Myocardial infarction associated with homozygous resistance to activated protein C

State-of-the-Art Review: Activated Protein C Resistance: Clinical Implications

The discovery of inherited resistance to activated protein C (APC) as a major risk factor for venous thrombosis has dramatically improved our understanding of the pathogenesis of venous thrombosis. In a majority of cases, APC resistance is associated with a single point mutation in the factor V gene (FV) that results in substitution of arginine, R, at position 506 by glutamine, Q. (FV:Q506). The mutation renders factor Va partially resistant to degradation by APC. A functional APC resistance test, which includes predilution of the patient plasma with factor V-deficient plasma, is found to be 100% sensitive and specific for the presence of FV:Q506and is useful as a screening assay. Carriers of the FV:Q506allele have increased thrombin generation, resulting in hypercoagulability and a lifelong increased risk of venous thrombosis. In Western countries, APC resistance due to the FV mutation is present in 20-60% of thrombosis patients and in 1-15% of healthy controls, whereas the mutation is virtually absent from ethnic groups other than Caucasians. This may explain the high incidence of venous thrombosis in Western countries. The thrombotic risk in APC-resistant individuals may be further increased by other genetic defects, e.g., protein C or protein S deficiency, and by exposure to circumstantial risk factors, e.g., oral contraceptives, pregnancy, immobilization, and surgery. The question is thus raised as to whether general screening for APC resistance before circumstantial risk factors occur is warranted in Western countries. Key Words: Factor V—APC resistance-Protein C-Protein S—Thrombosis—Mutation.

Selective Thrombophilia Screening in Young Patients with Retinal Artery Occlusion

Purpose: To investigate the prevalence of various thrombophilic disorders among young patients with retinal artery occlusion (RAO). Procedures: We retrospectively reviewed thrombophilia screening data of young patients ≤60 years of age with RAO and healthy controls matched for gender and age. Results: Thrombophilia screening data of 25 young patients and 62 healthy controls were analyzed. Mean patient age by the time of the RAO was 43.3 ± 10.8 years. Overall, thrombophilic defects were found to be present in 17 patients (68%) compared with 11 of 62 controls (17.7%; p < 0.0001). Multivariate logistic regression analysis confirmed a statistically significant association between the development of RAO and increased levels of lipoprotein(a) (odds ratio: 9.48; p = 0.001) and factor VIII (odds ratio: 6.41; p = 0.024). There was a strong association between the presence of thrombophilic disorders and a personal or family history of thromboembolism (p = 0.01). Conclusions: Our results indicate that screening for thrombophilic disorders among selected young patients with RAO yields positive results in a high percentage of cases.

Factor V Leiden mutation is a risk factor for hepatic artery thrombosis in liver transplantation

BACKGROUND

Hepatic artery thrombosis (HAT) after orthotopic liver transplantation (OLT) is associated with significant morbidity and mortality. Factor V Leiden (FVL) mutation is the most common genetic defect that predisposes to thrombosis. The reconstruction of hepatic artery with arterial graft is a documented risk factor for HAT. However, the relationship among FVL mutation, arterial graft, and HAT remains to be determined.

METHODS

We randomly genotyped 485 patients who underwent OLT from April 2002 to January 2011 and studied the incidence of Hepatic artery thrombosis in the presence of FVL mutation.

RESULTS

Of 485 patients, 21 patients (4.3%) developed HAT (13 male, 8 female); 10 patients (4 male, 6 female) were heterozygous for the FVL mutation. The incidences of HAT in patients without versus with the FVL mutation were 3.8% and 30% (P = .007). Of patients with HAT, 8 hepatic arteries were reconstructed with infrarenal aortic conduits. All 3 patients (100%) with vs 5 (28%) without FVL who received arterial grafts developed HAT (P = .042).

CONCLUSION

Our study suggested that the FVL mutation may be a risk factor for HAT in liver transplantation; the risk is augmented in the presence of an arterial graft.

Myocardial infarction and normal coronary arteries: the experience of the cardiology department of Sfax, Tunisia

OBJECTIVE

The purpose of the present study is to describe our experience with patients who have a transmural myocardial infarction (MI) in the presence of a normal coronary artery. The clinical profile, demographic characteristics and outcomes of these patients are discussed.

METHODS

Between January 2006 and August 2011, 21 patients who presented with a Q-wave myocardial infarction were found to have normal coronary arteries. The prevalence rate of this entity was 1.5% (21 out of 1,400 Q wave MI patients). These patients were characterized by their young age (the mean age=44.95±14.86), male dominance (90.47%), and a high prevalence of smoking (85.71%). In this study, 4 patients have an evident spontaneous spasm shown on coronary angiography which disappeared after intracoronary injection of nitrates. Coagulation Disorders, such as activated protein C resistance (APC) resistance, protein C deficiency and antiphospholipid antibody syndrome were found in 4 of 12 patients who underwent systematic examination. One patient had a history of lung cancer which may be associated with a hypercoagulable state and may explain the occurrence of myocardial infarction with a normal coronary artery. The mean left ventricle ejection was 56. 5±12. The mean follow-up was 24±10 months. Six patients developed residual chest pain which was generally easily controlled by anti-spastic therapy and no patient had a major cardiovascular event.

