Telesensor integrated circuits.

Progress in personal computing has recently permitted small research programs to design and simulate application-specific integrated circuits (ASICs). Inexpensive fabrication of silicon chips can then be obtained using chip foundries, and quite complex circuits can be greatly reduced in size with an accompanying increase in certain performance characteristics. Within the past 5 years it has also become possible to design ASICs which can transmit and receive radio signals and which thus may be employed in applications in which wired connections for input and output of signals are not practicable. We are currently developing research-grade prototype ASICs for the monitoring of human vital signs. In this case one or more sensors placed on an ASIC provides a signal to be transmitted a distance of 2-3 meters to a receiver/display unit. The use of ASIC telesensors provides the possibility of wireless monitoring, including long-term monitoring, with inexpensive and unencumbering devices. Their self-contained nature permits a number of potential uses in future biomedical applications as new sensors are devised which are amenable to deployment on silicon.

Pathways of coronary care--a computer-simulation model of the potential for health gain.

A computer-simulation model of the need for cardiology services is described. The model simulates the potential for health gain, in terms of a fall in mortality, determining the effect of alterations in prevention and treatment rates. The model was initially developed from a pathways-of-care flow chart, which originated from a working group consisting of a consultant cardiac surgeon, cardiologists, and public-health physicians, together with statisticians and an operational-research analyst. The original purpose of the model was as a communication tool, to help nonclinicians to have a better understanding of how and why doctors work as they do, but it has since been developed for use in setting and meeting health targets. It enables quantification of the effects of changing different combinations of key variables over time. It is designed to answer 'what if?' questions of the type 'What would the effect of a 10% reduction in the incidence of angina be on the number of deaths, angiograms, angioplasties, and coronary-artery bypass grafts. The model has been made available in a form which only requires a Lotus 123 spreadsheet package to enable it to run, and it is designed to be easy to use with the assistance of simple two-key commands throughout. The model has been used by district health authorities to calculate the response required in their own local areas to achieve targets for the year 2000.

Vitamin D and femoral neck fractures in elderly South Australian women.

The vitamin D status of women with femoral neck fractures and of male and female nursing-home residents in South Australia was assessed and compared with that of ambulant normal elderly women and young male and female controls. Serum 25-hydroxyvitamin D (25OHD) was assayed with a competitive protein-binding method including a chromatography step. The mean serum 25OHD levels in the patients with femoral neck fractures (39.2 [SE 2.6] nmol/L) and in the nursing-home residents (28.9 [SE 1.3] nmol/L) were significantly lower than those in the ambulant elderly women (67.6 [SE 3.9] nmol/L) and young controls (76.9 [SE 3.7] nmol/L) (P less than 0.001 in each case). The serum 25OHD levels were unrelated to age in the normal ambulant subjects. There was a significant seasonal variation in the results of routine 25OHD assays performed in our laboratory, but no such variation was seen in the nursing-home residents. We conclude that vitamin D deficiency is common in housebound subjects, and that femoral neck fractures occur mainly in subjects who were housebound before the fracture.

Clinical cardiovascular experiences with iopamidol: a new non-ionic contrast medium.

Iopamidol, a new non-ionic water-soluble contrast medium, has been compared with standard ionic media in a number of cardiovascular applications. It is stable in aqueous solution, is much less viscous and only slightly more osmolar than metrizamide. Compared to sodium meglumine diatrizoate in a series of 40 coronary arteriograms, it produced a consistent and highly significant decrease in the incidence and severity of hypotension and bradycardia following intracoronary injection. In the same group and in 62 children undergoing ventricular or great vessel angiocardiography, a subjective assessment of patient reaction showed that iopamidol was better tolerated than the ionic medium. There was a very strong patient preference for iopamidol in a group of 20 of the adult patients who had also consented to femoral artery injections of both media. Throughout these series there was no detectable difference in arterial image quality between the media. Venous phase opacification during arterioportography was assessed in 11 cases comparing iopamidol with sodium meglumine iothalamate. No significant difference was found. We conclude that iopamidol is clearly preferable to ionic media for routine cardiovascular applications.

Cardiac arrhythmias 48 hours before, during, and 48 hours after discharge from hospital following acute myocardial infarction.

