Long-term anticoagulation of outpatients with adverse events to oral anticoagulants using low-molecular-weight heparin

Heparin-Peptide Nanogranules for Thrombosis-Actuated Anticoagulation

Despite nearly a century of clinical use as a blood thinner, heparin's rapid serum clearance and potential to induce severe bleeding events continue to urge the development of more effective controlled delivery strategies. Subcutaneous depots that steadily release the anticoagulant into circulation represent a promising approach to reducing overdose frequency, sustaining therapeutic concentrations of heparin in plasma, and prolonging anticoagulant activity in a safe and effective manner. Subcutaneously deliverable heparin-peptide nanogranules that allow for long-lasting heparin bioavailability in the circulatory system, while enabling on-demand activation of heparin's anticoagulant effects in the thrombus microenvironment, are reported. Biophysical studies demonstrate this responsive behavior is due to the sequestration of heparin within self-assembling peptide nanofibrils and its mechanically actuated decoupling to elicit antithrombotic effects at the clotting site. In vivo studies show these unique properties converge to allow subcutaneous nanogranule depots to extend heparin serum concentrations for an order of magnitude longer than standard dosing regimens while enabling prolonged and controlled anticoagulant activity. This biohybrid delivery system demonstrates a potentially scalable platform for the development of safer, easier to administer, and more effective antithrombotic nanotechnologies.

Past, present, and future perspectives of heparins in clinical settings and the role of impaired renal function

Heparin, whose discovery goes back one hundred years, was first detected as a thromboplastin from liver tissue, and its anticoagulant action was only identified later. The procoagulant action of heparin, which was later characterized as an immunologic reaction by binding to platelet-factor IV, presenting as heparin-induced thrombocytopenia, remains as a side effect. For more than 60 years heparin has been the immediate anticoagulant of choice in many clinical indications. Further development of heparins resulted in the production of low-molecular weight heparins and Fondaparinux, which substituted heparin for many indications and has received many more new indications, including administration for non-anticoagulant purposes. This development is still ongoing and has resulted in more than 300 registered clinical trials at the end of 2015. All types of heparins are still investigated in patients with impairment of renal function to improve the safety of treatment. New therapeutic strategies for the prevention and treatment of thromboembolism, as well as of the non-anticoagulant actions of natural and modified types of heparins, are studied intensively. The clinical study designs include treatment with vitamin-K and non-vitamin K oral anticoagulants. Consequently, heparins, low-molecular weight heparins and Fondaparinux play an important role in the human health care system.

Measuring anti-factor xa activity to monitor low-molecular-weight heparin in obesity: a critical review

BACKGROUND

The choice of whether to monitor anti-factor Xa (anti-Xa) activity in patients who are obese and who are receiving low-molecular-weight heparin (LMWH) therapy is controversial. To the authors' knowledge, no systematic review of monitoring of anti-Xa activity in such patients has been published to date.

OBJECTIVE

To systematically ascertain the utility of monitoring anti-Xa concentrations for LMWH therapy in obese patients.

DATA SOURCES

MEDLINE (1946 to September 2014), the Cochrane Database of Systematic Reviews, Embase (1974 to September 2014), PubMed (1947 to September 2014), International Pharmaceutical Abstracts (1970 to September 2014), and Scopus were searched using the terms obesity, morbid obesity, thrombosis, venous thrombosis, embolism, venous thromboembolism, pulmonary embolism, low-molecular weight heparin, enoxaparin, dalteparin, tinzaparin, anti-factor Xa, anti-factor Xa monitoring, anti-factor Xa activity, and anti-factor Xa assay. The reference lists of retrieved articles were also reviewed.

STUDY SELECTION AND DATA EXTRACTION

English-language studies describing obese patients treated with LMWH or reporting anti-Xa activity were reviewed using a 9-step decision-making algorithm to determine whether monitoring of LMWH therapy by means of anti-Xa activity in obesity is warranted. Studies published in abstract form were excluded.

DATA SYNTHESIS

The analysis showed that anti-Xa concentrations are not strongly associated with thrombosis or hemorrhage. In clinical studies of LMWH for thromboprophylaxis in bariatric surgery, orthopedic surgery, general surgery, and medical patients, and for treatment of venous thrombo embolism and acute coronary syndrome, anti-Xa activity can be predicted from dose of LMWH and total body weight; no difference in clinical outcome was found between obese and non-obese participants.