CONCLUSION

Patients with Q-wave MI and with normal coronary arteries seem to have a good short and long-term prognosis especially when they are treated with an exclusive medical strategy.

Venous thromboembolism does not share strong familial susceptibility with coronary heart disease: a nationwide family study in Sweden

AIMS

This nationwide study aimed to determine whether venous thromboembolism (VTE) shares familial susceptibility with coronary heart disease (CHD).

METHODS AND RESULTS

Data from the Swedish Multigeneration Register for subjects aged 0-76 years old for the period 1964-2008 were linked to the Hospital Discharge Register and Cause of Death Register. Familial risks of VTE and CHD were examined in two ways: risk of CHD in offspring whose parents had been diagnosed with VTE, and risk of VTE in offspring whose parents had been diagnosed with CHD. The analyses were repeated separately for siblings and spouses. In total, 174 768 offspring had CHD and 56 302 VTE. No association between VTE and CHD was observed among siblings. Among offspring, a lower risk of CHD was observed in subjects whose parents had suffered from VTE [standardized incidence ratio (SIR) 0.94 (95% confidence interval (CI) 0.92-0.95)], while offspring of parents with CHD had an increased risk of VTE [SIR 1.03 (95% CI 1.01-1.04)]. In spouses of VTE patients, an increased risk of CHD was observed [SIR 1.02 (95% CI 1.01-1.03)]. Conversely, risk of VTE was increased among spouses of CHD patients [SIR 1.03 (95% CI 1.02-1.03)]. Subanalyses of cases of myocardial infarction and pulmonary embolism/deep venous thrombosis showed similar results.

CONCLUSION

The familial background of CHD is different from that of VTE. The present study suggests that it is unlikely that shared disease-causing mutations exist to a large extent in the population.

Case reports: heritable thrombophilia associated with deep venous thrombosis after shoulder arthroscopy

Thromboembolic complications after shoulder arthroscopy are rare and their cause has not been well determined. Heritable thrombophilia has been studied in relation to numerous clinical conditions, and it has been associated with thromboembolic complications after some orthopaedic surgeries, especially after total hip or knee arthroplasty. We report three patients who had deep vein thrombosis develop after shoulder arthroscopy. All three tested positive for heritable thrombophilia, a condition undetected until this complication occurred. This report highlights the possibility that unrecognized coagulation disorders might seriously influence the clinical outcome of minimally invasive surgery. We suggest heritable thrombophilia is a possible risk factor for or etiology of deep vein thrombosis after shoulder arthroscopy.

Decreased activated protein C levels as a clinical predictor in patients with ST-elevation myocardial infarction

BACKGROUND

Circulating markers that indicate atherosclerotic plaque instability may have diagnostic and prognostic value in patients with acute coronary syndromes. We evaluated activated protein C (APC), which has antithrombotic, anti-inflammatory, and profibrinolytic properties, as a possible clinical predictor in ST-elevation myocardial infarction (STEMI), including return of spontaneous circulation after sudden cardiac arrest.

METHODS

Patients with STEMI whose APC level was measured upon arrival at the emergency room were enrolled in this study (n=335). The primary end point was inhospital death from any cause.

RESULTS

The APC level ranged from 29% to 142% with a median of 80%. The unadjusted death rate increased in a stepwise fashion with decreasing APC levels (33.7% in quartile 1, 12.7% in 2, 6.0% in 3, and 3.6% in 4, P<.001). This association remained significant in subgroups of patients with STEMI only (P=.04) or with return of spontaneous circulation (P=.01). After adjusting for independent predictors of inhospital death, the odds ratio for death among those in the first quartile of APC levels was 9.4 (95% CI 1.1-81.6, P=.04). A cutoff APC level of 65% had the highest combined sensitivity and specificity in predicting death.

CONCLUSIONS

Measuring APC levels provides predictive information for use in risk stratification across the STEMI spectrum. Decreased APC levels may be a unifying feature among patients at high risk for death after STEMI.

Simultaneous subacute coronary drug-eluting stent thrombosis in two different vessels of a patient with factor V Leiden mutation

We review the case of a 46-year-old man who underwent elective percutaneous coronary intervention and stenting of the left anterior descending artery and right coronary artery with two sirolimus- and paclitaxel-eluting stents. Four days after angioplasty, he was readmitted with cardiogenic shock due to acute anterior and inferior myocardial infarction. Coronary angiography revealed subacute thrombosis of both stents, and balloon dilation was performed successfully thereafter. The follow-up investigations revealed that the patient was a carrier of factor V Leiden. We hereby discuss the importance of factor V Leiden as the most common cause of hypercoagulable state and its probable role in acute and subacute coronary stent thrombosis in drug-eluting stents.

