The Mechanisms Responsible for Lack of Reproducible Induction of Atrioventricular Nodal Reentrant Tachycardia

Lack of AVNRT Induction. Introduction : AV nodal reentrant tachycardia (AVNRT) is not always reproducibly inducible. The purpose of this study was to determine the mechanisms responsible for the lack of reproducible induction of AVNRT.
Methods and Results : The induction of AVNRT was assessed with atrial burst pacing, and with atrial and ventricular programmed stimulation, each with one and two extrastimuli, in 103 patients with AVNRT. The stimulation protocol was repeated 10 times in the baseline state, during isoproterenol infusion, and after atropine administration, or until AVNRT was induced in 7 of 10 attempts. The mechanisms responsible for < 7 of 10 inductions were classified as: (1) the inability to achieve critical AH prolongation; (2) fast pathway block; and (3) slow pathway block. The induction endpoint was achieved in 90 patients: 55 in the baseline state, 34 during isoproterenol infusion, and 1 after atropine. Tbe mechanism of noninducibility in the baseline state (n = 48) was the inability to achieve a critical AH interval in 20%, fast pathway block in 49%, and slow pathway block in 31% (P = 0.02). During isoproterenol administration (n = 14) and after atropine administration (n = 13), the three mechanisms were equally responsible for nonreproducible induction of AVNRT.
Conclusions : The induction of AVNRT is poorly reproducible in approximately 10% of patients. In the baseline state, the most common reason for the inability to reproducibly induce AVNRT is fast pathway block. In the presence of isoproterenol or atropine, each of the three mechanisms was equally responsible for noninducibility of AVNRT.     

NMR spectra and restrained moleclar dynamics of the mushroom toxin viroisin

The conformation of viroisin, the monocyclic toxic heptapeptide of the virotoxin family from mushroom Amanita virosa, was analysed using two-dimensional nuclear magnetic resonance spectroscopy and restrained molecular dynamics simulations. All proton signals were completely assigned, and interproton distances were determined using data from rotating-frame nuclear Overhauser enhancement. The backbone dihedral angles were deduced from measurements of coupling constants. The temperature dependence of the amide proton chemical shifts provided information about hydrogen bonding. Six probable solution conformations of viroisin were derived from the use of distance geometry and restrained molecular dynamics based on a set of distance constraints obtained from experimental data. The results of the structural analysis indicate that viroisin has a well ordered conformation in solution. In all these conformations the functional groups essential for toxicity orient themselves in the same direction so as to bind to the target proteins. This feature is consistent with previous results about the formation of a hydrophobic pocket on one side of the molecule.     

淮南地区蠕形螨性睑缘炎的调查

目的:探讨淮南地区蠕形螨性睑缘炎的患病率及流行特点。方法:取受检者睫毛每人5根,置洁净载玻片上,滴一滴甘油,盖上盖玻片镜检。结果:共检查睑缘炎患者426例,阳性率为26.76％（114/426）;对照组400人,阳性率为7％（28/400）,两组差异显著（P<0.001）。114例阳性者中,男68人,占受检男性29.06％（68/234）;女46人,占受检女性23.96％（46/192）,差异无显著性（P>0.05）。不同年龄组阳性率亦无差异（P>0.05）。结论:临床应充分重视蠕形螨性睑缘炎的发生,诊治睑缘炎患者须予以病原学检查,避免与其它病原体引起的睑缘炎相混淆,导致误诊误治。     

The Impact of Catheter Ablation on the Dynamic Function of the Left Atrium in Patients with Atrial Fibrillation: Insights from Four‐Dimensional Computed Tomographic Images

Functional Evaluation of the LA by Dynamic CT. Introduction: Elucidating the functional properties and remodeling process of the entire left atrium (LA) is important not only for offering the mechanistic insight into atrial fibrillation (AF) but also for assessing the effectiveness of catheter ablation. Methods: We included 65 patients with paroxysmal AF and 29 controls. Baseline multidetector computed tomography (MDCT) was acquired in all subjects and a follow‐up MDCT was available in 48 patients after pulmonary vein and LA ablation. The 3‐dimensional images at atrial end‐diastole (ED) and end‐systole (ES) were analyzed. Results: The LA volume (ED: 61.11 ± 15.94 vs 54.12 ± 8.94 mL/m², P = 0.03; ES: 45.29 ± 17.64 vs 33.38 ± 7.78 mL/m², P < 0.001) was increased, and ejection fraction (EF) (26.93 ± 13.40 vs 38.09 ± 11.62%, P < 0.001) decreased in AF patients as compared to controls. After ablation, the ES LA volume (44.73 ± 14.93 vs 38.04 ± 11.51 mL/m², P = 0.04) decreased and the LA EF (25.04 ± 13.13 vs 30.82 ± 7.85%, P = 0.03) increased in patients without any AF recurrence. The wall motion (WM) analysis of the 18 segments of LA revealed increased motional magnitudes of entire LA except for the anterior roof. In contrast, the volume, EF, and WM of LA remained similar in patients with recurrence. Conclusion: Dilated LA with global hypokinesia was noted in AF patients. Improved LA transport function was demonstrated in patients without any recurrence after ablation. However, the anatomic and functional reverse remodeling was not significant in patients with AF recurrence. (J Cardiovasc Electrophysiol, Vol. 21, pp. 270–277, March 2010)