123rc/medical_text huggingface dataset:
Spontaneous termination of reentry after one cycle or short nonsustained runs. Role of oscillations and excess dispersion of refractoriness. This study describes factors that contribute to spontaneous termination of reentry lasting one to 10 cycles after induction by a single premature stimulus. Reentry was studied in vitro in rings of canine atrial tissue from around the tricuspid valve orifice. Activation was recorded from a circular array of 10 extracellular bipolar electrodes equally spaced around the ring. In some experiments, transmembrane or monophasic action potential recordings were made near critical sites. Termination of reentry within one cycle after induction was recorded 110 times in 11 of 35 experiments. Important factors contributing to termination were 1) an obligatory reversal of the activation sequence that resulted in a long coupling interval in the critical region beyond the site of unidirectional block after the premature stimulus and 2) much longer refractory periods limited to this critical region, which facilitated unidirectional block but contributed to termination when this region was first activated with a short coupling interval at the end of the first reentrant cycle. Termination of nonsustained reentry lasting longer than one cycle resulted from oscillations of conduction and refractoriness initiated by the abrupt shortening of cycle length after initiation of reentry. Oscillations of conduction resulted from interval-dependent conduction of reentrant impulses that encountered partially refractory tissue. For reentry to become sustained, the oscillations after induction of reentry must dampen. Thus, damped cycle length oscillations after induction may identify clinical tachycardias caused by reentry with a partially excitable gap.
The value of symptom directed evaluation in the surveillance for recurrence of carcinoma of the breast. Specific postoperative tests used to diagnose recurrent carcinoma of the breast were evaluated for their ability to have an impact on the over-all course of the disease. Sixty-four patients with recurrent or new contralateral primary disease were divided into two groups based on the method of diagnosis. Those patients with a new complaint at an interval between scheduled follow-up visits and who went on to have tests to document a recurrence were categorized as interval follow-up. Those who were seen at a prearranged regular follow-up period and received tests as recommended by the attending physician or surgeon and had a documented recurrence were classified as routine follow-up. Thirteen patients presented with new contralateral primary disease and 51 with metastatic disease (16, bone; 13, lung; 11, local; three, liver, and eight, multiple). The median time to discovery of recurrence from the primary treatment was 29 and 28 months for the interval and routine groups, respectively. Ninety per cent of the failures occurred by 53 months. The survival time after recurrence was significantly greater in those patients diagnosed routinely (p = 0.003). However, the over-all survival time (from primary therapy to death) was only significantly improved for the routine group when the contralateral new primary diseases were included (p = 0.009). The method of diagnosis of a contralateral primary carcinoma was physical examination and mammogram. Strong recommendations for follow-up testing can be limited to mammogram and physical examination.
Quality of life among hypertensive patients with a diuretic background who are taking atenolol and enalapril. The cardioselective beta-blocker atenolol and the angiotensin-converting enzyme inhibitor enalapril were compared for efficacy, safety, and quality-of-life factors in 30 patients with hypertension whose hypertension was inadequately controlled with diuretic alone. Atenolol (50 to 100 mg once a day) and enalapril (2.5 to 40 mg once a day), combined with hydrochlorothiazide (25 mg once a day), had similar levels of efficacy and safety. A comprehensive battery of psychologic assessments for quality of life was administered, including measures of anxiety, depression, psychiatric symptoms, memory, and psychomotor function. These five conceptually based clusters were first analyzed by multivariate analysis of variance procedures, followed by univariate analyses of the individual variables composing each domain. In general, neither atenolol nor enalapril was associated with major changes in psychologic functioning. The only data cluster with a statistically significant change was memory function, primarily as a result of lower scores of the digit span (backward) test, for atenolol relative to enalapril. These preliminary findings suggest that atenolol and enalapril have comparable degrees of efficacy and safety, with no major disparities in quality-of-life effects, for hypertensive patients with a history of taking diuretics and this sort of quality-of-life assessment can be performed during trials of antihypertensive drugs.
