during a 12-month follow-up in all patients.

Conclusion

Left AFL in patients without a history of surgery or ablation is rarely observed in clinical practice. The successful site of ablation was within the anterior wall near the mitral annulus showing the double potentials as the critical part of the reentrant circuit. This suggests that perhaps a double potential-targeted ablation may be effective for these patients.     

Ablação epicárdica para prevenção da fibrilhação ventricular em doente com síndrome de Brugada

We present the case of a 60‐year‐old woman with Brugada syndrome, permanent type 1 electrocardiographic pattern, who had previously received an implantable cardioverter‐defibrillator. She suffered frequent syncopal episodes and multiple appropriate shocks (around five per month) due to polymorphic ventricular tachycardia/ventricular fibrillation, refractory to quinidine therapy. Combined epicardial and endocardial electroanatomical mapping was performed with a view to substrate ablation. An area of abnormal fractionated electrograms, lasting up to 370 ms and up to 216 ms after the end of the surface QRS, was identified in the epicardium in the lower anterior part of the right ventricular outflow tract. Extensive epicardial ablation of this area, which eliminated the fractionated electrograms, led to the disappearance of the Brugada electrocardiographic pattern six weeks after ablation. Despite discontinuation of quinidine, no further ventricular arrhythmias occurred during follow‐up, which is still of short duration.     

Le diagnostic de l’amylose cardiaque par résonance magnétique : les éléments discriminants

Infiltrative cardiomyopathies refers to deposits of substances in the myocardial tissue resulting in a structural abnormality and/or alteration of cardiac function. Cardiac amyloidosis is an extracellular infiltration of amyloid fibril. Cardiac magnetic resonance imaging (MRI) is essential (in the) for its diagnosis. MRI sequences (morphological, viability and parametric mapping) allow a structural and dynamic analysis of the cardiac function as well as a characterization of the myocardial tissue: edema, fatty infiltration, fibrosis. In cardiac amyloidosis, the morphological sequences classically highlight ventricular hypertrophy and thickening of the heart valves. Ventricular functions are assessed by the cine sequences (The cine sequences make it possible to evaluate the ventricular functions.) The viability sequences show (a more diffuse distribution of hypersignals) an abnormal pattern of late gadolinium enhancement in both circumferential and sub-endocardial distribution. The relaxometry sequences or parametric T1 and/or T2 mapping allow the spatial visualization of quantitative changes of the myocardium. The presence of macroscopic myocardial edema or fibrosis causes a prolongation of the native T1 and an increase of the extracellular volume.     

Ventricular tachycardia in ischemic heart disease substrates

Advances in the treatment of myocardial infarction (MI) have improved survival after ischemic cardiac injury. Post-infarct structural and functional remodeling results in electrophysiologic substrates at risk for monomorphic ventricular tachycardia (MMVT). Characterization of this substrate using a variety of clinical and investigative tools has improved our understanding of MMVT circuits, and has accelerated the development of device and catheter-based therapies aimed at identification and elimination of this arrhythmia.This review will discuss the central role of the ischemic heart disease substrate in the development MMVT. Electrophysiologic characterization of the post-infarct myocardium using bipolar electrogram amplitudes to delineate scar border zones will be reviewed. Functional electrogram determinants of reentrant circuits such as isolated late potentials will be discussed. Strategies for catheter ablation of reentrant ventricular tachycardia, including structural and functional targets will also be examined, as will the role of the epicardial mapping and ablation in the management of recurrent MMVT.     

不同起源部位局灶性房性心动过速的心电图P波形态分析及导管消融

目的：评价局灶性房性心动过速（房速）心房内不同起源部位的心电图房性P波形态特征及导管消融疗效。方法：通过三维电解剖标测系统的精确定位17例局灶性房速的起源部位，并回顾性分析体表心电图房性P波的形态特点，探讨二者的联系。结果：17例房速起源部位均获得精确定位并成功行导管消融。9例右心房起源房速包括上腔静脉房间隔侧1例，中上部界嵴1例，房间隔右侧3例，冠状静脉窦口内1例，希氏束旁2例，右心耳1例；8例左心房起源房速包括左上肺静脉2例，右上肺静脉1例，二尖瓣环2例，左心耳1例，房间隔左侧1例，无冠窦1例。V1导联P波负向者房速多起源于右心房；P波正向者，房速除起源于左心房外，尚可能起源于右心房上部、后部；P波等电位线者，房速多起源于Koch三角附近的相关解剖结构，如冠状静脉窦口、房间隔以及希氏束。结论局灶性房速常起源于肺静脉附近、瓣环、房间隔等心房内有特殊解剖结构的部位，心电图P波形态，尤其是V1导联可初步定位房速起源部位，而三维标测系统可快速对此作进一步精确定位，缩短导管消融及放射线透视时间。     

神经反应遥测技术在人工耳蜗术后调试中的应用

目的通过对小儿人工耳蜗植入者术后言语处理器调试中运用NRT（神经反应遥侧）技术效果的分析．探讨NRT在人工耳蜗术后调试中的应用价值。方法选取10例术后主观调试配合欠佳的儿童．用Cochlear公司NRT3．0编程软件进行ECAP波形检测并测定ECAP阈值，利用测试结果判断主观阈值（T-值）和最大舒适阈（C-值），并得出言语处理器映射图（Map）。术后6个月行声场听阈测听。结果86．2％的电极引出ECAP波形，开机调试时反应阈值较小，以后逐渐升高，3～4个月左右闽值逐渐趋于稳定，而且靠近蜗底的阈值比蜗尖高。声场平均听阈为30～40dBSPL。经过言语康复训练，获得良好的效果。结论NRT技术可为术后快速准确地调试言语处理器提供客观依据．     

A miniature, moveable electrode for brain stimulation in small animals

A moveable, nonrotating electrode of tiny dimensions for brain stimulation in small animals is described. Its usefulness is demonstrated in a mapping study of circling behavior in mesencephalic areas of the rat.     

Temporal and spatial congruence of components of motion-onset evoked responses investigated by whole-head magneto-electroencephalography

Motion-onset related components in averaged whole head co-recorded MEG and EEG responses of 24 adults to a low-contrast checkerboard pattern were studied. The aims were to identify these components, to characterize quantitatively their maps and to localize the underlying sources by equivalent-current-dipole (ECD) analyses with a spherical head model.After a weak P1, a large start-elicited negativity arises, comprising the novel N2a (occipital positive and parieto-central negative, peak-latency 141 ms) and the N2 like N2b (bilateral parieto-temporal, 175 ms) component. It is followed by a large positive stop-related component, P2 (156 ms after motion-offset). The corresponding MEG components N2am and N2bm showed bilateral dipole fields with considerable overlap. P1m has a single dipole field around the midline. N2a(m) and N2b(m) can be modelled with two bilateral ECDs with significant different locations. The study shows that accurate mapping and ECD analyses can distinguish two neighbouring areas of the visual cortex, 21+/-4 (SE) mm separated, which activities are reflected in both spatio-temporally closely related N2(m) components. N2a(m) and N2b(m) originate in the extrastriate cortex, possibly close to or in V3/V3A and MT/V5 respectively. Motion-evoked activity in (near) V3/V3A is novel on the basis of EEG data.