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Biomedical subjects

R Vincent

Publications and source records attributed to R Vincent.

At least 19 recordsLinked to original sources
PubMed1992

Fast ECG data compression algorithms suitable for microprocessor systems.

ECG data compression techniques have received extensive attention in ECG analysis. Numerous data compression algorithms for ECG signals have been proposed during the last three decades. We describe two algorithms based on the scan-along polygonal approximation algorithm (SAPA) that are suitable for multichannel ECG data reduction on a microprocessor-based system. One represents a modification of SAPA (MSAPA) which adopts the method of integer division table searching to speed up data reduction; the other (CSAPA) combines MSAPA and TP, a turning-point algorithm, to preserve ST segment signals. Results show that our algorithms achieve a compression ratio of more than 5:1 and a percent rms difference (PRD) to the original signal of less than 3.5%. In addition, the maximum execution time of MSAPA for processing one data point is about 50 microseconds. Moreover, the CSAPA algorithm retains all of the details of the ST segment, which are important in ischaemia diagnosis, by employing the TP algorithm.

Algorithms↗
PubMed1992

Intracerebral haemorrhage after thrombolytic therapy for acute myocardial infarction.

Seven cases of intracerebral haemorrhage were identified following the use of thrombolytic therapy in a total of 710 patients with acute myocardial infarction. Each case was reviewed in detail with particular attention to the presenting symptoms. A confusional state was the commonest initial feature. Increased age and male sex were associated with increased risk of cerebral bleed. The possible role of intravenous heparin in increasing risk and the management of affected cases is discussed. Early recognition and action is emphasized.

Age Factors↗
PubMed1991

Quantitative analysis of signal-averaged P waves in idiopathic paroxysmal atrial fibrillation.

Detailed analysis of the QRS complex can identify patients at risk from ventricular arrhythmias, but similar techniques applied to the atria have been disappointing. This study attempts to quantitate differences in the fine morphology of P waves in a group of 9 patients with paroxysmal atrial fibrillation (AF) versus 15 control subjects. Atrial triggered signal-averaging was combined with a detailed investigation of P-wave duration, high-frequency spatial voltage and spatial velocity. Signal-averaged P-wave duration was significantly increased in patients with paroxysmal AF (135 +/- 8 vs 126 +/- 4 ms, p less than 0.05). The root-mean-square voltage at frequencies greater than 35 Hz in these patients was also significantly greater (16 +/- 3 vs 12 +/- 1 microV, p less than 0.05). Similar observations were made at frequencies greater than 40 Hz (10 +/- 3 vs 7 +/- 1 microV, p less than 0.05). These differences appeared to be confined to the third quarter of the P wave (third quarter root-mean-square voltage at greater than 40 Hz expressed as a ratio of total P-wave root-mean-square voltage, 1.4 +/- 0.1 vs 1.2 +/- 0.1, p = 0.005). Spatial velocity was also increased in the paroxysmal AF group (peak spatial velocity 6.4 +/- 1.8 vs 4.6 +/- 0.5 mV/s, p less than 0.05). These observations support previous intracardiac data that implicate delay and fragmentation of intraatrial conduction in the pathogenesis of paroxysmal AF.

Adult↗
PubMed1990

Reduction in hospital time to thrombolytic therapy by audit of policy guidelines.

Despite the importance of early thrombolysis in the treatment of acute myocardial infarction, unacceptable delays in drug administration still occur in hospital. From March 1989 we decided to monitor our performance, and thereby to reduce avoidable in-hospital delay to a minimum. Potential candidates for thrombolytic therapy were identified by paramedic ambulancemen whenever this was feasible. Rapid check-lists were used for inclusion and exclusion criteria in the Accident and Emergency Department. A target of 15 min was set for time to treatment, and reasons for any gross deviation (greater than 30 min) were explored in each instance. As a result of these strategies, we achieved a median time from admission to initiation of thrombolysis in 50 consecutive patients of 17 min. The 39 patients treated with injections of APSAC as opposed to infusions of streptokinase had a median in-hospital delay to treatment of only 13 min.

Aged↗
PubMed1990

The European Community and dental education.

