Computerized electrocardiographic interpretation: an analysis of clinical utility in 5110 electrocardiograms

This study describes the initial experience with a computerized electrocardiographic interpretation system in a teaching hospital. The sensitivity and specificity of the 13,375 diagnostic statements that were used to describe the first 5110 electrocardiograms were analysed to determine the predictive accuracy of computerized electrocardiographic interpretation. Reviewing cardiologists inserted 1320 statements, deleted 1792 statements and modified 484 computerized statements. The over-all sensitivity and specificity (and standard error [SE]) of computerized diagnosis was 90.1% +/- 0.3% and 89.6% +/- 0.2%, respectively, with an over-all positive predictive accuracy (+/- SE) of 87.1% +/- 0.3% and a negative predictive accuracy (+/- SE) of 92.2% +/- 0.2%. Sensitivity and specificity were lowest for the category of ST-T wave changes (83.1% +/- 0.8% and 84.1% +/- 0.7%, respectively) and were highest for the category of sinus rhythm (96.6% +/- 0.3% and 97.0% +/- 0.6%, respectively). The positive predictive accuracy of computerized diagnosis was lowest for the category of hypertrophies (74.2% +/- 1.0%) and was highest for the category of sinus rhythm (99.5% +/- 0.1%), while for the category of myocardial infarctions it was 87.6% +/- 0.8%. The negative predictive accuracy ranged from 96.7% +/- 0.3% for the category of hypertrophies to 81.8% +/- 1.3% for the category of sinus rhythm. We conclude that the computerized analysis of electrocardiograms has a satisfactory predictive accuracy when used in an environment with a high prevalence of abnormalities. Electrocardiograms that are classified as normal by computerized analysis may not require checking; however, all electrocardiograms with abnormalities should be interpreted by a competent electrocardiographer.

Growth of rubella virus in a glass bead propagator

A glass sphere propagator with an air lift pump to circulate the medium, has been successfully used to produce large volumes of rubella virus. The system was productive, flexible and easy to operate.

Exercise stress-induced changes in systemic arterial potassium in angina pectoris

Large fluctuations in systemic arterial potassium have been found during and after exercise in normal subjects. To determine whether similar changes occur in patients with angina pectoris, arterial potassium levels were measured before, during and immediately after maximal bicycle exercise in 20 patients with exertional angina. In 10 of these patients, leg blood flow and arteriovenous potassium levels also were measured. During exercise, arterial potassium increased significantly both from rest to submaximal exercise (4.3 +/- 0.1 to 4.7 +/- 0.1 mmol/liter, p less than 0.01) and from submaximal to maximal exercise (5.4 +/- 0.1 mmol/liter, p less than 0.01). Within 1 minute of cessation of exercise, arterial potassium had decreased to 4.7 +/- 0.1 mmol/liter (p less than 0.001) and continued to decrease to a minimum of 4.1 +/- 0.1 mmol/liter between 3 and 5 minutes after exercise, significantly less than the rest value (p less than 0.05). At maximal exercise (99 +/- 9 watts), the calculated release of potassium from each leg reached 2.7 +/- 1.3 mmol/min. Four minutes after exercise, the leg muscles were resorbing potassium at 0.24 mmol/min. In these patients with exertional myocardial ischemia, the magnitude and rapidity of arterial potassium changes during and after exercise resemble those found in normal subjects, but occurred at much lower workloads. Release and resorption of potassium by exercising muscle in patients with angina pectoris may cause potentially arrhythmogenic arterial potassium fluctuations.

Effects of nisoldipine on systemic and leg blood flow, oxygen transport and metabolism, and hemodynamics during exercise in effort angina pectoris

The acute effects of 10 mg of oral nisoldipine on hemodynamics, oxygen transport and metabolism, and distribution of cardiac output, at rest and during semiupright bicycle exercise, were evaluated in 10 men with effort angina receiving long-term beta 1 blockade. Cardiac output and leg blood flow were measured using the thermodilution technique. At rest, nisoldipine decreased systemic resistance from 18.9 +/- 1.0 to 15.9 +/- 1.2 dynes.s.cm-5.10(2) (p less than 0.05) and cardiac output increased from 4.8 +/- 0.2 to 5.3 +/- 0.3 liters/min (p less than 0.05) without changing leg blood flow. During maximal exercise with nisoldipine, systemic resistance was reduced (10.6 +/- 0.9 to 8.6 +/- 0.5 dynes.s.cm-5.10(2), p less than 0.05) and cardiac output increased 18% (10.3 +/- 0.7 to 12.2 +/- 0.6 liters/min, p less than 0.05) when compared with control values. Exercise heart rate was higher with nisoldipine (113 +/- 4 vs 106 +/- 4 beats/min, p less than 0.01), but the mean arterial pressure was not significantly changed, giving a higher rate-pressure product. The increase in mean pulmonary artery wedge pressure was attenuated (26 +/- 3 vs 30 +/- 3 mm Hg during control exercise, p less than 0.05), but ST depression was unaltered. Exercise leg flow was reduced by nisoldipine from 4.3 +/- 0.4 to 3.9 +/- 0.3 liters/min (p = 0.07) and the proportion of cardiac output distributed to the legs was reduced from 42 +/- 3 to 33 +/- 3% (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of response elements for androgens, glucocorticoids and progestins in mouse mammary tumour virus

