Antithrombotic Therapy in Valvular Heart Disease—Native and Prosthetic

Use of anticoagulation in elderly patients with atrial fibrillation who are at risk for falls

OBJECTIVE

To evaluate data addressing use of anticoagulation in elderly patients with atrial fibrillation (AF), in particular those at risk of falls.

DATA SOURCES

Primary literature was identified through PubMed MEDLINE (1966-December 2007) and EMBASE (1980-December 2007) using the search terms anticoagulation, warfarin, aspirin, elderly, falls, older persons, atrial fibrillation, bleeding, education, stroke, and use. Additional references were obtained through review of references from articles obtained.

STUDY SELECTION AND DATA EXTRACTION

Clinical studies evaluating warfarin and aspirin efficacy in AF, as well as studies evaluating anticoagulation and falls, elderly patients, and bleeding were considered for inclusion. Selection emphasis was placed on randomized studies of AF and those evaluating anticoagulation and falls.

DATA SYNTHESIS

Uncertainties over the optimal treatment for elderly patients with AF still exist. Variance in the guidelines is reflected in current practice, as some discrepancies are present. Warfarin is underprescribed in elderly patients, with only about 50% of eligible patients receiving therapy. Falls are most often cited as the reason for not using anticoagulants in an elderly patient. Three risk-benefit analyses have been performed, and all found that despite risks associated with warfarin, its benefits outweigh its risks even in patients who fall. Warfarin should be used rather than aspirin or no therapy in elderly patients at risk of falls. Anticoagulation education has been shown to reduce the risk of bleeding in the elderly and should be a vital part of warfarin management.

CONCLUSIONS

The risk of falls alone should not automatically disqualify a person from being treated with warfarin. While falls should not dictate anticoagulant choice, assessment and management of fall risk should be an important part of anticoagulation management. Efforts should be made to minimize fall risk.

[Nonbacterial thrombotic endocarditis and gastric carcinoma]

We report a 74-year-old woman with acute heart failure and recurrent ischemic strokes as the presenting features of a nonbacterial thrombotic endocarditis complicating a gastric adenocarcinoma. The treatment only allowed a few months remission. Diagnosis of nonbacterial thrombotic endocarditis is rarely obtained while the patient is alive. Coagulation abnormalities due to the tumoral process are responsible of the valvular thrombotic process. Anticoagulation with heparin is recommended. Valvular surgery remains controversial.

Improving anticoagulation therapy using point-of-care testing and a standardized protocol

PURPOSE

Many patients in primary care require anticoagulation with warfarin for the prevention of venous and systemic embolism. Achieving the goal international normalized ratio (INR) with warfarin is challenging. The purpose of this quality improvement initiative was to increase the proportion of patients taking warfarin with an INR value within the goal range.

METHODS

We included all patients identified on an anticoagulation log in the family medicine residency practice during 3 time periods: baseline, after point-of-care (POC) testing was initiated (intervention period 1), and after a standardized warfarin-dosing protocol was implemented (intervention period 2). Educational sessions were conducted during each intervention period. Measures included the frequency of INR monitoring and the percentage of office visits in which patients' values were within the goal INR range. Data were analyzed using descriptive statistics, the Student t test, and the chi2 test.

RESULTS

At baseline, patients had an average of 2.6 INR tests performed, and 30.8% were within the INR goal range. Using POC testing, the frequency of monitoring increased to 4.3 INR tests per patient (P = .04), but the percentage of patients within the INR goal remained low at 32.1% (P=.88). When physicians implemented the standardized protocol to guide warfarin dosing, the frequency of testing was similar (3.8 tests per patient), but the percentage of patients within the INR goal increased to 45.9% (P<.04).

CONCLUSIONS

POC testing increased the frequency of INR testing, and additional use of a standardized protocol for warfarin dosing increased the percentage of patients within the INR goal range. This model of anticoagulation management could be easily implemented in any family medicine office.

MECHANICAL HEART VALVES AND PREGNANCY

Mechanical heart valves pose a particular challenge in pregnancy, as the primary agent used to prevent valve thrombosis, coumadin (warfarin), is a known teratogen. Alternatives to coumadin, such as unfractionated heparin (UFH) and low-molecular weight heparin (LMWH) are safer for the fetus, particularly during the first trimester of pregnancy, but expose the mother to potential valve failure. This review will examine these controversies and the complex literature regarding management in pregnancy.

