Chronic granulomatous disease: A different pattern in Hong Kong?

From July 1988 to December 1989, six boys with chronic granulomatous disease were diagnosed in our institutions. Their clinical features were reviewed in order to delineate the pattern of infections which seems to have both similarities and differences when compared with published reports of Caucasian patients. The most striking differences was the lack of skin sepsis and chronic lymphadenitis in our six patients. Gram-negative organisms were the commonest pathogens while Staphylococci sp. were not isolated. Clinical features which should alert one to the diagnosis were also highlighted. Prophylactic co-trimoxazole was effective in reducing the frequency of bacterial infections. Early diagnosis is not only essential for optimal patient management but also for genetic counselling for the extended family.     

Parental perception of the effect of venepuncture in preschool children in non-therapeutic research

Non-therapeutic research in children is said to be justified in part if the risk involved is no more than minimal, but there is little information on the risk of venepuncture to make that judgement. This prospective study was carried out to assess the effect of venepuncture on 425 healthy children aged between 3.6 and 6.6 years old who participated in a non-therapeutic research project. A parental questionnaire was sent out 1 month after the blood was taken. Three hundred and ninety-one parents (92%) returned the questionnaires. Parental responses indicated the risk of complications was of the order considered to be minimal. A large majority of parents (78%) felt this experience would be helpful for the child if blood had to be taken again and a significant proportion (40%) felt the child would be more confident when going to see a doctor or dentist afterwards. Venepuncture in preschool children causes minimal harm and might even have some positive effects.     

Comparative Evaluation of Chronotropic Responses of QT Sensing and Activity Sensing Rate Responsive Pacemakers

The rate responses of activity sensing (ATS) and QT sensing (QTS) rate responsive pacemakers to different forms and durations of exercises were compared. Nine patients with ATS and five with QTS were studied. All had complete heart block and atrial arrhythmias. At the onset, the pacemakers were programmed to achieve a pacing rate of 100-110 bpm by the end of stage 1 of the Bruce protocol, and to a pacing rate range of 70-150 bpm. With progressive exercise, using a treadmill (Bruce protocol), the maximum pacing rates in the two groups were not significantly different (mean +/- SD: 123 +/- 18 vs 129 +/- 23 bpm, ATS vs QTS). The time taken to return to the baseline pacing rate during recovery was significantly longer with QTS (178 +/- 70 vs 264 +/- 68 s, p less than 0.05). Brief exercise tests on a treadmill were performed for 3 min each with different combinations of treadmill speeds (1.2 and 2.5 mph) and gradients (0, 5, 10 and 15%). In both groups of patients, faster walking speed was associated with a faster pacing rate at each gradient. However, with increasing gradients, at each speed, there was a rise in the maximum pacing rate only in patients with QTS. During brief exercise tests, the maximum rate was achieved by the end of exercise in patients with ATS, but was delayed by 33 +/- 20 s after exercise in patients with QTS.(ABSTRACT TRUNCATED AT 250 WORDS)     

Synergistic Effects of Inward Rectifier (IK1) and Pacemaker (If) Currents on the Induction of Bioengineered Cardiac Automaticity

Introduction: Normal heart rhythms originate in the sinoatrial node. HCN‐encoded funny current (I_f) and the Kir2‐encoded inward rectifier (I_K1) counteract each other by respectively oscillating and stabilizing the negative resting membrane potential, and controlling action potential firing. Therefore, I_K1 suppression and I_f overexpression have been independently exploited to convert cardiomyocytes (CMs) into AP‐firing bioartificial pacemakers. Although the 2 strategies have been largely assumed synergistic, their complementarity has not been investigated. Methods and Results: We explored the interrelationships of automaticity, I_f and I_K1 by transducing single left ventricular (LV) CMs isolated from guinea pig hearts with the recombinant adenoviruses Ad‐C MV‐G FP‐I RES‐HCN1‐ÄÄÄ and/or Ad‐CGI‐Kir2.1 to mediate their current densities via a whole‐cell patch clamp technique at 37°C. Results showed that Ad‐CGI‐HCN1‐ÄÄÄ but not Ad‐CGI‐Kir2.1 transduction induced automaticity (181.1 ± 13.1 bpm). Interestingly, Ad‐CGI‐HCN1‐ÄÄÄ/Ad‐CGI‐Kir2.1 cotransduction significantly promoted the induced firing frequency (320.0 ± 15.8 bpm; P < 0.05). Correlation analysis revealed that the firing frequency, phase‐4 slope and APD₉₀ of AP‐firing LV CMs were correlated with I_f (R² > 0.7) only when ?2 >I_K1 >?4 pA/pF but not with I_K1 over the entire I_f ranges examined (0.02 < R² < 0.4). Unlike I_f, I_K1 displayed correlation with neither the phase‐4 slope (R²= 0.02) nor phase‐4 length (R²= 0.04) when ?2 > I_f > ?4 pA/pF. As anticipated, however, APD₉₀ was correlated with I_K1 (R²= 0.4). Conclusion: We conclude that an optimal level of I_K1 maintains a voltage range for I_f to operate most effectively during a dynamic cardiac cycle.     

