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Biomedical subjects

A Markel

Publications and source records attributed to A Markel.

At least 19 recordsLinked to original sources
PubMed2003

Deep venous thrombosis: rate of spontaneous lysis and thrombus extension.

AIM: Although recanalization occurs after an episode of venous thrombosis, the exact timing for this process, the rate of clearing at the different venous segments and the nature of the mechanisms involved and their progression are not well known. Recognition of these competing events is important in understanding the natural history and the mechanisms responsible for lysis of the thrombus and for the development of the post-thrombotic syndrome METHODS: During the course of 5 consecutive years, 110 patients (126 legs) with deep vein thrombosis (DVT) were prospectively followed using ultrasonic duplex. Follow-up studies were performed at intervals of 1 and 7 days, 1 month, every 3 months for the 1(st) year, and yearly thereafter. Mean duration of follow-up was 329 days. RESULTS: When only legs with initial complete occlusion are considered, the prevalence of occlusion progressively decreases to 33% after 6 months, 17% after the 1(st) year, and 0% after 3 years. Recanalization of individual segments occurred even more rapidly. After 3 months, recanalization of completely occluded segments was present in 93% of common femoral veins, 79% of superficial femoral veins (proximal segment), 84% of popliteal veins, and 72% of posterior tibial veins. The rate of recanalization was highest for multisegmental disease. Propagation of thrombi to adjacent venous segments occurred in 15% of the limbs. Propagation was usually limited to 1 or 2 adjacent segments. CONCLUSION: Lysis occurred early and was progressive. After 1 year most legs have recanalized. After 3 years recanalization occurred in all legs although residual thrombosis (partial obstruction) was still present in 50% of the limbs. Propagation of the thrombus was a limited process.

Adolescent↗
PubMed1999

Efficacy and safety of cerivastatin for type 2 diabetes and hypercholesterolaemia. Hyperlipidaemia in Diabetes Mellitus investigators.

BACKGROUND: The prevalence of coronary heart disease (CHD) is markedly increased in diabetic patients compared with non-diabetic individuals, and its prognosis is less good. Serum total and low-density lipoprotein (LDL) cholesterol concentrations have been shown to be powerful predictors of CHD morbidity and mortality in patients with type 2 diabetes. The available data suggest that the target cholesterol concentration in patients with diabetes should be similar to that in non-diabetic individuals with a previous myocardial infarction. This led us to investigate the efficacy, tolerability and safety of a new, highly potent statin, cerivastatin, in diabetic hyperlipidaemia. METHODS: This was a multinational, multicentre, double-blind, randomized study in type 2 diabetic patients with hypercholesterolaemia (LDL cholesterol >3.35 mmol/l; triglycerides <4.56 mmol/l). Eligible patients were randomly assigned to groups to receive cerivastatin 0.1 mg or 0.3 mg or placebo in a ratio of 2:2:1 for 12 weeks. They were monitored in the clinic every 4 weeks. RESULTS: Of the 453 patients screened, 265 were allocated to the study groups. Fifty-one received placebo and 107 patients were assigned to each active treatment group (0.1 mg and 0.3 mg cerivastatin). At the close of the study, total cholesterol had decreased by 13.7% and 23.5%, LDL cholesterol decreased by 20.2% and 33.8%, and triglyceride concentrations decreased by 3.9% and 12.3% in the cerivastatin 0.1 mg and 0.3 mg groups, respectively. There was no significant difference between the groups in haemoglobin A1c, adverse events or increases in liver and muscle enzymes during the study period. CONCLUSIONS: Hypercholesterolaemic patients with type 2 diabetes had a significant reduction in LDL cholesterol and total cholesterol concentrations after cerivastatin treatment once daily. The dose of 0.3 mg cerivastatin is effective in diabetic hypercholesterolaemia, with co-reduction of triglyceride concentrations. The effect of cerivastatin on coronary morbidity and mortality is currently being investigated in clinical trials.

