The clinical challenge of bridging anticoagulation with low-molecular-weight heparin in patients with mechanical prosthetic heart valves: an evidence-based comparative review focusing on anticoagulation options in pregnant and nonpregnant patients

Biomaterials-Enabled Antithrombotics: Recent Advances and Emerging Strategies

Antithrombotic and thrombolytic therapies are used to prevent, treat, and remove blood clots in various clinical settings, from emergent to prophylactic. While ubiquitous in their healthcare application, short half-lives, off-target effects, overdosing complications, and patient compliance continue to be major liabilities to the utility of these agents. Biomaterials-enabled strategies have the potential to comprehensively address these limitations by creating technologies that are more precise, durable, and safe in their antithrombotic action. In this review, we discuss the state of the art in anticoagulant and thrombolytic biomaterials, covering the nano to macro length scales. We emphasize current methods of formulation, discuss how material properties affect controlled release kinetics, and summarize modern mechanisms of clot-specific drug targeting. The preclinical efficacy of these technologies in an array of cardiovascular applications, including stroke, pulmonary embolism, myocardial infarction, and blood contacting devices, is summarized and performance contrasted. While significant advances have already been made, ongoing development efforts look to deliver bioresponsive "smart" biomaterials that will open new precision medicine opportunities in cardiology.

Mechanical Mitral Valve Thrombosis Secondary to Tinzaparin as an Anticoagulation Bridging Strategy

For patients with mechanical heart valves, oral vitamin K antagonists effectively reduce the risk of valve thrombosis. Bridging strategies that use intravenous unfractionated heparin or subcutaneous low molecular weight heparin (LMWH) are required when reversal of anticoagulation is needed for invasive procedures or bleeding complications. There is limited data comparing anticoagulation efficacy between subtypes of LMWH and dosing regimens in this context. This report describes the case of a 45-year-old man with acute mechanical mitral valve thrombosis and suggests that the use of once daily dosing of subcutaneous tinzaparin may be an inappropriate anticoagulation bridging strategy.

Transanal hemorrhoidal dearterialization (THD): a safe procedure for the anticoagulated patient?

Background

Approximately one in five persons living in the USA is maintained on oral anticoagulation. It has typically been recommended that anticoagulation be withheld prior to hemorrhoidal procedures. Transanal hemorrhoidal dearterialization (THD) is a minimally invasive treatment for symptomatic hemorrhoids, and outcomes with patients on anticoagulation who have undergone this procedure have not been previously reported. Here, we report our preliminary results of patients who underwent THD while on anticoagulation.

Methods

During a 53-month period (February 2009–July 2015), patients with symptomatic hemorrhoids refractory to medical management who underwent surgical treatment with THD were retrospectively reviewed. The subset of patients who underwent THD while anticoagulated was compared to a cohort of patient who were not taking anticoagulation and who otherwise demonstrated normal coagulation profiles and who did not have a known predisposition to bleeding or inherited coagulopathy. The primary study endpoint was to assess postoperative bleeding in patients who were maintained on anticoagulation before and after surgery.

Results

During the 53-month study period, 106 patients underwent the THD procedure for symptomatic hemorrhoids. Of these, seventy patients underwent THD without anticoagulation therapy, while 36 patients underwent THD while taking one or more oral anticoagulants. The postoperative morbidity between the two cohorts was similar, and specifically there was no statistical difference in the rate of postoperative hemorrhage (19.4 vs. 15.7 %; odds ratio 1.295, 95 % CI 0.455–3.688, p = 0.785). No patient, in either cohort, required re-intervention for any reason during the study period. Patients who underwent THD while on anticoagulation were less likely to have recurrent hemorrhoidal disease during the study’s 6-month median follow-up period (2.8 vs. 7.1 %, p = 0.049).

Conclusions

These preliminary data reveal that THD can be performed on anticoagulated patients without cessation of oral agents without increasing morbidity from postoperative bleeding.

Endoscopy in patients on antiplatelet or anticoagulant therapy, including direct oral anticoagulants: British Society of Gastroenterology (BSG) and European Society of Gastrointestinal Endoscopy (ESGE) guidelines

The risk of endoscopy in patients on antithrombotics depends on the risks of procedural haemorrhage versus thrombosis due to discontinuation of therapy. P2Y12 RECEPTOR ANTAGONISTS CLOPIDOGREL, PRASUGREL, TICAGRELOR: For low-risk endoscopic procedures we recommend continuing P2Y12 receptor antagonists as single or dual antiplatelet therapy (low quality evidence, strong recommendation); For high-risk endoscopic procedures in patients at low thrombotic risk, we recommend discontinuing P2Y12 receptor antagonists five days before the procedure (moderate quality evidence, strong recommendation). In patients on dual antiplatelet therapy, we suggest continuing aspirin (low quality evidence, weak recommendation). For high-risk endoscopic procedures in patients at high thrombotic risk, we recommend continuing aspirin and liaising with a cardiologist about the risk/benefit of discontinuation of P2Y12 receptor antagonists (high quality evidence, strong recommendation).

