Hemorrhagic complications of anticoagulant treatment

Current issues regarding the use of drotrecogin alfa (activated)

The key issues clinicians are facing regarding drotrecogin alfa (activated) include questions concerning the pathophysiology and appropriate patient selection for administration of this drug. In the Recombinant Human Activated Protein C Worldwide Evaluation in Severe Sepsis (PROWESS) trial, the efficacy of drotrecogin alfa (activated) was demonstrated in patients with severe sepsis. Because of this trial's strict inclusion and exclusion criteria, however, the applicability of the study criteria to different types of patients raises important issues. Coupling the data from the PROWESS trial with additional information being gained from expanding clinical experience, as well as additional studies, clinicians will be able to better understand and refine the use of activated protein C within their respective practices.

Comparison of contrast-enhanced magnetic resonance angiography and conventional pulmonary angiography for the diagnosis of pulmonary embolism: a prospective study

BACKGROUND

Diagnostic strategies for pulmonary embolism are complex and consist of non-invasive diagnostic tests done to avoid conventional pulmonary angiography as much as possible. We aimed to assess the diagnostic accuracy of magnetic resonance angiography (MRA) for the diagnosis of pulmonary embolism, using conventional pulmonary angiography as a reference method.

METHODS

In a prospective study, we enrolled 141 patients with suspected pulmonary embolism and an abnormal perfusion scan. Patients underwent MRA before conventional pulmonary angiography. Two reviewers, masked with respect to the results of conventional pulmonary angiography, assessed MRA images independently. Statistical analyses used chi(2) and 95% CI.

FINDINGS

MRA was contraindicated in 13 patients (9%), and images were not interpretable in eight (6%). MRA was done in two patients in whom conventional pulmonary angiography was contraindicated. Thus, MRA and conventional pulmonary angiography results were available in 118 patients (84%). Prevalence of pulmonary embolism was 30%. Images were read independently in 115 patients, and agreement obtained in 105 (91%), kappa=0.75. MRA identified 27 of 35 patients with proven pulmonary embolism (sensitivity 77%, 95% CI 61-90). Sensitivity of MRA for isolated subsegmental, segmental, and central or lobar pulmonary embolism was 40%, 84%, and 100%, respectively (p<0.01 for isolated subsegmental vs segmental or larger pulmonary embolism). However, subgroups contained small numbers. MRA identified pulmonary embolism in two patients with normal angiogram (98%, 92-100).

INTERPRETATION

MRA is sensitive and specific for segmental or larger pulmonary embolism. Results are similar to those obtained with helical computed tomography, but MRA has safer contrast agents and does not involve ionising radiation. MRA could become part of the diagnostic strategy for pulmonary embolism.

Strategies incorporating spiral CT for the diagnosis of acute pulmonary embolism: a cost-effectiveness analysis

OBJECTIVE

To assess the cost-effectiveness of spiral CT for the diagnosis of acute pulmonary embolism.

DESIGN

Computer-based cost-effectiveness analysis.

PATIENTS

Simulated cohort of 1,000 patients with suspected acute pulmonary embolism (PE), with a prevalence of 28.4%, as in the Prospective Investigation of Pulmonary Embolism Diagnosis study.

INTERVENTIONS

Using a decision-analysis model, seven diagnostic strategies were compared, which incorporated combinations of ventilation-perfusion (V/Q) scans, duplex ultrasound of the legs, spiral CT, and conventional pulmonary angiography.

MEASUREMENTS AND RESULTS

Expected survival and cost (in Canadian dollars) at 3 months were estimated. Four of the strategies yielded poorer survival at higher cost. The three remaining strategies were as follows: (1) V/Q +/- leg ultrasound +/- spiral CT, with an expected survival of 953.4 per 1,000 patients and a cost of $1,391 per patient; (2) V/Q +/- leg ultrasound +/- pulmonary angiography (the "traditional" algorithm), with an expected survival of 953.7 per 1,000 patients and a cost of $1,416 per patient; and (3) spiral CT +/- leg ultrasound, with an expected survival of 958.2 per 1,000 patients and a cost of $1,751 per patient. The traditional algorithm was then excluded by extended dominance. The cost per additional life saved was $70,833 for spiral CT +/- leg ultrasound relative to V/Q +/- leg ultrasound +/- spiral CT.

CONCLUSIONS

Spiral CT can replace pulmonary angiography in patients with nondiagnostic V/Q scan and negative leg ultrasound findings. This approach is likely as effective as-and possibly less expensive than-the current algorithm for diagnosis of acute PE. When spiral CT is the initial diagnostic test, followed by leg ultrasound, expected survival improves but costs are also considerably higher. These findings were robust to variations in the assumed sensitivity and specificity of spiral CT.

Influence of body weight on response to subcutaneous vitamin K administration in over-anticoagulated patients

PURPOSE

To determine the influence of body weight on the international normalized ratio (INR) response to a fixed dose of vitamin K in overanticoagulated patients.

METHODS

Retrospective review of records of patients who received 1 mg of vitamin K subcutaneously to correct excessive INR. Dose of vitamin K in milligrams per kilograms plotted against change in INR in 24 hours.

RESULTS

Fifteen patients were identified who met all inclusion criteria. Linear regression analysis plotted INR response at 24 hours versus dose of vitamin K adjusted for body weight. Pearson's product moment correlation (R = 0.85) indicated a significant relationship between INR response at 24 hours to an adjusted body weight dose of subcutaneous vitamin K (P = 0.0000523). A strong correlation (r = 0.69) also existed between INR response at 24 hours and the actual body weight dose of subcutaneous vitamin K (P = 0.004).

