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PubMedDate not supplied

Effects of hemodynamics on thromboembolism in coronary stents and prototype flow cells in vitro.

Thromboembolism was studied as heparinized (3 U/ml) bovine blood was gravity fed through a conduit with a deployed coronary stent or a prototype flow cell. The initial flow rate was established with a pinch valve, and monitored with a clamp-on ultrasonic probe. Emboli production was continuously monitored using a light scattering microemboli detector. Accumulated thrombus at the end of the experiment was assessed gravimetrically in stents or by magnetic resonance imaging in flow cells. Hemodynamic parameters were varied to assess their effects on thromboembolism. With the flow cells, the hemodynamics were controlled by varying the geometry of the stagnation zones. With the stents, the flow characteristics were altered by placing 75% stenoses upstream and/or downstream of the stent. The average values of the shear stress and residence time around the stent were modeled using the commercial fluid dynamics software FLUENT. Combining the computed hemodynamic parameters with the experimental results showed that 1) thrombus accumulation decreased with increasing shear stress and increased with increasing residence time; 2) embolization was promoted by high shear, and did not correlate with the amount of thrombus accumulated at the end of the experiment; and 3) a reconfiguration of the magnetic resonance imaging system is necessary to monitor thrombus accumulation continuously.

Animals↗
PubMed1996

Aspirin and warfarin for thromboembolic disease after total joint arthroplasty.

This study compares the benefits of aspirin and warfarin prophylactic agents for patients with thromboembolic disease after total joint arthroplasty. It is a prospective randomized study of 388 patients having total hip or total knee surgery. All consecutive patients having total hip or total knee surgery were entered into this study and evaluated with preoperative and postoperative ventilation perfusion scans and a postoperative venogram. The aspirin and warfarin treatment groups were compared by size and location of venographically revealed clots and changes in ventilation perfusion scans. The results showed that there was no difference in the size or location of deep venous thrombosis in the aspirin or warfarin treatment groups. The venogram was negative in 44.5% of patients; 28.8% had small ++calf clots, 16% had large calf clots, 3.9% had popliteal clots, and 6.7% had femoral clots. Patients with total knee replacement had a 2.6 times greater incidence of calf deep venous thrombosis than patients with total hip replacement. There was no difference between the aspirin and warfarin groups in the incidence of changes in ventilation perfusion scans (18.9%). There was no difference between the 2 groups in bleeding complications. The results suggest that aspirin and warfarin are equivalent in prophylaxis against thromboembolic disease, as determined by prevention of venographic changes or changes in ventilation perfusion scans.

Aged↗
PubMed1996

Thromboembolic complications in patients with pelvic trauma.

Patients with pelvic trauma are known to be at increased risk for the development of thromboembolic complications. The incidence of deep venous thrombosis in patients with pelvic fractures is 35% to 60%. Proximal deep venous thrombosis, which is most likely to result in pulmonary embolism, occurs in 25% to 35% of these patients, and almost 1/2 of all proximal thrombi will be in the pelvic veins. The incidence of symptomatic pulmonary embolism in the pelvic trauma population is 2% to 10% whereas a greater proportion of patients will have clinically silent pulmonary embolism. Fatal pulmonary embolism occurs in 0.5% to 2% of patients with pelvic trauma. The cornerstone of effective management is prophylaxis and the most commonly used forms include low dose heparin, low molecular weight heparin, mechanical devices, and in some studies, inferior vena caval filters. Based on a critical review of the literature, in algorithm is proposed for the management of thromboprophylaxis in this trauma subgroup. This includes prophylaxis, screening, and treatment when proximal thrombosis is identified. Such a systematic approach to this potentially catastrophic problem may decrease the morbidity and mortality associated with thromboembolic complications in these patients.

Fractures, Closed↗
PubMedDate not supplied

Experimental renal artery thromboembolism.

