The Effect of 50 Hz External Electrical Interference on Implanted Cardiac Pacemakers

The effects of injected 50 Hz alternating current on the function of cardiac pacemakers has been observed in 18 patients with implanted unipolar VVI units. Current, in the range 0-600 microA was applied via electrodes attached to the patients' upper body and feet and fed from a specially designed current injection unit at the bedside. Most implanted pacemakers reverted to interference mode in the current range 29-250 microA. At current levels just below the reversion current all units developed irregular and inappropriate pacing. This current level was pacemaker dependent and varied in the range 27-246 microA. The total reversion current depended on the location of the injecting electrodes and on the patients' posture. The sensitivity of the units to injected interference was increased by deep inspiration. Temporary pacing catheters fitted to an additional ten patients were used to monitor the interference voltage which would be sensed by an implanted unit. This voltage was similarly dependent on patient posture and on deep respiration. Current injection has proved to be a safe, controllable and reproducible method of testing the sensitivity of implanted pacemakers to 50 Hz external interference.     

THE PATHOLOGICAL AND BIOLOGICAL NATURE OF SCREEN-DETECTED BREAST CARCINOMAS: A MORPHOLOGICAL AND IMMUNOHISTOCHEMICAL STUDY

Traditional and immunohistochemical markers of prognosis were examined in 455 mammary carcinomas derived from breast cancer screening and compared with those of 277 carcinomas presenting symptomatically over the same period. Tumours detected by population screening under the U.K. National Health Service Programme do not differ from those detected by other screening projects, but compared with symptomatic cancers, screen-detected cancers are more likely to be in situ and if invasive, to be smaller, of lower grade, and to have invaded vessels, perineural spaces, and lymph nodes less frequently. Tubular and cribriform types are more often represented in screened patients. Immunohistochemical markers which have been proposed as being related to likely tumour behaviour (epidermal growth factor receptor, c-erbB-2 protein, oestrogen and progesterone receptors, cathepsin D, p53, and retinoblastoma protein) do not distinguish screen-detected from ‘clinical’ cancers. It is concluded that cancers diagnosed at screening do not differ biologically from those presenting clinically, but are the same lesions detected at an earlier stage of their natural history. © 1997 John Wiley & Sons, Ltd.     

The Effect on Plasma Glucose,Insulin and Glucagon Levels of Treatment of Diabetic Rats with the Medicinal Plant Rhazya stricta and with Glibenclamide,Alone and in Combination

Because many diabetic patients in the United Arab Emirates use medicinal plants as a supplement to treatment with insulin or oral hypoglycaemic agents, the effect on plasma glucose, insulin and glucagon concentrations of simultaneous treatment of streptozotocin-diabetic rats with Rhazya stricta extract and glibenclamide has been examined. Treatment of control rats with the extract at oral doses of 0.5, 20 and 4.0 g kg^? did not significantly affect the concentration of glucose, insulin or glucagon for up to 4 h after administration of the extract. The same doses in diabetic rats reduced the glucose level 1 h (2 and 4 gkg^?) and 2h (4 gkg^?) after administration of the extract. This was accompanied by significant increases in insulin concentration 1, 2 and 4 h after administration of the extract at doses of 2 and 4 gkg^?. Glibenclamide (2.5, 5.0 and 10.0 mgkg^?) dose-dependently reduced glucose and glucagon levels, and increased that of insulin in normal and diabetic rats. Simultaneous treatment of normal and diabetic rats with the plant extract (0.5, 20 and 5.0 gkg^?) and glibenclamide (5.0 mg kg^?) significantly exacerbated the effects on glucose, insulin and glucagon induced by the extract or by glibenclamide when given separately. When the plant extract was given at doses of 0.5, 2 and 4 g kg^? per day for 6 consecutive days the glucose level was reduced by approximately 6, 8 and 30%, respectively. No significant effect was seen on the levels of cholesterol or protein. These results imply that co-administration of the extract with glibenclamide might adversely interfere with glycaemic control in diabetic patients.     

Quality of Life in Patients with Rate Responsive Pacemakers: A Randomized, Cross-Over Study

Eleven patients with rate responsive pacemakers (7 men, 4 women, mean age 41 years with a range of 23-60) were randomly assigned to a cross-over study in order to assess their overall exercise capacity and quality-of-life (QOL) scores. All of the pacemakers were implanted for complete AV block or sick sinus syndrome. The pacemakers were randomly programmed into VVI or rate responsive (VVIR) pacing modes for 3-week study periods in each mode. At the end of each period, an exercise test was performed and the QOL was evaluated by the "Hacettepe Quality-of-Life Questionnaire". All patients exercised longer in the VVIR mode (mean 10.54 ± 0,73 min) than in the VVI mode (mean 7.81 ± 0.62 min) (P < 0.05). QOL scores were also found to be significantly higher in the VVIR mode (mean 173.81 ± 16.22 points) compared to the VVI mode (mean 156.27 ± 21.22 points) (P < 0.01). In conclusion, our results suggest that VVIR pacing offers a better QOL in addition to an improved exercise capacity, compared to the single chamber nonrate modulated pacing (VVI).     

