Relation of factor V Leiden genotype to risk for acute deep venous thrombosis after joint replacement surgery

Total shoulder arthroplasty in patients with factor V Leiden

BACKGROUND

Anatomic and reverse total shoulder arthroplasty (TSA) are effective treatment options for end-stage glenohumeral osteoarthritis. However, consideration for pre-existing conditions must be taken into account. Factor V Leiden (FVL), the most common inherited thrombophilia, is one such condition that predisposes to a prothrombotic state and may affect perioperative and longer-term outcomes following TSA.

METHODS

Adult patients undergoing primary TSA for osteoarthritis indication were identified in the 2010 through October 2021 PearlDiver M157 database. Patients with or without FVL were matched at a 1:4 ratio based on age, sex, and Elixhauser Comorbidity Index. Ninety-day adverse events and 5-year revision rates were assessed and compared with multivariable logistic regression and rank-log tests, respectively. Finally, the relative use and bleeding/clotting outcomes were assessed based on venous thromboembolic (VTE) prophylactic agents used, with categories defined as (1) warfarin, heparin, or direct oral anticoagulant (DOAC) or (2) aspirin/no prescription found.

RESULTS

Of 104,258 TSA patients, FVL was identified for 283 (0.27%). Based on matching, 1081 patients without FVL and 272 patients with FVL were selected. Multivariable analyses demonstrated that those with FVL displayed independently greater odds ratios (ORs) of deep vein thrombosis (DVT, OR = 9.50, P < .0001), pulmonary embolism (PE, OR = 10.10, P < .0001), and pneumonia (OR = 2.43, P = .0019). Further, these events contributed to the increased odds of aggregated minor (OR = 1.95, P = .0001), serious (OR = 6.38, P < .0001), and all (OR = 3.51, P < .0001) adverse events. All other individual 90-day adverse events, as well as 5-year revision rates, were not different between the study groups. When compared to matched patients without FVL on the same anticoagulant agents, FVL patients on warfarin, heparin, or DOAC agents demonstrated lesser odds of 90-day DVT and PE (OR = 4.25, P < .0001, and OR = 2.54, P = .0065) than those on aspirin/no prescription found (OR = 7.64 and OR = 21.95, P < .0001 for both). Interestingly, those on VTE prophylactic agents were not at greater odds of bleeding complications (hematoma or transfusion).

DISCUSSION AND CONCLUSIONS

TSA patients with FVL present a difficult challenge to shoulder reconstruction surgeons. The current study highlights the strong risk of VTE that was reduced but still significantly elevated for those with stronger classes of VTE chemoprophylaxis. Acknowledging this risk is important for surgical planning and patient counseling, but also noted was the reassurance of similar 5-year revision rates for those with vs. without FVL.

Complications of Factor V Leiden in Adults Undergoing Noncardiac Surgical Procedures: A Systematic Review

Factor V Leiden is the commonest hereditary prothrombotic allele, affecting 1% to 5% of the world's population. The objective of this study was to characterize the perioperative and postoperative outcomes of patients with Factor V Leiden compared to patients without a diagnosis of hereditary thrombophilia. This was a focused systematic review of studies including adult (>18 years) patients with Factor V Leiden (heterozygous or homozygous) undergoing noncardiac surgery. Included studies were either randomized controlled trials or observational. The primary clinical outcomes of interest were thromboembolic events occurring from the perioperative period up to 1 year postoperatively, defined as deep venous thrombosis, pulmonary embolism, or other clinically significant thrombosis occurring during or after a surgical procedure. Secondary outcomes included cerebrovascular events, cardiac events, death, transplant-related outcomes, and surgery-specific morbidity. Pediatric and obstetrical patients were excluded, as were case reports and case series. Databases searched included MEDLINE and EMBASE from inception until August 2021. Study bias was assessed through the CLARITY (Collaboration of McMaster University researchers) Risk of Bias tools, and heterogeneity through analysis of study design and end points, as well as the I 2 statistic with its confidence interval and the Q statistic. A total of 5275 potentially relevant studies were identified, with 115 having full text assessed for eligibility and 32 included in the systematic review. On the whole, the literature suggests that patients with Factor V Leiden have an increased risk of perioperative and postoperative thromboembolic events compared to patients without the diagnosis. Increased risk was also seen in relation to surgery-specific morbidity and transplant-related outcomes, particularly arterial thrombotic events. The literature did not support an increased risk for mortality, cerebrovascular, or cardiac complications. Limitations of the data include predisposition toward bias due in many study designs and small sample sizes across the majority of published studies. Variable outcome definitions and durations of patient follow-up across different surgical procedures resulted in high study heterogeneity precluding the effective use of meta-analysis. Factor V Leiden status may confer additional risk for surgery-related adverse outcomes. Large, adequately powered studies are required to accurately estimate the degree of this risk by zygosity.

Tranexamic acid is safe and effective in patients with heterozygous factor V Leiden mutation during total joint arthroplasty

INTRODUCTION

Patients with an inherent hypercoagulable state are at a higher risk of venous thromboembolism (VTE) following total joint arthroplasty (TJA). Further administration of tranexamic acid (TXA) during TJA may increase the risk of VTE in these high-risk patients. There is no study that specifically analyzes the safety and efficacy of TXA during TJA in patients with factor V Leiden (FVL) mutation; therefore, the purpose of this study was to evaluate the safety and efficacy of TXA use on the risk of VTE and bleeding in patients carrying FVL mutation.

MATERIALS AND METHODS

A total of 42 patients with FVL mutation (22 hips, 20 knees) and 40 control patients (20 hips, 20 knees) who underwent TJA were retrospectively reviewed. All patients received 1 g TXA intravenously 15 min before the skin incision and 2 g of TXA was administered locally at the surgical site as a periarticular injection. Pharmacological thromboprophylaxis (low-molecular-weight heparin) was administered to all patients. Estimated blood loss and in-hospital thromboembolic complications were compared between the groups.

RESULTS

In both total knee arthroplasty (TKA) and total hip arthroplasty (THA) patients, there was no significant difference in the amount of estimated blood loss among the groups (p = 0.980, and p = 0963, respectively). None of the patients in the THA group received a blood transfusion. The transfusion rate was similar in the TKA group (p = 0.756, one patient in each group). No VTE, myocardial infarction, or any other complications related to TXA use were observed in any of the patients.

CONCLUSIONS

The combined local and systemic administration of TXA could be safely used in patients with heterozygous FVL mutation receiving pharmacological thromboprophylaxis during TJA without increasing the risk of VTE.