CONCLUSIONS

In overanticoagulated patients, variability in response to vitamin K may be explained by variability in body weight. Dosing vitamin K according to body weight may result in a more predictable INR response.

Use of transesophageal echocardiography to guide cardioversion in patients with atrial fibrillation

BACKGROUND

The conventional treatment strategy for patients with atrial fibrillation who are to undergo electrical cardioversion is to prescribe warfarin for anticoagulation for three weeks before cardioversion. It has been proposed that if transesophageal echocardiography reveals no atrial thrombus, cardioversion may be performed safely after only a short period of anticoagulant therapy.

METHODS

In a multicenter, randomized, prospective clinical trial, we enrolled 1222 patients with atrial fibrillation of more than two days' duration and assigned them to either treatment guided by the findings on transesophageal echocardiography or conventional treatment. The composite primary end point was cerebrovascular accident, transient ischemic attack, and peripheral embolism within eight weeks. Secondary end points were functional status, successful restoration and maintenance of sinus rhythm, hemorrhage, and death.

RESULTS

There was no significant difference between the two treatment groups in the rate of embolic events (five embolic events among 619 patients in the transesophageal-echocardiography group [0.8 percent]) vs. three among 603 patients in the conventional-treatment group [0.5 percent], P=0.50). However, the rate of hemorrhagic events was significantly lower in the transesophageal-echocardiography group (18 events [2.9 percent] vs. 33 events [5.5 percent], P=0.03). Patients in the transesophageal-echocardiography group also had a shorter time to cardioversion (mean [+/-SD], 3.0+/-5.6 vs. 30.6+/-10.6 days, P<0.001) and a greater rate of successful restoration of sinus rhythm (440 patients [71.1 percent] vs. 393 patients [65.2 percent], P=0.03). At eight weeks, there were no significant differences between the two groups in the rates of death or maintenance of sinus rhythm or in functional status.

CONCLUSIONS

The use of transesophageal echocardiography to guide the management of atrial fibrillation may be considered a clinically effective alternative strategy to conventional therapy for patients in whom elective cardioversion is planned.

Lung scintigraphy and helical computed tomography for the diagnosis of pulmonary embolism: a meta-analysis

To assess the diagnostic value of lung scintigraphy and helical computed tomography (hCT) in patients with suspected pulmonary embolism (PE), all English-language articles that described lung scintigraphy and hCT in patients with suspected PE were retrieved. Articles were assessed for strength of methodology, based on nine a priori-defined criteria. Parameters of diagnostic accuracy and results of management studies were calculated and evaluated. Lung scintigraphy is diagnostic in approximately 50% of patients with suspected PE. A normal perfusion scan has a chance of recurrent PE in two of 693 patients (0.3%; 95% CI: 0.2-0.4%; fatal in 0.15%). A high-probability lung scan is correlated with angiographically proven PE in 308 of 350 patients (88%; 95% CI: 84-91%). Pulmonary embolism was proven in 385 of 1529 patients (25%; 95% CI: 24-28%) with a nondiagnostic lung scan. Helical CT studies were compared with angiography and lung scintigraphy in 1171 patients, with a prevalence of PE of 39%. The sensitivity and specificity of hCT was 283/320 (88%; 95% CI: 83-91%) and 374/408 (92%; 95% CI: 89-94%), respectively. Only one prospective management study using hCT was available. In patients in whom anticoagulants were withheld based on a normal hCT study, recurrent thromboembolic events occurred in six of 109 patients (5.5%; 95% CI: 2-12%), with one fatality (1%; 95% CI: 0.02-4.3%). Lung scintigraphy is evaluated extensively and yields a diagnostic result in 50% of patients. Helical CT has similar positive predictive value to a high-probability lung scan. However, the exact role of hCT in the management of patients with suspected PE needs to be determined in prospective studies.

Developing a novel antithrombotic in the academic environment

In recent years, academic research institutions have increasingly sought to commercialize their discoveries, providing the opportunity to raise venture capital and benefit financially from their developments. In the last 6 years, Hamilton Civic Hospitals Research Center, affiliated with McMaster University, Ontario, Canada, has set up two companies, Vascular Therapeutics and Osteokine, to commercialize its discoveries in thrombosis and osteoporosis. Epidemiological evidence shows a continuing socioeconomic burden of both of these disorders, thereby offering opportunities for new drug development. Key areas in the field of thrombosis include novel parenteral anticoagulants to replace heparin as adjunctive therapy in acute coronary syndromes, safer and more practical oral anticoagulants that do not require monitoring to replace coumarins, and oral antiplatelet drugs for use in combination with aspirin. Since their creation, Vascular Therapeutics and Osteokine have attracted major funding and developed several patentable compounds that show clinical and commercial promise.

Prevention, diagnosis, and treatment of venous thromboembolic complications of gynecologic surgery

Deep vein thrombosis and pulmonary embolism, collectively referred to as venous thromboembolic events, are a source of significant morbidity and mortality after gynecologic surgical procedures. In this literature review the advantages and disadvantages of various preventive measures for deep venous thrombosis, including low-molecular-weight heparins, are discussed. The most appropriate prophylactic methods for patients in varying risk categories are recommended. Current methods of diagnosing deep venous thrombosis and pulmonary embolism, including ultrasonography, venography, ventilation-perfusion scan, helical computed tomographic scan, and D -dimer measurement are then discussed. Finally, treatment modalities for deep venous thrombosis and pulmonary embolism, including heparin, low-molecular-weight heparin, warfarin, and thrombolytic therapy, are detailed.

