Heart rate variability: two eras of investigation

Changes in membrane potential are a regulatory signal for voltage-gated ion channels including the family of Ca2+ channels. This regulatory role includes the voltage-dependent opening, closing, and inactivation of ion channels and the control of drug access and affinity for discrete channels states. Membrane potential is both a short- and long-term regulatory signal controlling the number and function of these voltage-gated channels. Depolarization of neuronal and neurosecretory cells produces down-regulation of L-type voltage-gated Ca2+ channels. These processes are described and their relevance to physiologic and pathologic processes of neuronal development and neuroprotection are indicated.     

Giant cell myocarditis. Report of a case

The authors report a case of giant cell myocarditis leading to rapidly progressive cardiac failure despite immuno-suppressor treatment in a 20 year old woman. The cardiac failure was successfully managed by implantation of a left ventricular assist device and then cardiac transplantation. The problems encountered underline the importance of accurate diagnosis by endomyocardial biopsy before undertaking treatment and the difficulties in the choice of appropriate method of assistance in this indication. Giant cell myocarditis is a rare cause of cardiac failure and should be considered in the differential diagnosis in view of its clinical features and risk of progression. The literature and the therapeutic implications are discussed.     

Fatigue crack initiation and propagation of binder-treated powder metallurgy steels

Many of the targeted applications for powder-metallurgy materials, particularly in the automotive industry, undergo cyclic loading. It is, therefore, essential to examine the fatigue mechanisms in these materials. The mechanisms of fatigue-crack initiation and propagation in ferrous powder-metallurgy components have been investigated. The fatigue mechanisms are controlled primarily by the inherent porosity present in these materials. Since most, if not all, fatigue cracks initiate and propagate at the specimen surface, surface replication was used to determine the role of surface porosity in relation to fatigue behavior. Surface replication provides detailed information on both initiation sites and on the propagation path of fatigue cracks. The effect of microstructural features such as pore size and pore shape, as well as the heterogeneous microstructure on crack deflection, was examined and is discussed. Fracture surfaces were examined to elucidate a mechanistic understanding of fatigue processes in these materials.     

99Tcm-MDP scintigraphy in high-voltage electrical burn patients

In high-voltage electrical burn injuries (> 1000 V), it is difficult to identify the site and extent of non-viable deep tissue damage for debridement to avoid further tissue injury from wound infection and the risk of sepsis. This prospective study was designed to evaluate the usefulness of 99Tcm-methylene di-phosphonate (99Tcm-MDP) scintigraphy in detecting the extent of tissue injury and determining the level of amputation required for electrical burn patients. Over a 5 year period, 33 high-voltage electrical burn patients were studied. Blood flow and blood pool studies revealed absent perfusion in 37 limbs, all of which eventually were amputated. In addition to a routine three-phase bone scan, images were obtained at 30-60 min (early images) to evaluate whether soft tissue injury could be detected better at that time. For comparison of the detection rate from the early images and bone (delayed) images, 164 corresponding spot views of both images were reviewed. Eighty-three and 125 tissue necrotic lesions were demonstrated by the early images and bone images respectively. All of the 83 lesions found by the early images were more clearly identified by the bone images. All but one of the 125 lesions underwent surgical debridement or amputation. We concluded that the blood flow and blood pool images correlated well with the level of amputation required. The site and extent of tissue necrotic lesions can be clearly identified on 99Tcm-MDP bone scans. Because the early images were less sensitive in detecting tissue necrosis, we suggest that early imaging is not necessary.     

Anaemia in malaria control: a practical approach

Mortality from malarial anaemia and malarial infection in those who are already anaemic yet have some degree of compensation is now beginning to receive the attention it deserves. It is of particular concern in Africa and especially in young children and pregnant women. The asymptomatic parasitaemia remaining after poor response to full antimalarial treatment may lead to life-threatening anaemia; as drug-resistant strains of the malarial parasite proliferate this is becoming increasingly important. It is now possible to estimate haemoglobin levels, simply, cheaply, easily and safely, using a haemoglobin colour scale which is being developed by the World Health Organization. The potential and practical value of this scale in malaria-control programmes was demonstrated in a small, preliminary trial in 1995. Estimation of anaemia should become an additional parameter in the traditional malariometric survey. Haemoglobin concentrations should also be taken into consideration in the management of malaria patients at the primary-care level, particularly in deciding whether a patient should be referred to an appropriate treatment centre. The accurate prediction of clinical outcome of malaria and anaemia, and indication of the appropriate action (determined by a case-based reasoning device) should be possible in the near future.     

Methotrexate therapy in rheumatoid arthritis: a life table review of 587 patients treated in community practice

To determine whether methotrexate (MTX) maintains its effectiveness in rheumatoid arthritis (RA) in the setting of community based private rheumatology practice we used life table analysis to review the combined experience of a group of these practices. Of 587 patients with RA who started to take MTX, total termination rate at 70 months was 24.4% with most terminations prompted by drug toxicity. Older age (greater than 65 years) was associated with higher rates of toxicity. Treatment termination rates varied substantially between rheumatologists. We conclude that MTX therapy for RA is well tolerated and maintains effectiveness for at least 70 months.