The Effect of Bipole Tip-to-Ring Distance in Atrial Electrodes upon Atrial Tachyarrhythmia Sensing Capability in Modern Dual-Chamber Pacemakers

Introduction: Accurate atrial arrhythmia discrimination is important for dual chamber pacemakers and defibrillators. The aim was to assess the accuracy of atrial arrhythmia recording using modern devices and relate this to atrial tip-to-ring (TTR) distance.
Methods: One hundred eighty-two patients (72 ± 9 years, 55% male) with paroxysmal atrial fibrillation were enrolled and were included in the study if they had an atrial fibrillation (AF) burden of 1–50% during a monitoring phase. Seventy-nine patients fulfilled these criteria and were followed for at least 5 months. Electrodes were classified as having short (<10 mm), medium (10–12), or long (13–18) atrial TTR spacing.
Results: Two thousand eight hundred eighty-three detailed onset reports were analyzed; 730 (25%) demonstrated aberrant sensing. Six percent were due to farfield R wave oversensing (FFRWO) and 19% due to undersensing, sometimes occurring in the same patient and study phase. FFRWO was significantly reduced with short TTR electrodes (P < 0.05). Undersensing due to sensitivity fallout was 18% (short), 24% (medium), and 17% (long) (P = ns). Undersensing due to pacemaker blanking was 11% (short), 11% (medium), and 12% (long) (P = ns). Active fixation electrodes did not show any difference from passive fixation.
Conclusion: Atrial electrodes with a short TTR (<10 mm) significantly reduce FFRWO without increasing undersensing and should be used routinely in patients with paroxysmal atrial tachyarrhythmias. However, 20% of atrial tachyarrythmia episodes were incorrectly classified as terminated by these modern devices due to undersensing. Clinicians should be wary of using device-derived endpoints that rely on AF episode number or duration as these may be falsely increased or reduced, respectively. (PACE 2010; 85–93)     

Assessment of Alcohol Withdrawal: the revised clinical institute withdrawal assessment for alcohol scale (CIWA-Ar)

A shortened 10-item scale for clinical quantitation of the severity of the alcohol withdrawal syndrome has been developed. This scale offers an increase in efficiency while at the same time retaining clinical usefulness, validity and reliability. It can be incorporated into the usual clinical care of patients undergoing alcohol withdrawal and into clinical drug trials of alcohol withdrawal.     

The Role of Ultrasound in the Diagnosis of Parenchymal Disease in Transplanted Kidneys

The accuracy of ultrasonic diagnosis of parenchymal disease in renal transpiants was deter mined by comparing the ultrasonic diagnosis with the clinical diagnosis in 120 studies on 50 patients. The clinical diagnosis was based on clinical, biochemical and radionuclide studies, and in some cases, biopsy. At the time of the original ultrasound report clinical information was available (biopsy reports were not). All ultrasound studies were subsequently reported in random order without any clinical information and without comparison with previous or subsequent scans. This study suggests that ultrasound with or without clinical information cannot be used as a reliable basis for the diagnosis of parenchymal disease of transplanted kidneys.     

"Supernormal" Conduction and Excitability

"Supernormal" Conduction and Excitability. Electrocardiograph manifestation of "supernormal" conduction is defined as conduction that is more rapid than expected or presence of conduction when block is anticipated. It is not supernormal in the sense of being more rapid than normal. Therefore, the term relative supernormality or "supernormality" is more appropriate. The mechanism of "supernormal" conduction is conduction during a period of supernormal excitability and conduction associated with altered membrane potential. Some of the more common phenomena that are not dependent on conduction during the supernormal period but manifest better than expected conduction, thus simulating "supernormal" conduction, include dual AV nodal conduction, the "gap" phenomenon, "peeling back" of the refractory period, summation of subthreshold responses, diastolic phase 4 depolarization, and phasic autonomic influences.     