Integrative analyses of genes about venous thromboembolism: An umbrella review of systematic reviews and meta-analyses

BACKGROUND

In recent years, many studies have found possible links between gene polymorphisms and venous thromboembolism (VTE). By identifying genetic risk factors before facing environmental risk factors such as surgical interventions and COVID-19 vaccination, we could rapidly respond to the risk of VTE. The aim of this study was to perform an umbrella review of genetic variants related to VTE. Integrative gene analysis of VTE was performed to identify critical genetic variations.

METHODS

This study conducted an umbrella review of systematic reviews and meta-analyses. All included studies were selected from the PubMed/MEDLINE database. To select eligible studies, the following variables were extracted: first author name; effect size of each study genetic variant; year of publication; the number of studies included in each article; ethnicity, sample size, P values, and heterogeneity estimates. To assess cumulative evidence in genetic epidemiology about effects of gene polymorphisms on VTE, Human Genome Epidemiology Network's Venice criteria were used. Methodological quality assessment was conducted with JBI Critical Appraisal Checklist for Systematic Reviews and Research Syntheses.

RESULTS

Genes provided in the present study with genetic variants associated with VTE were FVL (G1691A), Prothrombin (G20210A), MTHFR (C677T, A1298C), PAI-1 (4G/5G), factor VII activating protease (1601G > A), and endothelial protein C receptor (g.6936A_G, c.4600A_G). Among them, variants in FVL, Prothrombin, MTHFR, and PAI-1 showed high significance. Particularly, variants in Prothrombin (G20210A), MTHFR (C677T), and PAI-1 (4G/5G) had more than 2 types of model significance.

CONCLUSION

The present study performed a systematic review of genetic variants associated with VTE. Our results could lead to a more comprehensive understanding of VTE etiology. These results could give a strategy of prediagnosis about evaluating individual risks of VTE who might be exposed to environmental risk factors.

Maxillofacial and oral surgery in patients with thrombophilia: safe territory for the oral surgeon? A single-center retrospective study

OBJECTIVE

The aim of this study was to analyze patients with thrombophilia who underwent oral and/or maxillofacial surgery at our center.

STUDY DESIGN

We performed a retrospective analysis of patients with hereditary or acquired thrombophilia who had undergone oral/maxillofacial surgery between January 1, 2000 and December 31, 2019. Data regarding demographic and patient characteristics, surgical treatment modalities, antithrombotic therapies, and complications were analyzed.

RESULTS

A total of 76 eligible patients (26 male, 50 female) were included in this study, with a mean follow-up period of 3.8 months (range, 0-51 months). The mean age at time of surgery was 44.7 ± 19.4 years. Seven different hereditary and acquired thrombophilia were identified: factor V Leiden (n = 31; 40.8%), prothrombin G20210A mutation (n = 5; 6.6%), protein C deficiency (n = 4; 5.3%), protein S deficiency (n = 11; 14.5%), antiphospholipid syndrome (n = 10; 13.2%), hyperhomocysteinemia (n = 8; 10.5%), and elevated factor VIII (n = 2; 2.6%). Complications occurred in 9 patients (11.8%) and included postoperative infections (n = 6; 7.9%) and postoperative bleeding (n = 3; 3.9%).

CONCLUSION

Our data suggest that oral and/or maxillofacial surgery in patients with a confirmed diagnosis of thrombophilia is not associated with a burden of thrombosis or high complication rates. Furthermore, we formulated a guideline for preoperative antithrombotic therapy for patients with thrombophilia undergoing oral and/or maxillofacial surgery.

Patients Undergoing Primary Total Joint Arthroplasty with Primary Hypercoagulable States

Objective

To analyze perioperative complications, resource consumption, and inpatient mortality of patients who receive total joint arthroplasty (TJA) with a concomitant diagnosis of a primary hypercoagulable state (PHS). The following questions were posed in the present paper. First, do patients undergoing TJA with PHS have increased risk of deep venous thrombosis (DVT), pulmonary embolism (PE), and periprosthetic joint infection (PJI)? Second, what other in‐hospital complications are more likely among PHS patients undergoing TJA? Third, do TJA patients with PHS usually consume greater in‐hospital resources? Fourth, do PHS patients suffer higher mortality rates compared to non‐PHS patients? Finally, have PHS patients received proper anticoagulant management in past arthroplasties?

Methods

The National Inpatient Sample (NIS) database for the years between 2003 and 2014 was searched to identify patients undergoing primary TJA. Patients with PHS were identified with the ICD‐9‐CM code 289.81. The χ²‐test, the Pearson test, and adjusted multivariate regression analysis were performed to evaluate the difference and odds ratios between the positive and negative diagnosis groups.

Results

From 2003 to 2014, a total of 2,044,356 patients were identified in the NIS as undergoing primary total hip arthroplasty (THA) or total knee arthroplasty (TKA) in the United States. A total of 4664 patients (0.2%) were identified as having PHS. Compared with the non‐PHS group, TJA patients with PHS had a higher risk of DVT (THA: odds ratio [OR] = 8.343, 95% CI: 5.362–12.982, P < 0.001; TKA: OR = 4.712, 95% CI: 3.560–6.238, P < 0.001) but did not have increased risk of PE (THA: OR = 1.306, 95% CI: 0.48–3.555, P = 0.602; TKA: OR = 1.143, 95% CI: 0.687–1.903), and only PHS patients in the THA group had higher risks of inpatient mortality (OR = 3.184, 95% CI: 1.348–7.522, P = 0.008) and periprosthetic joint infection (OR = 3.343, 95% CI: 1.084–10.879, P = 0.036). In addition, PHS patients had extended length of stay, higher total costs, and increased risks of certain other complications, such as peripheral vascular disease, hemorrhage, and thrombophlebitis.

Conclusion

In the present study, PHS patients had higher risks of DVT, greater in‐hospital resource consumption, and certain other perioperative complications. However, PHS was not associated with increased risk of PE in TJA patients in the United States between 2003 and 2014. While potential hazards of PHS have already been recognized, the present study revealed additional concerns and demonstrated that further improvements in the perioperative management of patients with hereditary hypercoagulable disorders are essential.

Pharmacogenetics to prevent heparin-induced thrombocytopenia: what do we know?