Non-bacterial thrombotic endocarditis

Non-bacterial thrombotic endocarditis (NBTE) is a disease characterised by the presence of vegetations on cardiac valves, which consist of fibrin and platelet aggregates and devoid of inflammation or bacteria. NBTE has increasingly been recognised as a condition associated with numerous diseases and a potentially life-threatening source of thromboembolism. NBTE is not a common entity; however it is frequently underestimated, probably due to underlying diseases (cancer, autoimmune disorders, HIV). NBTE is difficult to diagnose and relies on strong clinical suspicion. NBTE is also difficult to manage and each case should be individually managed by identifying and treating the underlying pathology. Surgical intervention is not recommended unless the patient is in acute congestive failure.

Determinants and measures of quality in oral anticoagulation therapy

BACKGROUND

Anticoagulation management services or clinics have been recommended as the preferred method in the long-term management of oral anticoagulation with vitamin K antagonists and have been shown to increase the time patients spend in the therapeutic range. This surrogate marker of the quality of anticoagulation control is a well accepted predictor of bleeding and thromboembolic events and is generally used as a quality measure. However, the method of calculating the time in the therapeutic range can give different results and there is no consensus on the methodology that should be used or the benchmark targets that should be aimed for. Additionally, the expected rates of bleeding and thromboembolic complications are dependent on the indications for anticoagulation in the patient population being evaluated. These issues need to be taken into account when setting quality standards for anticoagulation clinics.

METHODS

An informal survey and group discussion with anticoagulation clinic personnel attending a workshop at the 9th National Conference on Anticoagulant Therapy was used to generate a list of pragmatic barriers to measuring these quality indicators and to share ideas on other quality markers. A narrative review of selected literature was used throughout the workshop to exemplify potential benchmark rates for therapeutic time in range, bleeding, and thromboembolic complication rates.

RESULTS

Approximately 65% of the workshop attendees measure time in range in their anticoagulation clinics, however, only 15% used the linear interpolation method which has a quality measurement target of 65%. Less than half of the attendees measure bleeding or complication rates and very few adjust these rates based on the indication for anticoagulation. There was strong agreement regarding pragmatic barriers to collect this information and difficulties in extrapolating standards from the literature. Several clinics also measure the percent of extremely high International Normalized Ratios (INR) and also track late patients.

CONCLUSIONS

Using clinical trial bleeding and thromboembolic complication rates to set quality measurement targets for anticoagulation clinics may not be appropriate, given the inherent difference in these patient populations. Additionally, there are pragmatic issues affecting the completeness and accuracy of adverse event gathering outside of a trial scenario that could be misleading. The time in the therapeutic range, however, is relatively easy to calculate and is a well substantiated surrogate marker for complication rates and should be a standard quality indicator. Benchmark targets for time in range are dependent on the methodology used in the calculation and should be adjusted accordingly.

Influence of age on the cost-effectiveness of diagnostic strategies for suspected pulmonary embolism

BACKGROUND

Age has a marked effect on the diagnostic yield of D-dimer measurement and lower limb compression ultrasonography (CUS) in patients with suspected pulmonary embolism (PE), suggesting that specific diagnostic strategies may be needed in elderly patients.

OBJECTIVE

To evaluate the cost-effectiveness of including D-dimer and CUS in the workup of PE, with particular attention to patient age.

SUBJECTS AND METHODS

We analyzed data from two recent outcome studies that enrolled 1721 consecutive outpatients with suspected PE. Both studies used a sequential diagnostic strategy that included assessment of clinical probability, D-dimer measurement, CUS, and helical computed tomography (hCT). A decision analysis model was created for analyzing cost-effectiveness according to six classes of age. The main outcome measures were 3-month quality-adjusted expected survival and costs per patient managed.

RESULTS

All strategies were equally safe, with variations in the 3-month survival never exceeding 0.5% as compared to the most effective strategy. D-dimer measurement was highly cost-saving under the age of 80 years. Above 80 years, the cost-sparing effect of D-dimer was diminished, but not completely abolished. Inclusion of CUS increased the costs of diagnostic strategies irrespective of age. Results were unchanged over a wide range of the variables of interest (costs, sensitivity, and specificity of the tests).

CONCLUSIONS

Diagnostic strategies using D-dimer are less expensive. The cost-sparing effect of D-dimer is reduced but not abolished above 80 years, suggesting that adapting specific diagnostic strategies in elderly outpatients is not mandatory. CUS is costly, and only marginally improves the safety of diagnostic strategies for PE.