Adult↗
PubMed1996

Interactions of Escherichia coli tryptophanase with quasisubstrates and monovalent cations studied by the circular dichroism and fluorescence methods.

The reaction of tryptophanase and its W330F and W248F mutant forms with quasi-substrates forming an external pyridoxal phosphate aldimine or quinonoid is accompanied by the appearance of a positive circular dichroism (CD) peak at 290 nm. The peak seems to arise from a Tyr residue undergoing reorientation during the reaction. The peak does not appear upon formation of non-covalent Michaelis complexes of the enzyme with quasi-substrates such as indolepropionate, beta-phenyllactate and alpha-methylphenylalanine. The non-covalent complexes and external aldimines exhibit similar absorption spectra but can be distinguished by their CD and by the intensity of their fluorescence. Formation of the non-covalent complexes leads to an increase in positive CD at 420 nm while formation of the external aldimines leads to disappearance of the positive CD at 420 nm and its replacement by negative CD; it also leads to strong quenching of the coenzyme fluorescence at 500 nm. The quantum yield of fluorescence of the external aldimines is 6-times lower than that of the internal aldimine. Activating cations (K+, NH4+) strongly diminish the intensity of a negative protein CD band at 275 nm. From a comparison of the intensity of this band in the spectra of the wild-type holo- and apoenzyme and in the tryptophan mutants, it was deduced that the band belongs to a Tyr residue, which may be a part of the cation-binding site or located in its immediate vicinity.

Binding Sites↗
PubMed1995

Application of a bedside whole blood D-dimer assay in the diagnosis of deep vein thrombosis.

Cross-linked fibrin degradation products have been used to detect venous thrombosis. While the sensitivity of plasma D-dimer measured by ELISA in the diagnosis of deep vein thrombosis (DVT) is high, the utility of ELISA methods is limited in a clinical setting. This study analysed the diagnostic value of a rapid D-dimer assay performed on whole blood samples (SimpliRed D-dimer) compared with latex and ELISA in 86 patients suspected of having DVT. SimpliRed D-dimer was positive in 47/50 of patients with DVT established by Doppler ultrasound (DU; sensitivity 94%). SimpliRed D-dimer was positive in 35/37 of patients with proximal DVT, nine out of nine with popliteal DVT and three out of four with superficial thrombophlebitis. The specificity of SimpliRed D-dimer in the diagnosis of DVT was 61%. The sensitivity of the SimpliRed D-dimer assay was at least comparable with the ELISA (87%) and superior to the latex assay (80%). The positive predictive value (77%), the negative predictive value (88%) and the overall accuracy (80%) of the SimpliRed assay were better than the ELISA and latex methods. It is concluded that SimpliRed D-dimer is a rapid useful assay for screening of patients suspected of having deep vein thrombosis.

Adolescent↗
PubMed1995

Doppler ultrasound in the diagnosis of venous thrombosis.

Deep vein thrombosis (DVT) has known morbidity and mortality. New noninvasive techniques such as B-mode scanning and Doppler ultrasonography (duplex) are highly accurate in the diagnosis of this problem but are relatively expensive and time consuming. Continuous-wave Doppler, a precursor noninvasive technique, is simple, cheap, and easy to perform at the patient's bedside. To test the effectiveness of this technique the authors prospectively studied patients with clinical suspicion of DVT by Doppler ultrasound and compared the results with those from venography. During fourteen consecutive months, patients with a clinical suspicion of DVT underwent continuous-wave Doppler examination of both inferior limbs. Each case was diagnosed as positive, negative, or inconclusive. In addition, the patients underwent a questionnaire regarding risk factors, symptoms, and mean relevant physical findings. Doppler examination was blinded to venography results. A total of 116 patients with clinical suspicion of DVT were examined by Doppler ultrasound. Their mean age was fifty-five years (range: eighteen to eighty-eight). There were 57 men and 59 women, and from this group a total of 40 patients underwent both Doppler ultrasound examination and venography in the course of forty-eight consecutive hours. When cases with an inconclusive result were excluded, Doppler ultrasound showed a sensitivity of 89%, a specificity of 100%, and an accuracy of 94% for the diagnosis of DVT when compared with venography. When a similar analysis was done for the proximal named veins, continuous-wave Doppler examination showed a very high specificity and positive predictive value and a moderate sensitivity and negative predictive value.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

[Left-sided group A streptococcal endocarditis and mitral valve prolapse].

