Electrophysiologic effects of d-sotalol in humans

Sotalol is a beta-adrenergic blocking agent that prolongs the duration of the cardiac action potential in humans, without affecting the upstroke velocity of depolarization. The dextrorotatory isomer, d-sotalol, retains these class III effects, but has little beta-blocking activity in vitro. d-Sotalol has not been studied extensively in humans. The electrocardiographic (ECG) and electrophysiologic effects of d- and d,l-sotalol were therefore assessed in a prospective randomized study of 20 patients. Each patient received either d-sotalol (1, 1.5 or 2 mg/kg body weight) or d,l-sotalol (1 mg/kg) by intravenous infusion. The QT and QTc intervals were prolonged and refractoriness increased in the atrium, atrioventricular (AV) node, His-Purkinje system and right ventricle after both d- and d,l-sotalol. After d-sotalol, the increases in both QT and QTc intervals and in atrial and ventricular effective refractory periods were dose dependent. Highly significant linear correlation was demonstrated between the plasma sotalol level and the change in QT (r = 0.86, p = 0.001) and QTc intervals (r = 0.79, p = 0.002), and between the plasma sotalol level and the effective refractory period of the right atrium (r = 0.75, p = 0.005) and ventricle (r = 0.70, p = 0.025). This study confirms that d-sotalol has effects consistent with class III properties. It demonstrates these effects in humans, and suggests that d-sotalol may prove to be a useful antiarrhythmic agent.     

Treatment of ventricular arrhythmias

Within the past 20 years, our knowledge concerning the epidemiology, natural history, and treatment of VT has expanded greatly. A variety of effective pharmacologic, surgical and electrical therapies for VT are now available to the clinician. Patients who present with ventricular, tachyarrhythmias should undergo a comprehensive medical evaluation directed at identifying and treating such factors as ischemia, congestive heart failure, valvular heart disease, sensitivity to cardioactive drugs, and metabolic derangements. Many patients who present with asymptomatic ventricular arrhythmias do not require specific antiarrhythmic drug therapy. However, certain patients who have already suffered a life-threatening arrhythmia or who are at high risk for such arrhythmia should be vigorously treated with specific antiarrhythmic therapy guided for that individual patient. The efficacy of any antiarrhythmic treatment should be assessed by ECG monitoring, exercise testing, and/or electrophysiologic study. In the near future, potentially revolutionary new electrical therapies for ventricular tachyarrhythmias will be evaluated. It is to be hoped that these devices used in combination with pharmacologic and surgical therapies may dramatically reduce the incidence of sudden cardiac death in high-risk patients.     

Model of reentrant ventricular tachycardia based on infarct border zone geometry predicts reentrant circuit features as determined by activation mapping

BACKGROUND: Infarct border zone (IBZ) geometry likely affects inducibility and characteristics of postinfarction reentrant ventricular tachycardia, but the connection has not been established. OBJECTIVE: The purpose of this study was to determine characteristics of postinfarction ventricular tachycardia in the IBZ. METHODS: A geometric model describing the relationship between IBZ geometry and wavefront propagation in reentrant circuits was developed. Based on the formulation, slow conduction and block were expected to coincide with areas where IBZ thickness (T) is minimal and the local spatial gradient in thickness (DeltaT) is maximal, so that the degree of wavefront curvature rho proportional, variant DeltaT/T is maximal. Regions of fastest conduction velocity were predicted to coincide with areas of minimum DeltaT. In seven arrhythmogenic postinfarction canine heart experiments, tachycardia was induced by programmed stimulation, and activation maps were constructed from multichannel recordings. IBZ thickness was measured in excised hearts from histologic analysis or magnetic resonance imaging. Reentrant circuit properties were predicted from IBZ geometry and compared with ventricular activation maps after tachycardia induction. RESULTS: Mean IBZ thickness was 231 +/- 140 microm at the reentry isthmus and 1440 +/- 770 microm in the outer pathway (P <0.001). Mean curvature rho was 1.63 +/- 0.45 mm(-1) at functional block line locations, 0.71 +/- 0.18 mm(-1) at isthmus entrance-exit points, and 0.33 +/- 0.13 mm(-1) in the outer reentrant circuit pathway. The mean conduction velocity about the circuit during reentrant tachycardia was 0.32 +/- 0.04 mm/ms at entrance-exit points, 0.42 +/- 0.13 mm/ms for the entire outer pathway, and 0.64 +/- 0.16 mm/ms at outer pathway regions with minimum DeltaT. Model sensitivity and specificity to detect isthmus location was 75.0% and 97.2%. CONCLUSIONS: Reentrant circuit features as determined by activation mapping can be predicted on the basis of IBZ geometrical relationships.     