Failure of guideline-based anticoagulation in a patient with mitral prosthetic valve and recurrent thromboembolism

Prosthetic valve (PV)-related thromboembolism is a rare but serious complication of implanted mechanical valves. There is not a design that has yet achieved mechanical perfection; therefore, using these mechanical valves is not free of mortality and morbidity. Some of the complications of using such valves include PV thrombosis, systemic embolization, bleeding, endocarditis, perivalvular leak, and structural valve failure. These valves are thrombogenic, and their use requires anticoagulation postoperatively to prevent systemic embolization and PV thrombosis. This intervention also carries the risk of bleeding, which can be detrimental for a subset of patients, especially elderly, pregnant, and those with other systemic comorbidities. In this case we present a patient with recurrent thromboembolic events and a nonobstructing St. Jude mitral PV thrombosis despite vigorous anticoagulation with Coumadin (Bristol-Myers Squibb Co., Princeton, NJ) and aspirin.

Racial/ethnic differences in the risk of intracranial hemorrhage among patients with atrial fibrillation

OBJECTIVES

This study was designed to study racial/ethnic differences in the risk for intracranial hemorrhage (ICH) and the effect of warfarin on ICH risk among patients with atrial fibrillation (AF).

BACKGROUND

Nonwhites are at greater risk for ICH than whites in the general population. Whether this applies to patients with AF and whether warfarin therapy is associated with comparable risk of ICH in nonwhites are unknown.

METHODS

We retrospectively identified a multiethnic stroke-free cohort hospitalized with nonrheumatic AF. Warfarin use and anticoagulation intensity were assessed by searching pharmacy and laboratory records. Crude ICH event rates were calculated by Poisson regression. Cox proportional hazard models were constructed to assess the independent effect of race/ethnicity on ICH after adjusting for age, gender, hypertension, diabetes, heart failure, and warfarin exposure.

RESULTS

Between 1995 and 2000, we identified 18,867 qualifying AF hospitalizations (78.5% white, 8% black, 9.5% Hispanic, and 3.9% Asian) and 173 qualifying ICH events over 3.3 years follow-up. Achieved anticoagulation intensity was lower among blacks but not different between the other groups. Warfarin was associated with increased ICH risk in all races, but the magnitude of risk was greater among nonwhites. There were no gender differences. The hazard ratio for ICH with whites as referent was 4.06 for Asians (95% confidence interval [CI] 2.47 to 6.65), 2.06 for Hispanics (95% CI 1.31 to 3.24), and 2.04 (95% CI 1.25 to 3.35) for blacks.

CONCLUSIONS

Nonwhites with AF were at greater risk for warfarin-related ICH. Blacks, Hispanics, and Asians were at successively greater ICH risk than whites.

The headache over warfarin in British neurosurgical intensive care units: a national survey of current practice

OBJECTIVE

To ascertain current British practice regarding the emergency medical management of patients who sustain a spontaneous intracerebral haemorrhage (ICH) whilst receiving warfarin therapy and to compare this with established national and international guidelines.

DESIGN

Standardised, telephone based, questionnaire survey.

SETTING

All 32 adult British neuroscience intensive care units (ICUs)

PARTICIPANTS

Duty consultant of each neuroscience ICU.

RESULTS

Response rate was 100%. The international normalised ratio (INR) would be reversed by over 90% of ICU consultants treating patients on warfarin with an ICH, except patients with mechanical heart valves (MHV), when only 59.4% would reverse. Prothrombin complex concentrate (PCC) was used by 15 ICUs (46.9%); however, only six units (18.8%) apply reversal strategies with PCC and intravenous vitamin K in accordance with national guidelines. Fresh frozen plasma (FFP) continues to be used by 71.9% of the ICUs. A protocol for warfarin reversal in ICH was present in five ICUs, of which four followed national guidelines. None of the units that use FFP had a protocol. Following ICH, two-thirds of the ICUs (65.6%) would commence bridging heparinisation in the first 4 days for MHV patients and 25% would recommence warfarin before, and 64.5% after, 7 days.

CONCLUSION

There is considerable variation in practice amongst clinicians who regularly manage these patients and, in most cases (81.2%), practice is not in keeping with national or international guidelines. This study has demonstrated the need amongst senior ICU clinicians for a heightened awareness of current treatment recommendations and the availability of effective haemostatic therapies.