Group A beta-hemolytic streptococcus is an infrequent cause of endocarditis. Left-sided endocarditis in intravenous drug abuse is likewise uncommon; it carries a poor prognosis. A case of left-sided group A beta-hemolytic streptococcal endocarditis in a 20-year-old male drug addict with mitral valve prolapse is presented. This association has not been reported previously.

Adult↗
PubMed1994

Hypoglycaemia-induced ischaemic ECG changes.

A patient with an 8 year history of insulin-dependent diabetes mellitus was admitted to the emergency ward for hypoglycaemic coma (blood glucose 1.11 mmol/l). The initial electrocardiogram revealed a junctional rhythm and major ischaemia with an ST depression of 6-7 mm. Sinus rhythm and normal repolarization were recovered 15 minutes after administration of 50% glucose. No evidence of myocardial infarction appeared during follow-up. Such hypoglycaemia-induced ECG changes have rarely been documented and no conclusive explanation has been put forward although altered balance between energy supply and demand in myocardial tissue has been suggested. Special care should be taken when administering hypoglycaemic agents to patients at risk for myocardial ischaemia.

Diabetes Mellitus, Type 1↗
PubMed1994

A comparison of the cuff deflation method with Valsalva's maneuver and limb compression in detecting venous valvular reflux.

OBJECTIVE: This study was designed to test the results of Valsalva's maneuver and limb compression against the standing-cuff inflation-deflation method for the detection of venous valvular reflux. DESIGN: The study was conducted in 67 patients (134 extremities) who had an episode of deep vein thrombosis. An ultrasonic duplex scanner was used to evaluate two methods of testing for reflux. The most commonly used methods are Valsalva's maneuver and limb compression, both of which can raise the venous pressure and promote reflux. With the cuff method, the patient is studied in the standing position. The cuffs are segmentally placed (thigh to foot) with reflux encouraged when the inflated cuff is suddenly deflated. SETTING: The patients were a part of a long-term natural history study of acute deep vein thrombosis and its effects on venous valve function. OUTCOME MEASURES: Valvular reflux was documented by the appearance of retrograde flow in the vein when the normal transvalvular pressure gradient was reversed. RESULTS: Both limb compression and Valsalva's maneuver can elicit reflux, but the maneuvers are difficult to standardize and come up with meaningful results. With the cuff inflation-deflation method, the time to valve closure was less than 0.5 seconds in 95% of normal subjects. The results were easier to quantify and worked well for all segments of the venous systems--superficial and deep. CONCLUSIONS: The cuff inflation-deflation method provides more uniform quantifiable results for detecting reflux in the superficial and deep veins of the leg.

Acute Disease↗
PubMed1994

Retroperitoneal lymphadenopathy: an extrahepatic feature of chronic active hepatitis.

We report a patient with chronic active hepatitis in whom one of the initial findings was retroperitoneal lymphadenopathy, detected by abdominal ultrasound examination. Extrahepatic presenting findings of chronic active hepatitis may include arthritis, urticaria, pleurisy and pericarditis, while abdominal lymphadenopathy has been only rarely described. Chronic active hepatitis should be included in the differential diagnosis of abdominal lymphadenopathy.

Adult↗
PubMed1994

Effect of dietary supplementation of red or white wine on human blood chemistry, hematology and coagulation: favorable effect of red wine on plasma high-density lipoprotein.