Heparin-induced thrombocytopenia (HIT) is a life-threatening, immune-mediated adverse reaction to heparin anticoagulants. The inability to predict HIT represents a considerable liability associated with heparin administration. Genetic studies of HIT are challenging due to the scarcity of true HIT cases, potential for misclassification, and many environmental risk factors. Genetic studies have not consistently identified risk alleles for HIT, the production of platelet factor 4/heparin antibodies or the thromboembolic complications of HIT. Genes implicated in HIT and platelet factor 4/heparin antibody levels include FCGR2A, TDAG8, HLA-DR and others. Compelling evidence also suggests that the FCGR2A H131R polymorphism is associated with HIT-related thrombosis. There is a need for well-powered, multiethnic studies with laboratory confirmation of HIT, detailed patient- and drug-specific data, and inclusion of both serologic and thromboembolic outcomes. Genomic biomarkers identified from such studies offer the possibility of shifting current clinical practice paradigms from early detection and treatment to prevention.

Postoperative Joint Replacement Complications in Swedish Patients With a Family History of Venous Thromboembolism

IMPORTANCE

The associations of a family history of venous thromboembolism (FH-VTE) with postoperative venous thromboembolism (VTE) and major bleeding after joint replacement surgical procedures are unknown.

OBJECTIVE

To determine the risk of VTE and major bleeding in patients after primary hip or knee replacement surgical procedures.

DESIGN, SETTING, AND PARTICIPANTS

Cohort study using nationwide population-based databases of Swedish patients without a history of VTE who underwent joint replacement surgical procedures. Patients who had primary hip or knee replacement surgical procedures between July 1, 2005, and August 31, 2012, were identified. Patients born after 1931 without previous VTE were identified in the Swedish Multi-Generation Register. Only individuals with at least 1 parent and 1 full sibling alive between 1964 and the date for the surgical procedure were included. The data analysis was performed from September 1, 2017, to June 15, 2018.

EXPOSURES

Family history of VTE in a parent and/or a full sibling before the date of the surgical procedure.

MAIN OUTCOMES AND MEASURES

Venous thromboembolism and major bleeding within 90 days of the surgical procedure.

RESULTS

Of 69 505 study participants, 37 989 (54.7%) were women, and the median (interquartile range) age at the date of discharge was 65 (59-70) years. A total of 803 of 69 505 (1.2%) patients experienced postoperative VTE and 1285 (1.8%) experienced major bleeding. The cumulative VTE risk for those with FH-VTE was 231 of 15 858 (1.5%) and for those without an FH-VTE was 572 of 53 647 (1.1%) (P < .001). The cumulative bleeding risk for those with FH-VTE was 261 of 15 858 (1.6%) and for those without an FH-VTE was 1024 of 53 647 (1.9%) (P = .03). There was an association of patients with an FH-VTE who had increased VTE risk (adjusted hazard ratio [HR], 1.36; 95% CI, 1.17-1.59) and reduced bleeding risk (adjusted HR, 0.84; 95% CI, 0.74-0.97). There was an interaction between time after discharge and FH-VTE regarding VTE and major bleeding. An FH-VTE was not associated with VTE after discharge during the first week (HR, 1.13; 95% CI, 0.86-1.49). After 7 days from discharge, FH-VTE was associated with VTE (HR, 1.49; 95% CI, 1.24-1.79). An FH-VTE reduced major bleeding risk during the first 7 days after discharge (HR, 0.78; 95% CI, 0.66-0.91) but not thereafter (HR, 1.10; 95% CI, 0.84-1.44). Postoperative VTE heritability (SE) was 20% (6%).

CONCLUSIONS AND RELEVANCE

Familial and most likely genetic factors appear to affect VTE and major bleeding risk following hip and knee replacement surgical procedures. Prolonged VTE prophylaxis might be beneficial in predisposed individuals. There may be a possible evolutionary advantage of prothrombotic genes protecting against traumatic bleeding.

Perioperative Management of Factor V Leiden and Pancreatic Adenocarcinoma

Background: Perioperative management of a patient with factor V Leiden has been infrequently reported with most studies focused in the orthopedic literature.

Case Presentation: We report a case of a 74-year-old woman who underwent a pylorus-preserving pancreaticoduodenectomy without immediate perioperative embolic or thrombotic phenomena and her management throughout her hospital course.

Conclusion: To the best of our knowledge, this is the first known report regarding factor V Leiden and surgical management of pancreatic ductal adenocarcinoma.

Who are at risk for thromboembolism after arthroplasty? A systematic review and meta-analysis

BACKGROUND

Thromboembolism, including deep venous thrombosis and pulmonary embolism, is a grave threat to patients undergoing total joint replacement. Using a systematic review and meta-analysis we asked whether gene mutations or polymorphisms could be risk factors for thrombosis after arthroplasty.

METHODS

We performed a comprehensive search of Medline, PubMed, Embase, Cochrane databases, China National Knowledge Infrastructure (CNKI), and Google Scholar, and identified 19 studies detailing genetic investigations of patients with thromboembolism following joint replacement.

RESULTS

Our meta-analyses included 5149 patients who underwent arthroplasty surgery. Significant associations with venous thromboembolism were identified for factor G1691A (odds ratio (OR) 1.41, 95% confidence interval (CI) 1.03 - 1.94, p=0.03), prothrombin G20210A (OR 2.16, 95% CI, 1.27- 3.69, p=0.005), and MTHFR/C677T/TT (OR 2.36, 95% CI 1.03 - 5.42, p=0.04) in Caucasian populations. No significant gene mutation was identified in Asian populations.

CONCLUSION

This study suggests a way to identify patients scheduled for arthroplasty who are at higher risk of thrombosis, enabling individualized treatment.

Factor V Leiden thrombophilia

Factor V Leiden is a genetic disorder characterized by a poor anticoagulant response to activated Protein C and an increased risk for venous thromboembolism. Deep venous thrombosis and pulmonary embolism are the most common manifestations, but thrombosis in unusual locations also occurs. The current evidence suggests that the mutation has at most a modest effect on recurrence risk after initial treatment of a first venous thromboembolism. Factor V Leiden is also associated with a 2- to 3-fold increased relative risk for pregnancy loss and possibly other obstetric complications, although the probability of a successful pregnancy outcome is high. The clinical expression of Factor V Leiden is influenced by the number of Factor V Leiden alleles, coexisting genetic and acquired thrombophilic disorders, and circumstantial risk factors. Diagnosis requires the activated Protein C resistance assay (a coagulation screening test) or DNA analysis of the F5 gene, which encodes the Factor V protein. The first acute thrombosis is treated according to standard guidelines. Decisions regarding the optimal duration of anticoagulation are based on an individualized assessment of the risks for venous thromboembolism recurrence and anticoagulant-related bleeding. In the absence of a history of thrombosis, long-term anticoagulation is not routinely recommended for asymptomatic Factor V Leiden heterozygotes, although prophylactic anticoagulation may be considered in high-risk clinical settings. In the absence of evidence that early diagnosis reduces morbidity or mortality, decisions regarding testing at-risk family members should be made on an individual basis.