The natural history of experimental renal artery embolism with autogenous thrombus in 16 mongrel dogs has been investigated by sequential selective renal angiography and correlated with examination of the kidneys following autopsy. Angiography in the early (0-24 hr) post-thromboembolism period shows evidence of arterial obstruction and/or spasm which progressively disappears leaving no apparent permanent damage. However, within one or two weeks arterial and nephrographic changes and loss of renal size are discernible by careful comparison with the pre-embolism angiogram. At autopsy multiple disseminated microscopic infarcts involving the convoluted tubules were demonstrable in all cases. Occasionally large wedge-shaped infarcts involving the full thickness of the cortex were superadded. The potential importance of these findings relating to angiographic technique and assessment of treatment of renal thromboembolism is discussed.

Angiography↗
PubMed1988

The role of catheters and guidewires in the production of angiographic thromboembolic complications.

Thromboembolic complications occurring during angiography may result from a number of different causes. Catheters and guidewires can interact with blood to form thrombi; this tendency is related to wall defects and the chemical composition and structural characteristics of the catheters and guidewires. Nonthrombic sources of emboli may consist of foreign bodies derived from surgical equipment or may exist in the flushing solution and contrast media. Plastic emboli may be shed from catheters and guidewires when the guidewires are passed through the catheters. Air emboli may result from poor technique or loose fitting connections between the catheter and injector or syringe; they can mimic emboli from catheters and guidewires. A number of strategies for decreasing the risk of thromboembolic complications during angiography are reviewed.

Angiography↗
PubMed2002

Magnetic resonance angiography of thromboembolic stroke in rats: indicator of recanalization probability and tissue survival after recombinant tissue plasminogen activator treatment.

Magnetic resonance angiography (MRA) was performed in a thromboembolic stroke model of the rat to characterize intracranial vessel occlusion patterns and to test its predictive power for tissue recovery after recombinant tissue plasminogen activator (rt-PA) treatment. After rt-PA-treated selective middle cerebral artery (MCA) occlusion, full recanalization was observed in two of three animals, whereas additional occlusion of the circle of Willis (CW) resulted in full vascular flow restitution in only one of six rats. Tissue reperfusion markedly lagged the onset of treatment, and the delay correlated with the pattern of vessel occlusion (20 to 23 minutes for selective MCA occlusion vs. 71 to 79 minutes for combined MCA/CW occlusion). In lateral cortex and striatum the apparent diffusion coefficient decreased to 78 +/- 15% of control after embolization, recovered to 80% to 85% after rt-PA treatment of selective MCA occlusion, but further declined to 66% to 69% after combined MCA/CW occlusion. Correspondingly, T2 relaxation time increased to 107% to 118% of control after selective MCA occlusion and to 112% to 124% after combined MCA/CW occlusion in these regions. The present investigation shows that MRA provides valuable information on the severity of thromboembolic stroke and has the power to predict, before the initiation of treatment, the functional tissue outcome after rt-PA-induced thrombolysis.

Animals↗
PubMed1994

Prevention of venous thromboembolism in trauma patients.

Trauma patients are at risk for thromboembolic complications, but effective methods of prophylaxis have not been established for this heterogenous population. In this prospective trial, 400 trauma patients were assigned to one of three groups, depending upon their injuries, and randomized within each group to a treatment mode: Group I: sequential gradient pneumatic leg compression (SCD), low-dose subcutaneous heparin (H), or control (C); Group II: H or C; Group III: SCD or C. Venous duplex ultrasound examinations were performed on admission and weekly thereafter. Of the 251 patients who completed the study, 15 (6%) developed lower extremity venous thrombosis and two additional patients developed pulmonary embolism (one fatal). Significant risk factors associated with the development of thromboembolism included immobilization > 3 days, age 30 years or older, and the presence of pelvic or lower extremity fractures. In patients with neurotrauma who cannot receive heparin (Group III), the SCD was more effective than control in preventing DVT (p = 0.057). Neither H nor SCD appeared to offer protection for the other groups of trauma patients, but surveillance with ultrasound examinations allowed for prompt recognition and treatment of occult deep vein thrombosis.