Antiplatelet therapy in patients receiving aortic bioprostheses: A report of clinical and instrumental safety

OBJECTIVE

The main advantage of bioprostheses, avoidance of anticoagulant therapy, is compromised during the early postoperative period; in fact, warfarin is often administered during the first 3 postoperative months.

METHODS

We analyzed 250 patients undergoing tissue aortic valve replacement between January 2002 and December 2005. The patients received either aspirin (group 1) or oral anticoagulation (group 2) during the first 3 months. In a subgroup of these patients, we investigated the possible presence of clinically silent microembolization by means of transcranial Doppler for microembolic signal detection.

RESULTS

Thirty-day mortality was 0%. No major neurologic events occurred. Two episodes of bleeding were observed in both groups. Follow-up time was 24 +/- 14 months. Overall late mortality rate was 0.8% in group 1 versus 12% (mainly cancer related) in group 2. In group 2, 2 deaths were due to major ischemic neurologic events; overall, 3 major neurologic episodes occurred (international normalized ratio was within therapeutic range). There were no neurologic events in group 1 (P = .12). Stroke-free survival did not reach statistical significance between the 2 groups. Transcranial Doppler was performed after a mean interval of 55 +/- 19 days, with no detection of microembolic signals in patients receiving either aspirin or warfarin. There were no episodes of bleeding or neurologic events.

CONCLUSIONS

Aspirin therapy appears to be the appropriate response to both cardiac surgeons' and patients' needs in the early postoperative course after aortic valve replacement with tissue valves, demonstrating adequate antithromboembolic efficacy with no added risk for bleeding as well as ease of administration.

[Perioperative hemostasis management]

Hemostasis management plays an important role in surgery. Anti-platelet drugs and oral anticoagulants are taken by an increasing number of patients. Perioperative management must take into account bleeding as well as thromboembolic risks when withholding these medications. Patients with inherited or acquired hemostatic disorders should receive interdisciplinary care in order to optimise perioperative substitution therapy. For the diagnosis of acquired coagulopathy secondary to massive bleeding, point of care tests have been introduced that should help focus substitution therapy in emergency situations. However, physicians should be aware of the limitations of these methods, and a full diagnostic workup should be done in order to uncover hemorrhagic diatheses not detected by point of care testing.

Burden of Potentially Avoidable Anticoagulant-Associated Hemorrhagic and Thromobembolic Events in the Elderly

BACKGROUND

On average, patients receiving therapy with oral anticoagulants (OACs) in the community are in the therapeutic range only 55% of the time. Anticoagulation control strongly influences the risk of hemorrhagic and thromboembolic events in such patients. However, not all anticoagulation-associated events are attributable to poor anticoagulation control, nor do all hemorrhagic or thromboembolic events occur in anticoagulated patients.

OBJECTIVE

Measure the proportion of serious hemorrhagic and thromboembolic events that would be avoided if anticoagulation control was perfect.

METHODS

A retrospective cohort study of eastern Ontario using population-based administrative databases. Anticoagulation control was determined for each day of OAC exposure using linear interpolation. Incident hemorrhagic or thromboembolic hospitalizations for control and OAC patients were identified. Hemorrhages and thromboemboli in OAC patients were deemed to be avoidable if they occurred at international normalized ratios of > 3 and < 2, respectively.

RESULTS

The study included > 183,000 patient-years of observation with 6,400 patient-years of OAC exposure. Anticoagulation control could be determined for 51.5% of OAC exposure time. Control patients had hemorrhagic and thromboembolic event rates of 1.8% and 1.5% per year, respectively. A total of 10,020 people were exposed to OACs, and spent 14.2% and 26.7% of the time, respectively, with excessively high and low anticoagulation intensity. Excessively high anticoagulation intensity explained 25.6% (95% confidence interval [CI], 19.4 to 31.7) and 2.0% (95% CI, 1.5 to 2.5) , respectively, of all serious hemorrhages in the anticoagulated and entire population. Excessively low anticoagulation intensity explained 11.1% (95% CI, 4.4 to 17.7) and 1.1% (95% CI, 0.7 to 1.6) of all thromboemboli, respectively.

CONCLUSIONS

Our study showed that extreme anticoagulation intensity significantly impacted the health of the population. Improving anticoagulation control will have significant effects on the incidence of serious hemorrhagic and thromboembolic events in the both the anticoagulated and entire populations.