Absent inferior vena cava resulting in exercise-induced epidural venous plexus congestion and lower extremity numbness: a case report and review of the literature

STUDY DESIGN

Case report and clinical discussion.

OBJECTIVE

To describe a unique etiology for a patient presenting with exercise-induced lower extremity numbness found to have agenesis of the infrarenal inferior vena cava (IVC) and a large vein draining the confluence of the iliac veins through the L4 foramen into the epidural plexus.

SUMMARY OF BACKGROUND DATA

Epidural venous abnormalities are infrequently determined to be the etiology of nerve root compression syndromes. Such cases have been described in patients with absent IVC with thrombosis. We are unaware of any previously described cases of absent IVC with a primary route of venous return through the epidural venous plexus, resulting in symptoms in the absence of thrombosis.

METHODS

We describe a case of a 34-year-old man who presented complaining of numbness of legs as well as cauda equina symptoms occurring during exercise. He was found to have infrarenal absence of the IVC with the confluence of the iliac veins forming a large draining vein which entered the L4 foramen into the epidural venous plexus. Pre- and postexercise magnetic resonance imaging scans were performed to compare change in the size of the plexus.

RESULTS

Postexercise magnetic resonance imaging showed notable increase in the volume of the epidural venous plexus of the lower lumbar spine. The patient was referred to neurosurgery and vascular surgery, which did not intervene. On follow-up 2 years later, the patient developed significant right deep venous thrombosis and was found to be heterozygous for factor V Leiden mutation.

CONCLUSION

This case demonstrates the breadth of anatomic and physiologic understanding a clinician must draw on when approaching patients with nerve root compression symptoms. It is also pertinent to consider performing a hypercoagulable work-up in patients with vascular deformations, as this may prevent future thrombosis.

Assessment of thrombotic risk factors predisposing to thromboembolic complications in prosthetic orthopedic surgery

BACKGROUND

Congenital thrombophilia is responsible for thromboembolic complications despite prolonged low-molecular-weight heparin (LMWH) prophylaxis following hip and knee endoprosthesis surgery.

METHODS

A series of 86 patients with hip or knee endoprosthesis surgery were assessed 1 year after operation. Antithrombin III, protein C, and protein S were determined, and the activated protein C sensitivity ratio was measured. We screened for the presence of lupus anticoagulant, factor V Leiden mutation, and polymorphism of prothrombin G20210A. The lower limb venous circulation was monitored by color Doppler ultrasonography. Pulmonary embolism (PE) was diagnosed using ventilation and perfusion scintigraphy.

RESULTS

In all, 33 patients had thromboembolic complications, 18 with thrombophilia (7 with combined form). Of the 53 patients without complications 12 had thrombophilia (2 with combined form). The differences were statistically significant. The risk score, the prevalence of FV Leiden and prothrombin G20210A mutations, and lupus anticoagulant were also significantly higher in the symptomatic group. Deep vein thrombosis (DVT) developed preoperatively in 15 patients; DVT and PE in 4 patients; thrombophilia was diagnosed in 53% and 75% of these cases. In all, 17 patients had postoperative thromboembolic complications: DVT developed in nine and PE in one patient (all with thrombophilia); DVT + PE developed in seven patients (all but one had thrombophilia).

CONCLUSIONS

Significant differences were found in the incidence (P < or = 0.01) of thrombophilia and the risk score (P < or = 0.02) between symptomatic and asymptomatic patients. We recommend preoperative thrombophilia screening for patients with a history or familial prevalence of thromboembolism and/or with a high risk score (> or =15). In cases of thrombophilia, the form and duration of anticoagulant treatment must be decided individually.

Genetic polymorphisms in venous thrombosis and pulmonary embolism after total hip arthroplasty: a pilot study

Deep venous thrombosis (DVT) after major orthopaedic surgery is a substantial concern. We asked whether the single or combined presence of thrombophilic genetic polymorphisms might further increase the already high risk for venous thrombosis and pulmonary embolism (PE) after THA. We therefore compared the prevalence of factor V Leiden, prothrombin G20210A, methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C, and plasminogen activator inhibitor 4G/5G polymorphisms between 50 patients with symptomatic DVT within 3 weeks after elective THA and an asymptomatic control group of 85 patients. We found no major difference for the presence of a single mutation between the groups. Factor V Leiden and homozygous MTHFR C667T mutations were of borderline significance with odds ratios (95% confidence intervals) of 3.73 (0.89-15.63) and 2.93 (0.92-9.29), respectively. Patients with homozygous or combined heterozygous status of MTHFR C677T and A1298C mutation had a higher frequency of DVT after elective THA (odds ratio, 2.86; 95% confidence interval, 1.32-6.35) than those with wild-type. The presence of a single mutation may not further increase the already high risk for symptomatic DVT after THA, whereas combinations of mutations of distinct polymorphisms might be important. However, prospective studies with a larger number of patients are needed before we would recommend preoperative screening.

LEVEL OF EVIDENCE

Level III, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.

The 2007 ABJS Nicolas Andry Award: three decades of clinical, basic, and applied research on thromboembolic disease after THA: rationale and clinical results of a multimodal prophylaxis protocol

Total hip arthroplasty is an operation with a high risk for venous thromboembolism. Three decades of research conducted at the Hospital for Special Surgery identified the exact timing of the thrombogenic stimulus during surgery, defined the role of magnetic resonance venography, and established the role of certain genetic and acquired predispositions. Based on these studies, we implemented a multimodal prophylaxis consisting of a series of safe preventive measures applied before, during, and immediately after surgery to reduce the risk of venous thromboembolism. If these safe preventive measures are strictly observed, postoperative pharmacologic prophylaxis does not need to be aggressive in the patient without predisposing factors who mobilizes promptly, thus diminishing the risk of bleeding associated with the use of anticoagulants and the overall cost of care. Our clinical experience with more than 5000 total hip arthroplasties performed during the last decade and closely followed prospectively for a minimum of 3 months clearly shows this multimodal prophylaxis is safe and effective resulting in a very low prevalence of thromboembolism.

Mini-gastric bypass in a patient homozygous for Factor V Leiden

A 42-year-old morbidly obese female, homozygous for Factor V Leiden, underwent mini-gastric bypass without complications. The recommendations for prophylaxis in this high-risk population are unclear and most likely involve a combination of pharmacologic and non-pharmacologic measures.