QTc Dispersion in Hyperthyroidism and Its Association with Pulmonary Hypertension

Background: Several studies have reported that hyperthyroidism is associated with prolonged QT interval corrected by the heart rate (QTc) and pulmonary hypertension (PHT). Methods: Forty‐seven patients with newly diagnosed overt hyperthyroidism and 20 healthy people were enrolled in the study. Transthoracic echocardiography, 12‐lead surface electrocardiogram, and thyroid hormone levels were studied at the time of enrollment and after achievement of euthyroid state with propylthiouracil treatment. Results: Baseline clinical characteristics were similar. However, heart rate (90.5±19.6 vs 79.2±13.7 bpm, P = 0.024), pulmonary artery systolic pressure (PASP) (26.0±12.0 vs 10.6±4.0 mmHg, P < 0.001), E deceleration time (DT) (191.8±25.6 vs 177.0±10.7 ms, P = 0.016), isovolumetric relaxation time (IVRT) (91.38±12.3 vs 79.6±10.5 ms, P < 0.001), and QTc dispersion (QTcD) (50.3±17.2 vs 38.9±11.6 ms, P = 0.009) were significantly higher in hyperthyroid patients compared to control group. Heart rate (to 74.1±13.8, P < 0.001), QTcD (to 37.3±10.1 ms, P < 0.001), DT (to 185.3±19.7 ms, P = 0.008), IVRT (to 88.6±10.3 ms, P = 0.056), and PASP (23.1±10.1 mmHg P < 0.001) were significantly decreased after achievement of euthyroid state. Although PHT was present in 16 patients before treatment only six patients still had PHT during euyhyroid state. Compared to patients with normal PASP, QTcD was significantly longer in patients with PHT (56.5±15.8 vs 37.9±12.8 mmHg P < 0.001). There were also significant correlations between QTcD and presence of PHT (r = 0.516, P < 0.001) and PASP (r = 0.401, P = 0.009). Conclusions: Hyperthyroidism is a reversible cause of PHT and diastolic dysfunction. Increased QTcD observed in hyperthyroidism may be associated with PHT and diastolic dysfunction. These abnormal findings in hyperthyroidism often normalize with the achievement of euthyroid state.     

Some effects of furazolidone on the testis and plasma levels of testosterone, luteinizing hormone and prolactin in mature male turkeys

Adult male turkeys were treated orally with furazolidone at doses of 1, 2.5, S or 20 mg/kg for 14 days and their plasma analysed for luteinizing hormone (LH), testosterone and prolactin (PRL) concentrations before, during and after treatment. At 20 mg/kg the drug produced a significant decrease in the plasma levels of LH and testosterone at the end of treatment, whereas at 5 mg/kg the drug had no significant effect. Prolactin concentrations were unaffected by any of the drug doses used. Intramuscular injection of luteinizing hormone releasing hormone (LHRH) at a dose of 5 μg/kg produced after 30 min a significant rise in plasma levels of LH, an effect that was decreased significantly by treatment with 20 mglkg furazolidone. Incubation of normal turkey semen with graded doses of furazolidone or nitrofura-zone for up to 30 min resulted in a dose- and time-dependent decrease in sperm motility. At a concentration of 20 mg/ml a complete absence of sperm motility was observed after incubation with either drug, although, on the whole, nitrofurazone seemed more potent than furazolidone as a sperm-immobilizing agent. Histological changes occured in the 20 mg/kg group and consisted of a decrease in spermatocyte production, corrugation of sperm cell nuclear envelopes and distention of the endoplasmic reticulum of elongate spermatids. It is concluded that furazolidone depresses pituitary LH output but may, in addition, directly affect spermatogenesis and sperm motility.     

Neuromuscular and Microvascular Changes Associated with Chronic Administration of an Extract of Teucrium stocksianum in Mice

This work examines the effect on the weights of vital body organs, on blood biochemical variables, on neuromuscular coordination and on cerebral microcirculation of aqueous extracts of Teucrium stocksianum, given to mice in drinking water at concentrations of 2 and 4% for 56 days. The treatment caused progressive impairment of neuromuscular coordination, as evidenced by the time spent on the rota-rod. After photochemical challenge, the time for first observable platelet aggregation in arterioles was shorter than for the control group by 22 and 45% in the 2 and 4% T. stocksianum-treated groups, respectively. Platelet aggregation on the venular side was not affected by the treatment nor were microvascular diameters. Treatment with the plant extract produced no statistically significant effect on the plasma biochemical variables that are considered indices of liver and kidney function. Histologically, brains obtained from mice treated with T. stocksianum showed loss of cerebellar Purkinje cells. Although it is likely that the accelerated platelet aggregation might have contributed to an ischaemic effect which could, at least in part, have caused the cytotoxicological changes, this does not exclude the possibility of a direct cytotoxicological effect of the plant extract. Further pharmacological and toxicological investigations on Teucrium species seem warranted.     

The use of preoperative lidocaine to prevent stridor and laryngospasm after tonsillectomy and adenoidectomy

The most important complications from tonsillectomy and adenoidectomy are bleeding, stridor, and laryngospasm. This controlled, double-blind study was designed to investigate the effects of topical and intravenous lidocaine on stridor and laryngospasm. A total of 134 patients scheduled for elective tonsillectomy and/or adenoidectomy were randomly separated into four groups. In the topical lidocaine group 4 mg/kg of 2% lidocaine was applied to subglottic, glottic, and supraglottic areas before endotracheal intubation. Normal saline solution was used topically for the first control group. In the intravenous lidocaine group, patients were given 1 mg/kg of 2% lidocaine before extubation, and the same amount of 0.9% NaCl was given to the second control group. Postoperative stridor, laryngospasm, cyanosis, bleeding, sedation degree, and respiratory depression were observed, and plasma lidocaine levels were measured. Both topical and intravenous lidocaine groups revealed less stridor and laryngospasm than the control groups, and no difference was found between the topical and intravenous lidocaine groups except the higher sedation scores in the early postoperative period for the intravenous lidocaine group. (Otolaryngol Head Neck Surg 1998;118:880-2.)