Adolescent↗
PubMed1991

Venous thromboembolism after brain tumor surgery: a retrospective review.

We retrospectively reviewed the incidence rate of clinical postoperative deep vein thrombosis and/or pulmonary embolism in 1703 patients undergoing initial craniotomy for meningioma, glioma, or cerebral metastasis. The incidence rate of clinical thromboembolic complications was 1.59% for all tumor groups within the first 4 weeks of surgery. Patients undergoing surgery for meningiomas had a statistically significant increased risk of thromboembolism despite fewer overall perioperative risk factors, when compared with the other tumor groups. The tumor-specific incidence rates of deep vein thrombosis and/or pulmonary embolism for meningioma, glioma, and metastasis were 3.09%, 0.97%, and 1.03%, respectively. Whether this difference was a result of increased surgical time or an inherent property of meningiomas could not be ascertained.

Adult↗
PubMed1977

A multifaceted approach to prevention of thromboembolism: a report of 529 cases.

The morbidity and incidence of thromboembolic complications can be reduced by patient awareness, nursing staff concern, and physician responsibility using mechanical measures and drugs. Preoperative exercise instrutions, early ambulation, calf exercise, antiembolism hose, postoperative circle-bed turning and use of the Trendelenburg position, the use of intravenous dextran postoperatively and, in selected cases, low doses of sodium warfarin (Coumadin) form the foundation of our approach to the prophylaxis of thromboembolic phenomena. In the presence of thrombophlebitis, phenylbutazone (Butazolidin) is used. Dextran is used with caution in the presence of diminished biliary function. Heparin is avoided except in proven pulmonary embolism. No complications have resulted from this regimen.

Aspirin↗
PubMed2000

Vertebral artery anomaly with atraumatic dissection causing thromboembolic ischemia: a case report.

STUDY DESIGN: A case report is presented. OBJECTIVES: To illustrate a rare cause of atraumatic vertebral artery dissection resulting from anomalous entry of the vessel at the C3 transverse foramen induced by normal physiologic head and neck motion, and to review vertebral artery anatomy and mechanisms whereby it is vulnerable to pathologic compression. SUMMARY OF BACKGROUND DATA: The vertebral artery usually enters the transverse foramen at C6. Rarely, the artery enters at C5 or C4. Only one prior case with entry at C3 has been reported. That patient experienced recurrent quadriplegia and locked-in syndrome caused by vertebral artery obstruction. A 27-year-old woman with a history of classic migraine experienced neurologic symptoms on three occasions related to physiologic neck and arm movements. Magnetic resonance angiogram was not diagnostic, but standard arteriography demonstrated anomalous vertebral artery entry into the C3 transverse foramen and focal dissection. METHODS: Pertinent literature and the patient's history, physical examination, and radiologic studies were reviewed. RESULTS: Standard cervico-cerebral arteriogram demonstrated focal dissection at C4 and thromboembolic complications in distal vertebral and basilar arteries. Initially, diagnosis by magnetic resonance angiogram was elusive. However, arteriography allowed prompt diagnosis followed by anticoagulation with resolution of neurologic symptoms. CONCLUSIONS: Vertebral artery dissection without trauma is rare, but should be considered when neurologic symptoms accompany physiologic cervical movements. For cases in which vertebrobasilar thromboembolic ischemia is suspected, magnetic resonance angiogram may prove inadequate for demonstrating the causative vascular pathology. Therefore, standard cervico-cerebral arteriography should be performed.

Adult↗
PubMed2000

Long-term treatment for venous thromboembolism.