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.

Homozygous factor V Leiden mutation in two siblings presenting with acute myocardial infarction: a rare cause of myocardial infarction in the young

Although factor V Leiden mutation, is the most common established genetic risk factor for venous thrombosis, its effect on the development of myocardial infarction remains unclear. We describe a family case of homozygous factor V Leiden mutation in two siblings presenting with acute myocardial infarction as a rare cause of myocardial infarction in the young.

Prevalence of resistance against activated protein C resulting from factor V Leiden is significantly increased in myocardial infarction: investigation of 507 patients with myocardial infarction

BACKGROUND

A point mutation in the gene encoding coagulation factor V is a cause of resistance against activated protein C. The presence of factor V Leiden is linked to 50% of congenital defects causing venous thrombosis. Its relationship to arterial thrombosis, particularly to myocardial infarction, has not been defined. Therefore, we performed a study on the role of factor V Leiden in patients with myocardial infarction. The study was carried out in Bavarians of German origin, a relatively homogeneous population.

METHODS AND RESULTS

The study group consisted of 507 patients with documented myocardial infarction (77.5% (393/507) men, 22.5% (114/507) women), with a mean age of 56.1 (range 18-86) years. Strict criteria for patient selection and highly sensitive and specific functional tests for factor V Leiden were used. In addition, all patients with pathological test results were genotyped. The prevalence of factor V Leiden in patients with myocardial infarction was 8.7% (44/507), a significant increase in the prevalence of this mutation compared with the control group (3.7%, P =.0025). The odds ratio was 2.46 (95% CI 1.35-4.50).

CONCLUSIONS

A significantly increased prevalence of factor V Leiden in patients with documented myocardial infarction was seen. Patients with this mutation appear to have a predisposition for myocardial infarction.

Prothrombotic coagulation defects and cardiovascular risk factors in young women with acute myocardial infarction

We investigated the effect of prothrombotic coagulation defects in combination with smoking and other conventional risk factors on the risk of myocardial infarction in young women. In 217 women with a first myocardial infarction before the age of 50 years and 763 healthy control women from a population-based case-control study, factor V Leiden and prothrombin 20210A status were determined. Data on major cardiovascular risk factors and oral contraceptive use were combined with the presence or absence of these prothrombotic mutations, and compared between patients and controls. The overall odds ratio for myocardial infarction in the presence of a coagulation defect was 1.1 [95% confidence interval (CI) 0.6-1.9]. The combination of a prothrombotic mutation and current smoking increased the risk of myocardial infarction 12-fold (95% CI 5.7-27) compared with non-smokers without a coagulation defect. Among women who smoked cigarettes, factor V Leiden presence versus absence increased the risk of myocardial infarction by 2.0 (95% CI 0.9-4.6), and prothrombin 20210A presence versus absence had an odds ratio of 1.0 (95% CI 0.3-3.5). We conclude that factor V Leiden and prothrombin 20210A do not add substantially to the overall risk of myocardial infarction in young women. However, in women who smoke, the presence of factor V Leiden increased the risk of myocardial infarction twofold.

Prospective cross-sectional study of haemostatic factors in patients with and without coronary artery disease

The role of haemostatic factors for arterial thrombosis, especially the prevalence of activated protein C (APC) resistance in patients with coronary artery disease (CAD), is controversial. Between November 1996 and August 1997, 665 patients were analyzed. Diagnosis of CAD was confirmed by coronary angiography, exclusion of CAD was accepted in the presence of negative stress testing or a negative coronary angiography. CAD was present in 370 (56%) and excluded in 295 (44%) patients. Patients with CAD were older (64 +/- 9.2 versus 57.7 +/- 16 years; P <or= 0.001), more often male [74.1 versus 48.5%; odds ratio (OR) = 3.0, 95% confidence interval (CI) = 2.2-4.2] and had a higher body mass index (27.2 +/- 3.6 versus 26 +/- 4.3; P <or= 0.001). Most conventional risk factors showed a higher prevalence in patients with CAD. An APC ratio < 2.0 showed a tendency towards a higher prevalence in patients with CAD (10.5 versus 6.4%; OR = 1.7, 95% CI = 1.0-3.0). This difference was significant in men (11.7 versus 4.2%; OR = 3.0, 95% CI = 1.3-7.1), but not in women (7.3 versus 8.6%; OR = 0.8, 95% CI = 0.3-2.2). Multiple logistic regression analysis showed an independent association of the presence of CAD with age, male gender, current smoking, arterial hypertension, lipoprotein(a) levels and an APC ratio < 2.0 (OR = 2.87, 95% CI = 1.08-8.12). APC resistance with an APC ratio < 2.0 was the only haemostatic factor that was independently associated with the presence of CAD. This association was significant only for men. It may indicate a contribution of the APC resistance to the development of CAD, which has to be proven by the follow-up.

