Search PubMed⌕ Search

Biomedical subjects

J M Neilson

Publications and source records attributed to J M Neilson.

At least 37 records · Page 2Linked to original sources
PubMed1990

QT interval length and diabetic autonomic neuropathy.

QT interval length was measured in ECG recordings from three groups of age-matched male subjects: 36 normal subjects, 41 diabetic patients without (DAN-ve), and 34 with (DAN+ve) autonomic neuropathy. ECG samples were selected from previously recorded 24-h ECGs on the basis of a clearly defined T wave and a steady RR interval over 2 min of around 750 ms (80 beats min-1). There were no significant differences in RR interval between the groups. The two diabetic groups had slightly longer QT measurements (normal 365 +/- 14 (+/- SD) ms, DAN-ve 373 +/- 18 ms, DAN+ve 375 +/- 23 ms, p = 0.05), and corrected QT (QTc) values (normal 423 +/- 15 ms, DAN-ve 430 +/- 20 ms, DAN+ve 435 +/- 24 ms, p = 0.05). Ten diabetic patients fell above our defined upper limit of normal for QTc (greater than mean + 2SD). There was a significant correlation in the DAN-ve group between the QT indices and 24-h RR counts (QT r = -0.38, p less than 0.01; QTc r = -0.40, p less than 0.01). We conclude that there are some small alterations in QT interval length in the steady state in diabetic autonomic neuropathy. The changes appear to be due to autonomic impairment, rather than diabetes per se.

Adult↗
PubMed1989

Cardiac parasympathetic activity during the early hours of acute myocardial infarction.

Cardiac parasympathetic activity was assessed in 21 patients during the first 24 hours of acute myocardial infarction by measuring abrupt beat by beat changes in RR interval, which are expressed as "RR counts". Eleven patients had inferior wall infarction and 10 had anterior wall myocardial infarction. The whole recording period was analysed in 11 patients (five inferior and six anterior), and intermittent hourly periods were analysed in all 21 subjects. Mean RR counts were significantly lower in patients with anterior than inferior infarction, and below the normal range. Although mean heart rates were faster in the group with anterior infarction, there was a dissociation between RR counts and mean heart rate that was consistent with RR interval variability being an independent measure of parasympathetic activity. This study indicates that cardiac parasympathetic activity during acute myocardial infarction can be simply and reliably assessed from continuous electrocardiographic recordings, and it showed significantly lower cardiac parasympathetic activity in patients with anterior infarction.

Adult↗
PubMed1987

Effects of beta-adrenoceptor blockade on heart rate and physiological tremor in diabetics with autonomic neuropathy. A comparative study of epanolol, atenolol and pindolol.

Eight diabetics with autonomic neuropathy were given single oral doses of epanolol (200 mg), atenolol (50 mg), pindolol (5 mg) and placebo in a double-blind randomised order at weekly intervals. Supine resting heart rate, physiological tremor and blood glucose were measured before, 2 and 4 h after dosing, and ambulatory heart rate monitored for 24 h. Supine resting heart rate was significantly lowered by atenolol both at 2 and 4 h, and increased on pindolol at 4 h. Heart rate was unaffected by epanolol compared with placebo. Heart rate during the 'waking' period (14.00-23.00 h) was lower than placebo after epanolol and atenolol but unaffected by pindolol. During the 'sleeping' period (23.00 h-08.00 h) heart rate was significantly increased by pindolol, lowered with atenolol and unaffected on epanolol. Pindolol significantly increased physiological tremor at 4 h. No differences were seen between epanolol, atenolol and placebo. Plasma glucose was significantly increased by pindolol 2 h after dosing. These results suggest that pindolol probably produces its partial agonist activity at both beta 1- and beta 2-adrenoceptors, while the partial agonist activity of epanolol is beta 1-selective. Despite abnormal cardiovascular reflex tests in these diabetics, the heart rate responses obtained in this study after beta-adrenoceptor blockade were surprisingly normal, and suggest that the concept of 'cardiac denervation' in diabetes requires modification.