CONCLUSIONS

Routinely determining anti-Xa concentrations in obese patients to monitor the clinical effectiveness of LMWH is not warranted on the basis of the current evidence. Circumstances where measurement of anti-Xa concentration may help in clinical decision-making in either obese or non-obese patients would be cases where elimination of LMWH is impaired or there is an unexpected clinical response, as well as to confirm compliance with therapy or to identify deviation from predicted pharmacokinetics.

Population pharmacokinetics of enoxaparin in infants, children and adolescents during secondary thromboembolic prophylaxis: a cohort study

BACKGROUND

Enoxaparin has been extensively studied in adults on its safety and efficacy during prevention of symptomatic thromboembolism when acute anticoagulation or secondary prevention is required as a result of venous thrombosis or stroke. In children, it is still used off-label and little is known about the pharmacokinetics in children.

OBJECTIVES

The aim of the present study was to evaluate whether a once- or twice-daily dosing regimen would be feasible in children to achieve appropriate plasma levels of enoxaparin.

PATIENTS/METHODS

A population pharmacokinetic model was developed using anti-factor (F)Xa activity data from 126 children (median age: 5.9 years) receiving enoxaparin either as a once- or twice-daily dosing regimen.

RESULTS

A two-compartment model was adequate for describing the enoxaparin kinetics. Body weight proved to be the most predictive covariate for clearance and central volume of distribution: clearance 15 mL h⁻¹ kg⁻¹, central volume of distribution 169 mL kg⁻¹, intercompartmental clearance 58 mL h⁻¹, peripheral volume of distribution 10 L and absorption rate 0.414 h⁻¹. Interindividual variability was found to be 54% for clearance and 42% for volume of distribution.

CONCLUSION

The model is capable of describing all age groups and dosing levels of our population and predicts 12 h and 24 h enoxaparin activities sufficiently. According to our results, a once-daily enoxaparin dosing regimen with frequent monitoring is feasible. In 53.2% of the patients the median 24 h trough level was above the desired range of 0.1 IU mL⁻¹ anti-FXa activity for prophylaxis therapy.

Gastrointestinal bleeding in the setting of anticoagulation and antiplatelet therapy

GOAL

To review the literature on the significance, risk factors, and management of occult and gross gastrointestinal (GI) bleeding in patients on antiplatelets and/or anticoagulants.

STUDY

Relevant original and review articles and their bibliographies were analyzed. Estimates of risks and therapeutic outcomes were obtained from randomized trials, whereas risk factor identification was gathered from cross-control and prospective cohort studies.

RESULTS

Antiplatelets and anticoagulants do not diminish the positive predictive value of fecal occult blood testing to find GI pathology. They increase the risk of gross GI bleeding, and predictors of hemorrhage include history of GI bleeding or ulcer disease, higher intensity of anticoagulation, combination therapy, and presence of comorbid conditions. A bleeding site is identified in most patients with peptic ulcer being the most common. In case of significant bleeding, complete or partial reversal of anticoagulation is undertaken on the basis of the balance of risks between bleeding and thromboembolic events. Early endoscopy can reveal lesions requiring endoscopic hemostasis, which can be performed in the setting of low-intensity anticoagulation. In patients with history of peptic disease or bleeding from an acid-related lesion, proton-pump inhibitors and Helicobacter pylori eradication reduce the risk of upper GI bleeding even when antiplatelet therapy is continued.

CONCLUSIONS

Predictors of bleeding on antiplatelets and/or antithrombotics therapy have been identified, but formulation and validation of a GI bleeding index for stratification of risk in individual patients is suggested. Reversal of anticoagulation in bleeding patients is associated with a low risk of thromboembolic events and permits the performance of diagnostic and therapeutic endoscopy. Proton-pump inhibitors and H. pylori eradication reduce the risk of rebleeding in those with acid-related disease.