Role of activated protein C resistance in left atrial thrombogenesis in patients with mitral stenosis

Activated protein C resistance (APC-R) is the most common inherited cause of clinically apparent venous thromboembolism. Previous data indicate that left atrial thrombus (LAT) formation is a common complication in mitral stenosis (MS) and a hypercoagulable state exists in these patients. The aim of this study was to invastigate the association between APC-R and LAT formation in patients with MS. Seventy-seven consecutive patients with rheumatic MS were included in this study. Transesophageal echocardiography was performed on all patients to assess the presence of any thrombus or spontaneous echo contrast (LASEC) in the left atrial cavity or appendage. Thirty four of the patients had LAT and 43 did not. Prevelance of APC-R was smiliar between the two groups of patients with and without LAT (23% vs 16%, p=0.425). LAT(+) patients had higher incidence of atrial fibrillation (AF, 74% vs 51%, p=0.046) and LASEC (71% vs 19%, p<0.001) compared to LAT(-) patients. On multivariate regression analysis, only the presence of LASEC achieved statistical significance as an independent risk factor for LAT formation (p=0.0001, odds ratio=9.589, 95% confidence interval [CI] =3.143-29.251). Because onunivariate analysis both LASEC and AF were associated with LAT, we also compared the prevelance of APC-R in the subgroups of patients who have these risk factors with and without LAT. There was a correlation between the presence of APC-R and LAT in the AF(+) subgroup of MS patients (p=0.033, odds ratio=8.167, 95% CI=1.001-72.812). However, the presence of APC-R was not associated with the increased risk of LAT in LASEC(+) patients (p=0.217, odds ratio=1.200, 95% CI=1.003-1.435). Although the presence of APC-R itself is not an independent risk factor for LAT formation in MS, it may increase the risk of LAT when present in combination with AF (as an additional risk factor) in these patients.

Comparison of thrombotic risk between 85 homozygotes and 481 heterozygotes carriers of the factor V Leiden mutation: retrospective analysis from the Procare Study

Factor V Leiden is the most common risk factor in thrombophilia. However, whether homozygosity confers a higher risk than heterozygosity remains questionable. The first phase of the Procare Study was to collect clinical and biological data from individuals carrying the R506Q mutation. To date, 566 individuals have been included in 23 French centres. Data from 85 homozygotes were compared with those of 481 heterozygotes. Mean age at first thrombosis was earlier for homozygous females versus heterozygous females (P = 0.02) or versus homozygous males (P < 0.005). Thrombosis occurred more frequently spontaneously in homozygotes than in heterozygotes [odds ratio, 4.1; 95% confidence interval (CI), 2.27-7.42]. Idiopathic events occurred earlier in homozygous females compared with males (P < 0.001). In our homozygous population, the 20210A allele of the prothrombin gene may constitute one associated risk condition. Recurrence after a first event was statistically more frequent in homozygotes than in heterozygotes (odds ratio, 1.95; 95% CI, 1.08-3.53). Therefore, homozygosity seems to confer a higher risk of thrombosis than heterozygosity, particularly in women.

Incidence of factor V Leiden in patients with acute myocardial infarction

The genetic defect of coagulation factor V known as factor V Leiden produces a resistance to degradation by activated protein C (APC) and increases the risk of venous thromboembolism. The data on arterial thrombosis associated with APC resistance are still not clearly defined. We conducted a study in patients presenting with acute myocardial infarction (MI) to assess whether factor V Leiden increases the risk of arterial thrombosis. We studied 109 patients who had a diagnosis of acute MI (69 males and 40 females, aged 25-91 years), and 112 controls. The study population was identified by characteristic ECG changes and elevation of serum CK-MB, whereas the control subjects were anonymous healthy blood donors with no known history of coronary artery disease. Blood samples from the patients and controls were analyzed for the factor V Leiden mutation by DNA analysis, using the polymerase chain reaction. Heterozygous factor V Leiden mutation was found in 9 of 109 (8%) MI patients and 5 of 112 (4%) control subjects (P =.42). In conclusion, this study shows no evidence of an association between factor V Leiden and acute MI.

Retinal vascular occlusion and deficiencies in the protein C pathway

PURPOSE

To report abnormalities in the protein C pathway and other vascular occlusion risk factors in patients with retinal vascular occlusion.

METHODS

In a study, we investigated 76 consecutive patients who had in-patient evaluation of venous or arterial retinal vascular occlusion. All patients underwent comprehensive tests for coagulation disorders including determinations of protein C, protein S, lupus anticoagulants, and resistance to activated protein C and were screened for vascular disease risk factors. Resistance to activated protein C was confirmed by a polymerase chain reaction method to detect the specific factor V R506Q mutation. For comparative purposes, we also screened 209 consecutive inpatients with deep vein thrombosis from the same geographic region for resistance to activated protein C as well as protein C and protein S deficiencies.