Adrenergic beta-Antagonists↗
PubMed1984

New method for assessing cardiac parasympathetic activity using 24 hour electrocardiograms.

Cardiac parasympathetic activity was assessed using 24 hour electrocardiographic recordings by measuring the incidence of larger changes in successive RR intervals, which in normal subjects occur frequently but irregularly. In 25 normal subjects the mean number of times per hour in which the change in successive RR interval was greater than 50 ms was 150-250 during waking and 350-450 during sleeping. By contrast, 30 diabetics with medically denervated hearts (12 with cardiovascular reflex evidence of parasympathetic damage and 18 with additional sympathetic damage) and six cardiac transplant patients with surgically denervated hearts had extremely low counts. Additionally, of 20 diabetics with normal cardiovascular reflexes, about half had abnormally low counts, suggesting that this method is better than currently available reflex tests in detecting early cardiac parasympathetic damage. This technique provides a valid and sensitive way of monitoring cardiac parasympathetic activity over prolonged periods.

Adult↗
PubMed1983

Abnormalities of ambulatory 24-hour heart rate in diabetes mellitus.

Twenty-one normal subjects and 64 diabetics with varying severity of autonomic damage underwent 24-h ambulatory EKG monitoring. No diabetics had the "sick sinus syndrome," and the frequency of arrhythmias was no higher than in the normal subjects. The diabetics had higher mean hourly heart rates, and with increasing autonomic damage there was reduction in diurnal heart rate variation. The mean waking and sleeping heart rates were higher in the diabetics. The maximum heart rates were not significantly different, but the minimum heart rates were significantly higher in the diabetics. These previously unrecognized abnormal 24-h heart rate patterns provide further evidence of damage to the heart rate-controlling mechanisms in diabetes mellitus.

Adult↗
PubMed1981

'Currents and clots'--an approach to the problem of acute variceal bleeding.

The Sengstaken-Blakemore tube will frequently control haemorrhage from oesophageal varices but a large proportion of patients rebleed soon after removing the tube and the hospital mortality in these patients is high. It has been demonstrated that the passage of an electric current across a blood vessel wall will precipitate a thrombus on the positively charged electrode, leading to complete occlusion of the vessel. A direct current of 3.2 mA/cm2 of electrode passed for 1 h produced complete occlusion of the femoral vein in the dog, without arterial occlusion or adjacent tissue damage. A system of longitudinal flexible gold-plated strip electrodes was placed around the oesophageal component of a Sengstaken tube. The technique has been applied in 8 poor risk patients with active variceal bleeding; haemorrhage was arrested in 7 of these on removal of the tube.

Acute Disease↗
PubMed1980

Autonomic mechanisms in the initial heart rate response to standing.

Autonomic mechanisms underlying the initial heart rate response to standing were analyzed in nine normal subjects. The normal pattern of response was altered by atropine to a small and gradual R-R interval shortening over 30 beats, with no rebound R-R interval lengthening. With additional propranolol, R-R interval shortening was even less and confined to the first 15-20 beats, whereas propranolol alone did not affect the normal response pattern, showing that this is under vagal control with increased cardiac sympathetic activity occurring only if the vagus is blocked. The response was reproducible in 23 normal subjects. Heart rate variation during quiet standing was almost completely abolished by atropine, but unaffected by propranolol, confirming that it is also under vagal control. In four normal subjects no rebound R-R interval lengthening occurred during either "fast" or "slow" tilt, whereas it was present during both "slow" and "fast" standing. The rebound R-R interval lengthening is determined by the muscular activity involved in standing up, rather than by the speed of the maneuver.

Adult↗
PubMed1979

Coupling interval, exit block, and periodicity of ventricular parasystolic rhythm.