Altered regulation of in-vivo coagulation in orthopedic patients prior to knee or hip replacement surgery

Up to 20% of patients develop venographically proven deep-vein thrombosis after elective orthopedic surgery even under the cover of heparin or low molecular weight heparin. The extent to which the chronic inflammation of osteoarthritis requiring elective orthopedic surgery alters in-vivo coagulation and whether any specific alteration influences the development of postoperative thrombosis are unknown. This study compared the concentrations of activated factor VII (FVIIa), tissue factor pathway inhibitor (TFPI), activated factor X (FXa)-TFPI, thrombin-antithrombin, and prothrombin fragment 1+2 (F1+2) in plasmas of 535 healthy individuals (ages 17-76) with those in the preoperative plasmas of 306 arthritis patients (ages 30-92) scheduled for elective knee or hip replacement surgery. C-reactive protein was also measured in the plasmas of approximately 15% of the participants. Age-adjusted concentrations of FVIIa, F1+2, and C-reactive protein were higher in patients than controls, while the concentrations of thrombin-antithrombin, TFPI and FXa-TFPI were similar. Chronic inflammation in the patients was thus associated with increased coagulation in vivo. Without compensatory increases in the concentrations of TFPI (natural inhibitor of prothrombinase), the elevated concentrations of FVIIa in the preoperative plasmas and the trauma associated with surgery may enhance the risk for developing postoperative deep-vein thrombosis.

Thromboembolic disease after total hip arthroplasty: who is at risk?

The strong activation of the clotting cascade that occurs during total hip arthroplasty places patients at increased risk for venous thromboembolism. The risk is higher in those patients with the following predisposing factors, listed in approximate order of importance: hip fracture; malignancy, particularly if associated with chemotherapy; antiphospholipid syndrome; immobility; history of venous thromboemholism; administration of tamoxifen; raloxifene; oral contraceptives or estrogen; morbid obesity; stroke; atherosclerosis; and an American Society of Anesthesiologists physical status classification of 3 or greater. The following risk factors are weak or controversial: advanced age; diabetes mellitus; congestive heart disease; atrial fibrillation; varicose veins; and smoking. However, 50% of patients who develop thromboembolism after total hip arthroplasty have no clinical predisposing factors. In a matched, controlled study, we defined the major genetic predispositions that increase the risk of venous thromboembolism after total hip arthroplasty: deficiency of antithrombin III (< 75%) and protein C (< 70%), and prothrombin gene mutation. Preoperative genetic screening in conjunction with the recognized clinical risk factors can help categorize postoperative venous thromboembolism risk and differentiate patients who can be protected with milder and safer prophylaxis (eg, aspirin, intermittent pneumatic compression) compared with those at higher risk who need to be anticoagulated.

The factor XIII Val34Leu polymorphism: is it protective against idiopathic venous thromboembolism?

The substitution of leucine for valine at amino acid position 34 of the factor XIII gene is commonly referred to as FXIII Val34Leu polymorphism. The homozygous leucine/leucine genotype has been reported to confer protection against venous thromboembolism, but previous studies have not evaluated a population limited to those with idiopathic venous thromboembolism. The primary objective of the study was to determine whether the FXIII Val34Leu polymorphism is independently associated with the occurrence of idiopathic venous thromboembolism. We prospectively enrolled consecutive patients with at least one objectively confirmed idiopathic venous thromboembolism. Friends of cases were recruited as controls and matched to cases by sex, ethnicity, and age. All participants were tested for the FXIII Val34Leu polymorphism in addition to several well-known thrombophilias. Data from 309 cases and 306 controls were analyzed. The FXIII leucine/leucine genotype was present in 4.9% of cases and 6.5% of controls. An adjusted odds ratio of 0.59 (95% confidence interval, 0.25-1.38) was found for the recessive model and 0.69 (95% confidence interval, 0.46-1.02) for the dominant model. Our results do not support an independent association of the FXIII Val34Leu polymorphism with idiopathic venous thromboembolism in our Caucasian Canadian study population.

The John Charnley Award: heritable thrombophilia and development of thromboembolic disease after total hip arthroplasty

We retrospectively assessed whether heritable thrombophilia-hypofibrinolysis was more common in patients developing venous thromboembolism after total hip replacement than among control patients who did not develop venous thromboembolism, as an approach to better identify causes of venous thromboembolism after total hip arthroplasty. Twenty patients with proximal deep venous thrombosis after THA and 23 patients with symptomatic pulmonary embolism were compared with 43 control patients who did not have postoperative venous thromboembolism. Five of 42 patients with venous thromboembolism (12%) and 0 of 43 control patients (0%) had antithrombin III deficiency (< 75%). Nine of 42 patients with venous thromboembolism (21%) and 2 of 43 control patients (4.7%) had protein C deficiency (< 70%). Ten of 43 patients with venous thromboembolism (9 heterozygous, 1 homozygous; 23%) and 1 of 43 control patients (heterozygous; 2%) had the prothrombin gene mutation. Patients who had venous thromboembolism after total hip arthroplasty were more likely than matched control patients to have heritable thrombophilia with antithrombin III or protein C deficiency, or homo-heterozygosity for the prothrombin gene mutation. Screening for these three tests of heritable thrombophilia before total hip arthroplasty should improve the identification of patients with a reduced risk of venous thromboembolism who may need only mild thromboprophylaxis, and of those patients with heritable thrombophilia in whom prophylaxis should be more aggressive.

LEVEL OF EVIDENCE

Prognostic study, Level II-1 (lesser-quality RCT). See the Guidelines for Authors for a complete description of levels of evidence.

Arterial thrombosis associated with heterozygous factor V Leiden disorder, hyperhomocysteinemia, and peripheral arterial disease: Importance of synergistic factors

A 47-year-old man with heterozygous factor V Leiden disorder and intermittent hyperhomocysteinemia developed spontaneous acute popliteal artery thrombosis. Homocysteine levels were above normal limits at presentation. Intra-arterial thrombolysis was used successfully to treat the acute thrombosis; long-term treatment included anticoagulation, folic acid, and risk factor modification. Although factor V Leiden is strongly associated with deep venous thrombosis, additional cofactors such as hyperhomocysteinemia may predispose to an increased risk of acute arterial thrombosis in areas of pre-existing peripheral arterial disease.