Anticoagulation is the corner stone of therapy for venous thromboembolism. The optimal duration of this therapy depends on the balance between the risk of recurrent thrombosis if anticoagulants are stopped, and the risk of bleeding if patients remain on treatment. The risk of recurrence is low if thrombosis was precipitated by a major reversible risk factor such as surgery. Patients with idiopathic thrombosis (no apparent risk factor) and those with persistent risk factors (eg, cancer), have a high risk of recurrence. Some hereditary (eg, protein C, protein S or antithrombin deficiency; homozygous factor V Leiden) and acquired (eg, antiphospholipid antibodies) thrombophilic states are also risk factors for recurrence. Three months of anticoagulation is recommended when the risk of recurrence is low, whereas the duration of therapy should be extended to 6 months or longer when this risk is high, depending on the balance between the risk of recurrence and the risk of bleeding in each individual patient. Heparin preparations, at doses intermediate to those used for the acute treatment of venous thromboembolism and for primary prophylaxis, are an alternative to oral anticoagulants during the maintenance phase of treatment.

Anticoagulants↗
PubMed1999

Risk factors for venous thromboembolism in pregnancy.

Venous thromboembolism remains the leading cause of maternal mortality in the United Kingdom. In this review we highlight studies that have documented the incidence of objectively confirmed venous thromboembolism in pregnancy, consider the effect of pregnancy on the coagulation and fibrinolytic systems, and examine in detail current knowledge of the risk factors for the development of this condition.

Female↗
PubMed1999

Treatment and prevention of venous thromboembolic disease in pregnancy.

Pulmonary embolism is a major, but potentially preventable, cause of maternal mortality in North America and Europe. Because venous thromboembolism is an infrequent cause of maternal morbidity, there are few randomized clinical trials to guide clinical decision-making with respect to treatment, prevention, and evaluation of innovative management modalities such as low molecular weight heparin. This article focuses on the evidence supporting the current guidelines for the pharmacologic management of venous thromboembolic disease in pregnancy.

Anticoagulants↗
PubMed2000

Duration of anticoagulants in acute or recurrent venous thromboembolism.

While the most recent trend in secondary prophylaxis after venous thromboembolism has been toward a prolonged duration, it has become obvious that individualization according to risk factors is crucial. Subgroup analyses in a long-term follow-up of a previous trial, as well as new trials on patients with idiopathic thromboembolism, have now improved our base of evidence. Many studies on the influence of biochemical factors in the risk of recurrence have also been published recently. This review should be helpful in-the individual decision on how to tailor the duration of anticoagulation.

Anticoagulants↗
PubMed2001

Thromboembolism in brain tumors.

Venous thromboembolism commonly affects patients receiving treatment for primary and secondary cerebral tumors. We review the recent literature on the molecular mechanisms underlying this hypercoagulable state and clinical studies of antithrombotic prophylaxis and therapy in this population. A computerized search of the MEDLINE database for articles from 1966 to the present day. Keywords/search terms used were glioma, astrocytoma, glioblastoma multiforme, cerebral tumor, primary brain tumour, secondary brain tumour, venous thromboembolism, thromboprophylaxis, heparin, warfarin, anticoagulants, and caval filters. Although neurological deficit has been identified as an independent risk factor for thrombosis it is also clear that malignant brain tumors induce changes in the makeup of circulating blood, making it more likely to clot. Concern for the perceived risk of perioperative intracranial bleeding with antithrombotic prophylaxis appears not to be justified by the available evidence. Prospective assessment of low molecular weight heparins for prophylaxis and treatment of established thrombosis is required. Antithrombotic therapy may also offer advantages over intracaval devices in prevention of secondary pulmonary embolism in patients with brain tumors.

Anticoagulants↗
PubMed2003

Hyperprolactinemia in patients on antipsychotic drugs causes ADP-stimulated platelet activation that might explain the increased risk for venous thromboembolism: pilot study.

