Unfractionated and low-molecular-weight heparin. Comparisons and current recommendations

Relationship between degree of heparin anticoagulation and clinical outcome in patients receiving potent P2Y12-inhibitors with no planned glycoprotein IIb/IIIa inhibitor during percutaneous coronary intervention in acute myocardial infarction: a VALIDATE-SWEDEHEART substudy

Aims

Heparin is the preferred choice of anticoagulant in percutaneous coronary intervention (PCI) for acute myocardial infarction (MI). An established dosage of heparin has not yet been determined, but treatment may be optimized through monitoring of activated clotting time (ACT). The aim of this study was to determine the relationship between heparin dose or ACT with a composite outcome of death, MI, or bleeding using data from the registry-based, randomized, controlled, and open-label VALIDATE-SWEDEHEART trial, although patients were not randomized to heparin dose in this substudy.

Methods and results

Patients with MI undergoing PCI and receiving treatment with a potent P2Y12-inhibitor and anticoagulation with heparin, without the planned use of glycoprotein IIb/IIIa inhibitor (GPI), were enrolled in this substudy. The primary endpoint was a composite endpoint of death, MI, and bleeding at 30 days. The individual components and stent thrombosis were analysed separately. We divided patients into groups according to the initial dose of unfractionated heparin during PCI (<70 U/kg, 70–100 U/kg, and >100 U/kg) or ACT (ACT <250 s, 250–350 s, and >350 s) as well as investigating them as continuous variables in Cox proportional hazards models using univariable and multivariable analyses. No major differences were noted between heparin stratified in groups (P = 0.22) or heparin as a continuous variable in relation to the primary composite endpoint hazard ratio (HR) 1.0 confidence interval (CI) (0.99–1.01) for heparin dose/kg. No differences were found between ACT stratified in groups (P = 0.453) or ACT in seconds HR 1.0 CI (0.99–1.00) regarding the primary endpoint. The individual components of death, MI, major bleeding, and stent thrombosis were not significantly different across heparin doses or ACT levels either.

Conclusion

We found no association between heparin dose or ACT levels and death, MI bleeding complications, or stent thrombosis. Therefore, there is no strong support for a specific heparin dose or mandatory ACT monitoring in patients treated with potent P2Y12-inhibitors with no planned GPI.

Effect of hirulog-like peptide on middle cerebral artery occlusion-induced brain injury in mice

Hirulog-like peptide (HLP) and low-molecular-weight heparin (LMWH) are thrombin inhibitor peptides. Our previous study demonstrated that HLP could reduce vascular neointimal formation or restenosis in animals undergoing balloon catheter injury in the carotid artery. However, the function of HLP during ischemic stroke is largely unknown. The present study investigated the effect of HLP on brain injury, which was induced by suture of middle cerebral artery occlusion in mice. Mice were divided into four groups, which included a sham group and three treatment groups. Ischemia was induced by transient suture insertion into the middle cerebral artery for 90 min, and mice were either treated with saline, HLP or LMWH. Infarct volume, neurologic deficits and apoptotic factors were measured following 1-14 days of ischemia. We demonstrated that HLP intravenous injection alleviated brain infarct volume and improved neurologic outcomes (p<0.05). HLP decreased levels of protease-activated receptor-1 (PAR-1), caspase-3, malondialdehyde (MDA) and Bcl-2-associated X protein (Bax), increased the activities of catalase and B cell lymphoma-2 (Bcl-2), and improved the ratio of Bcl-2/Bax compared with the control (p<0.05). This study indicates that HLP and LMWH reduced infarct volume and improved neurobehavioral outcomes induced by transient middle cerebral artery occlusion (tMCAO). In addition, HLP had a beneficial effect on the regulation of the thrombin receptor and key apoptosis regulators in the mouse brain. These results suggest that HLP may be a potential alternative therapy for arterial occlusion-induced cerebral ischemia.

Assessment and management of the obese patient

BACKGROUND

The perioperative care of the clinically severe obese patient presents numerous unique challenges. As an increasing number of people in North America fall into the category of the clinically severe obese, the care of these patients will become increasingly more challenging and prevalent. These patients have unique issues with regards to cardiovascular, pulmonary, and thromboembolic complications. In addition, hospital equipment must be able to accommodate the body habitus of this population.