Outpatient-Based Primary and Secondary Thromboprophylaxis With Low-Molecular-Weight Heparin

Although oral vitamin K antagonists such as warfarin have been the mainstay of thromboprophylaxis in the outpatient setting, warfarin has potential disadvantages, including food and drug interactions, the need for drug monitoring, intolerance, failure, and hypersensitivity syndromes. The use of low-molecular-weight heparin as a primary or secondary thromboprophylactic drug in the outpatient setting for extended prophylaxis or as outpatient bridging therapy has been addressed less extensively. Available evidence shows that low-molecular-weight heparin can be used as extended outpatient-based primary thromboprophylaxis for major orthopedic and cancer surgery and is a safe and effective alternative to warfarin in long-term secondary thromboprophylaxis, especially in cancer patients and in pregnant women. Low-molecular-weight heparin can also be used as an alternative to unfractionated heparin as outpatient-based bridging therapy. In addition to good clinical outcomes and financial benefits, mainly resulting from a reduction in the length of hospital stay, the use of extended-duration low-molecular-weight heparin in the outpatient setting appears to be feasible, with high patient compliance.

Low-molecular-weight heparin for thromboprophylaxis in pregnant women with mechanical heart valves

BACKGROUND

Pregnancy in a woman with a mechanical heart valve is a life-threatening situation. Due to the inability of unfractionated heparin to prevent valvular thromboses, warfarin or other vitamin K antagonists have been the preferred anticoagulants for the mother. They are, however, potentially harmful to the fetus. With the advent of low-molecular-weight heparins, clinicians were hopeful for an alternative that was safe for the fetus, but more effective than unfractionated heparin, which carries a 29-33% risk of life-threatening thromboses and a 7-15% chance of mortality. Unfortunately, fatal thromboses have occurred with low-molecular-weight heparin as well.

METHODS

We searched the MEDLINE database and other sources to identify cases of the use of low-molecular-weight heparin for thromboprophylaxis in women with mechanical heart valves.

RESULTS

We found 73 cases and added three of our own for a total of 76. There were 17 thrombotic events (22%). Thirteen were valve thromboses, two were strokes, and two were myocardial infarctions. There were three deaths (4%).

CONCLUSIONS

While pregnant women with mechanical heart valves who receive low-molecular-weight heparin for thromboprophylaxis are at extremely high risk of life-threatening thromboses, there is no evidence that low-molecular-weight heparin is inferior to unfractionated heparin.

Use of low molecular weight heparin in cats: 57 cases (1999-2003)

OBJECTIVE

To determine duration of administration, complications, and frequency of aortic thromboembolism associated with administration of low molecular weight heparin (dalteparin) in cats.

DESIGN

Retrospective study.

ANIMALS

57 cats treated with dalteparin

PROCEDURE

Data were recorded from the medical records of cats treated with dalteparin, and owners were contacted by telephone for information regarding ease of administration and possible adverse effects.

RESULTS

Dalteparin was easily administered by owners. Median dose was 99 U/kg (45 U/lb) once or twice daily. Bleeding complications were infrequent. Of 43 cats with cardiomyopathy that received owner-administered dalteparin for a median follow-up time of 172 days, 8 cats developed documented or possible arterial thromboembolism.

CONCLUSIONS AND CLINICAL RELEVANCE

Dalteparin was easily administered by owners and was well tolerated by cats. Whether dalteparin administration can reduce the frequency or severity of arterial thromboembolism is not yet known.

Safety and Efficacy of Enoxaparin Compared With Unfractionated Heparin and Oral Anticoagulants for Prevention of Thromboembolic Complications in Cardioversion of Nonvalvular Atrial Fibrillation

Background— Anticoagulation in cardioversion of atrial fibrillation is currently performed with unfractionated heparin (UFH) and oral anticoagulants, with or without guidance by transesophageal echocardiography (TEE). Low-molecular-weight heparins may reduce the risk of bleeding, may obviate the need for intravenous access, and do not require frequent anticoagulation monitoring.