RESULTS

Ten (29%) of 35 patients with central retinal vein occlusion (CRVO) had factor V R506Q mutation. The factor V R506Q mutation was detected in four (19%) of 21 patients with branch retinal vein occlusion. The higher frequency in factor V R506Q mutation compared with the expected 9% mutation prevalence in a white population was highly significant for the central retinal vein occlusion group but not for the branch retinal vein occlusion group. In all patients with resistance to activated protein C, the factor V R506Q mutation was detected; 16 were heterozygous, one homozygous. No cases of lupus anticoagulants, protein C, or protein S deficiencies were detected. Forty (19%) of 209 patients with deep vein thrombosis were carriers of the factor V R506Q mutation.

CONCLUSIONS

The prevalence of the factor V R506Q mutation is similar in patients with central retinal vein occlusion and patients with deep vein thrombosis and represents a relevant risk factor. Screening for this mutation is therefore recommended in all patients with central retinal vein occlusion.

Prevalence of factor V Leiden (APCR) and other inherited thrombophilias in young patients with myocardial infarction and normal coronary arteries

OBJECTIVE

To investigate the role of activated protein C resistance (APCR, factor V Leiden) in coronary artery thrombosis.

METHODS

The prevalence of APCR and of congenital deficiencies of antithrombin III, protein C, protein S, plasminogen, and factor XII was investigated in adult patients under 45 years of age with acute myocardial infarction. The results were compared with those of a group of 53 age and sex matched control subjects.

RESULTS

Among 75 patients under the age of 45 years who were admitted from November 1994 to April 1996 for acute myocardial infarction, 22 (29.3%) had normal coronary arteriography (group I) and 53 (70.7%) had significant coronary artery disease (group II). Inherited thrombophilia was more often found in group I (4/22, 18.2%) than in group II (4/53, 7.5%) but the difference was not significant (F test: p = 0.22). The prevalence of APCR was 9.1% (2/22) in group I, 3.8% (2/53) in group 2 (p = 0.57), and 3.8% (2/53) in the normal control group (p = 0.57).

CONCLUSIONS

The prevalence of congenital thrombophilias, including APCR, does not seem to be increased in young patients with myocardial infarction and normal coronary angiograms, compared with young patients with coronary atherosclerosis and with normal control subjects. However, the statistical power of the study is too low to detect a significant difference and these results are published to allow a meta-analysis of this problem in the future.

Role of factor V Leiden mutation in patients with angiographically demonstrated coronary artery disease

The study sought to determine whether coagulation factor V Leiden (FV Leiden) plays a role in the pathogenesis of coronary artery disease and/or myocardial infarction. Association of FV Leiden with venous thromboembolism is well established in the literature, but the role of the mutation in arterial thrombotic events is controversial. Some studies have documented an association between the mutation and myocardial infarction and stroke in juveniles. Few studies have explored its possible contribution to coronary atherosclerosis. We screened FV genotype in 850 predominantly white coronary angiography patients. Coronary artery disease risk factors and history of myocardial infarction were then analyzed by genotype. The FV Leiden mutation occurred in 54 (6.4%) patients. There was one homozygote; a 37-year-old, white male smoker with a history of myocardial infarction. Gene frequencies for white males and females were similar: 0.965 for the normal allele and 0.035 for FV Leiden. Gene frequencies for both genders were in Hardy-Weinberg equilibrium. FV Leiden was not a useful predictor (p=0.23) of the presence of clinically defined atherosclerosis (> or = 50% stenosis) in a logistic regression model adjusting for age, lipoprotein (a), total cholesterol, triglycerides, high density lipoprotein cholesterol, and fibrinogen. In addition, there was no difference in frequency of FV Leiden among those with and without medical histories of myocardial infarction (p=0.51). Allelic frequencies of FV Leiden in this patient group do not differ significantly from those reported for white populations. The FV Leiden mutation in its heterozygous state is not independently associated with coronary artery disease or myocardial infarction.

Age as a risk factor for myocardial infarction in Leiden mutation carriers

A single factor V gene G-A mutation (Arg506Gln) underlying activated protein C (APC) resistance is a common risk factor for venous thromboembolism. It is still unclear whether the factor V Leiden predisposes patients to arterial thrombosis and myocardial infarction (MI). To determine a correlation between the factor V Leiden mutation and MI in different age categories, DNA samples from 287 patients with "early" and "late" MI were investigated. As control groups 373 young subjects (mean age 11 years) and 110 elderly ones (mean age 80 years) were studied. We found a significant difference in mutant allele distribution in the "late" MI group compared to the "early" MI group (chi2 = 9.86, OR = 13,7, P < 0.005) and the control group of elderly subjects (chi2 = 5.92, OR = 8.6, P < 0.02). The mean age of MI patients carrying the Leiden mutation was 72 years, i.e., 12 years higher than the mean age of all investigated MI patients (60 years). Thus, we found a statistically significant correlation between MI and factor V Leiden mutation in elderly subjects.