This paper traces the impact of the Rome Treaty of March 1957 on the countries of the European Economic Community relative to dental education. It also reviews the studies that have been conducted to help determine how best to implement the freedom of movement of dentists throughout the Community.

Education, Dental↗
PubMed1989

Multiple microemboli after disintegration of clot during thrombolysis for acute myocardial infarction.

Seven of 475 consecutive patients treated with thrombolysis for acute myocardial infarction had severe embolic complications that were believed to be caused by disintegration of pre-existing clot. Three patients had symptoms that persisted for many weeks, and five died. Any potential site of pre-existing blood clot within the vascular system, notably an enlarged left atrium, ventricular aneurysm, or aortic aneurysms, should be regarded as a contraindication to treatment with thrombolytic agents.

Aged↗
PubMed1989

Evolution of late potential activity in the first six weeks after acute myocardial infarction.

The evolution of surface ventricular late potential activity was studied in 50 patients during the 6 weeks after first acute myocardial infarction (AMI). In 15 of 47 patients (32%) late potential activity appeared within 6 hours of the onset of major symptoms. Its prevalence overall remained approximately 30% at each recording time but with marked individual variability in appearance. Late potential activity was associated with late ventricular arrhythmias (greater than 24 hours after AMI) but not with early ventricular arrhythmias (less than 24 hours after AMI). Late ventricular arrhythmias or sudden death occurred only in the 6 patients with late potential activity (p less than 0.05). Early ventricular fibrillation (15 patients) occurred equally in the patients with and without late potential activity. Thus, late potential activity occurs at some stage in the first 6 weeks after AMI in 50% of patients, but its timing is variable. It is a sensitive but not specific predictor of late ventricular arrhythmias and sudden death, but not of early ventricular fibrillation.

Adult↗
PubMed1989

Techniques of convergent beam electron diffraction.

The techniques required to record standard convergent beam electron diffraction patterns in an analytical electron microscope are discussed in detail, with emphasis on the design of electron optics in commercial instruments. Practical comments are included on specimen preparation, the influence of crystal defects, tilting to major zone axes, and alignment of the instrument. The influence of parameters under experimental control such as probe size, accelerating voltage, temperature, specimen thickness, and convergence angle is discussed in detail. Some comments are included on the alignment and limitations of large angle patterns formed by a defocused probe.

Crystallography↗
PubMed1989

The response of the pulmonary surfactant-associated alkaline phosphatase following acute cadmium chloride inhalation.

In order to identify sensitive and specific biochemical indicators of pulmonary damages caused by industrial contaminants, male Long-Evans rats were exposed to a cadmium chloride (CdCl2) aerosol (5 mg Cd/m3; MMAD = 1.4 microns; SDg = 1.8) for 1 hr. The rats were sacrificed at 1, 4, 8, and 16 days after treatment. The response of the pulmonary surfactant (SF) system, which prevents alveolar collapse during expiration by lowering the surface tension at the air-liquid interface, was of particular interest. The effect of CdCl2 inhalation on the SF system was monitored by assaying the alkaline phosphatase (AKP) activity and phospholipid (PL) content in an enriched surface active SF fraction purified from bronchoalveolar lavages. The AKP activity of the SF fraction was markedly decreased (99%) on Day 1, indicating an inhibition of AKP by Cd. The PL content remained at control level while the total protein content was significantly increased (199%). On day 4, the high recovery of PL (207%) and AKP activities (639%) may reflect an increased secretion caused by Type II cell hyperplasia. By Day 8 these parameters returned to baseline levels. On Day 16 both the AKP activity and the PL content of the SF fraction were decreased significantly. Concurrently, the activities of the acid phosphatase and the B-N-acetylglucosaminidase followed, but to a lesser extent, the response of the AKP activity on Days 1 and 4. They differed from AKP, however, in that their activities remained significantly elevated on Day 8 and in that they returned to baseline levels on Day 16.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylglucosaminidase↗
PubMed1989

Recurrent ventricular tachycardia associated with anomalous left coronary artery from the pulmonary artery in a child managed by revascularisation and map-guided endocardial resection.