Role of transesophageal echocardiography-guided cardioversion of patients with atrial fibrillation

Electrical cardioversion of patients with atrial fibrillation (AF) is frequently performed to relieve symptoms and improve cardiac performance. Patients undergoing cardioversion are treated conventionally with therapeutic anticoagulation for three weeks before and four weeks after cardioversion to decrease the risk of thromboembolism. A transesophageal echocardiography (TEE)-guided strategy has been proposed as an alternative that may lower stroke and bleeding events. Patients without atrial cavity thrombus or atrial appendage thrombus by TEE are cardioverted on achievement of therapeutic anticoagulation, whereas cardioversion is delayed in higher risk patients with thrombus. The aim of this review is to discuss the issues and controversies associated with the management of patients with AF undergoing cardioversion. We provide an overview of the TEE-guided and conventional anticoagulation strategies in light of the recently completed Assessment of Cardioversion Using Transesophageal Echocardiography (ACUTE) clinical trial. The two management strategies comparably lower the patient's embolic risk when the guidelines are properly followed. The TEE-guided strategy with shorter term anticoagulation may lower the incidence of bleeding complications and safely expedite early cardioversion. The inherent advantages and disadvantages of both strategies are presented. The TEE-guided approach with short-term anticoagulation is considered to be a safe and clinically effective alternative to the conventional approach, and it is advocated in patients in whom earlier cardioversion would be clinically beneficial.

Recurrence phenomena after immunoglobulin therapy for snake envenomations: Part 2. Guidelines for clinical management with crotaline Fab antivenom

Recurrent local and coagulopathic effects (worsening after clinical improvement) have been described after treatment with Fab antivenom for envenomation by North American crotaline snakes. Although similar phenomena have been described previously in snakebite, few studies have examined recurrence or its management. Recurrence is consistent with known venom and antivenom kinetics and dynamics. The clinical significance of late coagulopathy after snakebite is uncertain, but clinically significant bleeding is a possibility. Prevention and treatment of recurrence with Fab antivenom require repeated dosing for at least 18 hours, with close monitoring of at-risk patients in the follow-up period. Duration of therapy depends on individual risk factors and coagulation response.

Hemorrhagic complications of anticoagulant treatment

Bleeding is the major complication of anticoagulant therapy. The criteria for defining the severity of bleeding varied considerably between studies, accounting in part for the variation in the rates of bleeding reported. Since the last review, there have been several meta-analyses published on the rates of major bleeding in trials of anticoagulants for atrial fibrillation and ischemic heart disease. The major determinants of oral anticoagulant-induced bleeding are the intensity of the anticoagulant effect, underlying patient characteristics, and the length of therapy. There is good evidence that low-intensity oral anticoagulant therapy (targeted INR of 2.5; range, 2.0 to 3.0) is associated with a lower risk of bleeding than therapy targeted at a higher intensity. Lower-intensity regimens (INR < 2.0) are associated with an even smaller increase in major bleeding. In terms of treatment decision making for anticoagulant therapy, bleeding risk cannot be considered alone, ie, the potential decrease in thromboembolism must be balanced against the potential increased bleeding risk. The risk of bleeding associated with IV heparin in patients with acute venous thromboembolism is < 3% in recent trials. There is some evidence to suggest that this bleeding risk increases with the heparin dosage and age (> 70 years). LMW heparin is not associated with increased major bleeding compared with standard heparin in acute venous thromboembolism. Standard heparin and LMW heparin are not associated with an increase in major bleeding in ischemic coronary syndromes, but are associated with an increase in major bleeding in ischemic stroke.

Prevalence of ocular hemorrhage in patients receiving warfarin therapy

BACKGROUND

Warfarin, the drug most commonly used for outpatient anticoagulation therapy, has bleeding as its main side effect. The objective of this study was to determine the prevalence of ocular hemorrhage in patients receiving warfarin and to compare it to the prevalence in the general population.

METHODS

Patients receiving warfarin therapy who were attending the anticoagulation clinic at a tertiary care hospital in Montreal between October and December 1996 received a flyer inviting them to have their eyes examined to look for "ocular bleeding." Consenting patients were examined for subconjunctival hemorrhage, gross hyphema, and vitreous and retinal hemorrhages through external ocular examination and funduscopic examination with the pupils dilated using direct and indirect ophthalmoscopy.

RESULTS

Of the 1225 patients seen at the clinic 126 (10%) agreed to participate. Four patients (3%) were found to have intraretinal hemorrhage at the time of examination. All hemorrhages were visually insignificant.

INTERPRETATION

The risk of retinal hemorrhage in patients without preexisting ocular disease, such as retinal neovascularization or choroidal vasculopathy, who are receiving warfarin therapy is so small that it should not deter physicians from prescribing this drug when indicated.

Thromboembolism in heart failure: who should be treated?

The risk of thromboembolic complications in patients with heart failure and/or chronic left-ventricular systolic dysfunction is increased. Nevertheless, anticoagulant therapy in these patients is still a subject of debate. Atrial fibrillation is the only prospectively evaluated, proven thromboembolic risk factor and patients with atrial fibrillation benefit from long term anticoagulant therapy. The significance of other proposed thromboembolic risk factors in heart failure and/or chronic left-ventricular dysfunction such as gender, cause of myocardial disease, severity of heart failure, left-ventricular ejection fraction, left-ventricular thrombus, left ventricular aneurysm and history of previous thromboembolic event is less clear. This article summarizes key studies, assesses the incidence of thromboembolism, evaluates risk factors and proposes guidelines for anticoagulation of patients with heart failure and/or left ventricular systolic dysfunction.

