Experience with the Clarion device in children: surgical aspects, choice of strategy for stimulation and rehabilitation and preliminary results.
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Audiometry, Speech↗
Biomedical subjects
D Ballantyne
Publications and source records attributed to D Ballantyne.
Effect of exercise training on the total ischaemic burden: an assessment by 24 hour ambulatory electrocardiographic monitoring.
OBJECTIVE: To examine the effect of prolonged high intensity exercise training on total ischaemic burden in men with chronic stable angina pectoris. DESIGN: A randomised controlled trial based on 24 hour ambulatory electrocardiographic monitoring of patients on two occasions a year apart. SETTING: Cardiology department of a large general hospital. SUBJECTS: 40 men under 60 years of age with chronic stable angina pectoris and no previous myocardial infarction. RESULTS: After training the exercise group showed a 30% reduction in frequency of ST segment depression. There were significant reductions in painful episodes of ischaemia and those triggered by changes in heart rate. There was also a trend towards a reduction in silent ischaemia and episodes not triggered by changes in heart rate. The duration of ischaemic episodes was also reduced. No significant change in frequency or severity of dysrhythmia was shown. CONCLUSIONS: Exercise training reduces total ischaemic burden in patients with angina pectoris by reducing the frequency and duration of all types of ischaemic episode.
Adult↗
Influence of power and aerobic exercise training on haemostatic factors after coronary artery surgery.
OBJECTIVES: To determine the effects of aerobic and power exercise training on haemostatic factors after coronary artery surgery and to compare the effect of the two exercise programmes. DESIGN: A prospective randomised controlled study of six months aerobic and power exercise training in men after coronary artery surgery. SETTING: Exercise rehabilitation classes in a teaching hospital in Glasgow. PATIENTS: 55 men within 12 months of coronary artery surgery recruited from surgical centres and medical clinics and asked to participate in the study. INTERVENTIONS: Assessments, including a treadmill test, measurements of haemoglobin, platelet, fibrinogen, factor VIIc, and fibrinopeptide A concentrations, and packed cell volume, done at baseline, three months, and six months. Patients in the two exercise groups attended training sessions three times weekly for six months. Control patients had no formal exercise training but continued with their leisure time activities. MAIN OUTCOME MEASURES: Exercise performance on a treadmill, haematology, and haemostatic factor assays at baseline, three months, and six months. RESULTS: In the aerobic trained group exercise performance increased significantly over baseline at three months (interval change 146.7, 95% confidence interval (95% CI) 52.5 to 240.9 s, p = 0.003) and was maintained at six months (interval change 172.1, 95% CI 63.3 to 280.9 s, p = 0.002). In the power trained groups significant improvement in exercise performance was delayed until six months (interval change 99.9 s, 95% CI 20.3 to 170.5 s, p = 0.01). Exercise performance in the control did not change significantly. Haemoglobin, concentration, packed cell volume, and platelet counts did not change significantly at any time. Fibrinogen concentration was significantly lower in the aerobic group than the other two groups at three months (2.96 g/dl compared with 3.3 g/dl and 3.87 g/dl in the power and control groups, p = 0.01). The power group had a lower fibrinogen concentration than the control group (p = 0.04). The lower fibrinogen concentration in the aerobic group was maintained at six months. There was a gradual rise in factor VIIc concentrations in the aerobic and control groups compared with a small fall in the power group. Fibrinopeptide A concentrations showed no consistent changes. CONCLUSIONS: Aerobic exercise training after coronary artery surgery causes an early favourable change in treadmill performance and in fibrinogen concentrations, that is maintained with further training. Power exercise training causes delayed benefit in treadmill performance. It also causes a small fall in fibrinogen concentrations. These changes may be relevant in reducing cardiovascular morbidity from graft failure and occurrence of myocardial infarction after coronary artery surgery.
Adult↗
Effects of daily high-intensity exercise on myocardial perfusion in angina pectoris.