WARFARIN

The advice for warfarin is fundamentally unchanged from British Society of Gastroenterology (BSG) 2008 guidance.

DIRECT ORAL ANTICOAGULANTS DOAC

For low-risk endoscopic procedures we suggest omitting the morning dose of DOAC on the day of the procedure (very low quality evidence, weak recommendation); For high-risk endoscopic procedures, we recommend that the last dose of DOAC be taken ≥48 h before the procedure (very low quality evidence, strong recommendation). For patients on dabigatran with CrCl (or estimated glomerular filtration rate, eGFR) of 30-50 mL/min we recommend that the last dose of DOAC be taken 72 h before the procedure (very low quality evidence, strong recommendation). In any patient with rapidly deteriorating renal function a haematologist should be consulted (low quality evidence, strong recommendation).

Efficacy and safety of low molecular weight heparin in patients with mechanical heart valves: systematic review and meta-analysis

BACKGROUND

Low molecular weight heparins (LMWHs) are not approved for patients with mechanical heart valves (MHVs). However, in several guidelines, temporary LMWH off-label use in this clinical setting is considered to be a valid treatment option. Therefore, we reviewed the efficacy and safety of LMWHs in patients with MHVs.

METHODS

MEDLINE and CENTRAL databases were searched from inception to June 2013. Review articles and references were also searched. We included experimental and observational studies that compared LMWHs with unfractionated heparin (UFH) or vitamin K antagonists (VKAs). Data were analyzed and pooled to estimate odds ratios (ORs) with 95% confidence intervals (CIs) for thromboembolic and major bleeding events. Statistical heterogeneity was evaluated with the I(2) -test.

RESULTS

Nine studies were included: one randomized controlled trial (RCT) and eight observational studies, with a total of 1042 patients. No differences were found between LMWHs and UFH/VKAs in the risk of thromboembolic events (OR 0.67; 95% CI 0.27-1.68; I(2) = 9%) or major bleeding events (OR 0.66; 95% CI 0.36-1.19; I(2) = 0%).

CONCLUSIONS

The best evidence available might support the temporary use of LMWHs as a prophylactic treatment option in patients with MHVs. However, conclusions are mostly based on observational data (with large CIs), and an adequately powered RCT is urgently needed in this clinical setting.

Update on perioperative bridging in patients on chronic oral anticoagulation

Oral anticoagulation (OAC) with vitamin K antagonists is commonly used for long-term prevention or treatment of arterial or venous thromboembolism. In the USA alone, approximately 250,000 patients will require temporary interruption of OAC annually. Managing anticoagulation in those patients on chronic OAC who require invasive procedures continues to be a major clinical dilemma. This article summarizes the existing evidence in light of the recommendations of the American College of Chest Physicians. Management of anticoagulation in the perioperative period will continue to be an important clinical challenge and an evolving area of research. If new oral anticoagulants are successful in replacing warfarin, the entire perioperative anticoagulation scene will change.

Chronically anticoagulated patients who need surgery: can low-molecular-weight heparins really be used to "bridge" patients instead of intravenous unfractionated heparin?

Patients at high risk of arterial or venous thromboembolic events often receive chronic treatment with long-term oral anticoagulants such as warfarin. However, if these patients require an invasive procedure, they may require a temporary interruption of their warfarin therapy to minimize their bleeding risk during the procedure. As warfarin has a long half-life and an unpredictable pharmacokinetic profile, short-acting parenteral anticoagulants, such as unfractionated heparin (UFH) and low-molecular-weight heparin (LMWH), may be of benefit in protecting the patient from thromboemboli while their warfarin dose is withheld. Such "bridging therapy" has traditionally been provided in-hospital with intravenous UFH; however, recent data have suggested that LMWH may be an effective alternative, with potential cost-savings due to the ability to provide bridging therapy in the outpatient setting.