Cost effectiveness of therapies for atrial fibrillation. A review

Atrial fibrillation is the most common supraventricular tachyarrhythmia encountered in clinical practice, affecting over 5% of persons over the age of 65 years. A common pathophysiological mechanism for arrhythmia development is atrial distention and fibrosis induced by hypertension, coronary artery disease or ventricular dysfunction. Less frequently, atrial fibrillation is caused by mitral stenosis or other provocative factors such as thyrotoxicosis, pericarditis or alcohol intoxication. Depending on the extent of associated cardiovascular disease, atrial fibrillation may produce haemodynamic compromise, or symptoms such as palpitations, fatigue, chest pain or dyspnoea. Arrhythmia-induced atrial stasis can precipitate clot formation and the potential for subsequent thromboembolism. Comprehensive management of atrial fibrillation requires a multifaceted approach directed at controlling symptoms, protecting the patient from ischaemic stroke or peripheral embolism and possible conversion to or maintenance of sinus rhythm. Numerous randomised trials have demonstrated the efficacy of warfarin--and less so aspirin (acetylsalicylic acid)--in reducing the risk of embolic events. Furthermore, therapeutic strategies exist that can favourably modify symptoms by restoring and maintaining sinus rhythm with cardioversion and antiarrhythmic prophylaxis. However, the risks and benefits of various treatments is highly dependent on patient-specific features, emphasising the need for an individualised approach. This article reviews the findings of cost-effectiveness studies published over the past decade that have evaluated different components of treatment strategies for atrial fibrillation. These studies demonstrate the economic attractiveness of acute management options, long term warfarin prophylaxis, telemetry-guided initiation of antiarrhythmic therapy, approaches to restore and maintain sinus rhythm, and the potential role of transoesophageal echocardiographic screening for atrial thrombus prior to pharmacological or electrical cardioversion. Further, we discuss the merits and limitations of the cost-effectiveness analyses in the context of overall treatment strategies. Finally, we identify areas that will require additional research to achieve the goal of effective and economically efficient management of atrial fibrillation.

Course, management and outcome of oral-anticoagulant-related intracranial haemorrhages

The aim of this study was to compare the clinical course and radiological features of oral anticoagulant (OAC)-related intracranial haemorrhages with those of haemorrhages unrelated to OAC use admitted over the last six years to a tertiary care centre in the North of Scotland. We furthermore wished to determine the measures taken for reversal of OAC therapy and the resulting short-term outcome. Sixty-eight patients had been treated with OACs at the time of intracranial haemorrhage (32% subdural, 62% intracerebral). Patients admitted with OAC-related and unrelated haemorrhages did not differ significantly in any of the clinical features considered. On CT scan, there was no significant difference according to OAC use in the mean size of subdural (depth 15 +/- 5 vs. 18 +/- 8 mm, p = 0.36), or intracerebral haematomas (max. diameter 40 +/- 21 vs. 41 +/- 20 mm, p = 0.73). No reversal measures were taken in 38% of OAC-treated patients. In-hospital mortality was significantly higher for OAC-related haemorrhages compared to unrelated haemorrhages (38% vs. 18%, p = 0.001). To further elucidate the effects of anticoagulant reversal on the outcome of OAC-related intracranial haemorrhages, a large-scale prospective study is warranted.

Frequency of anticoagulation for atrial fibrillation and reasons for its non-use at a Veterans Affairs medical center

Randomized clinical trials have led to guidelines for anticoagulation in atrial fibrillation (AF). However, it is unclear how successfully these guidelines are being implemented in clinical practice and there is concern that anticoagulation is underused. Therefore, we examined the rate of anticoagulation in 998 patients with AF who attended a Veterans Affairs Medical Center over a 2-year period. Warfarin was prescribed for 504 patients (51%) and not prescribed for 494 patients (49%). Of these 494 patients, 446 had sufficient data for further assessment. Warfarin was judged not indicated in 200 because AF was transient or lone. Warfarin was indicated in 246 patients, 63% having > or =3 risk factors for thromboembolism. However, 184 of these patients also had at least 1 contraindication to anticoagulation. Thus, warfarin was prescribed to 67% of patients with AF in whom anticoagulation was indicated and to 89% of such patients in whom it was indicated and who had no contraindications. However, 25% of AF patients with strong indications for anticoagulation had concomitant contraindications, which precluded its use. We conclude that the use of warfarin for AF in this setting is higher than previously reported and approaching ideal levels. However, there remains a large, problematic subgroup of patients with AF in whom indications for and contra-indications to anticoagulation coexist.

A prospective, randomized, sequential crossover trial of large-volume versus normal-volume leukapheresis procedures: effects on serum electrolytes, platelet counts, and other coagulation measures

BACKGROUND

LVL procedures with the administration of heparin as an additional anticoagulant are increasingly performed because of the potentially higher yield of autologous peripheral blood HPCs. A prospective, randomized crossover trial was performed to evaluate the influence of leukapheresis volume-that is, large versus normal-on serum electrolytes, platelet count, and other coagulation measures in 25 patients with breast cancer and 14 patients with non-Hodgkin's lymphoma.

STUDY DESIGN AND METHODS

Patients were randomly assigned to start either with an LVL on Day 1 followed by a normal-volume leukapheresis (NVL) on Day 2 or vice versa. In LVL, heparin was administered in addition to ACD-A. Bleeding complications, transfusion support, whole-blood counts, and several coagulation measures as well as plasma heparin levels were evaluated.