Transmission of schistosomiasis in an urban population and prevalence of intestinal helminthiasis in Bamako, Mali

Parasitological, malacological and anthropological studies were performed to assess the prevalence of Schistosoma haematobium and S. mansoni in schoolchildren living in the suburban area of Bamako. A total of 1017 schoolchildren aged 6-14 years were selected in two different areas between September 1997 and December 1999. In Djikoroni, the prevalence of S. haematobium and S. mansoni was 80.7% (339/420) and 22.8% (85/372) respectively. There was no significant difference of prevalence and intensity of infection with S. haematobium between schools, gender and age (p > 0.05), whereas, those of S. mansoni were higher in the vicinity of (+/- 100 m from) major sites where infected Biomphalaria pfeifferi were found (p < 0.001). In Niomirambougou, S. haematobium was prevalent in 46.7% (279/597) and S. mansoni in 28.2% (134/475). Boys and children aged 11-14 years were more infected (p < 0.001). Associated intestinal helminths (Hymenolepis nana, Necator americanus and Ascaris lumbricoides) were relatively scarce (prevalence < 1%). The prevalences of schistosome infected snails intermediate host were relatively high, 49.3% (100/203) in B. pfeifferi, 20.6% (88/138) in B. truncatus and 24.1% (7/29) in B. globosus. We recorded a total of 2514 water contacts about which 1130 in December and 1384 in January. Most of the children, 42.9% (1077/2511) were attracted to water bodies for bathing, swimming and playing, suggesting the lack of recreational facilities in these areas. Developing local control programmes in schools located in the vicinity of water bodies would contribute to break the parasite transmission cycle in Bamako.     

青光眼类型及静态阈值视野损害

目的:探讨青光眼类型与静态阈值视野损害间的关系.方法:对确诊的147例、228只青光眼分类进行静态阈值视野检查.结果:不同类型的青光眼在静态阈值视野缺损出现的最大象限上差异无显著性.青光眼静态阈值视野缺损最大象限的分布依次为颞上、鼻上、鼻下,颞下象限分布最少.结论:不同类型的青光眼所致静态阈值视野损害的主要机制可能是相同的.     

儿童塑型性支气管炎的诊断与治疗

目的　报告 5例儿童塑型性支气管炎病例 ,并复习相关文献 ,总结诊断及治疗方法。方法　 2 0 0 1年5月至 2 0 0 3年 10月 ,对 5例年龄 9个月至 10岁 ,主诉为反复咳嗽、气促并出现急性呼吸窘迫的塑型性支气管炎患儿 ,给予支气管镜检及气道内异物取出术 ,配以反复纤维支气管气道内冲洗、呼吸机机械通气、胸部物理治疗、强化护理及吸痰等综合治疗。结果　 5例中 ,4例支气管镜检取出异物 ,1例为吸痰时吸出支气管状条形异物 ,经病理检查确诊。双侧支气管病变 1例 ,左侧支气管病变 2例 ,右侧支气管病变 1例 ,另 1例吸痰时可吸出。死亡 2例 ,其余 3例均痊愈出院。病理组织学分型按Seear方法 :Ⅰ型 3例 ,Ⅱ型 2例。结论　塑型性支气管炎是一种高危性疾病 ,确诊需依靠支气管镜检查和病理组织学检查。支气管镜异物取出术是唯一有效的治疗方法。气道护理和胸部物理治疗是重要的辅助治疗手段。     

不同年龄组儿童阻塞性睡眠呼吸暂停综合征257例临床分析

目的　探讨儿童不同年龄组阻塞性睡眠呼吸暂停综合征 (OSAS)的主要病因、临床表现、睡眠监测及治疗方法。方法　分析广州市儿童医院耳鼻喉科 1999年 10月至 2 0 0 2年 9月收治的 2 5 7例OSAS患儿 ,分组分析病因 ,对所有患儿应用睡眠呼吸监护仪 ,并进行分度 ,针对不同的病因进行扁桃体摘除术和 (或 )腺样体刮除术。结果　 ( 1)儿童OSAS最主要的临床表现依次为鼻鼾 ( 92 2 % ) ,张口呼吸 ( 89 5 % ) ,憋气 ( 6 7 3% ) ,易醒 ( 5 4 9% )等。 ( 2 )发病因素依次为腺样体增生 ( 91 8% ) ,扁桃体肥大 ( 6 9 6 % ) ,鼻窦炎 ( 5 8% ) ,过敏性鼻炎 ( 2 3% )。 ( 3)睡眠多导仪监测 (PSG)监测结果呼吸紊乱指数 (AHI)轻、中、重所占比例分别是 32 3%、4 9 8%、17 9%。氧饱和度下降轻、中、重所占比例分别是 8 5 %、5 6 0 %、35 4 %。 ( 4 )治疗方法主要是扁桃体摘除术 腺样体刮除术 ( 75 1% ) ,其次是腺样体刮除术 ( 15 2 % )和扁桃体摘除术 ( 9 7% )。结论　各年龄组儿童均可发生OSAS ,4～ 7岁是高发组。引起小儿OSAS的主要病因是扁桃体肥大和 (或 )腺样体增生。睡眠时鼻鼾、张口呼吸、憋气是儿童OSAS特征。确诊 分度依靠多导睡眠图 ,手术是治疗儿童OSAS的有效手段