Methods and Results— In a randomized, prospective multicenter trial, we compared the safety and efficacy of enoxaparin administered subcutaneously with intravenous UFH followed by the oral anticoagulant phenprocoumon in 496 patients scheduled for cardioversion of atrial fibrillation of >48 hours’ and ≤1 year’s duration. Patients were stratified to cardioversion with (n=431) and without (n=65) guidance by TEE. The study aimed to demonstrate noninferiority of enoxaparin compared with UFH+phenprocoumon with regard to the incidence of embolic events, all-cause death, and major bleeding complications. Secondary end points included successful cardioversion, maintenance of sinus rhythm until study end, and minor bleeding complications. Of 496 randomized patients, 428 were analyzed per protocol. Enoxaparin was noninferior to UFH+phenprocoumon with regard to the incidence of the composite primary end point in a per-protocol analysis (7 of 216 patients versus 12 of 212 patients, respectively; P =0.016) and in an intention-to-treat analysis (7 of 248 patients versus 12 of 248 patients, respectively; P =0.013). There was no significant difference between the 2 groups in the number of patients reverted to sinus rhythm.

Conclusions— Enoxaparin is noninferior to UFH+phenprocoumon for prevention of ischemic and embolic events, bleeding complications, and death in TEE-guided cardioversion of atrial fibrillation. Its easier application and more stable anticoagulation may make it the preferred drug for initiation of anticoagulation in this setting.

Dental management considerations for the patient with an acquired coagulopathy. Part 2: Coagulopathies from drugs

Dental patients often give a medical history that suggests the possibility of a coagulopathy from drugs, with a corresponding risk for prolonged bleeding during and following an invasive procedure. Identification of patients who may be prone to oral bleeding requires specific medical history information and the proper use of laboratory tests. Some NSAIDs are reported to cause prolonged oral bleeding, but scientific evidence is lacking. Likewise, the risk of oral bleeding from anticoagulants such as warfarin is often over stated, and unnecessary adjustment of NSAID or warfarin dosage puts patients at risk for significant morbidity and mortality. Some commonly employed laboratory tests such as the prothrombin time provide helpful information when used in the appropriate setting, but others, such as the bleeding time test, provide little or no predictive value in the determination of patients at risk for oral bleeding. Dental management of patients with potential coagulopathies from medications requires an understanding of basic principles of coagulation. The vast majority of these patients can be managed in the community setting without risk and without alteration of anticoagulant drug regimes.

Utilisation and safety of low molecular weight heparins: prospective observational study in medical inpatients

AIMS

Low molecular weight heparins (LMWHs) are widely used as curative or preventive treatments of thromboembolic diseases. The aim of our study was to: investigate the pattern of prescription of LMWHs in different departments of French teaching hospitals; andestimate the incidence of adverse drug reactions (ADRs) induced by LMWHs and associated risk factors for the occurrence of bleeding events.

METHODS

This prospective study was performed in two teaching hospitals in Toulouse (south-western France) in March 1999 in different medical wards. All patients receiving a prescription for a LMWH were included in the survey. All data were prospectively recorded in each ward.

RESULTS

A total of 334 patients were included. Sex ratio (male/female) was 1.25 and mean age was 72.5 +/- 16.3 years (extremes:18-101). 450 prescriptions for LMWHs were collected (1.34 prescription per patient) and involved mainly enoxaparin (61%), which was more frequently used than tinzaparin in patients over 75 years old (71.7 vs 28.3%; p < 0.0001). Ninety-nine patients received a LMWH for curative treatment (corresponding to 127 prescriptions of which 99 were for enoxaparin and 28 were for tinzaparin [p < 0.0001]). Indications included therapy for deep venous thrombosis, pulmonary embolism, acute coronary syndrome, unstable angina pectoris, non-Q-wave myocardial infarction. Serious renal insufficiency was significantly more frequent in patients from the geriatrics department (p < 0.00001). Enoxaparin was prescribed more frequently in patients with serious or moderate renal insufficiency than tinzaparin (72 vs 61%, p < 0.05). The incidence of LMWHs-induced ADRs was 10.5% occurring in 22 cases during preventive treatment of deep venous thrombosis and in 13 cases during curative therapy. ADRs were classified as 'serious' in 11 cases (31.4%). Reported ADRs were bleeding events (n = 15), thrombocytosis (n = 13), thrombopenia (n = 4) and hepatic cytolysis (n = 1). The mean delay for the occurrence of bleeding effects was 8.0 +/- 9.1 days (range 1-40). Multivariate analysis of the influence of several criteria on the occurrence of haemorrhagic effects showed that the decrease of creatinine clearance (10 ml/min) was associated with an increased haemorrhagic risk (relative risk [RR] = 1.34, 95% CI 1.12-1.65; p < 0.05). Moreover, the risk of adverse bleeding effects increased for patients with a creatinine clearance <20 ml/min (RR = 2.8; 95% CI 1.00-7.8).