Challenges in managing anticoagulant therapy in patients with heart valve prostheses

There is a wide array of recommendations for the management of anticoagulant therapy in patients with mechanical heart valves. The optimal intensity of vitamin K antagonists, management of patients during noncardiac surgery and use of anticoagulants during pregnancy are all ongoing matters of debate. In this review, we discuss the various studies on these topics and the different guidelines. Based on these, literature recommendations for daily clinical practice are formulated.

Management of dental patients taking common hemostasis-altering medications

OBJECTIVE

Millions of patients worldwide are taking medications that alter hemostasis and decrease the risk for thromboembolic events. This systematic review is intended to provide recommendations regarding optimal management of such patients undergoing invasive dental procedures. The primary focus of this report is on warfarin therapy, although issues related to heparin and aspirin are briefly discussed because of the frequency with which they are encountered in dental practice.

STUDY DESIGN

The review of literature and development of recommendations was based on the Reference Manual for Management Recommendations for the World Workshop in Oral Medicine IV (WWOM IV). A total of 64 publications were identified for initial review. From these publications, the following types of articles were critically analyzed using WWOM standard forms: randomized controlled trials (RCT), non-RCT studies that assess effects of interventions, and studies that assess modifiable risk factors. Development of recommendations was based on the findings of these reviews as well as expert opinion.

RESULTS

The following evidence-based recommendations were developed: (1) For patients within the therapeutic range of International Normalized Ratio (INR) below or equal to 3.5, warfarin therapy need not be modified or discontinued for simple dental extractions. Nevertheless, the clinician's judgment, experience, training, and accessibility to appropriate bleeding management strategies are all important components in any treatment decision. Patients with INR greater than 3.5 should be referred to their physician for consideration for possible dose adjustment for significantly invasive procedures. (2) A 2-day regimen of postoperative 4.8% tranexamic acid mouthwash is beneficial after oral surgical procedures in patients on warfarin. (3) It is not necessary to interrupt low-dose aspirin therapy (100 mg/day or less) for simple dental extractions.

CONCLUSION

For most patients undergoing simple single dental extractions, the morbidity of potential thromboembolic events if anticoagulant therapy is discontinued clearly outweighs the risk of prolonged bleeding if anticoagulant therapy is continued.

Warfarin and Antiplatelet Combination Use Among Commercially Insured Patients Enrolled in an Anticoagulation Management Service

BACKGROUND

Although warfarin and antiplatelet medications have documented efficacy for prevention of primary and secondary cardiovascular events, the appropriateness of warfarin and antiplatelet combination therapy is not well described in national consensus guidelines.

METHODS AND RESULTS

Cross-sectional data from 4,557 Kaiser Permanente Colorado members > or = 18 years old who were receiving warfarin anticoagulation therapy were used to quantify the prevalence of warfarin and antiplatelet agent (ie, aspirin, clopidogrel, dipyridamole, and/or dipyridamole/aspirin) combination therapy as of September 30, 2005, and to identify characteristics of patients receiving combination therapy. The prevalence of warfarin and any antiplatelet combination therapy was 385/1,000 (95% confidence interval [CI], 371/1,000 to 399/1,000). The majority of combination therapy was warfarin and aspirin (prevalence, 378/1,000) with a daily dose of aspirin, 81 mg, being the most reported dose (prevalence, 328/1,000). Patients receiving combination therapy were more likely to be male (63.6% vs 46.4%; adjusted odds ratio, 1.5; 95% CI, 1.3 to 1.7) and have a comorbidity of heart failure (29.0% vs 15.6%; adjusted odds ratio, 1.2; 95% CI, 1.1 to 1.5), coronary artery disease (62.4% vs 17.5%; adjusted odds ratio, 7.6; 95% CI, 6.5 to 8.8), and/or stroke/transient ischemic attack (5.2% vs 1.6%; adjusted odds ratio, 3.5; 95% CI, 2.3 to 5.3).

CONCLUSION

Nearly 4 of 10 patients receiving warfarin management care were receiving warfarin and antiplatelet combination therapy. The findings suggest that this practice is widespread, especially among patients with established cardiovascular disease, and involves a substantially higher number of patients than previously reported. The clinical outcomes associated with this practice require further investigation.