Forty male patients with chronic stable angina pectoris and no prior myocardial infarction were studied by planar thallium scintigraphy with use of circumferential profile analysis. Ischemic defects were assessed by measuring degrees of circumference involved and area of defect. Data were collected for 3 vascular regions in each of 3 views (anterior, 45 degrees and 65 degrees left anterior oblique projection). Patients were then randomized to exercise and control groups, the former training for a period of 1 year using the Canadian Airforce plan for physical fitness. After 1 year, both groups were restudied. Exercise training produced a 34% reduction in degrees of ischemia overall (p less than 0.02), the most significant change being seen on the anterior view (72 degrees +/- 59 degrees before vs 30 degrees +/- 35 degrees after training). Regional analysis showed markedly improved perfusion anterolaterally and apically on the anterior view and anteroseptally on the 65 degrees left anterior oblique view. These improvements support the hypothesis that exercise training improves myocardial perfusion by enhanced collateral function.
Adult↗
Rhythm generation in brainstem cultures grown in a serum-free medium.
Electrophysiological studies were carried out on long term cultured brainstem tissue taken from neonatal rats with the object of investigating mechanisms underlying respiratory rhythm generation. The preparations were derived from 360 microns thick horizontal medullary slices which were explanted into a chemically defined nutrient medium and which remained organotypically intact for ca. 1 month. In 44 of the 50 explants examined both periodic and aperiodic bioelectric activity was detected, the cycle length of the former ranging from 0.5 to 10 s (mean, 2.7 s) at a pH of 7.4 and bath temperature of 32 degrees C. Periodic activity could take several forms, but commonly consisted of regularly repeated, 100-300 ms long, depolarizing (D-) waves or sequences of inhibitory and/or excitatory postsynaptic potentials. Lowering the pH of the superfusate by lowering the bicarbonate concentration, increasing the pCO2 or adding H+ shortened the interval between periodic events, and increased both the amplitude and duration of the D-waves. The interval was also shortened when the bath temperature was increased (Q10: ca.2.5). The mean resting membrane potential of neurons exhibiting periodic activity was -49 mV (n = 62) and not significantly different from that of aperiodically discharging neurons either in the same preparations or in cultured explants from the neocortex. These observations suggest that brainstem cultures constitute a useful 'model' system for studying pH-dependent rhythm generation in small neuronal networks of the medulla.
Action Potentials↗
Inhibition of caudal medullary expiratory neurones by retrofacial inspiratory neurones in the cat.
1. Comparisons between the spike discharge of inspiratory neurons within the retrofacial area (RFN), and the membrane potential of expiratory neurones within the caudal medulla were made in pentobarbitone-anaesthetized, vagotomized, artificially ventilated cats. Spike-triggered averaging (STA) of synaptic potentials, triggered by the discharge of inspiratory RFN neurones, was utilized to test for synaptic connectivity. 2. Eighty-nine neurons with respiratory-phased discharge patterns were recorded in the vicinity of the RFN. Fifty-four neurones discharged at or slightly before the onset of the inspiratory burst activity of the phrenic nerve and continued firing throughout inspiration. Two continued to fire during post-inspiration. Forty-five of fifty-four inspiratory RFN neurones exhibited incrementing discharge patterns, six discharged with a plateau pattern, while only three neurones had a decrementing discharge pattern. 3. The membrane potential trajectories of caudal expiratory neurones revealed a typical wave of early inspiratory hyperpolarization. Occasionally, a second wave of hyperpolarization occurred during late inspiration, in conjunction with increased phrenic nerve activity. 4. Spike-triggered averaging revealed averaged inhibitory postsynaptic potentials (IPSPs), indicative of inhibitory synaptic connections, between eight and sixty-three pairs of RFN inspiratory and caudal expiratory neurones. 5. Inhibitory postsynaptic potentials detected by STA exhibited a relatively long latency and a slow time course. The IPSPs began, on average, 3.8 ms after an RFN action potential. The rise times, half-widths and durations of IPSPs were longer than expected for a monosynaptic somal input from myelinated axons of inspiratory RFN neurones. It is suggested that an inhibitory relay neurone in the immediate vicinity of the expiratory neurones is activated by a collateral of the RFN inspiratory neurone. 6. Retrofacial inspiratory neurones were antidromically activated only when high-intensity electrical stimulation was applied in the vicinity of caudal expiratory neurones. 7. The averaged IPSPs were preceded by diphasic and triphasic 'spike potentials'. The averaged spike potentials were highly entrained to the action potentials of RFN inspiratory neurones which triggered IPSPs. The spike potentials may be terminal potentials recorded from axons of RFN inspiratory neurones. 8. Evidence for convergence of synaptic inputs was obtained from STA tests in a caudal expiratory neurone receiving IPSPs from four RFN neurones. 9. The functional significance of this observation is discussed. We conclude that RFN inspiratory neurones exert a moderate inhibitory influence and act conjointly with other types of medullary inspiratory neurones.