Carbamazepine overdose: a prospective study of serum levels and toxicity. A cooperative prospective study of consecutive cases of carbamazepine overdose was conducted to determine if serum levels were predictive of toxicity and if risk factors such as age, chronic exposure, or previous disorder or cardiovascular disease could be used as prognostic indicators. Seventy-three consecutive cases were collected from two regional certified poison control centers from January 1989 to August 1989. There were 25 exposures in children less than 6 yrs., 11 exposures in adolescents, and 37 exposures in adults. Ten adult cases and one adolescent case were excluded from the study due to the presence of coingestants or inadequate information. Peak measured serum levels ranged from 0.3 to 56 mcg/ml. Using the presence of coma, seizure activity or respiratory depression requiring mechanical ventilation as measures of toxicity, we found poor correlation between rising serum levels of carbamazepine and toxicity. Increased serum levels of carbamazepine did appear to correlate with increased hospital stay, but not with ICU stay. History of a seizure disorder appears to pose increased risk of a seizure in carbamazepine overdose. In this series chronic exposure to carbamazepine did not appear to increase the risk of coma or respiratory depression for a given toxic serum level and may add some protective effect. Serum levels below 40 mcg/ml do not appear to accurately predict the severity of toxicity. Cardiac conduction defects were rare (one child). Anticholinergic findings, as evidence by decreased bowel motility and sinus tachycardia were common. Previous cardiovascular disease and age did not appear to be important prognostic indicators.
Clinical significance of simple heart rate-adjusted ST segment depression in supine leg exercise in the diagnosis of coronary artery disease. To evaluate the clinical significance of simple heart rate-adjusted ST segment depression (delta ST/delta HR) in the diagnosis of coronary artery disease, 42 patients with stable exertional angina underwent supine leg exercise testing and cardiac catheterization. During exercise, heart rate, a multilead electrocardiogram, and pulmonary artery wedge pressure were recorded. The sensitivity and accuracy of the delta ST/delta HR criteria (greater than or equal to 3.0 microV/beat/min) were significantly greater than the conventional analysis of ST segment depression criteria (greater than or equal to 0.2 mV) for detecting three-vessel coronary artery disease at a matched specificity of 72% (100% versus 46%, 81% versus 64%, p less than 0.01). A significant linear correlation was found between maximum pulmonary artery wedge pressure increments during exercise (delta PAWP) or Gensini score and the delta ST/delta HR (delta PAWP: r = 0.51, p less than 0.001; Gensini score: r = 0.47, p less than 0.001). There were no statistically significant differences in the delta PAWP or Gensini score between patients with three-vessel disease who had delta ST/delta HR greater than or equal to 3.0 microV/beat/min and those with one- or two-vessel disease who had delta ST/delta HR greater than or equal to 3.0 microV/beat/min (delta PAWP: 18.1 +/- 2.0 versus 21.9 +/- 3.3, p = NS; Gensini score: 68.5 +/- 6.6 versus 66.3 +/- 11.3, p = NS). These findings demonstrate that delta ST/delta HR is more useful than a conventional analysis of ST segment depression for identifying not only anatomically severe coronary artery disease but also functionally severe coronary artery disease.
Effect of fibrin sealant on the healing colonic anastomosis in the rat. Fibrin adhesives have been advocated as a protective seal in colonic anastomosis to prevent leakage. In order to assess the effect of fibrin glue sealing we compared the healing of sutured colonic anastomosis in the rat (group 1) with the addition of human-derived fibrin sealant (group 2). As a control for a possible reaction to foreign protein, in group 3 the sutured anastomosis was sealed with specially prepared rat fibrin adhesive. On days 2, 4 and 7, ten animals in each group were killed. Adhesion formation was scored and the in situ bursting pressure was measured. The collagen concentration and degradation were estimated by measuring hydroxyproline. Adhesion formation was significantly increased in groups 2 and 3 compared with the control group. On days 2 and 7 the bursting pressure was not different between the groups. On day 4 the bursting pressure in groups 2 and 3 was significantly lower than in group 1 (P less than 0.001). These findings correspond with the results of collagen measurements. On day 4 the concentration of hydroxyproline was significantly reduced in groups 2 and 3. Histological examination showed infiltration of neutrophilic granulocytes into the sealant on days 2 and 4; on day 7 the sealant had vanished. From these results it is concluded that fibrin sealing of the colonic anastomosis in the rat does not improve healing, as demonstrated by bursting pressure and hydroxyproline concentration. On the contrary, it seems to have a negative influence.