Differential effects of pinacidil,cromakalim,and NS 1619 on electrically evoked contractions in rat vas deferens

目的：本文研究新近研制的ＡＴＰ敏感性钾通道开放剂，吡那地尔（Ｐｉｎ）和ｃｒｏｍａｋａｌｉｍ（Ｃｒｏ），以及钙离子激活性钾通道开放剂ＮＳ１６１９对电场刺激所致大鼠输精管收缩的作用．方法：利用电场刺激（０．３Ｈｚ，１ｍｓ，６０Ｖ）反复性引致输精管单相性收缩．结果：Ｐｉｎ和Ｃｒｏ浓度依赖性减低电刺激收缩．格列本脲（Ｇｌｉ）而非ｃｈａｒｙｂｄｏｔｏｘｉｎ拮抗上述两药的舒张作用．Ｐｉｎ右移去甲肾上腺素的浓度－收缩曲线，同时降低最高收缩反应．Ｇｌｉ抵消Ｐｉｎ的作用．Ｃｈａｒｙｂｄｏｔｏｘｉｎ而非Ｇｌｉ减低ＮＳ１６１９的平滑肌舒张作用．结论：ＡＴＰ敏感性和钙离子激活性钾通道参与调节输精管平滑肌的收缩性．     

Flecainide acetate in the treatment of tachycardias associated with Mahaim fibres

Patients with Mahaim fibres are susceptible to tachycardiaswhich can be refractory to conventional drug therapy, leadingto treatment with surgery and catheter ablation. The effectsof flecainide acetate were studied in 3 patients (61, 21 and35 years of age) with Mahaim fibres presenting with tachycardiasrefractory to beta-blockers, quinidine and verapamil. One alsohad ophthalmic side-effects from amiodarone. Three types oftachycardias were induced: a reentrant tachycardia with leftbundle branch block morphology (LBBBM) in all 3 patients, atrialflutter in one and atrial fibrillation in another. Intravenousflecainide acetate (2 mg kg–1) terminated reentrant tachycardiaand abolished duality of atrioventricular conduction in patient1. In patient 2, it abolished preexcitation during atrial flutterprior to termination. Atrial fibrillation could not be inducedin patient 3 after flecainide acetate. In all patients, retrogradeconduction was blocked, preexcitation was not present with atrialpacing and no tachycardia was induced after flecainide. Allhave remained asymptomatic on oral flecainide acetate (100 mgbd) for a mean follow-up period of 9 months. We conclude that (1) flecainide acetate is effective for thetreatment of various tachycardias associated with Mahaim fibres;(2) since different mechanisms responsible for the tachycardiawith LBBBM may be present in the same patient and difficultto determine in some, treatment with flecainide acetate whichaffects both the atrioventricular node and Mahaim fibre conductionmay be appropriate for the condition and; (3) its use shouldbe considered before more aggressive therapies.     

维拉帕米对阵发性房颤患者心房颤动负荷的影响

目的 :评估预防性地应用维拉帕米 （Verapam il）对安装植入型心房除颤器 （IAD）的慢性阵发性房颤患者心房颤动负荷的影响。方法 :因反复发作有症状的房颤而安装植入型体内心房除颤器 （IAD）患者 10例 ,随机交叉地进入维拉帕米 （2 40 mg/d）组或安慰剂组并持续 3个月。由 IAD储存并记录房颤发作的起始时间和每次发作的持续时间 ,必要时发放 R波同步电流进行体内除颤。结果 :93%的的症状性自发房颤片段由 IAD成功地转复。维拉帕米组体内除颤的成功率与安慰剂组比较无显著差异 （10 0 %vs88%,P=0 .8） ,且每次成功复律所发放的电击次数亦无显著差异 （1.7± 2 .4vs 1.8± 2 .1,P=0 .6 ）。房颤发作的平均次数 （8.0± 8.0 vs 9.1± 10 .8,P=0 .83） ,每次房颤发作的持续时间 （44± 84h vs45± 87h,P=0 .93）及总的房颤持续时间 （418± 5 11h vs5 86± 40 9h,P=0 .5 1） ,在安慰剂组和维拉帕米组之间无显著差异。结论 :慢性房颤患者中预防性地使用维拉帕米并不能有效地影响心房颤动的负荷。