Animals↗
Staffing in cardiology in the United Kingdom 1990. Sixth biennial survey: with data on facilities in cardiology in England and Wales 1989.
The Sixth Biennial Survey of Staffing in Cardiology was conducted in July 1990. This report summarises the data that were collected, together with the results of a survey of facilities in cardiology made in 1989. The total number of cardiologists in the United Kingdom, defined as individuals trained in the specialty and spending at least 40% of their time working in it, is now 323. Six individuals work part time only, making 320 whole time posts. This number has increased over the two years from 1988 to 1990 by 32, of which 23 work only in the specialty and nine as general physicians with a major interest in cardiology. The rate of increase in numbers over the past decade has been reasonably consistent with an average of approximately 4.4% per year. Thirty one districts in England and Wales still have no cardiologist and 13 other districts have little provision with an average of three (visiting) sessions each per week. The population in these 44 districts is 8.3 million. Scotland also has an inadequate distribution of service in the specialty. If recommendations for cardiac surgery and angioplasty made in the Fourth Report of a Joint Cardiology Committee of the Royal College of Physicians of London and the Royal College of Surgeons of England are to be met, we calculate that we need 63 more cardiologists in our major centres. To provide one cardiologist in every district hospital and two for larger districts would require 94 more specialists, making a total shortfall of 157 individuals. We have no excess of senior registrars to provide for a major expansion at consultant level. Time spent within the senior registrar (or academic equivalent) grade has tended steadily to decline and very few now reach the end of their contracts. The need for more individuals to pass through the senior registrar grade will be met in part by a planned reduction in the training period to three years. This will be inadequate, however, because projected retirements show that the number of consultant vacancies will increase sharply from 1997. We believe that additional senior registrar posts must be created if a serious shortfall in service provision by consultants is to be avoided. The provision of non-invasive facilities in cardiology is reasonable. The need for additional equipment for invasive cardiology has not been assessed. The number of physiological measurement technicians varies considerably between regions and is generally inadequate.
Allied Health Personnel↗
Doppler echocardiography in elderly patients with ejection systolic murmurs.
Thirty-nine elderly patients, mean age 77 years (range 65 to 96), with ejection systolic murmurs were studied to evaluate the functional significance of these murmurs. Subjects were evaluated clinically, by 2-D echocardiography, and by a full Doppler echocardiography study. Good quality Doppler signals were obtained in 35 subjects. Mitral regurgitation was found to be the only significant valvular lesion in 6 patients (17%). Doppler gradients in systole across the aortic valve were less than 30 mmHg in 28 subjects (80%) and were considered not significant. Gradients of greater than 30 mmHg representing significant aortic stenosis were found in 7 subjects (20%). The clinical sensitivity in detecting significant aortic stenosis was 44% and specificity was 81%. Doppler evidence of significant aortic stenosis was found in a substantial proportion of these elderly subjects. Neither clinical assessment nor 2-D echocardiography can be relied on to exclude this condition.
Aged↗
Antianginal efficacy of exercise training: a comparison with beta blockade.
Forty men with chronic stable angina and no prior myocardial infarction were studied. Exercise tolerance testing was carried out off treatment and after beta blockade. beta Blockers were stopped and the patients were randomised to a control group and a study group of patients who undertook a one year high intensity training programme. The groups were then restudied. Submaximum heart rate was reduced by 13 beats per minute by training and by 23 beats per minute by atenolol. Training increased the maximum heart rate by 10 beats per minute and atenolol reduced it by 29 beats per minute. The double produce ST threshold was increased from 183 to 205 by training but reduced to 143 by atenolol. Maximum ST depression was similarly reduced by both training and atenolol. As a result of the effects on maximum heart rate, training produced a greater improvement in exercise tolerance than atenolol with a treadmill time increased from 741 seconds to 1272 seconds with training compared with 974 seconds with atenolol. Other variables were similarly affected. Thus the antianginal efficacy of exercise training is as good as that achieved by beta blockade and represents an alternative to such treatment.