RESULTS

Although the duration, the infused amount of ACD-A, the flow rate, the drop in platelet count, and the drop in potassium were significantly greater in LVL, and although LVL patients also received heparin, there was no significant difference in clinical tolerance or bleeding complications. After LVL, patients exhibited a significantly longer activated partial thromboplastin time (APTT), with a median of 70 seconds (range, 44-100 sec), and a median anti-factor Xa activity of 0.69 IU per mL (range, 0.10-1.29 IU/mL). The value of the APTT after LVL correlated with anti-factor Xa activity (r = 0.37, p<0.05), but not with platelet count or heparin infusion rate. Markers for coagulation activation did not increase during NVL or LVL.

CONCLUSION

LVL with heparin as an additional anticoagulant seems to be a safe procedure in patients with low preleukapheresis platelet counts. No activation of coagulation occurred after NVL or LVL procedures.

A graphic nomogram for warfarin dosage adjustment

We assessed the ability of a graphic nomogram to adjust steady-state warfarin dosages and to predict international normalized ratios (INR) after a dosage change, compared with an anticoagulation clinic pharmacist and a Bayesian regression computer program. Study subjects were 108 men and 3 women receiving warfarin anticoagulation. In all patients the median absolute errors in predicted INR values for the nomogram, computer program, and pharmacist were 0.33, 0.46, and 0.48, respectively. The nomogram was significantly more precise than both other methods (p=0.036). In a subset of 50 patients who required dosage reductions, the median absolute INR prediction errors for the nomogram, computer program, and pharmacist were 0.35, 0.54, and 0.48 respectively. The nomogram was significantly more precise than the pharmacist (p=0.005) and computer (p=0.002). The ability to provide more precise dosage reductions of warfarin may be of clinical importance in light of current recommendations for higher-intensity warfarin therapy and maintenance of higher INR values. Prospective validation of the performance of this nomogram in a routine clinical setting is warranted.

Intravenous versus subcutaneous vitamin K1 in reversing excessive oral anticoagulation

Our data suggest that compared with the subcutaneous route of administration, intravenous vitamin K1 results in a more prompt reduction in the international normalized ration. However, for most patients, subcutaneous vitamin K1 is an effective and safe alternative when used in conjunction with modification of subsequent warfarin dosing, because virtually all patients achieved a safe level of anticoagulation within 72 hours with this route of administration.

Risk reduction in the intensive care unit

Many potentially preventable complications occur in patients who receive intensive care. We have reviewed the epidemiology of three important complications (venous thromboembolism, stress-related upper gastrointestinal bleeding, and vascular catheter-related infection) and evaluated common preventive treatments to provide evidence-based recommendations for prevention. We used English language articles located by MEDLINE or cross-citation, giving preference to articles published in the last 10 years, meta-analyses, and clinical trials that were randomized, double-blinded, and used intention-to-treat analysis. We recommend prophylaxis against venous thromboembolism in most patients, whereas those without respiratory failure or coagulopathy may not require prophylaxis against stress-related upper gastrointestinal hemorrhage. Chlorhexidine gluconate is the preferred antiseptic for disinfecting the skin prior to and during intravascular catheterization. Central venous catheters impregnated with antibacterial or antiseptic agents should be considered in patients at high risk for vascular catheter-related infection. Finally, central venous, pulmonary arterial, and systemic arterial catheters should be changed only when clinically indicated.

Developing and testing a system to improve the quality of heparin anticoagulation in patients with acute cardiac syndromes

We have taken a stepwise approach to improving the dosing of continuous intravenous heparin in patients with acute coronary syndromes. Our primary objective was to use computer modeling to develop a nomogram for managing heparin therapy and to put in place a continuous quality monitoring system to evaluate the nomogram's effectiveness. We prospectively collected data on 41 patients with unstable angina or myocardial infarction who were treated with heparin. Their response to heparin was computer modeled and the dose to achieve an activated partial thromboplastin time (aPTT) ratio of 2.0 was established. This dose was regressed against all demographic characteristics to establish predictors of heparin dose (phase I). The regression formula was used prospectively in 110 patients to initiate the infusion rate of heparin and a bolus dose to achieve an aPTT ratio of 2.5. Subsequent dosage adjustments were achieved by computer modeling the patient's aPTT response (phase II). A nomogram was developed that simulated the decisions achieved using computer-assisted methods. This was retrospectively tested and then prospectively tested in 50 patients using nursing staff (phase IV). The nomogram was then made generally available (phase IV) and has been tested in an additional 310 patients. Phase I: Of the original 41 patients, 32% of the aPTT ratios were in the therapeutic range, 36% were supratherapeutic, and 32% were subtherapeutic after the first 24 hours. Phases II and III resulted in 85% of the aPTT ratios between 1.5 and 2.5 at 24 hours. Phase 4 had similar results in 310 patients. The use of computer-assisted or a computer-generated nomogram to adjust heparin therapy results in better control of heparin therapy than using standard methods.

Risk of major hemorrhage for outpatients treated with warfarin

OBJECTIVE

To determine the incidence of major hemorrhage among outpatients started on warfarin therapy after the recommendation in 1986 for reduced-intensity anticoagulation therapy was made, and to identify baseline patient characteristics that predict those patients who will have a major hemorrhage.

DESIGN

Retrospective cohort study.

SETTING

A university-affiliated Veterans Affairs Medical Center.