Outpatient flexible cystoscopy and fulguration of recurrent superficial bladder tumors. Flexible cystoendoscopy and fulguration were used in the outpatient management of 185 patients with superficial bladder tumors followed for 24 months. This method provided optimal surveillance for recurrence and successful tumor control in selected cases.
Effects of the novel thromboxane antagonist Bay U 3405 on experimental coronary artery disease. Bay U 3405 is a novel thromboxane receptor blocker. The present investigations describe its effects on experimental canine and porcine cardiac damage. In anesthetized dogs, a coronary artery was occluded for 6 hours and reperfused for 30 minutes. Bay U 3405 was administered intravenously 15 minutes after occlusion (1 mg/kg) followed by infusion of 10 mg/kg/hr from 30 minutes after ligature. In a second study, the effects of Bay U 3405 on endoperoxide analogue U-46619-induced coronary constriction were studied in anesthetized, open-chest pigs. Bay U 3405 reduced myocardial infarct expansion by 65% (p less than 0.01) assessed with biochemical staining. Hemodynamics and collateral blood flow were unaffected. However, reperfusion arrhythmias were suppressed. In porcine experiments, 1 mg/kg Bay U 3405, given intravenously or intraduodenally, antagonized U-46619-induced coronary vasoconstriction over 5 hours. The studies demonstrate anti-ischemic and antivasoconstrictor properties of Bay U 3405 probably due to binding to platelet and smooth muscle thromboxane receptors. This may have clinical relevance in angina pectoris and myocardial infarction.
Extracranial metastatic glioblastoma: appearance on thallium-201-chloride/technetium-99m-HMPAO SPECT images. Sequential thallium-201-chloride and technetium-99m-hexamethylpropyleneamine oxime single-photon emission computed tomography (SPECT) images were obtained in a patient with extracranial metastatic glioblastoma multiforme. Thallium-201 uptake was high (three times the scalp background) in all pathologically confirmed extracranial metastases and moderate (1.6 times scalp background) intracranially, where most biopsy specimens showed gliosis with scattered atypical astrocytes. Technetium-99m-HMPAO uptake was decreased intracranially in the right frontal and parietal lobes which had been irradiated. It was also decreased in one well-encapsulated scalp lesion and high in another scalp mass with less defined borders. Possible mechanisms of tumor uptake of these agents are reviewed.
Inhibition of angiogenesis and tumor growth in the brain. Suppression of endothelial cell turnover by penicillamine and the depletion of copper, an angiogenic cofactor. Microvascular proliferation, a hallmark of malignant brain tumors, represents an attractive target of anticancer research, especially because of the quiescent nonproliferative endothelium of the normal brain. Cerebral neoplasms sequester copper, a trace metal that modulates angiogenesis. Using a rabbit brain tumor model, normocupremic animals developed large vascularized VX2 carcinomas. By contrast, small, circumscribed, relatively avascular tumors were found in the brains of rabbits copper-depleted by diet and penicillamine treatment (CDPT). The CDPT rabbits showed a significant decrease in serum copper, copper staining of tumor cell nuclei, microvascular density, the tumor volume, endothelial cell turnover, and an increase in the vascular permeability (breakdown of the blood-brain barrier), as well as peritumoral brain edema. In non-tumor-bearing animals, CDPT did not alter the vascular permeability or the brain water content. CDPT also inhibited the intracerebral growth of the 9L gliosarcoma in F-344 rats, with a similar increase of the peritumoral vascular permeability and the brain water content. CDPT failed to inhibit tumor growth and the vascularization of the VX2 carcinoma in the thigh muscle or the metastases to the lung, findings that may reflect regional differences in the responsiveness of the endothelium, the distribution of copper, or the activity of cuproenzymes. Metabolic and pharmacologic withdrawal of copper suppresses intracerebral tumor angiogenesis; angiosuppression is a novel biologic response modifier for the in situ control of tumor growth in the brain.