Twenty healthy males were divided into two groups: 10 subjects were supplemented for 2 weeks with 400 ml of red wine (11% alcohol) per day and the other 10 subjects were given 400 ml of white wine (11% alcohol) per day for a similar period. Blood samples were drawn prior to wine supplementation, after 1 week and at the end of the study. No significant effects were found on plasma concentrations of urea, creatinine, bilirubin, creatine kinase, amylase, blood cell counts, platelet counts and platelet aggregation. Both red- and white-wine supplementation resulted in a transient minor reduction in plasma glucose concentration and in a minor elevation in blood coagulation properties such as prothrombin time and partial thromboplastin time. Red (but not white) wine resulted in an 11 and 26% increment in plasma triglyceride concentrations after 1 and 2 weeks of supplementation, respectively. Plasma cholesterol, as well as very-low- and low-density-lipoprotein levels did not change during the 2 weeks of red- or white-wine supplementation. The most impressive effect of red-wine intake was a significant (p < 0.01) increase in plasma high-density lipoprotein (HDL) cholesterol and in plasma apolipoprotein A-I concentrations by up to 26 and 12%, respectively. These effects were not observed after the intake of white wine. We conclude that the major effect of red-wine supplementation (about 40 g of alcohol per day for a period of 2 weeks) was a significant increase in plasma HDL concentration which may contribute to the reduced risk for cardiovascular diseases observed in red-wine drinkers.

Adult↗
PubMed1994

Incidence and time of occurrence of valvular incompetence following deep vein thrombosis.

Commencing December 1986 and over the course of 4 years, the diagnosis of acute deep vein thrombosis (DVT) was established by duplex scanning in 286 patients referred to the University of Washington Medical Center in order to rule out this problem. From this group 107 patients (123 legs with DVT) were placed in a long-term follow-up program. The documentation of valvular reflux and its site was demonstrated by duplex scanning. The duplex studies were done at intervals of 1 and 7 days, 1 month, every 3 months for the first year and then yearly thereafter. The mean follow-up time was 341 days. The presence of reflux was also determined in 502 patients with a negative duplex study and no previous history of DVT or chronic venous insufficiency. In the patients with acute DVT, valvular incompetence was noted in 17 limbs (14%) at the time of the initial study. Reflux was absent in 106 limbs (86%). In this last group reflux developed in 17% of the limbs by day 7. By the end of the first month, 37% demonstrated reflux. By the end of the first year, more than two-thirds of the involved limbs had developed valvular incompetence. The distribution of reflux at the end of the first year of follow-up was: 1) popliteal vein, 58%; 2) superficial femoral vein, 37%; 3) common femoral vein, 33%; and 4) posterior tibial vein, 18%. Reflux in the greater saphenous vein occurred in 25% of the limbs after 1 year. Reflux developed more frequently in thrombosed venous segments.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

[Mediastinal abscess complicating perforated riding gastric ulcer].

Gastric ulcer in a diaphragmatic hernia is a specific clinical entity, different from other gastric ulcerations. A 71-year-old man with a perforated and bleeding gastric ulcer in a diaphragmatic hernia, complicated by a posterior mediastinal abscess, is presented.

Abscess↗
PubMed1993

Deep venous insufficiency: the relationship between lysis and subsequent reflux.