Angina Pectoris↗
Sex differences in autoregulation of juxtamedullary glomerular blood flow in hydronephrotic rats.
The technique of the split hydronephrotic kidney of anesthetized Wistar rats was used for the first time to study afferent and efferent arterioles of juxtamedullary (JM) glomeruli in vivo and to compare their behavior with that of the cortical glomeruli in female (F, 270 g body wt) and male (M, 400 g body wt) rats. The mean length of cortical efferent arterioles (F, 260; M, 380 microns) was less than 10% the length of JM efferent arterioles. Luminal diameters of the JM afferent arteriole (F, 17.1; M, 18.3 microns) and efferent arteriole (F, 25; M, 33.4 microns) were much larger than those of cortical arterioles (afferent: F, 9.1, M, 10.5 microns; efferent: F and M, 11.1 microns). In the hydronephrotic kidney, cortical glomerular blood flow (F, 17.5; M, 18.3 nl/min) is much reduced compared with the normal filtering kidney. This, however, is not true of JM glomerular blood flow (F, 120; M, 262 nl/min). During the reduction of renal perfusion pressure in females blood flow was autoregulated in cortical glomeruli within the pressure range of 110 to 80 mmHg; JM glomeruli failed to show any autoregulation. In males the glomerular blood flow was similarly autoregulated down to 90 mmHg in both cortical and JM nephrons. Local application of indomethacin to the kidneys from female rats reduced the glomerular flow rates by 30% but changed the autoregulatory behavior of cortical and JM glomerular blood flow so that it resembled that observed in untreated males. The data suggest that in females the autoregulatory response, particularly in JM glomeruli, is modified by prostaglandins.
Animals↗
Long-term effects of antihypertensives on blood lipids.
Considering the long-term effects of the commonly used antihypertensive agents, there appear to be no apparent adverse effects with calcium antagonists and angiotensin converting enzyme (ACE) inhibitors. The literature available concerning the effects of thiazide diuretics and beta-blockers is extensive and rather confusing. In the case of thiazide diuretics, a review of the literature indicates that in the short-term (therapy for less than six months) thiazide diuretics induce a rise in total cholesterol, total triglycerides and low density lipoprotein (LDL) cholesterol, with a possible fall in high density lipoprotein (HDL). If this was translated into long-term effects it could be associated with an increased risk of atherosclerotic disease. However, the long-term effects (therapy for more than six months) are unclear. Several large-scale trials of antihypertensive therapy using diuretics have suggested that the use of diuretics may have reduced the rate of decline of cholesterol levels which would otherwise have occurred. The literature on the effects of beta-blockers on blood lipids and lipoproteins is extensive and conflicting. The most consistent finding is a rise in triglycerides and there is some evidence that this may be due to the inhibition of lipoprotein lipase. Some authors have found an associated fall in total HDL cholesterol. However, analysis of the effects on the main HDL subfractions (HDL2 and HDL3) show an increase in HDL2 and a decrease in HDL3, which may counteract the possibly detrimental reduction in total HDL. Since triglyceride levels have only weak relationship to atherosclerotic risk it seems unlikely that beta-blockers significantly increase this risk.
Adrenergic beta-Antagonists↗
Different responses of cortical and juxtamedullary arterioles to norepinephrine and angiotensin II.
Cortical (C) and juxtamedullary (JM) glomerular blood flow were measured with intravitalmicroscopic techniques in the split hydronephrotic kidney of female Wistar rats under Inactin anesthesia. Intravenous injection of small, equivalent pressor doses of norepinephrine (NE) and angiotensin II (Ang II) reduced the diameter of C afferent arterioles by -16 +/- 2.4% and -14 +/- 1.9%, respectively, whereas that of JM afferent arterioles was reduced by only -3.8 +/- 2.7% and -3.8 +/- 1.5%. Blood flow under NE and Ang II was reduced in C glomeruli by -42 +/- 4.9% and -37 +/- 4.0%, respectively, but in JM glomeruli was reduced by -10 +/- 6.2% and -8.6 +/- 2.9% of control. Perfusion pressure reduction during NE or Ang II infusion to preinfusion values revealed autoregulatory behavior only in C glomeruli. In a second series of experiments cyclooxygenase inhibition by local administration of indomethacin (2.8 x 10(-5) M) induced C and JM vasoconstriction. The effects of NE and Ang II during local application of indomethacin were variable but different responsiveness of C and JM vessels disappeared. We assume that the differences in NE and Ang II responsiveness between C and JM vessels under control conditions are caused by a high prostaglandin content or sensitivity, particularly of JM vessels in the hydronephrotic kidney.
