Atrial Electrograms and Activation Sequences in the Transition Between Atrial Fibrillation and Atrial Flutter

Transition Between Atrial Fibrillation and Flutter. Introduction: The eletrophysiologic mechanism of atrial fibrillation (AF) has a wide spectrum, and it seems that some atrial regions are essential for the occurrence of a particular type of AF. We focused on one type of AF: AF associated with typical atrial flutter (AFI), which was right atrial (RA) arrhythmia, and sought to investigate intra-atrial electrograms and activation sequences in the transition between AF and AFL.
Methods and Results: Intra-atrial electrograms and activation sequences in the R.A free wall and the septum were evaluated in the transition between AF and AFL in seven patients without organic heart disease (all men; mean age 57 ± 11 years). In five episodes of the conversion of AFL into AF, the AFL cycle length was shortened (from 211 ± 6 msec in stable AFL to 190 ± 15 msec before the conversion, P, 0.001). Interruption of the AFL wavefront and an abrupt activation sequential change induced by a premature atrial impulse resulted in fractionation and disorganization of the septal electrograms. During sustained AF, septal electrograms were persistently fractionated with disorganized activation sequences. However, the RA free-wall electrograms were organized, and the activation sequence was predominantly craniocaudal rather than caudocranial throughout AF. In 12 episodes of the conversion of AF into AFL, the AF cycle length measured in the RA free wall increased (from 165 ± 26 msec at the onset of AF to 180 ± 24 msec before the conversion, P, 0.001). AFL resumed when fractionated septal electrograms were separated and organized to the caudocranial direction, despite the RA free-wall electrograms remaining discrete and sharp with an isoelectric line.
Conclusion: Changes of the electrogram and activation sequence in the atrial septum played an important role in the transition between AF and AFL.     

Managed Care and Cardiac Pacing and Electrophysiology

Managed care is having an increasing impact on the administrative and clinical practices of cardiovascular specialists including physicians providing cardiac pacing and electrophysiology services. This article provides an overview of the five key areas where managed care is affecting cardiovascular practices including the following: (1) administrative burdens; (2) competitive/economic pressures; (3) cost/efficiency requirements; (4) interference in the physician-patient relationship; and (5) disruption in physician-physician relationships. The issues associated with each of these areas of concern are discussed in detail with specific examples that are relevant to cardiac pacing and electrophysiology. (PACE, Vol. 16, August 1993) managed care. Health Maintenance Organizations (HMOs), Preferred Provider Organizations (PPOs)     

Lifetime costs of cerebral palsy

This study quantified the lifetime costs of cerebral palsy (CP) in a register-based setting. It was the first study outside the US to assess the lifetime costs of CP. The lifetime costs attributable to CP were divided into three categories: health care costs, productivity costs, and social costs. The population analysed was retrieved from the Danish Cerebral Palsy Register, which covers the eastern part of the country and has registered about half of the Danish population of individuals with CP since 1950. For this study we analysed 2367 individuals with CP, who were born in 1930 to 2000 and were alive in 2000. The prevalence of CP in eastern Denmark was approximately 1.7 per 1000. Information on productivity and the use of health care was retrieved from registers. The lifetime cost of CP was about €860 000 for men and about €800 000 for women. The largest component was social care costs, particularly during childhood. A sensitivity analysis found that alterations in social care costs had a small effect, whereas lowering the discount rate from 5 to 3 per cent markedly increased total lifetime costs. Discounting decreases the value of costs in the future compared with the present. The high social care costs and productivity costs associated with CP point to a potential gain from labour market interventions that benefit individuals with CP.     

Stereoselective Synthesis of Peptidyl Trifluoromethyl Alcohols and Ketones: Inhibitory Potency Against Human Leucocyte Elastase,Cathepsin G,Porcine Pancreatic Elastase and HIV-1 Protease

New fluorinated inhibitors have been designed to target two major proteases—human leucocyte elastase and HIV-1 protease. Two series of β-peptidyl trifluoromethyl alcohols (TFMAs) Z-L-Val-NH-*CH(Y)-*CH(OH)-CF₃, where *C is the chiral centre, varied in the nature of the substituent Y, a phenylethyl [-(CH₂)₂-C₆H₅] or an isopropyl [-CH(CH₃)₂] group. These TFMAs were first synthesized as two pairs of the syn and anti diastereoisomers. The inhibitory effects of these mixtures were then assessed on three serine proteases chosen on the basis of the aromatic and aliphatic nature of the substituents—human leucocyte elastase (HLE), human cathepsin G (HCG) and porcine pancreatic elastase (PPE). In the presence of detectable inhibition, each epimer at C2 was separated to determine its inhibition constant (K_i) towards HLE, HCG and PPE. The stereoisomerically pure TFMAs were then oxidized into peptidyl trifluoromethyl ketones = 5·65 × 10^?4 M). The tested compounds also had structural properties compatible with recognition by HIV-1 protease. The inhibition of the enzyme was observed with TFMK only (IC50 = 15–200 μM). The phenylethyl substituent promoted inhibition by a factor of 10 (IC50 = 15μM) compared with the isopropyl substituent (IC50 = 200 μM) leading to selective inhibition of HIV-1 protease. Isomerically pure TFMKs were more potent towards HLE than the alcohols from which they were obtained. However, an enantiomerically pure TFMA selectively inhibited HLE unlike its TFMK analogue which also inhibited PPE. This last result together with the selective inhibition of HIV-1 protease by TFMK with a phenylethyl substituent might be relevant to the design of specific HLE and HIV-1 inhibitors as therapeutic agents.     

Plasma membrane fluidity in isolated rat hepatocytes: A comparative study using DPH and TMA-DPH as fluorescent probes

The study of membrane fluidity is a rapidly expanding field of research and its interest in hepatology has been stressed recently. The present study is the first report concerned with the determination of membrane fluidity of isolated rat hepatocytes. The data have been compared with those obtained in plasma membrane fractions and subfractions (basolateral or canalicular) derived from homogenates. The fluorescent probes used to measure the fluidity were diphenylhexatriene (DPH) a 'classical' probe, and its derivative trimethylammoniodiphenylhexatriene (TMA-DPH) at 25 degrees C and at 37 degrees C. The values obtained with DPH were lower than those with TMA-DPH, probably due to the localization of the probes in different regions of the phospholipid bilayer. In addition, DPH revealed significant differences in the fluorescence polarization values obtained in isolated hepatocytes compared with membrane fractions, which was in contrast to TMA-DPH, where the respective values were of the same order of magnitude. This behaviour is probably due to the mobility of DPH in the membrane core and its rapid internalization into the cell, whereas TMA-DPH remains anchored for a long time on the cell surface. These findings suggest that TMA-DPH is a better probe than DPH for measuring the fluorescence polarization of whole isolated hepatocytes and that the use of different probes might be of help in exploring different zones of the membrane bilayer.     

MOLLUSCUM CONTAGIOSUM OF THE SOLE

SUMMARY.— A case is reported of molluscum contagiosum on the sole of the foot, which was diagnosed virologically. The difficulty of making the diagnosis on clinical grounds in this site is emphasized. The diagnosis may rather be missed than rare.