PURPOSE: Although venous valvular insufficiency is well recognized as the most important etiologic mechanism in the development of the postthrombotic syndrome, the factors contributing to valve incompetence after deep venous thrombosis remain obscure. METHODS: To establish the relationship between recanalization and valve competence, 113 patients with acute deep venous thrombosis were studied with serial duplex ultrasonography. RESULTS: Median lysis times for segments developing reflux (214 to 474 days) were 2.3 to 7.3 times longer than for corresponding segments not developing reflux (65 to 130 days) for all except the posterior tibial vein. In the posterior tibial vein, median lysis times for those with and without reflux were nearly identical (72 vs 80 days). The median time to onset of reflux was significantly less than the median lysis time in the mid and distal superficial femoral veins and was simultaneous with recanalization in all other segments. CONCLUSIONS: Early recanalization is important in preserving valve integrity for all but the posterior tibial segment. However, the small number of patients with reflux despite early lysis (< 1 month) or without reflux despite relatively late lysis (> 9 to 12 months) suggests that other factors may also contribute to the development of valvular incompetence. These factors may be particularly important in the posterior tibial vein, in which lysis time has little relationship to the ultimate development of reflux.

Adolescent↗
PubMed1992

Pattern and distribution of thrombi in acute venous thrombosis.

The location and extent of thrombosis in the deep venous system will determine immediate and long-term outcome. During the past 3 years, we have studied by duplex scanning 833 patients with suspected deep vein thrombosis. In this group, 209 patients (25%) had a positive study. The findings relative to location and extent of involvement are as follows. (1) The right leg was involved in 35% of patients, the left leg in 48%. Bilateral involvement was noted in 17%. (2) The veins most frequently affected by deep vein thrombosis were as follows: superficial femoral in 74%, popliteal in 73%, common femoral in 58%, posterior tibial in 40%, deep femoral in 29%, greater saphenous in 19%, and the inferior vena cava in 2%; multisegment involvement was common. (3) Total occlusion was present in 82% of the patients with deep vein thrombosis, and partial occlusion in 18%. (4) Isolated occlusion of single veins was uncommon. (5) The proximal (above-knee) area was involved in 95% of the cases with deep vein thrombosis, and the calf in 40% of the cases. Isolated calf deep vein thrombosis was found in 6% of the cases with right leg involvement and in 3% for the left. (6) Total leg involvement (iliocaval, femoropopliteal, and calf) occurred in 10% of the patients. Our data confirm the fallibility of the clinical diagnosis of deep vein thrombosis. The frequent involvement of both limbs stresses the importance of not examining just the symptomatic limb. Proximal venous thrombosis (popliteal to inferior vena cava) is much more common than isolated calf vein thrombosis as a cause for symptoms and the referral for study.

Adolescent↗
PubMed1992

The potential role of thrombolytic therapy in venous thrombosis.

BACKGROUND: Anticoagulant therapy for lower extremity deep-vein thrombosis (DVT) has been shown to reduce mortality from pulmonary embolism, but subsequent morbidity from the postthrombotic syndrome remains high. Thrombolytic therapy produces higher lysis rates of venous thrombi than heparin alone. Some studies suggest a lower incidence of postthrombotic sequelae after early use of streptokinase. These potential benefits are limited to those patients without contraindications for this therapy. METHODS: For the past 3 years we have prospectively studied patients with DVT documented by duplex scanning. The records of these patients were reviewed to determine what proportion of this population would have been candidates for thrombolytic therapy. For this analysis, contraindications to the use of thrombolytic agents included: (1) recent surgery (less than 1 month); (2) recent major trauma; (3) active or recent bleeding; (4) brain disease (cerebrovascular accident, brain tumor, arteriovenous malformation); (5) pregnancy; and (6) bleeding diathesis. Also, patients with prior ipsilateral DVT and those with acute symptoms present for 7 or more days were not considered to be candidates for thrombolytic therapy. RESULTS: A contraindication to thrombolytic therapy was present in 194 (93%) of 209 patients with a diagnosis of DVT, including four patients with a relative contraindication. Two or more contraindications were present in 65 cases (31%). Recent surgery was the most frequent factor precluding therapy, being present in 71 patients. A history of DVT in the affected leg was present in 45 patients. CONCLUSIONS: Only 15 (7%) of 209 patients with DVT exhibited no contraindications for thrombolytic treatment. Only a small fraction of patients with venous thrombosis will be potential candidates for this therapy.

Adult↗