We have characterized steroid response elements in mouse mammary tumour virus (MMTV) by transient transfection. Four partial inverted repeats of the sequence TGTTCT function as response elements for androgen, as well as for glucocorticoid and progestins, although the relative hormone inductions mediated by each oligonucleotide were different. Mutational analysis of the left half of the palindrome showed that a perfect dyad symmetry is not required for optimum activity as a steroid response element. To investigate potential interactions between steroid receptors and transcription factors we have analysed the minimum sequence requirements for a hormone response. Interestingly, a single 15 bp steroid response element and a TATA box are sufficient for steroid inductions. When the distance between the two elements was increased by up to two turns of the helix the hormone induction initially increased and then gradually declined with no obvious periodicity.

Regional distribution of cardiac output at rest and during exercise in patients with exertional angina pectoris before and after nifedipine therapy

The short-term effects of sublingual nifedipine (20 mg) on cardiac output and its distribution at rest and during exercise were evaluated by measurement of iliofemoral blood flow and cardiac output in 10 men with stable angina pectoris controlled by metoprolol. At rest, nifedipine significantly decreased iliofemoral vascular resistance from 294 +/- 36 to 165 +/- 29 dynes.s.cm-5.10(2) (p less than 0.01) and significantly increased iliofemoral blood flow from 0.34 +/- 0.04 to 0.57 +/- 0.11 liters/min (p less than 0.05). Systemic vascular resistance was reduced from 19 +/- 1 to 13 +/- 1 dynes.s.cm-5.10(2) (p less than 0.001) and cardiac output increased significantly from 4.7 +/- 0.3 to 5.8 +/- 0.5 liters/min (p less than 0.05). Mean arterial pressure decreased significantly and heart rate increased significantly. During maximal upright bicycle exercise during nifedipine therapy, iliofemoral vascular resistance and leg blood flow were unchanged compared with control (23 +/- 2 versus 21 +/- 3 dynes.s.cm-5.10(2) and 4.7 +/- 0.5 versus 4.4 +/- 0.6 liters/min), cardiac output remained significantly increased (12.8 +/- 0.8 to 15.2 +/- 1.2 liters/min, p less than 0.05) and systemic vascular resistance remained significantly reduced (8 +/- 1 to 5 +/- 1 dynes.s.cm-5.10(2); p less than 0.001). The proportion of cardiac output distributed to the working lower limbs was significantly reduced at all exercise levels. In summary, nifedipine caused a redistribution of cardiac output by vasodilating nonexercising vascular beds without altering the locally mediated vasodilation in exercising muscle. In patients with coronary artery disease given nifedipine therapy, an increase in exercise tolerance is due to relief of myocardial ischemia rather than to increased peripheral oxygen delivery.

Edinburgh Emergency Asthma Admission Service: report on 15 years' experience

A hospital self-admission service for asthmatic patients was started in December 1968. During a 15-year period, 195 asthmatic patients were responsible for 873 hospital self-admissions. During the last 3 years there were significantly more night admissions and shorter durations of asthma attacks prior to admission than during the first 3 years. Assisted ventilation was necessary on 36 occasions (4%), but one patient was responsible for 28 of these episodes. There were three hospital deaths. One patient died from a tension pneumothorax as mechanical ventilation was being started, and two patients were not actively resuscitated because of irreversible airways obstruction and ischaemic heart disease. There were six deaths outside hospital, one from myocardial infarction, four from asthma; one young female died on a holiday trip. The hospital death rate for patients admitted via this service is 0.34% (0.1% if the two patients who were electively not resuscitated are excluded). This low mortality rate suggests that this self-admission service saves lives. There are no costs and this service gives confidence to patients and general practitioners.

Endothelium-dependent relaxation in experimental atherosclerosis in the rabbit

The effect of feeding a diet supplemented with lipids and containing 2% cholesterol on the endothelium-dependent relaxation of rabbit aorta to acetylcholine was assessed. The effect of feeding a standard rabbit diet after an initial period of 2% cholesterol feeding was assessed also. Age-matched male, New Zealand white rabbits were fed either a 2% cholesterol diet or a standard rabbit diet. The animals were anesthetized with pentobarbitone sodium (25 mg/kg) and killed either at the beginning of the study (0 weeks) or at 4, 8, or 10 weeks. The animals in the reversal study were fed the 2% cholesterol diet for 6 weeks and killed after an additional 14 and 32 weeks on standard diet. The extent of atherosclerosis in the aorta was assessed by Sudan Red staining, estimation of tissue cholesterol, and light and electron microscopy. The relaxation response to acetylcholine was measured in rings of the thoracic aorta following precontraction with norepinephrine (-6.0 log mol/l). The relaxation was significantly impaired in aortas from rabbits fed the 2% cholesterol diet compared to aortas from animals fed the standard diet. The impairment of relaxation was apparent as early as 4 weeks after the start of the 2% cholesterol diet and remained impaired over the next 6 weeks. No improvement in endothelium-dependent relaxation was seen in rabbits on the reversal diet for 14 and 32 weeks. Thus, endothelium-dependent relaxation is attenuated in animals fed a 2% cholesterol diet, and the loss of relaxation persists for at least 32 weeks after the animals are returned to a standard diet.