The cardiac rate and rhythm were studied by 24-hour ambulatory electrocardiographic recording in 44 patients before, during, and after being discharged from hospital following an acute myocardial infarction. The first recordings were started 48 hours before discharge, the second on the morning of the day of discharge, and the third 48 hours after discharge (at home). While in hospital and after returning home the heart rate fell during sleep but there was no diurnal variation in the frequency of ventricular extrasystoles. Daytime heart rate and both the frequency and grade (severity) of ventricular arrhythmias were significantly raised 48 hours after discharge. The frequency of ventricular extrasystoles during sleep was also increased in the 48 hours post-discharge recording. Rises in heart rate and frequency and severity of ventricular extrasystoles were observed on the morning of the day of discharge, increasing up to the time of leaving hospital, but during the journey home they all diminished. No relation was found between ventricular arrythmias during early convalescence and (i) ventricular arrhythmias during the acute phase of acute myocardial infarction (including ventricular fibrillation); (ii) peak aspartate aminotransferase; (iii) the level of anxiety; or (iv) the personality type. Six patients taking beta-blocking drugs behaved similarly. Five patients taking anxiolytic drugs has significantly raised frequency of ventricular extrasystoles during each 24-hour electrocardiogram. In spite of the above findings, at the time of leaving hospital after acute myocardial infarction there does not appear to be a serious risk from the development of major cardiac arrhythmias.

Determinants of systemic vascular resistance in children with congenital heart disease.

It is well known on the basis of acute experiments that changes in systemic arterial oxygen saturation, haemoglobin concentration and acid-base state produce changes in systemic vascular resistance. However, it is not known whether the same changes occur in the chronic state. In order to investigate this problem, we measured systemic vascular resistance in a population in whom chronic changes in these variables are common, namely 195 subjects with congenital heart disease. The significance of these factors was assessed by their ability to predict systemic vascular resistance in a multiple regression equation which also took account of the size of the patient. No matter how the size of the patient was allowed for, haemoglobin concentration, systemic arterial pH (or non-respiratory pH) and systemic arterial oxygen saturation were significantly (P less than 0.025) and positively correlated with systemic vascular resistance. We conclude that, as far as these factors are concerned, the mechanisms operating in the acute state continue to function in the chronic state.

Incidence of coronary artery disease in patients with valvular heart disease.

The case notes, cardiac catheterisation data, and coronary arteriograms of 239 patients investigated for valvular heart disease during a five year period were reviewed. Angina present in 13 of 95 patients with isolated mitral valve disease, 43 of 90 patients with isolated aortic valve disease, and 18 of 54 patients with combined mitral and aortic valve disease. Significant coronary artery disease was present in 85 per cent of patients with mitral valve disease and angina, but in only 33 per cent of patients with aortic valve disease and angina. Patients with no chest pain still had a high incidence of coronary artery disease, significant coronary obstruction being present in 22 per cent with mitral valve disease, 22 per cent with aortic valve disease, and 11 per cent with combine mitral and aortic valve disease. Several possible clinical markers of coronary artery disease were examined but none was found to be of practical help. There was, however, a significant inverse relation between severity of coronary artery disease and severity of valve disease in patients with aortic valve disease. Asymptomatic coronary artery disease is not uncommon in patients with valvular heart disease and if it is policy to perform coronary artery bypass grafting in such patients, routine coronary arteriography must be part of the preoperative investigation.

Reflex inotropic responses of the heart from lung inflation in anaesthetized dogs.

In anaesthetized dogs a tracheal divider was inserted to allow inflation of one lung with various pressures. Left ventricular inotropic responses were assessed by measuring the maximum rate of change of left ventricular pressure (dP/dt max) using a preparation in which aortic pressure, carotid sinus pressure and heart rate were held constant. Heart responses to lung inflation were variable. In five dogs there was a consistent tachycardia, in three bradycardia and in six there was no change. In the dogs in which heart rate increased, inflation of one lung with pressures between 0.5 and 2.0kkPa (5 and 20 cm H2O) resulted in no significant change in dP/dt max. In the remaining dogs there was a decrease in dP/dt max which was more pronounced at the higher inflation pressures. The negative inotropic response was shown to be a reflex with afferent nerve endings in the lung and with the efferent pathway in the sympathetic nerves.

Controlled environment therapy in the management of lymphoedema: a case report.

A case of surgically-treated elephantiasis of a lower limb is reported in which preoperative controlled environment therapy (CET) proved to be an effective, rapid method of reducing the oedema.

Retrograde left atrial catheterization in children with congenital heart disease.

Entry into the left atrium during cardiac catheterization may be essential for full assessment of the hemodynamic situation, particularly for the accurate calculation of pulmonary blood flow and pulmonary arteriolar resistance. The retrograde transaortic transmitral technique of left atrial catheterization has been described in adults but no detailed reports are available for the pediatric age group. Experience of this technique in 43 children with congenital heart disease is now presented, with a success rate of 67 per cent and a low incidence of complications. This method compares favorably with other methods of left atrial catheterization when the interatrial septum is intact.