Nonbacterial Thrombotic Endocarditis in Cancer Patients: Pathogenesis, Diagnosis, and Treatment

Thrombophilia is a well-described consequence of cancer and its treatment. The pathogenesis of this phenomenon is complex and multifactorial. Nonbacterial thrombotic endocarditis (NBTE) is a serious and potentially underdiagnosed manifestation of this prothrombotic state that can cause substantial morbidity in affected patients, most notably recurrent or multiple ischemic cerebrovascular strokes. Diagnosis of NBTE requires a high degree of clinical suspicion as well as the judicious use of two-dimensional echocardiography to document the presence of valvular thrombi. In the absence of contraindications to therapy, treatment consists of systemic anticoagulation, which may ameliorate symptoms and prevent further thromboembolic episodes, as well as control of the underlying malignancy whenever possible.

Antithrombotic therapy following bioprosthetic aortic valve replacement

The life expectancy of the general population is increasing. This has meant that more elderly patients are requiring aortic valve replacement (AVR). The choice of valve replacement and its durability are important. Bioprosthetic (tissue) heart valves were introduced into clinical use in the 1960s and were developed primarily to reduce the complications associated with thromboembolism (TE) and the need for lifelong oral anticoagulation, due to their low thrombogenicity compared to mechanical prostheses. This makes them suitable for use in elderly patients (aged>65 years) and in others where the risks of anticoagulation are higher or anticoagulation is contraindicated. There is thought to be a higher risk of TE for up to 90 days following bioprosthetic AVR. Guidelines for the management of patients with valvular heart disease published by the American College of Cardiology (ACC)/American Heart Association (AHA), the American College of Chest Physicians (ACCP) and the European Society of Cardiology (ESC) all recommend the use of an anticoagulation regimen for the first 3 months following bioprosthetic AVR. However, there is division of opinion and practice, despite these recommendations, and more recent studies have not supported the evidence for these guidelines. In this article, we review the literature on the use of anticoagulation in the first 90 days following bioprosthetic AVR.

Anticoagulation or antiplatelet therapy of bioprosthetic heart valves recipients: an unresolved issue

Improvements in the performance and longevity of biological valve prostheses have steadily increased their rates of implantation in recent years. Aortic bioprostheses, which are commonly used in the elderly or when the risks of anticoagulating are high, have generally been associated with low rates of long-term complications. Freedom from anticoagulation, therefore, represents the main theoretical advantage of biological, compared with mechanical, aortic prostheses. While a variety of anticoagulant and antiplatelet drug regimens have been described, a precise antithrombotic protocol for the early postoperative period after bioprosthetic aortic valve replacement has not been developed. There are also important differences between the international guidelines published. This review examines the clinical evidence concerning the use of vitamin K antagonist and antiplatelet therapy in the early management of the antithrombotic complications after bioprosthetic aortic valve replacement.

The scientific basis for evaluation and management of thrombotic disorders

The hemostatic mechanisms at work in the body involve a complex series of interactions between platelets, the endothelium, and the coagulation cascade. Much has been learned regarding the molecular mechanisms governing these intricate processes. The hypercoagulable state involves a disruption of the normal homeostatic equilibrium. This state may be either inherent or acquired. The prevention of associated thromboembolic complications requires therapeutic anticoagulation. A broader understanding of the factors contributing to these prothrombotic tendencies and the subtleties involved in their management provides the surgeon with another weapon in the armamentarium to promote better and safer patient outcomes.

Antithrombotic and interventional treatment options in cardioembolic transient ischaemic attack and ischaemic stroke

Peer-reviewed data pertaining to anti-thrombotic and interventional therapy for transient ischaemic attack (TIA) or ischaemic stroke patients with non-valvular atrial fibrillation, atrial flutter, interatrial septal abnormalities, or left ventricular thrombus were reviewed. Long-term oral anticoagulant therapy with warfarin is the treatment of choice for secondary stroke prevention following TIA or minor ischaemic stroke in association with persistent or paroxysmal non-valvular atrial fibrillation or atrial flutter. If warfarin is contraindicated, long-term aspirin is a safe, but much less effective alternative treatment option in this subgroup of patients with cerebrovascular disease. Management of young patients with TIA or stroke in association with an interatrial septal defect is controversial. Various treatment options are outlined, but readers are encouraged to include these patients in one of the ongoing randomised clinical trials in this area. It is reasonable to consider empirical anticoagulation in patients with TIA or ischaemic stroke in association with left ventricular thrombus formation following myocardial infarction or in association with idiopathic dilated cardiomyopathy. If warfarin is prescribed, one should aim for a target international normalised ratio of 2.5 (range 2-3) to achieve the best balance between adequate secondary prevention of cardioembolic events and the risk of major haemorrhagic complications.