Healing of experimental intestinal anastomoses. Parameters for repair. Anastomotic dehiscence remains a major complication in surgery of the large bowel, and studies on the healing sequence of experimental anastomoses are necessary to define underlying mechanisms and find ways to improve surgical outcome, particularly in high-risk situations. For the quantitative description of anastomotic repair, both mechanical and biochemical parameters are employed, each with their own limitations. Mechanical parameters, either bursting pressure or breaking strength, only reflect growing anastomotic strength as long as disruption occurs within the anastomotic area, which is less than one week after surgery for the bursting pressure and probably up to two weeks for the breaking strength. The biochemical description of anastomotic repair has been limited to behavior of collagen, as represented by its rather unique constituent amino acid hydroxyproline. Conclusions based on collagen concentrations--per unit weight--should be considered with caution since they may change as a consequence of changes in noncollagenous substances. In this respect, collagen content, per unit length, is probably a better parameter to describe anastomotic collagen levels. Few investigations have addressed the quality of collagen (e.g., crosslinking or type). Since, at this time, no distinct correlations have been demonstrated between development of mechanical strength or occurrence of leakage and collagen levels in the healing anastomosis, attention should not be restricted to a description of the quantity of collagen present: the quality of anastomotic collagen should be investigated, perhaps even more so.
Prolonged extracorporeal life support of pediatric and adolescent cardiac transplant patients. Options for mechanical support of pediatric patients with severe heart failure who are awaiting transplantation or have undergone transplantation are limited. This report examines 3 patients placed on extracorporeal life support (ECLS) while awaiting transplantation and 3 patients who underwent transplantation and suffered subsequent heart failure due to rejection or postoperative myocardial dysfunction. The overall survival rate was 2 of 6. The 2 surviving patients had a failing transplanted heart. There were no survivors among the patients placed on ECLS as a bridge to transplantation. In each case a contraindication to transplantation developed before a donor heart could be obtained. The mean time of ECLS support was 147.5 hours (range, 70 to 370 hours). The ECLS circuit did not affect cyclosporin levels or antirejection therapy. Extracorporeal life support can be used to support pediatric cardiac transplant patients with biventricular failure due to acute rejection or postoperative dysfunction. Although the results have been discouraging, ECLS may still have a role as a bridge to transplantation. However, complications can develop during ECLS that may preclude transplantation.
A unique indexing splint for use in combined Le Fort and nasal injuries to avoid tracheostomy. Midface fractures with associated displaced and/or comminuted nasal fractures can require tracheostomy for a general anesthetic airway if these fractures are to be reduced simultaneously. We describe a unique indexing splint that allows oral intubation yet also allows simultaneous reduction of midface and nasal fractures under one anesthetic. Furthermore, tracheostomy with its potential complications is avoided. The case report illustrates the technique, and alternative treatments for these injuries are discussed.
Low-dose preoperative radiation postpones recurrences in operable rectal cancer. Results of a randomized multicenter trial in western Norway. A randomized, multicenter clinical trial was conducted in Western Norway to study the effectiveness of preoperative radiation therapy in operable rectal cancer, given at a dosage of 3150 cGy in 18 fractions, 2 to 3 weeks before radical surgery. Three hundred nine patients were entered into the trial between May 1976 and December 1985. After radiation no tumor was seen in 4.5% of the patients. There was no increased morbidity or mortality at surgery. The 5-year survival for evaluable patients was 57.5% in the control group and 56.7% in the radiotherapy group. For patients operated on for cure the 5-year survival was 60.9% and 64.2% in the control group and radiotherapy group, respectively. Radiation significantly delayed both local and distant recurrences in patients in the radiation group who had curative resection from 13.3 months in controls to 27.1 months. The local recurrence rate in the corresponding groups was 21.1% and 13.7%, respectively. We conclude that higher preoperative radiation doses should be used in new trials as a higher dosage may transform the observed positive effects into a survival benefit.