A 13 year old girl with recurrent ventricular tachycardia that occurred in association with anomalous origin of the left coronary artery from the pulmonary artery is described. Such an arrhythmia has not been described before. Ligation of the anomalous left coronary artery led to more frequent episodes of ventricular tachycardia with evidence of myocardial ischaemia. She was successfully managed by revascularisation (to establish a two coronary system) and map-guided left ventricular aneurysmectomy.

Adolescent↗
PubMed1988

Utilisation of energy substrates in treadmill-exercised domestic fowl (Gallus gallus domesticus): blood glucose.

1. Blood glucose concentration, glucose turnover and gas exchange were monitored in adult male domestic fowl at rest and during 90 min of continuous treadmill exercise. 2. During exercise oxygen consumption increased to about three times its resting value. Blood glucose concentration fell by 26% by the end of exercise. 3. Blood glucose turnover was not altered by exercise and oxidation showed only a moderate increase (35%). Glucose oxidation accounted for 23% of the total energy expenditure at rest and this value fell to 10% during exercise. At the same time the plasma free fatty acid concentration rose to three times its resting value suggesting an increased mobilisation of this substrate. 4. It is concluded that during exercise of this relatively moderate intensity glucose is a quantitatively minor fuel for the working muscles.

Animals↗
PubMed1988

Utilisation of energy substrates in treadmill-exercised domestic fowl (Gallus gallus domesticus): blood plasma free fatty acids.

1. Plasma free fatty acid (FFA) concentration, FFA turnover and gas exchange were measured in adult male domestic fowl at rest and during 90 min continuous treadmill exercise at a work load of approximately three times the resting metabolic rate. 2. Plasma FFA concentration and turnover increased 7-fold and 4-fold respectively during exercise. Of the FFA turnover 0.54 was oxidised at rest and this increased to 0.70 during exercise. The fraction of the total carbon dioxide production derived from plasma FFA oxidation rose from 0.33 at rest to 0.55 during exercise. 3. It is concluded that plasma FFA are the most important source of energy for the working muscles of domestic fowl during treadmill exercise of this intensity and duration.

Animals↗
PubMed1988

Effects of treadmill exercise on the transfer of plasma triglyceride into the ovary of the laying fowl.

1. The effects of 90 min continuous treadmill exercise on the plasma-to-ovary transfer of 14C-labelled triglycerides in laying hens were examined. 2. Exercised birds showed a 4-fold increase in plasma free fatty acid concentration, a 15% decrease in plasma glucose concentration and unchanged plasma triglyceride concentration compared with resting controls. The mean plasma-to-ovary triglyceride transfer rate was approximately halved by exercise. 3. The surface area-specific triglyceride transfer rate was greatest for oocytes weighing 0.25-1.5 g and decreased with increasing oocyte size. The lowest rates were in the small (less than 0.25 g) white oocytes. This pattern was largely unaffected by exercise. 4. Factors that might be responsible for the reduction in triglyceride transfer into the oocytes during exercise include hormonal effects on the permeability of the oocyte envelope, increased competition for plasma lipids by the working muscles and reduced blood flow to the ovary, as a result of the release of vasoconstrictors.

Animals↗
PubMed1988

Toxicity of inhaled cadmium chloride: early responses of the antioxidant and surfactant systems in rat lungs.

In order to establish an animal model for assessing early and sensitive biochemical indicators of pulmonary damage, we studied the effects of inhaled CdCl2 (5 mg/m3.h; mass median aerodynamic diameter (MMAD) = 1.4 microns; SDg = 1.8) on the antioxidant defense and pulmonary surfactant systems of rat lungs. Rats were sacrificed 1, 4, 8, and 16 d after inhalation. Pulmonary edema (wet/dry weight) was observed on d 1. The total activities of the enzymes superoxide dismutase (SOD) and glucose-6-phosphate dehydrogenase (G6PD) in the lung homogenates of the treated animals were significantly throughout the 16-d period. Glutathione reductase (GR) was increased on d 4 and after. The general increases of SOD, GR, and the lysosomal enzymes acid phosphatase and beta-N-acetylglucosaminidase could be attributed to changes in the cellularity of the lung tissue. The significant increase in the specific activity of G6PD on d 4 suggested enzyme stimulation. Concurrently, the response of the surfactant system was measured by assaying the alkaline phosphatase (AKP) and the phospholipid content in the homogenates and in the cell-free bronchoalveolar lavage (BAL) fluids. The AKP activity in the homogenates decreased by 30%, while no activity was detected in the BAL on d 1, suggesting an inhibition of AKP by Cd. The secretion of surfactant seemed altered at this early time: phospholipid in the BAL decreased by 44%, although it increased by 61% in the tissue. The high recovery of phospholipid (312%) in the BAL on d 4 and the important changes in the AKP activity in the BAL from d 4 to 16 may reflect alterations in the processing of the surfactant. The effect of Cd on AKP makes this enzyme a potential marker of the metal redistribution in the pulmonary alveolar region, which could be a useful tool in long-term studies.