CONCLUSION

Our data firstly show a different pattern of LMWHs prescription in different clinical wards. Secondly, the risk of bleeding ADRs in patients treated by LMWHs increases significantly with renal function impairment for the two LMWH preparations studied. More pharmacoepidemiological studies are necessary in patients with several risk factors, particularly in elderly people who often have renal impairment, in order to determine the optimal pattern use of each LMWH.

Arterial thromboembolism in pregnancy

Arterial occlusion resulting from primary thrombus formation in an artery or due to embolization from a site elsewhere in the circulation is uncommon in women of childbearing age. Myocardial infarction, stroke and peripheral arterial occlusion are rare in pregnant or puerperal women. Although atherosclerosis is the most common cause of arterial thromboembolism in the general population, other mechanisms--for example, prosthetic heart valves and drugs which cause vasospasm--are also important in young and pregnant patients. The clinical sequelae of arterial thromboembolism include sudden death and significant long-term morbidity. The best management must be the recognition of women at risk and, where possible, risk reduction and the introduction of measures to prevent acute events.

Prescribing patterns and outcomes of enoxaparin for anticoagulation of atrial fibrillation

STUDY OBJECTIVE

To determine prescribing patterns and clinical outcomes of enoxaparin for anticoagulation of atrial fibrillation.

DESIGN

Retrospective analysis.

SETTING

A 650-bed, tertiary care, community teaching hospital.

SUBJECTS

Two hundred thirteen patients who received enoxaparin for thromboprophylaxis during an episode of atrial fibrillation. Intervention. Data collection on demographics, antithrombotic usage, and thrombotic and bleeding episodes from January-June 2001.

MEASUREMENTS AND MAIN RESULTS

Patients were characterized as having acute (51.6%) or chronic (48.4%) atrial fibrillation and were categorized according to stroke risk. Three enoxaparin dosing strategies had been prescribed: therapeutic, prophylactic, or adjusted. Prescribed regimens did not reflect stroke risk or type of atrial fibrillation but did reflect the degree of renal impairment. No episodes of stroke occurred with therapeutic enoxaparin dosages, but five strokes occurred among patients receiving prophylactic or adjusted dosages. Bleeding was similar with all dosing strategies in patients with adequate renal function and appeared to be more frequent in those with renal impairment.

CONCLUSION

At a single hospital, wide variation in enoxaparin prescribing patterns existed. Further study is necessary to elucidate more fully the appropriate dosing strategy for this agent in the treatment of atrial fibrillation.

Outpatient management of the chronically anticoagulated patient for elective surgery

With the appropriate use of preadmission clinics, "hospital in the home" programs, and alternatives to intravenous heparin, the majority of chronically anticoagulated patients can be managed as outpatients prior to elective surgery. The preoperative management depends on the original indication for long-term anticoagulation, the interval since the last thromboembolic event, and the extent and type of surgery planned. Only patients who are undergoing major surgery, and who have a high risk of recurrent thrombosis or embolism, require preoperative admission to hospital and conversion to an intravenous heparin regimen. Patients undergoing minor surgery may require no change to their oral anticoagulation. The remainder require cessation of oral anticoagulation and alternative thromboprophylaxis preoperatively, which can be achieved on an outpatient basis using low molecular weight heparin. Outpatient anticoagulation management requires a clear protocol that is understood and agreed to by all parties involved in the care of surgical patients perioperatively.

Low-molecular-weight heparin for the treatment of patients with mechanical heart valves

BACKGROUND

The interruption of oral anticoagulant (OAC) administration is sometimes indicated in patients with mechanical heart valves, mainly before noncardiac surgery, non-surgical interventions, and pregnancy. Unfractionated heparin (UH) is currently the substitute for selected patients. Low-molecular-weight heparin (LMWH) offers theoretical advantages over UH, but is not currently considered in clinical guidelines as an alternative to UH in patients with prosthetic valves.