A single-centre prospective study of clinical and haemostatic risk factors for venous thromboembolism following lower limb arthroplasty

Previous studies report conflicting results concerning the potential significance of thrombophilic genotypes in postarthroplasty venous thromboembolism (VTE). This study assessed thrombophilic genotypes, haemostatic and clinical variables as independent risk factors for VTE postarthroplasty. A total number of 569 patients undergoing elective lower limb arthroplasty at a single centre were prospectively studied. All patients were interviewed and had blood samples collected preoperatively. Bilateral lower limb ultrasonography was performed at day 7 +/- 2 postoperatively in all patients (ventilation/perfusion lung scanning in symptomatic patients only). The incidence of inhospital postoperative VTE was 26%. In univariate analysis - increased age, knee arthroplasty, recent surgery, general anaesthesia, shorter operation time, non-receipt of blood transfusion and differences in surgical practice (including use of pneumatic calf compression, surgical drains and postoperative bandaging techniques) were significantly associated with VTE. Factor V Leiden, prothrombin G20210A and MTHFR C677T mutations were not significant risk factors for VTE, and of all haemostatic variables tested, only median activated partial thromboplastin time showed significant difference between VTE and non-VTE patients (34 s vs. 33 s). Multiple logistic regression analysis demonstrated that increased age, knee arthroplasty and individual surgeon's routine practices were the only significant independent risks for VTE; hence routine preoperative blood screening for a potential hypercoaguable state is not indicated in this surgical setting.

Factor V Leiden and perioperative risk

Factor V Leiden (FVL) is the most common known inherited cause of thrombophilia; it is present in approximately 5% of the Caucasian population. Although the risk of venous thrombosis associated with this polymorphism in various medical settings is well described, its effect on perioperative risk is only beginning to be explored. Specifically, there are few studies addressing the potential risks of FVL in the surgical population, in which both hemorrhagic and thrombotic complications convey substantial clinical and economic significance. There are speculations and unproven hypotheses regarding FVL in this population, and these therefore highlight the need to comprehensively address this issue. This review will describe the physiology of the FVL mutation, briefly clarify its risk in the nonsurgical setting, and assess current data regarding FVL in noncardiac and cardiac surgery. Finally, a summary of current clinical evidence and a plan for more detailed investigation of this potentially significant risk factor will be proposed.

Risk factors for pulmonary emboli after total hip or knee arthroplasty

Because it is difficult to predict which patients may sustain a pulmonary embolism after total hip or knee arthroplasty, we assessed multiple thrombophilic and hypofibrinolytic parameters to identify risk factors. Twenty-nine patients who survived a known pulmonary embolism after total knee or total hip arthroplasty were matched by age, gender, race, arthritic diagnosis, procedure, and surgery date with 29 patient-controls who had a total hip or knee arthroplasty but who did not have a symptomatic known pulmonary embolism or deep vein thrombosis. Twenty-one serologic measures and five genes associated with thrombophilia, hypofibrinolysis, or both were assessed without knowledge of group assignment. All patients with pulmonary embolism had at least one abnormality of plasminogen activator inhibitor activity, dilute Russell's viper venom time, prothrombin time, or total cholesterol versus 13 of 27 (48%) control patients. Forty-seven percent of patients who experienced pulmonary embolism had at least two abnormalities of plasminogen activator inhibitor activity, dilute Russell's viper venom time, prothrombin time, or total cholesterol, versus 7% of control patients. Preoperatively, to identify patients at high risk of pulmonary embolism, plasminogen activator inhibitor activity, dilute Russell's viper venom time, prothrombin time, and cholesterol levels were most predictive. Using at least one abnormality of these four measures as a screening test to detect risk of pulmonary embolism, the test is sensitive (100%), and the predictive value of a negative test is high (100%). After additional prospective study, this may allow identification of patients at low risk (the majority of patients) in whom anticoagulation may not be required and a small group of patients at high risk for pulmonary embolism in whom prophylactic anticoagulation should be provided.

Prothrombotic conditions in an unselected cohort of children with venous thromboembolic disease

Venous thromboembolic events (VTEs) in children are usually associated with underlying clinical conditions. The added contribution of prothrombotic conditions to the occurrence of VTEs in children is not clear. This study reports the prevalence of prothrombotic conditions in 171 consecutive children with VTE followed in the Hospital for Sick Children Thrombosis Outpatient Clinic. The median age of the children at the time of VTE was 2.3 months (range 1 day to 16.5 years). An underlying medical condition and a central venous line (CVL) were present in 156 (91%) and 132 (77%) of 171 children, respectively. A positive family history was present in 8% of children. The prevalence of factor V Leiden was 4.7%, prothrombin G20210A polymorphism was 2.3%, protein S deficiency was 1.2%, protein C deficiency was 0.6% and increased plasma lipoprotein (a) concentration (>30 mg dL-1) was 7.5% (tested in 107 children). The overall frequency of inherited prothrombotic coagulation proteins was 13% (95% confidence interval 7 to 19%) and the frequency was not significantly different between neonates and older children with VTE. Inherited prothrombotic coagulation proteins were not associated with gender, CVL-related VTE, a positive family history of thrombosis or spontaneous VTE in neonates. Increased frequency of inherited prothrombotic coagulation proteins was, however, found in older children with spontaneous VTE (60%) compared with older children with VTEs secondary to an underlying medical condition (10%) (P = 0.02). In conclusion, this study indicates that inherited prothrombotic coagulation proteins do not contribute significantly to the pathogenesis of VTEs in neonates and children, in whom the most significant etiological factors are the presence of a CVL and/or other medical conditions.

Clinical and laboratory evaluation of thrombophilia

Thrombophilia is the predisposition to venous thromboembolism and is caused by inherited and acquired factors, alone or in combination. With the discovery of APC resistance and the prothrombin gene mutation, more than half of all patients with clinical characteristics of thrombophilia are now diagnosed with an inherited disorder. The hypercoagulable work-up of patients with venous thromboembolism is important, because the causes can influence the duration and management of anticoagulation therapy, as well as affect other decisions regarding life and health issues.

Correlation of thrombophilia and hypofibrinolysis with pulmonary embolism following total hip arthroplasty: an analysis of genetic factors

BACKGROUND

The increased thromboembolic risk associated with total hip arthroplasty is multifactorial. We assessed whether the prevalence of abnormalities shown by newer genetic screening tests for thrombophilia and hypofibrinolysis was higher in patients in whom pulmonary embolism had developed after total hip arthroplasty than it was in matched control patients.