Nonbacterial thrombotic endocarditis with recurrent embolic events as manifestation of ovarian neoplasm

We describe the case of a 43-year-old woman with transient ischemic neurologic deficits and recurrent systemic and pulmonary emboli in whom infectious work-up and extensive thrombophilic evaluation were unremarkable. Transesophageal echocardiography (TEE) established the diagnosis of nonbacterial thrombotic endocarditis (NBTE). This is a rare condition often associated with hypercoagulable states or advanced malignancy such as adenocarcinomas, characterized by cardiac vegetations along valvular coaptation lines without destruction of leaflets. In our patient, we diagnosed an ovarian clear cell adenocarcinoma, a malignant disorder that has been rarely reported in association with NBTE. This case illustrates that NBTE can present as an atypical manifestation of malignancy and must be distinguished from infective endocarditis, which implies a different therapeutic strategy. When confronted with findings of NBTE without a clear etiology, an occult neoplasm must be excluded. Anticoagulant therapy is the mainstay of treatment. However, cardiac vegetations may require surgical intervention in rare instances.

Perioperative management of patients receiving vitamin K antagonists

PURPOSE

As the number of patients taking vitamin K antagonists (VKA) is growing, the clinician is increasingly faced with having to make decisions regarding anticoagulation therapy before, during and immediately after surgery. In this article we review the indications for VKA and assess their use in the perioperative period based on available pharmacological and clinical data.

SOURCE

An on-line computerized search of Medline was conducted limited to English and French language articles. The bibliographies of relevant articles and additional material from other published sources were retrieved and reviewed.

PRINCIPAL FINDINGS

Assessment of patients taking VKA who need surgery must include three factors: 1) the indication for anticoagulation, which determines the thromboembolic risk; 2) the pharmacokinetics of VKA, which determine the moment at which treatment should be discontinued; and 3) the type of surgery, which determines the hemorrhagic risk. Some patients will need to stop VKA treatment and start a substitution or "bridging" anticoagulant therapy, such as unfractionated heparin or low molecular weight heparin, prior to and after surgery. In patients requiring emergency surgery, prothrombin complex concentrate can be used to improve coagulation and is preferable to, although more expensive than fresh frozen plasma.

CONCLUSIONS

For the perioperative setting, further studies are required to determine the optimal substitution ("bridging") regimen and the clinical circumstances that necessitate substitution therapy.

Subcutaneous Low Molecular Weight Heparin for Management of Anticoagulation in Infants on Excor Ventricular Assist Device

Anticoagulation in infants and children on a ventricular assist device presents particular challenges. Unfractionated heparin has poor bioavailability; it can be difficult to achieve a stable anticoagulant effect; and, in the long-term, there is a risk of osteopenia. Long-term warfarin can be difficult to manage in infants on formula milk with vitamin K supplementation. We review our recent experience with subcutaneous low molecular weight heparin. Two patients received a left ventricular assist device (Excor, Berlin Heart AG) as a bridge to transplantation. Initial anticoagulation consisted of unfractionated heparin infusion beginning 6 hours after implantation to maintain an activated partial thromboplastin time of 70 seconds, checked every 4 to 6 hours. Platelet count (aim >80,000/microl) and thromboelastography were assessed daily. Antithrombin required substitution to maintain levels >70 IU/dl. To optimize anticoagulation, both infants were switched to subcutaneous low molecular weight heparin twice daily aiming for an anti-Xa activity between 0.5 and 1.0 IU/ml. Aspirin was added on day 4, checking platelet aggregation every 2 to 4 days, aiming at arachidonic acid stimulated aggregation 10% to 30% of baseline, collagen 100% of baseline. Dipyridamole was added once stability was reached if platelets count exceeded 150,000/microl. There were no clinical thromboembolic or bleeding events. Both patients had successful transplantation.