A calmodulin-like protein as an extracellular mitogen for the keratinocyte

This study investigated the importance of extracellular calmodulin to the proliferation of the keratinocyte. Normal keratinocytes in culture produced a calmodulin-like protein in their culture media, the level of which increased abruptly and transiently during their growth. This protein was calmodulin-like, in that it specifically bound to a calmodulin affinity column, exhibited calmodulin-like immunoreactivity in both an ELISA and on immunoblots when immunostained with a monoclonal antibody against calmodulin, had an apparent Mr between 18,000 and 20,000, and stimulated activity in a calmodulin-dependent phosphodiesterase enzyme assay. Addition of exogenous pure caimodulin was of no further mitogenic benefit to the keratinocytes. and slightly reduced proliferation under the culture conditions used. However, addition of either a neutralizing antibody to calmodulin, or W7-agarose, to the culture media of proliferating cells markedly inhibited their proliferation. Accordingly, a calmodulin-like protein was found to satisfy all but one of the criteria for its action as an autocrine growth factor for the keratinocyte. We propose that the lack of mitogenic response to calmodulin in vitro is due to the cell meeting its own requirement for extracellular calmodulin.     

The school entry medical examination. What do teachers think of it?

Questionnaires were sent to 76 schools in the Macclesfield district. Seventy-four of these were returned by head teachers and/or reception teachers. Replies concerned the school entry medical examination, information on individual children, general health information and access to professionals. Additional comments on any aspects of the service were also solicited. The results have been analysed. The majority of teachers considered that the school entry medical examination is of value, but the quality of information reaching teachers is viewed more critically. Meetings were the most favoured means of communication, but there are obvious defects in the system. Some teachers did not even know of access channels. If improvements do not occur some of the value of the examination will be lost. Suggestions for better communications are made. With local management of schools, teacher opinion must be considered if a better school health service is to be provided for the children of the district.     

The role of laminins in basement membrane function

Laminins are a family of multifunctional macromolecules, ubiquitous in basement membranes, and represent the most abundant structural noncollagenous glycoproteins of these highly specialised extracellular matrices. Their discovery started with the difficult task of isolating molecules produced by cultivated cells or extracted from tissues. The development of molecular biology techniques has facilitated and accelerated the identification and the characterisation of new laminin variants making it feasible to identify full-length polypeptides which have not been purified. Further, genetically engineered laminin fragments can be generated for studies of their structure-function relationship, permitting the demonstration that laminins are involved in multiple interactions with themselves, with other components of the basal lamina, and with cells. It endows laminins with a central role in the formation, the architecture, and the stability of basement membranes. In addition, laminins may both separate and connect different tissues, i.e. the parenchymal and the interstitial connective tissues. Laminins also provide adjacent cells with a mechanical scaffold and biological information either directly by interacting with cell surface components, or indirectly by trapping growth factors. In doing so they trigger and control cellular functions. Recently, the structural and biological diversity of the laminins has started to be elucidated by gene targeting and by the identification of laminin defects in acquired or inherited human diseases. The consequent phenotypes highlight the pivotal role of laminins in determining heterogeneity in basement membrane functions.     

Effect of magnesium on coagulation as measured by thrombelastography

Magnesium has long been assumed to have anticoagulant properties,but the effect has been poorly quantified. The thrombelastograph(TEG) was used to evaluate the effect of magnesium using bloodfrom volunteers. Magnesium sulphate was added to one blood sampleand another sample was used as a control. Both samples weretested simultaneously and the results evaluated against themagnesium concentration measured in each sample. At serum magnesiumconcentrations < 3 mmol litre^–1, there were no significanteffects of magnesium. With increasing magnesium concentrationsthere was a statistically significant but small prolongationof the r time, k time and r+k time. Maximum amplitude was affectedonly at magnesium concentrations > 7 mmol litre^–1 Magnesiumhas only minimal effects on coagulation which are unlikely tobe clinically important.     

High allergic reactivity in a tropical environment

The prevalence of atopic disease in tropical populations is often considered to be low, and this has been attributed to an immunological modulating effect of intestinal helminthiasis. We, however, report that the frequency of positive allergic history and skin-test reactivity to groups of major environmental allergens is extremely high (43 and 63% respectively) in children in Caracas, Venezuela (Lat. 10°N). These values were statistically significantly greater than in a group of children with a similar age and sex distribution studied in parallel, but having limited or no contact with a tropical environment (29 and 37% respectively). The two groups differed with respect to the sporadic and light intestinal helminthic infections (such as ascariasis) experienced by the Venezuelans, compared to rare contact in the ‘non-tropical’ group. This was probably the cause of the increased total serum IgE levels of the former children (369 vs 68 iu/ml), and possibly, therefore, their higher allergic reactivity.