PATIENTS

Five hundred seventy-nine patients who were discharged from the hospital after being started on warfarin therapy.

MEASUREMENTS AND MAIN RESULTS

The primary outcome variable was major hemorrhage. In our cohort of 579 patients, there were 40 first-time major hemorrhages with only one fatal bleed. The cumulative incidence was 7% at 1 year. The average monthly incidence of major hemorrhage was 0.82% during the first 3 months of treatment and decreased to 0.36% thereafter. Three independent predictors of major hemorrhage were identified: a history of alcohol abuse, chronic renal insufficiency, and a previous gastrointestinal bleed. Age, comorbidities, medications known to influence prothrombin levels, and baseline laboratory values were not associated with major hemorrhage.

CONCLUSIONS

The incidence of major hemorrhage in this population of outpatients treated with warfarin was lower than previous estimates of major hemorrhage measured before the recommendation for reduced-intensity anticoagulation therapy was made, but still higher than estimates reported from clinical trials. Alcohol abuse, chronic renal insufficiency, and a previous gastrointestinal bleed were associated with increased risk of major hemorrhage.

Low-molecular-weight heparins in the treatment of deep-vein thrombosis

OBJECTIVE

To compare the characteristics and clinical efficacy of low-molecular-weight heparins (LMWHs) and unfractionated heparin (UFH) in the treatment of deep-vein thrombosis (DVT). Adverse effects, dosing, and cost issues are also discussed.

DATA SOURCES

A MEDLINE search (January 1984-October 1997) was used to identify pertinent French and English literature, including clinical trials and reviews on LMWHs and their use in DVT.

STUDY SELECTION

Trials comparing dalteparin, enoxaparin, tinzaparin, and nadroparin with UFH were selected. As studies were numerous, only randomized trials including more than 50 patients were reviewed. Moreover, all patients studied had a first episode of symptomatic DVT confirmed by objective tests (i.e., venography, duplex ultrasonography, impedance plethysmography). Clinical efficacy and safety of LMWHs were assessed in these trials.

DATA EXTRACTION

Results pertaining to venographic assessment, recurrent thromboembolism, total mortality, and bleeding complications were extracted from the selected studies.

DATA SYNTHESIS

Compared with UFH, LMWHs have a longer plasma half-life, better subcutaneous bioavailability, more predictable anticoagulant response, and require less intense laboratory monitoring. Most trials demonstrate comparable effects on thrombus extension and incidence of recurrent thromboembolism. Compared with UFH, LMWHs do not alter total mortality. Although animal trials predict a lower hemorrhagic potential for LMWHs, the incidence of bleeding complications is generally similar to that observed with UFH. Outpatient management of DVT with LMWHs has shown comparable safety and efficacy with inpatient UFH use but a shorter hospital stay.

CONCLUSIONS

Because LMWHs are as safe and as effective as UFH, and because of their more convenient method of administration, they can be considered valuable alternatives for the treatment of DVT. Savings generated by less intensive laboratory monitoring and the possibility of early hospital discharge and outpatient therapy may outweight the higher acquisition cost of LMWHs.

A prospective study of the safety of joint and soft tissue aspirations and injections in patients taking warfarin sodium

OBJECTIVE

To determine the safety of joint or soft tissue aspirations and injections in patients taking warfarin sodium.

METHODS

The outcome of 32 joint or soft tissue aspirations or injections in patients receiving stable doses of warfarin sodium was assessed through a standardized interview 4 weeks after the procedure. The primary outcome measure was significant joint or soft tissue hemorrhage, ascertained by patient-reported increases in swelling or warmth at the procedure site.

RESULTS

None of 32 procedures was complicated by joint or soft tissue hemorrhage reported by the patients, yielding, by the "rule of threes," a risk of significant hemorrhage of < 10% (with 95% certainty). Diagnostic information was obtained for 53% of aspirated sites (8 of 15) and therapeutic benefit was noted in 74% of corticosteroid-injected sites (17 of 23).

CONCLUSION

Joint or soft tissue injections and aspirations in selected patients taking warfarin sodium are associated with a low risk of hemorrhage and are often of diagnostic or therapeutic value.

Preventing stroke recurrence in patients with patent foramen ovale: antithrombotic therapy, foramen closure, or therapeutic abstention? A decision analytic perspective

Emphasis on the role of patent foramen ovale as a potential risk factor for ischemic paradoxical stroke has recently increased. Current therapeutic options for secondary stroke prevention include long-term antithrombotic therapies and invasive closure of the defect, but selective indications have not been evaluated. Therefore we developed a Markov-based decision analysis model for a hypothetical cohort of patients 55 years of age with presumed paradoxical embolism, measuring for each therapy the risks of stroke recurrence, treatment-related complications, and death after 5 years and the quality-adjusted life-years. Over a wide range of stroke risk recurrence (0.8% per year to 7% per year), the gain provided by closure of the defect exceeded the one obtained by other therapeutic options. When the risk exceeded 0.8% per year and 1.4% per year, respectively, this was also verified for anticoagulation and antiplatelet therapies compared with therapeutic abstention. Therapeutic abstention was the preferred strategy under 0.8% per year. Sensitivity analyses identified key parameters influencing the choice of therapy. These included estimates of stroke recurrence, bleeding rates, surgery-related case fatality rates, and age. Considering the risks of treatment and the devastating consequences of a recurrent stroke, our model suggests that if the estimated risk of paradoxical stroke recurrence is > 0.8% per year, therapeutic abstention becomes the worst option. Above this threshold secondary stroke prevention with anticoagulation therapy or surgical closure of the defect is the preferred strategy, and assessment of both the risk of stroke recurrence and the risk related to therapeutic options should guide individual therapeutic decision making.