Renal hemodynamics in normal and hypertensive pregnancy: lessons from micropuncture. Rats are an excellent animal model in which to study the changes in renal hemodynamics associated with normal pregnancy. Midterm pregnant rats exhibit a maximal renal vasodilation leading to increases in glomerular filtration rate (GFR) and renal plasma flow (RPF). Micropuncture studies in midterm pregnant Munich-Wistar rats have shown that single-nephron GFR (SNGFR) increases, due entirely to increases in plasma flow and, importantly, glomerular capillary blood pressure (PGC) remains unchanged in normotensive pregnancy, due to parallel and proportionally similar reductions in preglomerular (RA) and efferent (RE) arteriolar resistance. Despite the chronic gestational renal vasodilation, pregnancy in normotensive rats with either normal kidneys or a variety of underlying diseases, causes no adverse changes in renal function, perhaps because the glomeruli are protected from damaging high PGC. In the presence of systemic hypertension, the renal vasodilation of pregnancy could put the maternal kidney at risk of injury due to increases in PGC. There are few renal functional studies in preexisting, essential hypertension, but micropuncture studies in spontaneously hypertensive rats (SHRs) have shown that repetitive pregnancies in SHRs cause no functional impairment. Surprisingly, SHRs demonstrated no gestational renal vasodilation, although gestational decreases in peripheral resistance certainly occur in the SHR. This absence of gestational renal vasodilation may be a protective mechanism; it remains to be determined whether hypertensive states in which renal vasodilation does occur are associated with increased risk to the maternal kidney.
Plasma HDL cholesterol concentrations are correlated to bile cholesterol saturation index in the African green monkey. In an attempt to determine if plasma lipoprotein concentrations correlate with the bile cholesterol saturation index in the African green monkey, we have studied a group of adult male animals available from a long-term study investigating the effects of dietary fat and cholesterol on cholesterol metabolism and atherosclerosis. The animals were fed diets containing 0.8 mg cholesterol/kcal or 0.03 mg cholesterol/kcal for five years. Within each dietary cholesterol group, animals received 42% of dietary calories as fat, enriched with either saturated or polyunsaturated fat. Using stepwise multiple linear regression, high density lipoprotein (HDL) cholesterol concentration was found to be the best plasma lipid predictor of the bile cholesterol saturation index. When the cholesterol saturation index of a fasting gallbladder bile specimen was compared to the plasma HDL cholesterol level for individual animals, a significant positive correlation was noted for animals fed polyunsaturated fat, (r = 0.68) and for animals fed saturated fat (r = 0.72). For any value of HDL cholesterol, however, the cholesterol saturation index was higher in animals fed polyunsaturated fat compared to saturated fat. Since plasma HDL cholesterol levels were positively correlated with the bile cholesterol saturation index in adult male African green monkeys, we conclude that a metabolic link exists between plasma HDL cholesterol concentrations and bile cholesterol saturation, perhaps due to enhanced delivery of cholesterol to the liver by HDL.
Long-term function of persons with atherosclerotic bilateral below-knee amputation living in the inner city. Long-term function of 24 elderly persons with atherosclerotic bilateral below-knee amputation living in an inner city for at least six months after the second amputation, was determined. Twenty-one (87.6%) subjects were living at home; three were living in nursing homes. Fourteen (70%) of 20 subjects who received bilateral prostheses were ambulators. At interview, the mean age was 75.2 years; 4.87 years was the mean time since the second amputation. Ten (50%) subjects remained ambulatory. Among the other ten who received prosthesis, loss of ambulation occurred mostly due to medical factors, at an average of 3.47 years after the second amputation. Those no longer ambulatory were older and "sicker," and the interval between amputations was shorter. Fifteen (62.5%) subjects were independent in dressing, 14 (58.4%) in toileting, and only nine (33.3%) in bathing. All but one subject required housekeeping assistance. The anticipated effect on function of environmental and socioeconomic factors could not be demonstrated in this sample. Survival time and retention of ambulatory skills for an average of nine years after the second amputation in eight (33.3%) subjects who died before the end of the study was longer than previously described. The high rate of success in rehabilitation and in maintenance of ambulatory skills fully justifies intensive restorative efforts for this group of amputees.