Standardized low-molecular-weight heparin bridging regimen in outpatients on oral anticoagulants undergoing invasive procedure or surgery: an inception cohort management study

BACKGROUND

Bridging therapy with low-molecular-weight heparin is usually recommended in patients who must stop oral anticoagulants before surgical or invasive procedures. To date, there is no universally accepted bridging regimen tailored to the patient's thromboembolic risk. This prospective inception cohort management study was designed to assess the efficacy and safety of an individualized bridging protocol applied to outpatients.

METHODS AND RESULTS

Oral anticoagulants were stopped 5 days before the procedure. Low-molecular-weight heparin was started 3 to 4 days before surgery and continued for 6 days after surgery at 70 anti-factor Xa U/kg twice daily in high-thromboembolic-risk patients and prophylactic once-daily doses in moderate- to low-risk patients. Oral anticoagulation was resumed the day after the procedure with a boost dose of 50% for 2 days and maintenance doses afterward. The patients were followed up for 30 days. Of the 1262 patients included in the study (only 15% had mechanical valves), 295 (23.4%) were high-thromboembolic-risk patients and 967 (76.6%) were moderate- to low-risk patients. In the intention-to-treat analysis, there were 5 thromboembolic events (0.4%; 95% confidence interval, 0.1 to 0.9), all in high-thromboembolic-risk patients. There were 15 major (1.2%; 95% confidence interval, 0.7 to 2.0) and 53 minor (4.2%; 95% confidence interval, 3.2 to 5.5) bleeding episodes. Major bleeding was associated with twice-daily low-molecular-weight heparin administration (high-risk patients) but not with the bleeding risk of the procedure.

CONCLUSIONS

This management bridging protocol, tailored to patients' thromboembolic risk, appears to be feasible, effective, and safe for many patients, but safety in patients with mechanical prosthetic valves has not been conclusively established.

Management of pregnant women with cardiac diseases at potential risk of thromboembolism--experience and review

Over a 7-year period, the chart records of six pregnant women with cardiac diseases at potential risk of thromboembolism were reviewed. All six patients survived and recovered well eventually. LMWH and beta-adrenergic blocker were effective to deal with atrial fibrillation. Digitalis and dobutamine were beneficial to prevent heart failure resulted from degenerated porcine valve and dilated cardiomyopathy. In a patient with mechanical mitral valve, low-dose warfarin did not cause fetal malformation, and was effective to prevent thrombus formation. Protamine sulfate was safely administered to neutralize intravenous heparin effect before vaginal delivery. Life-threatening postpartum pulmonary hemorrhage occurred as a result of pulmonary hypertension with an aberrant right pulmonary artery, absolutely necessitating a long-term cardiopulmonary bypass resuscitation. Patient with primary pulmonary hypertension gave birth safely with forceps assistance under epidural anesthesia. From literatures reviewed and successful experiences presented here, prenatal correction of the underlying cardiac malformation, precise switch of anticoagulant administration, optimizing cardiac function, early delivery prior to heart failure, postpartum fluid restriction, minimized peripartum blood loss, and meticulously intensive cares are essential to achieve satisfactory outcomes.

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.

Management of pregnancy in women with palliated and unpalliated congenital heart defects

Medical advancements have made it possible for more women with congenital heart defects (CHDs) to carry successful pregnancies. Most CHD surgeries or interventions are palliative with persistent residua and sequelae exacerbated by the physiologic stresses of pregnancy. Preconception assessment, a tailored multidisciplinary approach during pregnancy, and a planned, elective delivery followed by careful postpartum monitoring may improve outcomes. Teratogenic medications should be stopped and changed to safer alternatives. Major hemodynamic changes in pregnancy, labor, and delivery may aggravate the underlying cardiovascular defects. Interventions or surgeries, when anticipated, should be performed before pregnancy. Antibiotic prophylaxis is indicated for nearly all palliated and unpalliated defects.

Prosthetic Heart Valves and Arrhythmias in Pregnancy

The majority of women with bioprosthetic valves do not require anticoagulation during pregnancy. In women with mechanical valves, a detailed discussion of the advantages and disadvantages of the three anticoagulant options (warfarin, unfractionated heparin and low molecular weight heparin) is indicated. The majority of women with arrhythmias during pregnancy have a benign increased rate of atrial or ventricular premature beats. Those women who are hemodynamically stable can be reassured and do not usually require treatment. Women with more ominous arrhythmias should be managed in collaboration with a cardiologist, usually using the same agents that would be chosen in the non-pregnant patient, including electrical cardioversion when necessary. This is the fifth and final article in a series reviewing in detail the assessment and management of specific cardiac disorders in pregnancy.