No correlation between activated protein C resistance and free flap failures in 100 consecutive patients

This study evaluates whether thrombophilic disorders contribute to failures in microvascular surgery. A recently discovered condition is focused on, i.e., activated protein C resistance, which is a highly prevalent functional defect of a crucial endogenous anticoagulant system--the protein C anticoagulant pathway (up to 15 percent of Caucasians affected). One hundred consecutive patients were operated on with 103 free tissue transfers during a 2.5-year period, all of which received perioperative intravenous anticoagulation, principally based on dextran (1 liter) and a heparin bolus at vascular reperfusion (80 to 100 IU/kg). The patients underwent extensive laboratory analysis with respect to conditions predisposing for thrombosis. Eleven patients were found to be activated protein C resistant, and one patient had congenital protein S deficiency. There were six total and five partial flap losses, which, however, in only one case coincided with the presence of a thrombophilic disorder (activated protein C resistance). By contrast, a substantial portion of flap necroses could be related to nonconstitutional factors (for example, pedicle kinking). It is concluded that routine screening for hypercoagulable states such as activated protein C resistance is not necessary in microvascular surgery.

Intrinsic Anticoagulation: Protein C, Protein S, and Thrombomodulin

The protein C anticoagulant system provides important control over the blood coagulation cascade. Any alteration in this pathway, either hereditary, iatrogenic, or otherwise, may interfere with normal coagulation. In this review, current concepts and understanding of surface-dependent hemostatis are reviewed, effects of deficiencies in the intrinsic anticoagulant system are described, and potentially useful therapeutic strategies are proposed. The importance of protein C, protein S, and thrombomodulin in patients undergoing cardiac surgery is specifically addressed. Further work is required before complex interactions of individual components of the intrinsic anticoagulation pathway are fully understood.

Molecular Genetics of Factor V Leiden: Genetic Origins and Modern DNA-Based Detection Strategies

It has been acknowledged that a prothrombotic tendency may result from a specific genetic defect. Resistance to activated protein C (APC) (factor V Leiden) is now recognized as the most prevalent cause of increased thrombogenicity, being found in 2% to 5% of the world population. The APC-resistant phenotype arises from a well-characterized transitional mutation, resulting in an arginine(R)-506-glutamine(Q) amino acid substitution. Much remains to be uncovered concerning the importance of this mutation and how it relates to other conditions on a broader basis. Relevant and accurate detection methods that quickly identify the genetic lesion will play a major part in this strategy. This article details recent advances in identifying the factor V Leiden mutation by modern molecular techniques.

Factor V Leiden (Resistance to Activated Protein C) Increases the Risk of Myocardial Infarction in Young Women

Factor V Leiden (factor V Arg506Gln), the genetic defect underlying resistance to activated protein C, is the most common risk factor for venous thrombosis. The relationship between this genetic abnormality and arterial disease is still unresolved. To assess whether factor V Leiden increases the risk of myocardial infarction (MI), we conducted a population-based case-control study among women 18 to 44 years of age in western Washington state. We included 84 women with first MI and 388 control women, ie, women residing in the same area in the same age range without MI (n = 388). The control women were contacted by random digit dialing. Data on risk factor status were collected via personal interview, and data on the factor V genotype via polymerase chain reaction techniques. The factor V Leiden mutation was found more often in women with MI (10%) than among controls (4%). The odds ratio for MI was 2.4 [95% confidence interval (CI) 1.0 to 5.9]. The risk was increased fourfold (CIgs 1.2 to 12.1) when adjusted for major cardiovascular risk factors. Among nonsmokers the factor V Leiden mutation had little effect (odds ratio 1.1, CI95 0.1 to 8.5), whereas it had a large effect among smokers (odds ratio 3.6, CI95 0.9 to 14.4), which, because smoking was itself a strong risk factor for MI, led to an odds ratio for smoking carriers of the mutation that was 32-fold increased compared with nonsmoking noncarriers. We conclude that factor V Leiden increases the risk of MI in young women. This effect seems to be confined largely to current smokers.

Activated protein C resistance, factor V Leiden and peripheral vascular disease

Activated protein C resistance caused by factor V Leiden is an important thrombophilia disorder which predisposes to venous thromboembolism. Some studies also suggest a role in the pathogenesis of arterial thrombosis and atherosclerosis. The authors have investigated the prevalence of activated protein C resistance and factor V Leiden in a series of 45 patients with peripheral vascular disease. Twelve patients were receiving warfarin. The activated protein C resistance ratios were significantly lower in the group of 33 non-warfarinized patients with peripheral vascular disease (median 2.82 (range 1.36-3.83)) compared with 33 age- and sex-matched controls (median 2.97 range 2.24-4.11); P<0.005; Wilcoxon rank sum). Eight patients (24%) had activated protein C resistance (ratio <2.2). The prevalence of factor V Leiden in patients with peripheral vascular disease was 17.8% (8/45). This is significantly increased compared with the local population and UK published frequency of 3.5% for this genotype. The presence of factor V Leiden did not affect the late outcome of arterial reconstructive surgery in terms of graft patency (P=0.5, Fisher's Exact test).