HYPOTHESIS

The aim of the present study was to review the data accumulated so far on the use of LMWH in this patient population and to discuss its applicability in common practice.

METHODS

For this paper, the current medical literature on LMWH in patients with mechanical heart valves was extensively reviewed.

RESULTS

There were eight series and six case reports. None of the studies was randomized, and only one was prospective. Data to establish the thromboembolic risk were incomplete. After excluding case reports, the following groups were constructed: (a) short-term administration, after valve insertion (n = 212); (b) short-term, perioperative (noncardiac)/periprocedural (n = 114); (c) long-term, due to intolerance to OAC (n = 16); (d) long-term, in pregnancy (n = 10). The incidence rate of thromboembolism was 0.9% for all the studies and 0.5, 0, 20, and 0% in groups a, b, c, and d, respectively; for hemorrhage, the overall rate was 3.4% (3.8, 2.6, 10, and 0% for the respective groups).

CONCLUSIONS

In patients with mechanical heart valves, short-term LMWH therapy compares favorably with UH. Data on mid- and long-term LMWH administration in these patients are sparse. Further randomized studies are needed to confirm the safety and precise indications for the use of LMWH in patients with mechanical heart valves.

Clinical experiences with low-molecular weight heparins in pediatric patients

The courses of 79 children (2 weeks to 19 years old) treated with two different low-molecular weight heparins (LMWHs)--nadroparin (n=66) and enoxaparin (n=13)--were retrospectively analysed. In 62 patients, LMWHs were given for short-term prophylaxis (1-2 weeks) during immobilization after surgery or trauma. Thirteen children with thromboembolic events received long-term prophylaxis with LMWHs for 2-18 months--six after thrombolytic therapy and seven after therapy with unfractionated heparin (UFH). Because of thromboembolic events, four patients were initially treated with LMWHs. In all patients with short-term prophylaxis, no thrombosis occurred. After thrombolytic therapy, three children had no reocclusion, two had no thrombus apposition and one had complete recanalization. In the seven patients treated with LMWHs after UFH, four had no reocclusion, two had recanalization and one had reocclusion. In all patients receiving LMWHs for initial treatment of thrombosis, no thrombus apposition, but also no recanalization, occurred. For short-term prophylaxis, nadroparin was used independent of the body weight and without determination of anti-factor Xa (anti-FXa) activity. Long-term prophylaxis was given mainly as doses of 45-100 anti-FXa U/kg resulting in anti-FXa activities between 0.2 and 0.4 U/ml. For treatment of thrombosis, doses of 200-300 anti-FXa U/kg corresponded to 0.5-1.0 anti-FXa U/ml. Side effects--slight gastrointestinal bleeding and temporary reversible hair loss--were seen in two patients. In conclusion, LMWHs proved to be efficacious and safe especially in prophylaxis of thromboembolic events in children.

Cancer, thrombosis, and anticoagulants

Rapid progress has been made recently in our understanding of the pathogenesis of coagulation activation in malignancy and mechanisms by which the coagulation mechanism may control malignant growth. Idiopathic thromboembolic disease may be the sentinel presentation in patients subsequently diagnosed with malignancy. Thrombosis complicating the course of malignancy may be notoriously difficult to treat, but the introduction of the low-molecular-weight heparins has greatly improved management and may obviate the need for invasive approaches, such as the use of inferior vena cava filters, in many cases. Tantalizing clues from clinical trials of anticoagulant therapy in cancer have suggested that components of coagulation pathways may support tumor growth. Many of these can be intercepted using drugs that are well known and non-toxic. The importance of performing high-quality controlled clinical trials that build on past studies and on data from basic research cannot be overemphasized.

Low molecular weight heparin after mechanical heart valve replacement

BACKGROUND

Patients with mechanical heart valves require life-long anticoagulation. We report here the first large and comparative series of consecutive patients anticoagulated with low molecular weight heparin (LMWH) after mechanical heart valve replacement.