The electrocardiograms in this study of parasystolic rhythm were tape recorded and then analysed with a special purpose hybrid computer. The rate of appearance of specific inter-ectopic intervals was shown to change significantly with small changes in either the sinus or parasystolic pacemaker period. Natural changes in the period of the ectopic pacemakers were observed over several hours. Changes amounting to 14% within 10 min and 18% overall were observed in one patient, and a gradual lengthening of 10% over 3 h in another. A previously undescribed form of exit block has been discovered in one patient where the block remained active for a given time only after propagation from the parasystolic focus. Different interectopic intervals were shown to contribute to specific and restricted coupling interval locations in diastole. Hence this form of exit block, by preventing some inter-ectopic intervals from propagating, limited the locations in diastole in which parasystolic ectopic complexes could appear. In this case later diastolic complexes were inhibited and hence fusion complexes were completely absent. Parasystolic rhythm, with and without the exit block described, was simulated successfully by a digital computer. The simulations aided our understanding of the clinical data.

Aged↗
PubMed1978

Immediate heart-rate response to standing: simple test for autonomic neuropathy in diabetes.

The immediate heart-rate response to standing was measured in 22 normal controls and 25 patients with diabetes, 15 of whom had autonomic neuropathy. The response in the controls and patients without autonomic neuropathy was characteristic and consistent, with tachycardia maximal at around the 15th beat and relative bradycardia maximal at around the 30th beat. The diabetics with autonomic neuropathy, however, showed a flat response. In three controls the response was abolished with intravenous atropine but not with propranolol, showing that it is mediated through the vagus. A simplified test using routine ECGs and measuring the R-R interval at beats 15 and 30 with a ruler is easily performed as an outpatient procedure and may be used as a measure of autonomic function in diabetes.

Adult↗
PubMed1977

Praecordial ST segment elevation. New technique for continuous recording and analysis.

The measurement of praecordial ST segment elevation after myocardial infarction is of value in assessing the natural history of ischaemic injury and the effectiveness of intervention. Hand analysis is, however, time consuming and inaccurate. A technique for continuous recording from 35 praecordial leads and subsequent computer analysis is presented, together with illustrative case studies. Changes in body posture and in heart rate are of importance in subsequent data interpretation.

Adult↗
PubMed1977

Peripheral and autonomic nerve function in newly diagnosed diabetes mellitus.

Peripheral and autonomic nerve function was assessed in 10 newly diagnosed male diabetics (six insulin-treated and four sulfonylurea-treated) with repeated observations over the subsequent six months. There was significant impairment of motor-conduction velocity in the common peroneal nerve at diagnosis in both treatment groups, with improvement following treatment in only the insulin-treated patients. In contrast, although the blood glucose level fell in both groups, the mean level was significantly lower in the sulfonylurea-treated patients at two months and at each subsequent visit. In the autonomic function tests significant abnormality was found in the electrocardiographic R-R-interval (beat-to-beat) variation in resting heart rate in two of the insulin-treated patients and all of the sulfonylurea-treated group, with improvement in only one of the latter. One patient in the sulfonylurea-treated group also showed an abnormal response to the Valsalva maneuver (expressed as the Valsalva ratio), and this remained abnormal throughout the period of study. All other patients had normal responses to the Valsalva maneuver and sustained handgrip test. None of the patients had postural hypotension. Abnormalities in autonomic nerve function in diabetics at diagnosis have not been previously reported.

Adolescent↗
PubMed1976

Peripheral and autonomic nerve function in diabetic ketoacidosis.

Peripheral and autonomic nerve function was assessed at intervals over a 3-month period in seven diabetics after ketoacidosis. There was marked improvement in motor conduction velocity and terminal latency of both ulnar and common peroneal nerves in all patients. Five had one or more abnormal autonomic function tests but there were no consistent changes during the same period. It is postulated that peripheral nerves may be more susceptible to acute metabolic damage than autonomic fibres.

Adolescent↗