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.

Low-molecular-weight heparin as bridging therapy during interruption of oral anticoagulation in patients undergoing colonoscopy or gastroscopy

Nowadays, most patients under oral anticoagulant therapy (OAT) require invasive procedures such as colonoscopy (CC) or gastroscopy (GC). The goals of the management of OAT are to minimise the risk of thromboembolism and bleeding. We have performed the first prospective, observational study to evaluate these parameters using fixed-dose high-risk thromboprophylactic therapy with sodic bemiparin (Hibor) as bridging therapy. From January 2004 to January 2005, patients under OAT were included. Periprocedure prophylaxis consisted of: Acenocumarol patients: Day -3: withdrawal acenocumarol. Days -2,-1,0: Hibor 3500 UI/d sc and days +1,+2,+3: Hibor 3500 U/I + acenocumarol. And day +5: acenocumarol only. Warfarin patients: Days -5,-4: withdrawal warfarin, -3,-2,-1, 0; Hibor 3500 UI/day sc, days +1,+2,+3,+4: Hibor 3500 UI/day sc and warfarin and day +5; warfarin only. Thromboembolic complications and bleeding were recorded in a 3 month follow-up. We included 100 consecutive patients in the intention-to-treat group. The remaining 98 patients were 50 women and 48 men. Mean age of women was 71.1 (range: 46-87) years and 70.7 (range: 39-86) years in men. Eighty-three took acenocumarol, and 15 warfarin. Thirty-two gastroscopies and 61 colonoscopies were performed and in five patients both were performed. No thromboembolic and bleeding complications related to bemiparin were observed in the 103 endoscopies. Two patients developed pruritus at the punction site. Fixed-dose high-risk thromboprophilactic therapy with bemiparin (Hibor) is safe and effective as a bridging therapy in patients under OAT who require GC or CC.

[Pregnancy and heart disease]

Pregnancy and delivery are associated with substantial physiological changes that require adaptations in the cardiovascular system. These changes, well-tolerated in pregnant women without heart disease, expose woman with cardiovascular disease to serious risk. In fact, heart disease is the most frequent cause of maternal death, after psychiatric disorders, and the number of pregnant women with heart disease is expected to grow in the coming years. Preventing cardiovascular complications should be the main aim of every cardiologist involved in managing pregnant woman with congenital or acquired heart disease. Unfortunately, there is a lack of data which would help in the management of these patients during pregnancy and the clinical practice guidelines are often based on assumptions regarding how a specific substrate is going to respond to the physiological changes occurring due to pregnancy.

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.

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.

Valvular heart disease in pregnancy

Women with valvular disease who are pregnant or planning to conceive require careful evaluation and management. Pregnancy is associated with normal physiologic changes that can aggravate many valvular conditions and may require the initiation or increase of cardiovascular medications to manage fluid overload or arrhythmias. Most women will tolerate pregnancy and delivery without major complication, though some types of valvular heart disease are poorly tolerated and require more intensive management, or even termination of the pregnancy. In addition, patients at risk of thromboembolism and those who have prosthetic cardiac valves require anticoagulation. The decision regarding the choice and intensity of anticoagulation requires careful balance between the individual risks of thrombosis and bleeding in the mother and harm to the fetus.

Optimal antithrombotic treatment in patients with an indication for long-term anticoagulation undergoing coronary artery stenting

Dual antiplatelet treatment with aspirin and either ticlopidine or clopidogrel is recommended after percutaneous coronary intervention with stent implantation (PCI-S). However, in patients with an indication for oral anticoagulation (OAC) undergoing PCI-S with an indication for long-term OAC – because of atrial fibrillation, mechanical heart valve or previous thromboembolism – the optimal antithrombotic treatment is unknown. The limited evidence available shows substantial variability in the management of these patients, for whom the adopted strategies include substitution of OAC for dual antiplatelet therapy, addition of a single antiplatelet agent to OAC and institution of triple therapy with OAC, aspirin and a thienopyridine. Both the efficacy and safety of the various regimens appear suboptimal, with a 30-day occurrence of thrombotic and major bleeding complications of 4 and 3–7%, respectively. Large-scale registries and clinical trials are warranted to determine the optimal antithrombotic treatment in these patients whose number is likely to progressively increase over the coming years. In the meantime, periprocedural, medium-

and long-term antithrombotic treatment should be based on accurate risk stratification of thrombo(embolic) complications.