METHODS AND RESULTS

In this comparative, nonrandomized study, 208 consecutive patients who underwent a single or double heart valve replacement with mechanical prostheses were anticoagulated subcutaneously with unfractionated heparin (UH) in the first period (n=106) and LMWH in the second phase (n=102) of the study. Baseline characteristics were similar in the 2 groups. The mean durations of UH and LMWH treatments were 13.6+/-0.5 and 14.1+/-0.6 days, respectively (not significant). On the second day of treatment, 87% of patients treated with LMWH had an anti-Xa activity within the range of efficacy (0.5 to 1 IU/mL), but only 9% of UH-treated patients had an activated partial-thromboplastin time value within the therapeutic range (1.5 to 2.5 times control, P<0.0001 between the 2 groups). On the last day of prescription, all LMWH-treated patients had anti-Xa activity above 0.5 IU/mL, but 19% were above 1 IU/mL. In the UH group, 27% of patients had an activated partial-thromboplastin time above 1.5 times control, but 62% were overanticoagulated. Two major bleedings occurred in each group, and one stroke occurred in the UH group.

CONCLUSIONS

In this first comparative study, anticoagulation with LMWHs after mechanical heart valve replacement appears feasible, provides adequate biological anticoagulation, and compares favorably with UH anticoagulation. Randomized studies are now needed to further evaluate this new therapeutic approach.

Pharmacotherapy of atrial fibrillation

Atrial fibrillation (AF) remains a widespread health problem and the drugs available for its treatment suffer from several drawbacks, including potentially lethal proarrhythmia, serious non-cardiac toxicity and limited efficacy. The evidence for efficacy of currently available anti-arrhythmic agents for sinus rhythm restoration and maintenance is reviewed, with emphasis on randomised trials when available. The current approach to thromboembolism prophylaxis in AF is summarised.

Successful anticoagulation with dalteparin in a patient with mechanical heart valves

BACKGROUND

Standard thromboprophylaxis of patients with mechanical heart valves is achieved using warfarin. In certain patients this may be very difficult; thus, alternative pharmacotherapy must be used.

OBJECTIVE

To report a case of a patient who successfully used dalteparin, a low-molecular-weight heparin, for anticoagulation.

CASE SUMMARY

A 58-year-old white woman with mechanical aortic and mitral heart valves initially received warfarin for anticoagulation. Thromboprophylaxis was very challenging. Her international normalized ratios (INRs) were erratic and occasionally responded paradoxically to changes in dose. Finally, she experienced a left hemispheric stroke when her INR was extremely subtherapeutic. Subsequently, despite best efforts, her INR again was subtherapeutic; warfarin was discontinued and dalteparin was initiated with daily self-administered subcutaneous injections of 16 000 units. No complications have arisen since initiation of the new pharmacotherapy approximately 18 months ago.

DISCUSSION

The use of low-molecular-weight heparin for the treatment and prevention of venous thromboembolism is well described. There are few reports of its use for thromboprophylaxis of patients with mechanical heart valves. Our patient has been managed successfully with dalteparin.

CONCLUSIONS

Dalteparin was effectively and safely used for the thromboprophylaxis of a patient with mechanical heart valves whose anticoagulation was previously difficult to manage with warfarin. Dalteparin deserves further study in patients who are unable to tolerate warfarin.

Anticoagulant therapy of pregnant patients with prosthetic heart valves: rationale for a clinical trial of low molecular weight heparin

The management of anticoagulant therapy for the prevention of thromboembolism from prosthetic heart valves in the pregnant patient is far from ideal and deserves more clinical research. Warfarin therapy given alone throughout pregnancy poses high risks to the fetus because it crosses the placental barrier. Heparin alone throughout pregnancy poses high risks to the mother, which might be lessened somewhat by more intensive therapeutic regimens and careful monitoring of the heparin level or anticoagulated state of the blood. Because of the major risk of embryopathy in the fetus during the first trimester and latter half of the third trimester, heparin therapy during those times has been recommended. In the opinion of some experts, high-risk cases may benefit from low-dose aspirin in addition to anticoagulant therapy. The fact that warfarin is contraindicated during pregnancy (according to the pharmaceutical company that markets it) poses some problems for the physician who prescribes it. For the above reason, alternative drugs are worthy of consideration and should be given clinical trials. Low molecular weight heparin has the potential for greatly reducing drug-related risk for the fetus while providing greater safety for the mother.