Role of abciximab in the treatment of coronary artery disease

Glycoprotein IIb/IIIa complex is a crucial membrane receptor for platelet aggregation, binding platelets to fibrinogen and establishing interplatelet bridges. This receptor is the common end point of the multiple activation pathways of a platelet. Antiplatelet agents, such as aspirin or thienopyridines, including ticlopidine and clopidogrel, inhibit one or more but not all, of these pathways. Inhibitors of the receptor are powerful platelet antiaggregants and include two groups of agents: non-competitive receptor blockers, such as abciximab, and competitive antagonists, such as tirofiban and eptifibatide. Abciximab is a monoclonal antibody that binds to the glycoprotein IIb/IIIa complex, thus blocking the interaction with fibrinogen. It is used for treatment of coronary artery disease, being well-studied in the setting of acute coronary syndromes and percutaneous coronary intervention, in which a rapid and effective antiaggregation is clinically important.

Complicações da terapia anticoagulante com warfarina em pacientes com doença vascular periférica: estudo coorte prospectivo

OBJETIVO: Estudar prospectivamente a freqüência de complicações em pacientes tratados com warfarina e acompanhados no Ambulatório de Anticoagulação da Faculdade de Medicina de Botucatu da Universidade Estadual Paulista. MÉTODOS: Pacientes sorteados entre os agendados para consulta de junho de 2002 a fevereiro de 2004. Na primeira consulta, foi preenchida ficha com dados de identificação e clínicos. A cada retorno, ou quando o paciente procurou o hospital por intercorrência, foi preenchida ficha com a razão normatizada internacional, existência e tipo de intercorrência e condições de uso dos antagonistas da vitamina K. RESULTADOS: Foram acompanhados 136 pacientes (61 homens e 75 mulheres), 99 com tromboembolismo venoso e 37 com doença arterial; 59 pacientes eram de Botucatu, e 77, de outros municípios. Foram registradas 30 intercorrências: nove não relacionadas ao uso da warfarina e 21 complicações hemorrágicas (38,8 por 100 pacientes/ano). Uma hematêmese foi considerada grave (1,9 por 100 pacientes/ano). As demais foram consideradas moderadas ou leves. Não houve óbitos, hemorragia intracraniana ou necrose cutânea. A única associação significante foi da freqüência de hemorragia com nível médio de razão normatizada internacional. CONCLUSÃO: Nossos resultados mostram a viabilidade desse tratamento em pacientes vasculares em nosso meio, mesmo em população de baixo nível socioeconômico, quando tratados em ambulatório especializado.

Postanalytical external quality assessment of warfarin monitoring in primary healthcare

BACKGROUND

An increasing number of patients are treated with warfarin worldwide, and many are monitored in general practice, often with office instruments. Bleeding or thromboembolic episodes may be consequences of inadequate treatment. We have therefore examined some important aspects of general practitioners' (GPs') knowledge of warfarin treatment.

METHODS

A questionnaire including 2 case histories with familiar indications for warfarin treatment (mechanical heart valve prosthesis and pulmonary embolism) was circulated to 3781 GPs in Norway as a postanalytical quality assessment.

RESULTS

A total of 1547 GPs (41%) responded. There were substantial variations among GPs concerning the frequency of international normalized ratio (INR) monitoring, stated therapeutic ranges for arterial (but not venous) indications for anticoagulation therapy, and handling of a moderately high INR result of 5.9. Most GPs estimated an unrealistically high risk of serious bleeding in the latter situation (median, 15%; 10th and 90th percentiles, 4% and 50%, respectively). The critical difference necessary to change the warfarin dose was highly dependent on perceived therapeutic intervals, and about half of the GPs suggested a critical difference of 0.8 INR, which is attainable with office instruments. Sex and age of the GPs, practice size, and availability of an INR instrument in the office laboratory did not influence the results to any substantial degree, as variations within subgroups were similar.

CONCLUSIONS

Gross variations in practice were found, especially for aspects of warfarin treatment that lacked uniform guidelines. Evidence-based and practicable recommendations for treatment and monitoring of these patients are still needed.

Pregnancy in women with valvular heart disease

Patients with valvular disease who desire pregnancy or are already pregnant require specialised care. Ideally, women undergo preconceptual counselling that addresses any procedures needed to decrease the risks of pregnancy, including valve replacement, if the patient has symptoms at baseline. Management during pregnancy includes replacing any contraindicated medications with safer alternatives, optimising loading conditions, careful monitoring and aggressive treatment of any exacerbating factors. Rarely, percutaneous or surgical intervention is required during pregnancy. Labour and delivery often require invasive haemodynamic monitoring and a multi-disciplinary team for optimal maternal and fetal outcomes.