HYPOTHALAMIC HYPOPITUITARISM FOLLOWING CRANIAL IRRADIATION FOR NASOPHARYNGEAL CARCINOMA

Eight patients, one male and seven females, with no pre-existing hypothalamic-pituitary disease, who developed symptoms of hypopituitarism following cranial irradiation for nasopharyngeal carcinoma were studied 5 years or more after radiotherapy. All were GH deficient. Four of the patients with no GH response during insulin tolerance tests (ITT) showed increased GH in response to synthetic human growth hormone releasing factor (GRF-44). Four patients had impaired cortisol responses to ITT, and gradual but diminished cortisol responses to ovine corticotrophin releasing factor (CRF-41). There was no significant difference between mean peak increments in response to ITT and those in response to CRF-41. TSH responses to TRH were delayed in five and absent in two patients; four of these had low free T4 index. Prolactin was raised in all seven women and increased further in response to TRH. Two patients had impaired gonadotrophin responses to LHRH. None of the patients had clinical or biochemical evidence of diabetes insipidus. These data suggest that post-irradiation hypopituitarism in these patients results from radiation damage to the hypothalamus leading to varying degrees of deficiency of the hypothalamic releasing or inhibitory factors.     

Detection of Atrial Fibrillation During Sinus Tachycardia Induced by Exercise in Patients with Implantable Atrial Defibrillators

Accurate detection of atrial fibrillation (AF) is essential for appropriate operation of an implantable atrial defibrillator (IAD). However, during episodes of sinus tachycardia, distinction between AF and sinus rhythm (SR) using the "quiet interval" and "baseline crossing" analysis in the detection algorithm of the IAD may be difficult. The efficacy of this AF detection algorithm was tested in five patients implanted with an IAD (MFTRIX, Model 3000 or 3020, InControl Inc.) during treadmill exercise testing. The IADs were programmed to Monitor Mode with a wake up cycle of 1 minute for AF detection using the device nominal parameters or modified parameters, and to mark rhythms appropriate for shock delivery. A mean peak heart rate of 137 ± 26 beats/min was reached during maximum exercise, and one patient developed transient AF. Seventy-eight (75 in SR, 3 in AF) and 91 (89 in SR, 2 in AF) runs of AF detection were performed using the nominal and modified parameters, respectively. The IAD detected AF and SR accurately, except for one episode of false-positive AF detection during sinus tachycardia at the nominal settings, but inappropriate shocks were prevented by minimum RR interval criteria that limited discharge at high heart rate. These results indicate that the AF detection algorithm in the IAD may become more vulnerable to false-positive AF detection during sinus tachycardia, which were avoided by reprogramming the Quiet Interval and minimum RR interval criteria for AF detection. Exercise testing appeared useful to program optimal settings of the IAD in preparation for daily activities.     

Logistic回归模型中连续变量交互作用的分析

Rothman提出生物学交互作用的评价应该基于相加尺度即是否有相加交互作用,而logistic回归模型的乘积项反映的是相乘交互作用.目前国内外文献讨论logistic回归模型中两因素的相加交互作用以两分类变量为主,本文介绍两连续变量或连续变量与分类变量相加交互作用可信区间估计的Bootstrap方法,文中以香港男性肺癌病例对照研究资料为例,辅以免费软件R的实现程序,为研究人员分析交互作用提供参考.     

Atrial Fibrillation Induction and Determination of Atrial Vulnerable Period Using Very Low Energy Synchronized Biatrial Shock in Normal Subjects and in Patients with Atrial Fibrillation

The atrial vulnerable periods (A VP)for shock induction of atrial fibrillation (AF) in humans have not been clearly defined. Furthermore, the safety and efficacy of using low energy biatrial shock delivered transvenously for AF induction are unknown. We tested the safety and efficacy of using very low energy biatrial shocks, delivered between the right atrium and the coronary sinus for AF induction and used this technique to characterize the A VP in nine controls and nine patients with AF. Thirty-volt and 60-V 3/3-ms biphasic shocks were delivered, starting from 50 ms before the atrial effective refractory period with 20-ms increments until the end of the QRS interval to determine the AVP front, AVP end, and the AVP duration. Successful AF induction could be achieved in eight (89%) of the nine controls and in nine (100%) of the nine patients with AF without any complication. In patients with AF, the AVP front started significantly earlier within the QRS complex, and the AVP duration and the AVP duration/QRS percent ratios were also significantly greater as compared to controls. Furthermore, a higher induction shock energy in patients with AF was associated with an increase in AF inducibility and significantly increased the AVP duration and A VP duration/QRS percent ratio as compared to the controls. This study demonstrated the safe and efficacy of delivering a very low energy biatrial shock during the AVP within the R wave for AF induction. The characteristics of A VP in patients with AF were significantly different from normal subjects.     

Microcystic meningiomas—an unusual morphological variant of meningiomas

Evidence for tumour suppressor genes (anti-oncogenes, hemerogenes, flatogenes) has been obtained from the behaviour of familial childhood tumours in man, tumours in Drosophila caused by recessive mutations, experiments on fusing tumour cells to normal cells in tissue culture and revertants of oncogene-transformed cells. They may comprise more than one class of genes, one of which is likely to consist of genes responsible for normal differentiation. In large long-lived animals like man, which have a large potential somatic mutational load, mutant genes are associated with autosomal dominant behaviour in families. The susceptible individuals inherit heterozygosity of the tumour gene but the emergence of a tumour appears to follow a second somatic mutational event which results in homozygosity or hemizygosity. Hence, in tumour cells the mutations behave in a recessive manner. Success in isolating the normal genes may provide new tools for antenatal diagnosis of carriers and open up the possibility of developing new gene therapy.     

Emerging Energy Sources for Catheter Ablation of Atrial Fibrillation

Catheter-based ablation techniques have been increasingly used as a curative therapy for treating atrial fibrillation (AF). Currently, radiofrequency (RF) energy is the most widely accepted and used method for catheter ablation of AF. However, RF ablation has potential disadvantages, including endocardial disruption, charring, platelet activation, pulmonary vein stenosis, and thrombus formation, and has limited efficacy in performing atrial linear ablation. As a result, new alterative energy sources have been explored for AF ablation. These new technologies, including cryoablation, microwave, ultrasound, and laser have different potential advantages over RF, but all of them have limited clinical experiences. Furthermore, the emergence of these new ablation energy sources should be paralleled with development of new ablation catheters, mapping and imaging tools to improve the successful rate of AF ablation. In the future, conventional RF ablation will remain the standard approach for AF, but some of these energies may be used in combination at specific sites for safety reasons, such as the use of cryoablation inside PVs or the use of microwave to create long atrial linear ablation more effectively.