Mortality and Causes of Death in Families With the Factor V Leiden Mutation (Resistance to Activated Protein C)

To investigate whether resistance to activated protein C (APC resistance) because of a mutation in the factor V gene (factor V Leiden) leads to a decrease in life expectancy, we analyzed overall and cause-specific mortality in 171 parents whose offspring carried this mutation. Compared with the Dutch general population, and after adjustment for age, sex, and calendar period, we found no excess deaths in the parents (standardized mortality ratio [SMR], 1.0; 95% confidence interval [CI], 0.8 to 1.2). The cause-specific SMR for malignant neoplasms (1.0; 95% CI, 0.6 to 1.4), diseases of the circulatory system (1.0; 95% CI, 0.7 to 1.4), and cerebrovascular disease (1.0; 95% CI, 0.4 to 1.9) also did not differ from unity. The SMRs for diseases of the respiratory system (1.4; 95% CI, 0.6 to 2.6) and for ischemic heart diseases (1.1; 95% CI, 0.7 to 1.7) were slightly increased. Under the age of 45 years, there was a ninefold increase of dying from ischemic heart disease. Thromboembolic complications were mentioned only once (venous embolism or thrombosis) as an underlying (“primary”) cause of death (SMR, 2.3; 95% CI, 0.1 to 13.0) and three times (pulmonary embolisms) as a contributing (“secondary”) cause of death (SMR, 1.5; 95% CI, 0.3 to 4.4). We conclude that there is no major effect of APC resistance on life expectancy. Therefore, long-term anticoagulation in carriers of factor V Leiden, on the basis of the carrier state alone, is not indicated.

Activated protein C resistance due to a common factor V gene mutation is a major risk factor for venous thrombosis

Inherited resistance to activated protein C (APC) was recently discovered to be a cause of familial thrombophilia and is now known to be the most common genetic risk factor for venous thrombosis. It is caused by a single point mutation in the gene for factor V, which predicts substitution or arginine (R) at position 506 with a glutamine (Q). Accordingly, the activated form of mutated factor V (FVa:Q506) is more slowly degraded by activated protein C than normal FVa (FVa:R506) is, resulting in hypercoagulability and a lifelong 5- to 10-fold increased risk of venous thrombosis. Previously known inherited hypercoagulable states, i.e. deficiencies of the anticoagulant proteins antithrombin III, protein S, and protein C, are found fewer than 10-15% of thrombosis patients in western countries, whereas inherited APC resistance is present in 20-60% of such patients. The FV mutation is common in populations of Caucasian origin, with prevalences ranging from 1-15%, whereas it is not found in certain other ethnic groups such as Japanese and Chinese. The high prevalence of APC resistance, in combination with the availability of simple laboratory tests, will have a profound influence on the development of therapeutic and prophylactic regimens for thrombosis and will, it is hoped, result in a decreased incidence of thromboembolic events.

Clinical significance of the FV:Q506 mutation in unselected oncology patients

PURPOSE

A common germline mutation in the factor V gene (FV:Q506) has been associated with hypercoagulability in families with heritable predisposition to thrombosis. We examined the prevalence and clinical significance of the FV:Q506 mutation in cancer patients.

PATIENTS AND METHODS

We performed a retrospective cohort study by examining 353 consecutive, unselected patients in a general hematology/oncology clinic. We ascertained risk factors, obtained the clinical clotting history, and determined the heterozygous or homozygous presence of the FV:Q506 allele for each patient.

RESULTS

We detected a germline mutation in 5.4% (19 of 353) of patients, of whom 18 were heterozygous and 1 was homozygous for the FV:Q506 mutant allele. In 17 of 18 heterozygous patients, there was no history of venous thrombosis or catheter-associated thrombosis. These asymptomatic patients included 13 patients who had been diagnosed with cancer or leukemia for a mean of 66.2 months (median 69) and had received a variety of local and systemic treatments. In contrast, 1 of 18 heterozygous and 1 of 1 homozygous patients had developed deep vein thrombosis that was associated, respectively, with either recurrent thrombotic events or a strong family history for pulmonary embolus.

CONCLUSIONS

Routine screening for the FV:Q506 mutation in cancer patients without a personal or family history for venous thrombosis is not helpful in guiding management. In contrast, an episode of venous thrombosis in a patient with a mutant germline FV:Q506 allele was associated with recurrent thrombotic events. These findings suggest that patients heterozygous for the FV:Q506 allele may require an independent "susceptibility" element to manifest a venous hypercoagulable state. In addition, only 2 of 25 clinic patients with a venous clot carried the FV:Q506 allele suggesting this genetic defect plays a minor role in the hypercoagulable state of cancer.