MATERIALS AND METHODS

A Medline search using "perioperative care," "morbid obesity," "thromboembolic complications," "preoperative screening," and "postoperative care" as key words was performed for English-language articles. Further references were obtained through cross-referencing the bibliography cited in each work.

DISCUSSION

The management of the clinically severe obese patient requires meticulous preoperative, perioperative, and postoperative care. Careful preoperative planning is essential before taking the patient to the operating room. To have excellent outcomes, a multidisciplinary approach, including the primary care physician, anesthesiologist, surgeon, nursing staff, and social work, is necessary.

Heparin dose during percutaneous coronary intervention: how low dare we go?

Despite dramatic advances in percutaneous coronary intervention, including coronary stents and potent antiplatelet agents, unfractionated heparin remains the standard procedural anticoagulant. Tradition and habit may have considerable influence over dose selection. A review of the role and dosage of heparin during PCI appears to be overdue

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.

Dalteparin sodium treatment during resuscitation inhibits hemorrhagic shock-induced leukocyte rolling and adhesion in the mesenteric microcirculation

BACKGROUND

Ischemia/reperfusion-induced polymorphonuclear neutrophil leukocyte (PMN) adhesion and extravasation are pivotal for the development of postinjury multiple organ failure. We hypothesized that the deleterious microcirculatory consequences of hemorrhagic shock (HS) could be altered by low-molecular-weight heparin (LMWH) therapy. Our aim was to investigate the effects of dalteparin sodium on leukocyte-endothelial cell interactions when LMWH treatment was initiated before HS or during resuscitation.

METHODS

Anesthetized dogs underwent HS (40 mm Hg mean arterial pressure for 60 minutes) and resuscitation either with shed blood or with lactated Ringer's (LR) solution. LMWH or conventional heparin sodium pretreatment was administered subcutaneously before hemorrhage; or LMWH was given intravenously during resuscitation. Mesenteric postcapillary venules were observed by intravital video microscopy before and after HS, and 60 minutes, 120 minutes, and 180 minutes after resuscitation, and leukocyte rolling and firm adherence were determined.

RESULTS

HS significantly increased PMN rolling and adhesion in the mesenteric microcirculation. LMWH, but not heparin sodium pretreatment, significantly inhibited both primary and secondary interactions. LMWH treatment was also effective when initiated during resuscitation. LMWH exerted the same inhibitory effect regardless of the type of resuscitation.

CONCLUSION

LMWH treatment during resuscitation effectively inhibits PMN rolling and adhesion.

Low molecular weight heparin versus oral anticoagulants in the long-term treatment of deep venous thrombosis

PURPOSE

The purpose of this study was to evaluate whether low molecular weight heparin (LMWH) could be equal or more effective than conventional oral anticoagulants (OAs) in the long-term treatment of deep venous thrombosis (DVT).

METHODS

One hundred fifty-eight patients with symptomatic DVT of the lower limbs confirmed by means of duplex ultrasound scan were randomized to receive 3 to 6 months' treatment with nadroparine calcium or acenocoumarol. Quantitative and qualitative duplex scan scoring systems were used to study the evolution of thrombosis in both groups at 1, 3, 6, and 12 months.

RESULTS

During the 12-month surveillance period, two (2.5%) of the 81 patients who received LMWH and seven (9%) of the 77 patients who received OAs had recurrence of venous thrombosis (not significant). In the LMWH group no cases of major bleeding were found, and four cases (5.2%) occurred in the OA group (not significant). The mortality rate was nine (11.1%) in the LMWH group and 7.8% in the OA group (not significant). The quantitative mean duplex scan score decreased in both groups during the follow-up and had statistical significance after long-term LMWH treatment on iliofemoral DVT (1, 3, 6, and 12 months), femoropopliteal DVT (1-3 months), and infrapopliteal DVT (first month). Duplex scan evaluation showed that the rate of venous recanalization significantly increased in the common femoral vein at 6 and at 12 months and during each point of follow-up in the superficial and popliteal veins in the LMWH group. Reflux was significantly less frequent in communicating veins after LMWH treatment (17.9% vs 32.2% in the OA group). The reflux rates in the superficial (22.4% in the LMWH group, 30.6% in OA group) and deep (13.4% vs 17.7%) venous system showed no significant differences between groups.