Venous thromboembolic disease

The advent of spiral CT has encouraged investigation into the diagnosis of venous thromboembolic disease. It has also exposed the limitations of prior methods of investigation and raised questions as to the significance of small pulmonary emboli. This article discusses this new technique, the clinical detection of venous thromboembolic disease and possible current and future strategies in diagnosis.

Cardiac disorders and stroke

Cardiac disorders are increasingly recognised as an important source of cerebral embolism. Atrial fibrillation is the most common cardiac dysrrhythmia that can predispose to stroke. Recent advances have significantly increased the identification of clinical, hematological and echocardiographic risk factors that predict the occurrence of atrial fibrillation related stroke. Also, clinical risk stratification has been used to determine medical therapy (aspirin or warfarin) for prevention of atrial fibrillation related brain embolization. Among the various structural heart diseases causing stroke, the role of patent foramen ovale remains controversial. Strides have been made in the use of ultrasonographic techniques such as transesophageal echocardiography and contrast transcranial doppler to detect patent foramen ovale. Coronary artery bypass grafting is often performed in patients with concomitant aortic atheroma and carotid stenosis that may predispose to stroke in the perioperative period. It is now possible to identify perioperatively significant aortic atherosclerosis (using transesophageal echocardiography and aortic ultrasound) and significant carotid disease (using carotid ultrasound) and make appropriate modifications in surgical technique to reduce the incidence of coronary artery bypass grafting related stroke. Because of shared risk factors it is not surprising that coronary artery disease is frequently found in stroke patients. Recent studies suggest that more than one-third of stroke patients have asymptomatic coronary artery disease. Conversely, the brain damaged by infarction may itself be responsible for the production of cardiac structural and electrical abnormalities. Both these factors may contribute to the finding that cardiac events are the leading cause of death in stroke patients on long term follow-up. Recognition of these correlations has enhanced our ability to treat and prevent stroke related mortality.

Optimal Frequency of Patient Monitoring and Intensity of Oral Anticoagulation Therapy in Valvular Heart Disease

The antithrombotic effect of oral anticoagulation therapy and the incidence of anticoagulant-related bleeding complications are both closely correlated with the intensity of treatment. The optimal intensity of oral anticoagulation for an individual patient is the target INR that results in the lowest incidence of thromboembolic plus bleeding complications. For patients with native valve lesions, one must consider the cardiac morphology and pathophysiology, for example, the etiology of the disease, left atrial diameters, loss of active atrial contraction (atrial fibrillation), left ventricular pump function, and left ventricular diameters, to determine an optimal INR target. In patients with prosthetic devices, the "thrombogenicity" of the heart valve prosthesis is an additional risk factor for intracardiac thrombus formation and thromboembolic episodes. This "thrombogenicity" may vary significantly from device to device. INR self-testing improves the overall prognosis of patients on lifelong oral anticoagulation therapy because patients remain more precisely within that target therapeutic INR range. For most patients under phenprocoumon, one to two INR measurements per week are a sufficient frequency to provide a stable intensity of anticoagulation.

Major haemorrhagic complications during oral anticoagulant therapy in a Danish population-based cohort

OBJECTIVES

To estimate the incidence of bleeding leading to death or hospital admission in out-patients treated with oral anticoagulants.

DESIGN

Population-based historical cohort study 1 January 1992 to 31 September 1994.

SETTING

The County of North Jutland, Denmark (488,000 inhabitants).

SUBJECTS

Six hundred and eighty-two consecutive patients commencing oral anticoagulant therapy.

MAIN OUTCOME MEASURES

Fatal bleeding or bleeding demanding hospital admission.

RESULTS

In 756 treatment-years of follow-up, there were 45 major haemorrhagic events (6.0 per 100 treatment-years) in 42 patients, of which seven (0.9 per 100 treatment-years) were fatal. The risk of a first major haemorrhagic episode was highest during the first 90 days of treatment compared with duration above one year (incidence rate ratio, IRR, 1.9; 95% CI, 0.8-4.1). The rate was highest above the age of 60 years, 6.8 per 100 treatment-years, compared with 2.9 per 100 treatment-years below 60 years (IRR 2.3; 95% CI, 1.0-5.6). The rate for a bleeding event was slightly higher in females than in males (IRR 1.3; 95% CI, 0.7-2.3), but did not vary according to type of anticoagulant drug.

CONCLUSIONS

The reported rates of major bleeding in this routine community setting implied a higher bleeding risk than was found in randomized trials or when patients are monitored in specialist anticoagulation clinics.

The medical management of atrial fibrillation

Atrial fibrillation is an extremely common arrhythmia that is associated with significant sequelae. Certain aspects of therapy, such as anticoagulation, are studied in well-constructed randomized trials. Other therapy, such as the maintenance of sinus rhythm with antiarrhythmic agents, is supported by limited evidence. This article reviews the epidemiology and medical treatment of this arrhythmia, addressing anticoagulation, ventricular rate control, and restoration and maintenance of sinus rhythm. Randomized trials in progress that attempt to answer important questions in the management of atrial fibrillation are also discussed.

Is There a Relationship Between the Intensity of Heparin Treatment and Recurrent Thomboembolism?