METHODS

Fourteen patients with documented pulmonary embolism after total hip arthroplasty and fourteen matched control patients who had undergone total hip arthroplasty without any clinical indication of thromboembolism were evaluated for risks of thrombophilia and hypofibrinolysis. Functional tests of hemostasis included evaluations of prothrombin time; activated partial thromboplastin time; levels of fibrinogen, serum homocysteine, protein C and S, and antithrombin III; activated protein-C resistance; and dilute Russell viper venom time. Molecular genetic testing was performed for factor-V Leiden, prothrombin promoter G20210A, methylenetetrahydrofolate reductase C677T, plasminogen activator inhibitor-1 4G/4G, and platelet glycoprotein IIb/IIIa A1/A2 or A2/A2 mutations.

RESULTS

The total number of genetic thrombophilic abnormalities identified was higher in the pulmonary embolism group (twenty-four abnormalities) than in the control group (fifteen abnormalities). Only patients with pulmonary embolism were found to have heterozygosity or homozygosity for the prothrombin G20210A mutation (four of fourteen patients; p = 0.05 compared with the control group) and a decreased antithrombin-III level (three of thirteen patients; p = 0.10 compared with the control group). Patients with pulmonary embolism were much more likely than control patients to have at least one thrombophilic abnormality: seven of fourteen patients with pulmonary embolism had a low antithrombin-III level or the prothrombin G20210A gene mutation compared with none of the fourteen in the control group (Fisher exact test, p < 0.01). The presence of the prothrombin G20210A gene mutation was significantly correlated with pulmonary embolism (r = 0.41, p = 0.03), as was the presence of least one abnormality (a low antithrombin-III level or the presence of the prothrombin G20210A gene mutation) (r = 0.58, p = 0.001).

CONCLUSIONS

Genetic thrombophilia and hypofibrinolysis were more frequent in patients who had had pulmonary embolism after total hip arthroplasty than in those who had not. The presence of multiple genetic thrombophilic polymorphisms, particularly prothrombin G20210A and antithrombin III, rather than any single genetic prothrombotic abnormality, appears to signal an increased thromboembolic risk in patients undergoing total hip arthroplasty. Future refinements and availability of these tests will likely allow preoperative identification of patients with an increased genetic predisposition for thromboembolism.

Clinical utility of factor V leiden (R506Q) testing for the diagnosis and management of thromboembolic disorders

OBJECTIVE

To review the current state of the art regarding the role of the clinical laboratory in diagnostic testing for the factor V Leiden (FVL) thrombophilic mutation (and other protein C resistance disorders), and to generate, through literature reviews and opinions of recognized thought-leaders, expert consensus recommendations on methodology and diagnostic, prognostic, and management issues pertaining to clinical FVL testing.

DATA SOURCES, EXTRACTION, AND SYNTHESIS

An initial thorough review of the medical literature and of current best clinical practices by a panel of 4 experts followed by a consensus conference review, editing, and ultimate approval by the majority of a panel of 28 additional coagulation laboratory experts.

CONCLUSIONS

Consensus recommendations were generated for topics of direct clinical relevance, including (1) defining those patients (and family members) who should (and should not) be tested for FVL; (2) defining the preferred FVL laboratory testing methods; and (3) defining the therapeutic, prophylactic, and management ramifications of FVL testing in affected individuals and their family members. As FVL is currently the most common recognized familial thrombophilia, it is hoped that these recommendations will assist laboratorians and clinicians caring for patients (and families) with this common mutation.

Risk factors for venous thromboembolism after total hip and knee replacement surgery

Elective total hip and total knee arthroplasty surgeries are associated with an extraordinarily high incidence of asymptomatic venous thromboembolism (VTE). Symptomatic deep vein thrombosis (DVT) or pulmonary embolism (PE) is diagnosed in only 2%-4% of these patients. A number of studies have defined the incidence and time course of symptomatic thromboembolism after these procedures. Knee arthroplasty is associated with a very high incidence of asymptomatic calf vein thrombosis, with almost all symptomatic VTE events diagnosed in the first 21 days after surgery. Hip arthroplasty, however, is associated with a higher incidence of asymptomatic proximal thrombi and a modestly higher incidence of symptomatic VTE events, many diagnosed up to 6 or 8 weeks after hospital discharge. Extended medical thromboprophylaxis has been shown to reduce the incidence of symptomatic and asymptomatic VTE among hip arthroplasty patients but not among knee arthroplasty patients. Risk factors for VTE after knee arthroplasty are not well defined. Important risk factors that have been shown to be associated with the development of VTE after hip surgery include (1) a history of prior VTE, (2) obesity (body mass index > 25), (3) delay in ambulation after surgery, and (4) female sex. Factors associated with lower risk include (1) Asian/Pacific Islander ethnicity, (2) use of pneumatic compression among non-obese patients after surgery, and (3) extended thromboprophylaxis after hospital discharge.

Genetic polymorphisms associated with venous and arterial thrombosis: an overview

OBJECTIVE

To provide an overview of genetic polymorphisms associated with thrombotic cardiovascular disease.

DATA SOURCES

A literature search using the National Library of Medicine database.

STUDY SELECTION

The literature on genetic polymorphisms associated with venous and arterial thrombosis was reviewed.

DATA EXTRACTION

Based on the literature review, the clinical significance of polymorphisms in various coagulation proteins was assessed and a summary was developed.

CONCLUSIONS

Thrombosis is a multifactorial disorder, with both congenital and acquired risk factors. It is now clear that there are many genetic abnormalities that impart an increased risk for thrombophilia, and the presence of more than 1 abnormality results in a further increased risk of thrombosis. In hemostasis, there is a balance between procoagulant factors and natural anticoagulant proteins. The first genetic thrombotic disorders described were deficiencies of the natural anticoagulants, such as antithrombin, protein C, and protein S, but these abnormalities are rare and are caused by many different mutations. More recently, single polymorphisms that are relatively common in the general population have been described in procoagulant factors, such as factor V and prothrombin, which impart an increased risk for venous thrombosis. As more scrutiny is placed on the hemostatic system, further polymorphisms have come to light. The current challenge is to elucidate the relationship between these new polymorphisms and either venous or arterial thrombotic cardiovascular disease.

The relationship of the factor V Leiden mutation or the deletion-deletion polymorphism of the angiotensin converting enzyme to postoperative thromboembolic events following total joint arthroplasty

BACKGROUND

Although all patients undergoing total joint arthroplasty are subjected to similar risk factors that predispose to thromboembolism, only a subset of patients develop this complication. The objective of this study was to determine whether a specific genetic profile is associated with a higher risk of developing a postoperative thromboembolic complication. Specifically, we examined if the Factor V Leiden (FVL) mutation or the deletion polymorphism of the angiotensin-converting enzyme (ACE) gene increased a patient's risk for postoperative thromboembolic events. The FVL mutation has been associated with an increased risk of idiopathic thromboembolism and the deletion polymorphism of the ACE gene has been associated with increased vascular tone, attenuated fibrinolysis and increased platelet aggregation.