Arterial and venous thrombosis in two Italian families with the factor V Arg506-->Gln mutation

APC resistance, due to a point mutation in factor V at amino acid position Arg506, has been identified as a major cause of inherited thrombophilia. Here we report the presence of the factor V Arg506-->Gln mutation in 2 Italian families. In 1 family 3 subjects heterozygous and 2 subjects homozygous for the factor V Arg506-->Gln mutation were identified. The only subject who developed a thrombotic event was a 20-yr-old girl who was found to be homozygous for the factor V Arg506-->Gln mutation. In the second family 10 subjects were identified to be heterozygous for the factor V Arg506-->Gln mutation; among them 2 developed a thrombotic event. In the same family 2 individuals were found to be homozygous for the mutation: the first had a myocardial infarction at age 25 yr and the second suffered from multiple episodes of deep venous thrombosis and had a stroke at age 24 yr. These data show that the risk of developing deep venous thrombosis for the carriers of the factor V Arg506-->Gln mutation is high in the families investigated. Furthermore our data imply that the factor V Arg506-->Gln mutation in its homozygous form may relate to myocardial infarction and stroke.

Resistance to activated protein C: role in venous and arterial thrombosis

Activated protein C resistance is the most prevalent cause of thrombophilia: it is found in 20 to 30% of patients with a deep venous thrombosis history. Activated protein C resistance is due to an arginine 506 to glutamine mutation in factor V. This mutation prevents normal inactivation of activated factor V by activated protein C. The estimated increase in relative risk of venous thrombosis is 5- to 10-fold in heterozygotes, and 50- to 100-fold in homozygotes. Activated protein C resistance does not seem to play a role in arterial thrombosis and in the occurrence of myocardial infarction.

Familial thrombophilia: clinical and molecular analysis of Swedish families with inherited resistance to activated protein C or protein S deficiency

This report describes the characterization of Swedish families with inherited resistance to activated protein C (APC resistance) and/or protein S deficiency, two genetic disorders associated with functional impairment of the protein C anticoagulant pathway. The APC resistance phenotype was linked to the factor V gene locus in a kindred with independent inheritance of APC resistance and protein S deficiency. A point mutation changing Arg506 to a Gln (FV:Q506) in the factor V gene was the cause of APC resistance. In studies of 50 families with hereditary APC resistance, the FV:Q506 mutation was identified in 94% (47/50) of the families, and the thrombotic risk was found to be dependent on the factor V genotype. Moreover, 18 families with hereditary deficiency of free protein S were investigated. Type I protein S deficiency (low free and total protein S) and type III deficiency (low free but normal total protein S) coexisted in 78% (14/18) of the families, suggesting the two types to be phenotypic variants of the same genetic disorder. Deficiency of free protein S was caused by equimolar relationship between protein S and beta-chain containing isoforms of C4BP. Though protein S deficiency was a strong risk factor for thrombosis, the FV:Q506 mutation was identified as an additional genetic risk factor in 39% of the families. Thus, familial thrombophilia is a multiple gene disorder. The thrombophilic tendency associated with APC resistance or protein S deficiency was related to increased levels of prothrombin fragment 1 + 2, reflecting increased activation of the common coagulation pathway.

Activated protein C resistance: from phenotype to genotype and clinical practice

The anticoagulant protein C system is an important regulator of the blood coagulation process. Its targets are the procoagulant cofactors factor Va and factor VIIIa, which are cleaved and inactivated by activated protein C, protein S and intact factor V working as cofactors. Genetic defects of protein C or protein S were, together with antithrombin III deficiency, the previously established major causes of familial venous thromboembolism. However, these abnormalities are found in less than 5-10% of patients with thrombosis. Inherited resistance to activated protein C was recently identified as a major risk factor for venous thromboembolism. The activated protein C-resistance phenotype is found in 20-60% of the patients with venous thrombosis, depending on selection criteria and on the prevalence of activated protein C-resistance in the population. The frequency of activated protein C-resistance is 2-10% in the normal populations studied so far. In more than 90% of cases, the molecular background for the activated protein C-resistance is a single point mutation in the factor V gene, which predicts substitution of an arginine at position 506 by a glutamine. Mutated factor V is activated by thrombin or factor Xa in the normal way, but impaired inactivation of mutated factor Va by activated protein C results in a life-long hypercoagulability. Owing to the high prevalence of activated protein C-resistance in the population, it occasionally occurs in patients with deficiency of protein S, protein C or antithrombin III. Individuals with combined defects suffer more severely from thrombosis, and often at a younger age, than those with single defects, suggesting thrombophilia to be a multigenetic disease.