Effect of tracheobronchial suction on respiratory resistance in intubated preterm babies

Measurements of the resistance, time constant, and compliance of the respiratory system were made in 25 mechanically ventilated, preterm babies on 32 occasions, using the single breath technique. Patients were classified according to the level of respiratory resistance by reference to a population of 36 babies studied over the first two days of life before airway secretions had become apparent. There was a highly significant fall in both the resistance and time constant measurements after tracheobronchial suction or lavage for infants whose pretreatment values of resistance were greater than the reference mean. When tracheobronchial toilet was effective in removing secretions the changes in resistance and time constant values were again significant. No changes in compliance values were noted. Severe but clinically inapparent mucous obstruction of the airways was revealed in two infants by a progressively rising respiratory system resistance during continuous monitoring. The need for and efficacy of tracheobronchial suction and lavage could be determined by such techniques for monitoring the resistance of the respiratory system during mechanical ventilation.

Pressure-flow curves in infancy

Calibrated pressure-flow (P-V) curves were plotted by computer using data from both the plethysmographic method for measuring airway resistance and the esophageal balloon technique for measuring lung resistance. P-V curves from 100 sick, healthy, and convalescent infants (age range 2 days to 19 months, weight range 0.9-10.4 kg) were classified into five distinctive types according to shape and direction of looping. Two of these patterns, one with a virtually closed, the other with a narrow figure-of-eight loop, reflected the normal physiologic changes in airway caliber that may occur during tidal breathing. The remaining three patterns, with far more marked changes in resistance, were associated with particular pathophysiologic mechanisms of airway obstruction. A wide figure-of-eight configuration, in which the expiratory loop rotated clockwise with marked flow limitation toward end expiration, was found for infants with chronic lung disease. By contrast, a rise in initial expiratory resistance due to dynamic glottic narrowing, with an anticlockwise rotated expiratory P-V loop, occurred in infants with reduced or unstable lung volumes. A clockwise inspiratory loop was observed only for infants intubated during the neonatal period, many of whom had clinical evidence of extrathoracic airway obstruction. Inspection and analysis of P-V curves provides more information about the state of the airways than does a single numerical expression of resistance. However, since normal patterns of P-V curves are not restricted to infants with healthy airways, a combined qualitative and quantitative approach to these measurements is recommended.

The relative bioavailability of paracetamol after rectal administration of suppositories containing a mixture of paracetamol, codeine phosphate and buclizine hydrochloride in healthy volunteers

'New' and 'old' suppositories (6 months and 30 months since manufacture) containing 800 mg paracetamol, 16 mg codeine phosphate and 12.5 mg buclizine hydrochloride in an identical base were administered to 10 normal volunteers at an interval of 2 weeks. Blood samples were taken at intervals up to 300 minutes after administration for estimation of paracetamol plasma concentrations using high pressure liquid chromatography. Mean peak concentrations were obtained of 4.75 +/- 0.74 mg/ml at 1.75 hours with the new suppositories and of 4.6 +/- 0.67 mg/ml at 2.0 hours with the old suppositories. The difference was not significant. Mean elimination half-life was 4.4 +/- 0.42 hours and 3.73 +/- 0.28 hours, respectively. Again, the difference was not significant, indicating that the absorption characteristics for the suppositories did not appear to deteriorate with ageing for 24 months. Bioavailability data for paracetamol derived from the results were similar to those reported by other workers who studied suppositories containing paracetamol as the only active ingredient. This indicates that the inclusion of codeine phosphate and buclizine hydrochloride in the suppository formulation investigated in the present study did not affect adversely the absorption of paracetamol.

Single-breath measurement of lung mechanics in very low birth weight infants

The expiratory time constant of the respiratory system (Trs) and the total respiratory system compliance (Crs) were measured from the analysis of a flow-volume loop during relaxed expiration, and the total respiratory system resistance (Rrs) was derived from the relationship: Rrs = Trs/Crs. In ten intubated and mechanically ventilated very low birth weight infants, the values obtained for compliance (0.21 to 0.71 ml/cm H2O) were similar to those found using an occlusion technique during spontaneous breathing. The values of Trs were 0.03 to 0.14 sec. These Trs values were altered by adding known resistive loads. The corresponding derived values for Rrs were close to the values of the added resistance loads, suggesting that resistance values found in this group of ventilated babies (120 to 380 cm H2O/L X sec) were accurate.