Continuous intravenous heparin is widely used in the initial treatment of patients with venous thromboembolism. However, because it has a narrow therapeutic window and because the anticoagulant response to it varies among patients, it is standard practice to adjust the dose of heparin to achieve a predefined anticoagulant effect (therapeutic range) using the activated partial thromboplastin time (APTT). There is evidence to suggest that the efficacy of heparin is critically dependent on the starting dose used and that failure to maintain APTT results above the lower limit of the therapeutic range leads to increased rates of recurrence. We review the evidence for a rel~tic~nship between the intensity of heparin treatment and recurrence and provide recommendations for optimal dosing regimens.

Physician attitudes concerning warfarin for stroke prevention in atrial fibrillation: results of a survey of long-term care practitioners

BACKGROUND

The prevalence of atrial fibrillation (AF) increases dramatically with advancing patient age, and, as a result, this condition is common in persons residing in the long-term care setting.

OBJECTIVES

To assess the knowledge and attitudes of physicians regarding the use of warfarin for stroke prevention in patients with atrial fibrillation in long-term care facilities.

METHODS

We surveyed physicians actively providing primary care to older patients in 30 long-term care facilities located in New England, Quebec, and Ontario. Physicians were requested to complete a structured questionnaire about use of warfarin therapy for stroke prevention in patients with AF residing in long-term care facilities. The questionnaire included two clinical scenarios designed to provide substantial contrasts in patient characteristics including underlying comorbidity, functional status, bleeding risk, and stroke risk.

RESULTS

A total of 269 physicians were asked to participate in the survey, and 182 (67.7%) completed the questionnaire between February 1, 1995, and July 31, 1995. Only 47% of respondents indicated that the benefits of warfarin therapy "greatly outweigh the risks" in this setting; the remainder of physicians indicated that benefits only "slightly outweigh the risks" (34%) or that risks "outweigh benefits" (19%). The most frequently cited contraindications to warfarin use were: excessive risk of falls (71%), history of gastrointestinal bleeding (71%), history of other non-central nervous system bleeding (36%), and history of cerebrovascular hemorrhage (25%). Among the 164 physicians who reported using the international normalized ratio to monitor warfarin therapy, 27% indicated a target range with a lower limit less than 2, 71% indicated a target range between 2 and 3, and 2% indicated an upper limit greater than 3. Among respondents who answered questions about the two clinical scenarios, estimates of the risk of a stroke without warfarin therapy and the risk of an intracranial hemorrhage with therapy varied widely.

CONCLUSIONS

Our findings suggest that many uncertainties surround the decision to prescribe warfarin to patients with AF in the long-term care setting, as well as questions about the appropriate intensity of this treatment when it is prescribed. Concerns about the risks of bleeding appear to prevail over stroke prevention when physicians make such prescribing decisions.

Treatment of venous thrombo-embolism

Clinically suspected deep vein thrombosis (DVT) or pulmonary thromboembolism (PE) should be initially treated with heparin, and an objective diagnosis obtained. In pregnancy, heparin is usually continued until delivery, following which warfarin is substituted. In the absence of pregnancy, warfarin is substituted and usually continued for 3 months after a first thrombo-embolic event. Low molecular weight heparins are increasingly preferred to unfractionated heparin in non-pregnant patients with acute DVT, because of efficacy when given by daily subcutaneous injection without routine monitoring of coagulation assays, greater efficacy, and lower risks of major bleeding and of mortality. Unfractionated heparin requires monitoring by the APTT (target ratio 1.5-2.5), and warfarin requires monitoring by the International Normalized Ratio (INR) of the prothrombin time (target ratio 2.0-3.0). Graduated elastic compression stockings reduce post-thrombotic leg symptoms after DVT. Secondary prevention is important in future high risk situations.

Relationship between prothrombin activation fragment F1.2 and international normalized ratio in patients with atrial fibrillation. Stroke Prevention in Atrial Fibrillation Investigators

BACKGROUND AND PURPOSE

The prothrombin time (expressed as the international normalized ratio [INR]) is the standard method of monitoring warfarin therapy in patients with atrial fibrillation. Prothrombin activation fragment F1.2 provides an index of in vivo thrombin generation and might provide a better index of the effective intensity of anticoagulation. We examined the relationship between F1.2 and INR in patients with atrial fibrillation.

METHODS

We measured INR and F1.2 levels in 846 patients with atrial fibrillation participating in the Stroke Prevention in Atrial Fibrillation III study. Two hundred nineteen (26%) were taking aspirin alone, 326 (39%) were taking adjusted-dose warfarin, and 301 (36%) were taking a low fixed dose of warfarin (1 to 3 mg) plus aspirin (combination therapy). F1.2 levels were measured with an enzyme-linked immunosorbent assay.

RESULTS

Patients receiving adjusted-dose warfarin or combination therapy had significantly higher INR and significantly lower F1.2 values than those on aspirin alone (P < or = .0001 for each of the four comparisons). F1.2 values (nanomolar) were inversely correlated with INR (F1.2 = -0.1 + 2.3[1/INR]; R2 = .37; P < .0001; simple linear regression). However, significant variability remained. Among patients receiving warfarin, older patients had higher F1.2 values than younger patients after adjustment for INR intensity (P < .001) in the model. There was no difference in the relationship between F1.2 and INR between men and women.

CONCLUSIONS

Increasing intensity of anticoagulation, as measured by the INR, is associated with decreasing thrombin generation as measured by the F1.2 level, but significant variability exists in this relationship. Older anticoagulated patients have higher F1.2 values than younger patients at equivalent INR values. The clinical significance of these differences is not clear. F1.2 measurement might provide information regarding anticoagulation intensity in addition to that reflected by the INR.