CONCLUSIONS

The unmonitored subcutaneous administration of nadroparine in fixed daily doses was more effective than oral acenocoumarol with laboratory control adjustment in achieving recanalization of leg thrombi. With nadroparine, there was less late valvular communicating vein insufficiency, and it was at least as efficacious and safe as oral anticoagulants after long-term administration. These results suggest that LMWHs may therefore represent a real therapeutic advance in the long-term management of DVT.

Oral delivery of new heparin derivatives in rats

PURPOSE

In this study, conjugates of heparin and deoxycholic acid were synthesized in order to enhance the heparin absorption in the GI tract. Oral delivery of heparin is a preferred therapy in the treatment of patients who are at high risk of deep vein thrombosis and pulmonary embolism.

METHODS

Several different kinds of heparin derivatives were synthesized, and their absorption in the GI tract was determined by activated partial thromboplastin time (aPTT) and factor Xa (FXa) assay. Any histological changes caused by heparin derivatives were examined by hematoxylin and eosin (H&E) stain and transmission electron microscopy (TEM).

RESULTS

After administering heparin-DOCA orally, the clotting time in aPTT assay was increased with the increase of the coupled DOCA amount. The maximum clotting time of heparin-DOCA was 136+/-33 sec at 200 mg/kg of oral dose. This value was 7 times higher than the baseline. The absorption of heparin-cholesterol, heparin-palmitic acid, and heparin-lauric acid conjugates in the GI tract was lower than that of heparin-DOCA. Histological examination of the GI tract indicated that heparin derivatives did not cause any damage to the microvilli and the cell layer.

CONCLUSIONS

DOCA coupled with heparin greatly enhanced absorption of heparin in the GI tract, and this enhancing effect was induced without changing the tissue structure of the GI wall.

Dalteparin: an update of its pharmacological properties and clinical efficacy in the prophylaxis and treatment of thromboembolic disease

Dalteparin is a low molecular weight heparin (LMWH) with a mean molecular weight of 5000. Compared with unfractionated heparin (UFH), the drug has markedly improved bioavailability and increased plasma elimination half-life, and exerts a greater inhibitory effect on plasma activity of coagulation factor Xa relative to its effects on other coagulation parameters. Dalteparin also has less lipolytic activity than UFH. Dalteparin 2500U once daily subcutaneously is of similar antithrombotic efficacy to UFH 5000IU twice daily, and 2 studies have shown superiority over UFH 2 or 3 times daily of dalteparin 5000U once daily in patients requiring surgical thromboprophylaxis. After total hip arthroplasty, dalteparin was superior to adjusted-dosage warfarin and was of greater thromboprophylactic efficacy when given for 35 than for 7 days. Intravenous or subcutaneous dalteparin is as effective as intravenous UFH when given once or twice daily in the initial management of established deep vein thrombosis (DVT). The drug is also effective in long term home treatment. Dalteparin has been shown to be effective in combination with aspirin in the management of unstable coronary artery disease (CAD), with composite end-point data from 1 study suggesting benefit for up to 3 months. Current data indicate potential of the drug in the management of acute myocardial infarction (MI). Dalteparin is also of similar efficacy to UFH, with a single bolus dose being sufficient in some patients, in the prevention of clotting in haemodialysis and haemofiltration circuits. Pharmacoeconomic data indicate that overall costs relative to UFH from a hospital perspective can be reduced through the use of dalteparin in patients receiving treatment for venous thromboembolism. Dalteparin has also been shown to be cost effective when used for surgical thromboprophylaxis. Overall, rates of haemorrhagic complications in patients receiving dalteparin are low and are similar to those seen with UFH.