Recently, an increased risk of venous thromboembolism in patients on antipsychotic drugs has been reported, but the molecular etiology is still unknown. Most antipsychotic drugs act as dopamine antagonists, and some of them cause hyperprolactinemia. Hyperprolactinemia has recently been found to cause increased platelet activation via potentiating ADP effects on human platelets. We assessed prolactin values as well as ADP-stimulated and thrombin receptor activator 6-stimulated expression of the platelet activation marker P-selectin in 20 consecutive patients under therapy with antipsychotic drugs. We detected a significant correlation between prolactin values and ADP-stimulated P-selectin expression on platelets in patients on antipsychotic drugs, revealing a significant higher platelet stimulation in hyperprolactinemic patients on antipsychotic drugs than in normoprolactinemic controls. Therefore, hyperprolactinemia might be the yet unknown acquired risk factor in patients on antipsychotic drugs explaining the increased risk for venous thromboembolism in these patients.

Adolescent↗
PubMed2005

Low-molecular-weight heparin for the prevention of postoperative venous thromboembolism after abdominal surgery: a review.

PURPOSE OF REVIEW: To analyze the effect of low-molecular-weight heparin in abdominal surgery, which carries a significant risk of thrombosis, a risk further increased by cancer. RECENT FINDINGS: Searches in EMBASE and PubMed between 1980 and 2004 were conducted to identify studies of thromboprophylaxis in abdominal surgery patients. Sixteen comparative studies were identified. They showed that low-molecular-weight heparin is as effective as unfractionated heparin in reducing venous thromboembolism and, at appropriate doses, can reduce bleeding complications. In very-high-risk cancer patients, a higher dose of low-molecular-weight heparin may offer increased efficacy without increasing the risk of bleeding. Extending the standard 7-10-day low-molecular-weight heparin prophylaxis period may benefit certain high-risk patient groups. SUMMARY: Patients undergoing abdominal surgery should be stratified according to thromboembolism risk and given prophylaxis accordingly. Low-molecular-weight heparin is a recommended alternative to unfractionated heparin in moderate- or high-risk patients. In patients with cancer, high doses of low-molecular-weight heparin may offer increased efficacy without increased bleeding, and an extended 4-week period of prophylaxis could be beneficial.

Anticoagulants↗
PubMed2005

Clinical implications for the management of acute thromboembolic occlusion of the superior mesenteric artery: autopsy findings in 213 patients.

OBJECTIVE: To study findings at autopsy in patients with fatal acute thromboembolic occlusion of the superior mesenteric artery (SMA). SUMMARY BACKGROUND DATA: Acute occlusion of the SMA is difficult to diagnose and mortality remains high. In Malmo, Sweden, the autopsy rate between 1970 and 1982 was 87%, creating possibilities for a population-based study. METHODS: Among 23,496 clinical autopsies and 7569 forensic autopsies, 213 cases with acute thromboembolic occlusion of the SMA and intestinal infarction were identified. RESULTS: A clinical suspicion of intestinal infarction was documented in 32% of the patients, only 35% being in the care of surgeons. The embolus/thrombus ratio was 1.4 to 1. Thrombotic occlusions were located more proximally than embolic occlusions (P < 0.001), intestinal infarction was more extensive (P = 0.025) and thrombotic occlusions were associated with old brain infarction (P = 0.048), aortic wall thrombosis (P = 0.080), and disseminated cancer (P = 0.079). Patients with embolic occlusions (n = 122) had a higher frequency of acute myocardial infarction (AMI) than patients with thrombotic occlusions (P = 0.049). The embolic source was identified in 80%. In 115 (94%), synchronous embolism and/or source of embolus were present. There were findings of remaining cardiac thrombi in 58 (48%) and synchronous emboli affected 273 other arterial segments in 83 (68%). CONCLUSIONS: Early recognition and revascularization would have been a prerequisite for survival in at least half of the patients, since the jejunum, ileum, and colon were affected by infarction. A minority of all patients were under surgical care. AMI, cardiac thrombi, and synchronous emboli were common findings among patients with embolic occlusions.

Acute Disease↗