Angiotensin II↗
Peripheral chemoreceptor inputs to medullary inspiratory and postinspiratory neurons of cats.
The effect of peripheral chemoreceptor activation on inspiratory and postinspiratory medullary neurons was investigated using intracellular recording techniques. Peripheral chemoreceptors were activated by injecting CO2 saturated 1 N bicarbonate solution into the lingual artery or by electrically stimulating the carotid sinus nerve. Injections of 20-300 microliters bicarbonate solution evoked changes in respiratory frequency and in peak phrenic nerve discharge. The membrane potential of inspiratory alpha neurons, whether bulbospinal or not and independent of their anatomic location, was decreased during inspiration. A sequence of compound excitatory and inhibitory effects were observed when the stimulus was given during the postinspiratory and expiratory phases of the respiratory cycle. Inspiratory beta- and late-inspiratory neurons, however, were inhibited by peripheral chemoreceptor activation. Postinspiratory neurons were strongly activated during postinspiration. Neither class of respiratory neurons were shown to receive direct synaptic inputs from the peripheral chemoreceptors as tested by electrical stimulation of the carotid sinus nerve and signal averaging of the respiratory neuron membrane potential. The experiments revealed differential influences of afferent chemoreceptor activity on various components of the respiratory network. We conclude that chemoreceptor afferents activate non-respiratory modulated medullary neurons which, in turn, activate or inhibit various neurons of the medullary respiratory control network. The responses of each type of respiratory neuron to chemoreceptors afferents may then be considered in the context of this direct interaction as well as the network interactions of the various cells.
Animals↗
Acute metabolic effects of exercise in bodybuilders using anabolic steroids.
Four male bodybuilders who had started taking anabolic steroids were monitored during exercise. Most metabolic indicators were similar to bodybuilders not taking steroids; i.e. metabolic acidosis with little change in glucose. However, there is a marked elevation of creatine kinase.
Adult↗
Electrocardiographic findings in male veteran endurance athletes.
Twenty male veteran endurance runners and 20 controls underwent resting, exercise, and ambulatory electrocardiography. Four athletes and three controls satisfied voltage criteria for left ventricular hypertrophy. The PR interval was longer in the athletes and they had longer mean (SD) treadmill exercise times (19 (4) v 16 (2) min) than the controls. Four athletes but no controls had greater than 2 mm downsloping ST segment depression during exercise. During 48 hour ambulatory electrocardiography the athletes had a consistently lower heart rate but maintained a circadian variation. Profound bradycardia (less than 35 beats/min) occurred in eight athletes but only one control. Eight athletes and two controls had asystolic pauses ranging from 1.8 to 15 seconds. Six athletes had first degree heart block, four had Mobitz II second degree block, and three had complete heart block. Most conduction abnormalities occurred at night and resolved during exercise. Ventricular ectopic activity was not significantly different between the groups. Thus heart block patterns and profound bradycardia are more frequent in older athletes than their youthful counterparts.
Age Factors↗
Staffing in cardiology in the United Kingdom 1988. Fifth biennial survey.
This is the fifth survey of staffing (consultants and senior registrars) in cardiology in the United Kingdom. Data from previous years--including the fourth survey (1986) that was not published separately--are used to show the trends over the past decade. In 1988 there were less than six cardiologists per million population. The United Kingdom, with Ireland, has fewer cardiologists than all other European countries with reliable figures. The ratio for Europe as a whole is approximately 45 per million population; the recommended figure for the United States of America is 60 per million. The distribution of cardiologists in England and Wales is still very uneven. Seven million people--nearly 15% of the population--have no immediate access to special expertise in cardiology. Women are particularly poorly represented in the specialty. This survey indicates that the crisis in staffing for cardiology continues. It will worsen as the possibilities grow for effective management of heart disease and as needs increase with the greater average age of the population. Resolution of this crisis should be a major priority in policies aimed at countering the ravages of heart disease.
Cardiology↗
Lipoprotein profiles of elite veteran endurance athletes.
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Cholesterol↗