METHODS

The presence of these genetic profiles was determined for 38 patients who had a postoperative symptomatic pulmonary embolus or proximal deep venous thrombosis and 241 control patients without thrombosis using molecular biological techniques.

RESULTS

The Factor V Leiden mutation was present in none of the 38 experimental patients and in 3% or 8 of the 241 controls (p = 0.26). Similarly there was no difference detected in the distribution of polymorphisms for the ACE gene with the deletion-deletion genotype present in 36% or 13 of the 38 experimental patients and in 31% or 74 of the 241 controls (p = 0.32).

CONCLUSIONS

Our results suggest that neither of these potentially hypercoaguable states are associated with an increased risk of symptomatic thromboembolic events following total hip or knee arthroplasty in patients receiving pharmacological thromboprophylaxis.

Acquired activated protein C resistance is associated with lupus anticoagulants and thrombotic events in pediatric patients with systemic lupus erythematosus

Acquired activated protein C resistance (APCR) has been hypothesized as a possible mechanism by which antiphospholipid antibodies (APLAs) cause thrombotic events (TEs). However, available evidence for an association of acquired APCR with APLAs is limited. More importantly, an association of acquired APCR with TEs has not been demonstrated. The objective of the study was to determine, in pediatric patients with systemic lupus erythematosus (SLE), whether (1) acquired APCR is associated with the presence of APLAs, (2) APCR is associated with TEs, and (3) there is an interaction between APCR and APLAs in association with TEs. A cross-sectional cohort study of 59 consecutive, nonselected children with SLE was conducted. Primary clinical outcomes were symptomatic TEs, confirmed by objective radiographic tests. Laboratory testing included lupus anticoagulants (LAs), anticardiolipin antibodies (ACLAs), APC ratio, protein S, protein C, and factor V Leiden. The results revealed that TEs occurred in 10 (17%) of 59 patients. Acquired APCR was present in 18 (31%) of 58 patients. Acquired APCR was significantly associated with the presence of LAs but not ACLAs. Acquired APCR was also significantly associated with TEs. There was significant interaction between APCR and LAs in the association with TEs. Presence of both APCR and LAs was associated with the highest risk of a TE. Protein S and protein C concentrations were not associated with the presence of APLAs, APCR, or TEs. Presence of acquired APCR is a marker identifying LA-positive patients at high risk of TEs. Acquired APCR may reflect interference of LAs with the protein C pathway that may represent a mechanism of LA-associated TEs. (Blood. 2001;97:844-849)

Genetics University of Toronto Thrombophilia Study in Women (GUTTSI): genetic and other risk factors for venous thromboembolism in women

BACKGROUND: Women may be at increased risk for venous thromboembolism (VTE) as compared with men. We studied the effects of genetic and biochemical markers of thrombophilia in women, in conjunction with other established risk factors for VTE. METHOD: The present retrospective case-control study was conducted in a thrombosis treatment programme at a large Toronto hospital. The cases were 129 women aged 16-79 years with objectively confirmed VTE. Age-matched control individuals were women who were free of venous thrombosis. Neither cases nor control individuals had known cardiovascular disease. Participants were interviewed regarding personal risk factors for VTE, including smoking, history of malignancy, pregnancy, and oestrogen or oral contraceptive use. Blood specimens were analyzed for common single nucleotide polymorphisms of prothrombin, factor V and methylenetetrahydrofolate reductase (MTHFR; C677T, A1298C and T1317C), and the A66G polymorphism for methionine synthase reductase (MTRR).Fasting plasma homocysteine was also analyzed. RESULTS: Women with VTE were significantly more likely than female control individuals to carry the prothrombin polymorphism and the factor V polymorphism, or to have fasting hyperhomocysteinaemia. Homozygosity for the C677T MTHFR gene was not a significant risk factor for VTE, or were the A1298C or T1317C MTHFR homozygous variants. Also, the A66G MTRR homozygous state did not confer an increased risk for VTE. CONCLUSION: Prothrombin and factor V polymorphisms increased the risk for VTE in women, independent from other established risk factors. Although hyperhomocysteinaemia also heightens this risk, common polymorphisms in two genes that are responsible for homocysteine remethylation do not. These findings are consistent with previous studies that included both men and women.

Factor V Leiden mutation: a nursing perspective

The factor V Leiden mutation is a recently described autosomal dominant genetic risk factor for venous thromboembolism (VTE). Persons who are heterozygous or homozygous for this disorder are at 4 to 7 times and 50 to 100 times increased risk, respectively, for VTE. In particular, women have unique challenges because the presence of the Leiden mutation in combination with pregnancy or use of oral contraceptives results in an even greater increased risk for VTE. This article will review the factor V Leiden mutation, its association with VTE, and the genetic inheritance pattern and ethnic distribution. Oral contraceptive use, pregnancy, and hormone replacement therapy in women with the Leiden mutation will be discussed. Screening issues and management for all patients, and women in particular, will be addressed. Nursing implications for care management of this group of patients is complex and requires evaluation of the significance of newly defined genetic disorders such as the factor V Leiden mutation. Nurses need to be knowledgeable about genetic screening, risk factors, risk-reduction counseling, and considerations for long-term therapy, which include quality of life issues. Two case studies exemplify many of the issues that will be discussed.

Thrombophilia: disorders predisposing to venous thromboembolism

Venous thromboembolism continues to present a challenge to clinicians. Over the years, a number of risk factors which predispose to venous thromboembolism have been identified, and these risk factors are taken into account in the formulation of recommendations for the prevention and treatment of these disorders. In more recent years, there have been major advances in our understanding of congenital or acquired defects that predispose to thrombosis leading to these so-called acquired or inherited forms of thrombophilia. The list of acquired forms of thrombophilia now includes anti-thrombin, protein C, protein S, activated protein C resistance, the prothrombin 20210A mutant, homocysteinemia and a number of rare defects which either enhance coagulation or interfere with fibrinolysis. In spite of these advances, there are numerous families with thrombophilia in whom none of the known defects can be demonstrated. The challenge for the future is to discover some of these as yet unknown factors and to determine the most appropriate methods for the prevention and treatment of venous thromboembolism in susceptible individuals with thrombophilia.