CONCLUSIONS

Dalteparin is effective and well tolerated when given subcutaneously once daily in the prophylaxis and treatment of thromboembolic disease. The simplicity of the administration regimens used and the lack of necessity for laboratory monitoring facilitate home or outpatient treatment and appear to translate into cost advantages from a hospital perspective over UFH or warfarin. Dalteparin also maintains the patency of haemodialysis and haemofiltration circuits, with beneficial effects on blood lipid profiles and the potential for prophylaxis with a single bolus injection in some patients. Data are also accumulating to show dalteparin to be an effective and easily administered alternative to UFH in patients with CAD.

New-generation anticoagulants: the low molecular weight heparins

Heparin has been the mainstay of acute anticoagulation therapy for decades. Within the past 20 years, several different heparin fractions-collectively known as low molecular weight heparins (LMWHs)-have been evaluated in various medical and surgical settings in which anticoagulation is routinely warranted. The LMWHs are efficacious, safe, cost-effective, and easier to administer and monitor than standard, unfractionated heparin. As LMWH use becomes more widespread, emergency physicians will use these new agents instead of unfractionated heparin for unstable angina, non-Q-wave myocardial infarction, or thromboembolic disease. This review focuses on the pharmacologic properties of unfractionated heparin and LMWH, associated complications, and the use of these agents in acute ischemic coronary syndromes, thromboembolic disease, and other selected clinical situations.

Coronary heart disease. Stable and unstable syndromes

CHD in the elderly population will continue to be a source of major concern because of the increasing costs entailed and uncertainties about how the widespread array of diagnostic and therapeutic interventions, often expensive and sometimes hazardous, should be applied. Financial, political, and health policy decisions will continue to occupy much attention, but it is likely that philosophic considerations about aging and death, both from the individual and the societal perspective, will be of paramount importance of deciding how the substantial resources available to the elderly will be used. Randomized, controlled trials are unlikely to play a major role in resolution of management dilemmas in the elderly because of the extraordinary heterogeneity in this population. Registries (databases) involving carefully prospectively collected key variables are likely to be a more effective approach. Critical characterization of complications of procedures, adverse drug reactions, and collection of follow-up data on functional status are among the critical questions, and these can be answered by registry studies. Algorithms and clinical rules developed in younger cohorts are not directly transferable to the elderly cardiovascular patients, further emphasizing the need for prospectively collected, syndrome-specific data. Treatments convincingly demonstrated to reduce mortality in absolute terms more in the elderly than in the young are underused. The heterogeneity of aging emphasizes the wide variability in patients' ability to withstand the stress of procedures and complications of disease and makes clear the need to consider physiologic reserve and biologic age rather than chronology. With better characterization of biologic age and physiologic reserve, more precise estimates of outcomes of therapies and interventions can be made, and patients can be given better information and with their families have more realistic expectations. Better-informed decisions will result. Biologic age will be multifactorial, involving cognitive, emotional, physical, and nutritional attributes as well as specific organ function (lung, kidney, liver) because no single feature can characterize the total elderly patient. The concept of competing risks among the cardiovascular disease being treated, comorbidity, risks of study, and life expectancy will evolve because even the most successful therapy will have limited effect on longevity in the very old. Although important research at the cellular and molecular level will characterize and provide better understanding of the aging process, it is not likely that this basic information will be immediately useful in the management of the large number of elderly patients with major cardiovascular disease. Preventive measures, including physical exercise, mental stimulation, avoidance of depression, good nutrition, and abstinence from tobacco use, are useful approaches to postpone or ameliorate the consequences of aging and allow patients to tolerate cardiovascular diseases better when they become manifest.

Low-molecular-weight heparins

Low-molecular-weight heparins (LMWH) are a new group of parenteral anticoagulants. They represent a major clinical advance in anticoagulation since the identification of unfractionated heparin (UFH) in 1922 and the introduction of the synthetic coumarin derivative, warfarin, in 1948. Their predictable pharmacokinetics, increased bioavailability, and longer plasma half-life allow for once- or twice-daily dosing and eliminate the need for routine laboratory monitoring. This simplified administration stands to alter the clinical practice of anticoagulation. This review high-lights recent clinical trials and focuses on studies comparing LMWH with the other two major anticoagulants: UFH and coumadin.