Acetylglucosaminidase↗
PubMed1988

Identification of patients at low risk of dying after acute myocardial infarction, by simple clinical and submaximal exercise test criteria.

A consecutive series of 559 hospital survivors of acute myocardial infarction aged less than 66 years were studied; 93 were designated prospectively as low-risk because they were suitable for early submaximal exercise testing and had none of the following clinical or exercise test 'risk factors': (1) angina for at least one month prior to infarction; (2) symptomatic ventricular arrhythmias, or (3) recurrent ischaemic pain, both after the first 24 h of infarction; (4) cardiac failure; (5) cardiomegaly; and (6) an abnormal exercise test (angina, ST-depression or poor blood pressure response). Altogether 301 patients were exercised; their mortality over a median follow-up of 2.4 years was 10.2%, versus 24.6% in the 258 patients not exercised (P = 0.0005). Absence of clinical 'risk factors' alone, in the exercised patients, identified 156 with a mortality of 5.4% versus 15.6% in the 145 with at least one clinical 'risk factor' (P = 0.004). The fully defined low-risk group comprised 93 of the former patients who had neither clinical nor exercise test 'risk factors'. None of these patients died compared with 19 of those with at least one 'risk factor' (mortality = 14.7%; P = 0.002). Their respective rates of non-fatal reinfarction were similar and never exceeded 5% per annum. Therefore, simple clinical and exercise test criteria can positively identify low-risk patients after infarction in whom secondary prevention may be inappropriate.

Adrenergic beta-Antagonists↗
PubMed1988

Transcutaneous pacing for cardiac emergencies.

Transcutaneous cardiac pacing using the Pace-Aid (Cardiac Resuscitator Corporation) was assessed in 32 emergency patients presenting with profound bradycardia or asystole who had failed to recover with advanced life support including the use of epinephrine. Pacing stimuli, pulse width 20 ms at 50, 100, or 200 mA, were delivered through two 8 cm gel-pad electrodes placed antero-posteriorly on the chest. By ECG criteria, definite electrical capture was achieved in a total of five patients and possible capture in a further 16. Of the 21 patients presenting in asystole 11 showed possible electrical capture only. No evidence of capture was seen in one third of the patients studied. Use of the Pace-Aid resulted in a palpable pulse in a total of seven patients. Four of the 11 patients with profound bradycardia survived to receive temporary transvenous pacing; two were eventually discharged. None in the asystolic group survived. Difficulties in using the Pace-Aid resulted from electrical overload by the pacing impulse that obscured the evidence for electrical capture, and intense muscle contraction that hindered reliable palpation of the arterial pulse. Transcutaneous pacing can occasionally be of value even at a late stage in the emergency treatment of profound bradycardia but is unlikely to be worthwhile in complete asystole.

Aged↗
PubMed1988

Vasculitis complicating treatment with intravenous anisoylated plasminogen streptokinase activator complex in acute myocardial infarction.

Vasculitis developed in six of 253 patients treated with intravenous anisoylated plasminogen streptokinase activator complex (APSAC) after acute myocardial infarction. All patients recovered spontaneously with no evidence of renal impairment and no long term sequelae. Although leucocytoclastic vasculitis and serum sickness have been reported after streptokinase treatment, such allergic reactions have not been described as a complication of other thrombolytic agents.

Aged↗