Correlation of circulating von Willebrand factor levels with cardiovascular hemodynamics

Quantile-specific heritability of plasminogen activator inhibitor type-1 (PAI-1, aka SERPINE1) and other hemostatic factors

BACKGROUND

Plasminogen activator inhibitor type-1 (PAI-1, aka SERPINE1) is a moderately heritable glycoprotein that regulates fibrin clot dissolution (fibrinolysis).

OBJECTIVES

Test whether the heritabilities (h2 ) of PAI-1 and other hemostatic factors are constant throughout their distribution or whether they are quantile-specific (i.e., a larger or smaller h2 depending on whether their concentrations are high or low).

METHODS

Quantile regression was applied to 5606 parent-offspring pairs and 5310 full siblings of the Framingham Heart Study. Quantile-specific heritability was estimated from the parent-offspring regression slope (βPO , h2  = 2βPO /(1+rspouse )) and the full-sib regression slope (βFS , h2  = {(1+8rspouse βFS )0.5 -1}/(2rspouse )).

RESULTS

Heritability (h2  ± SE) increased significantly with increasing percentiles of the offspring's age- and sex-adjusted PAI-1 distribution when estimated from βPO (plinear trend  = 0.0001): 0.09 ± 0.02 at the 10th, 0.09 ± 0.02 at the 25th, 0.16 ± 0.02 at the 50th, 0.29 ± 0.04 at the 75th, and 0.26 ± 0.08 at the 90th percentile of the PAI-1 distribution, and when estimated from βFS (plinear trend  = 6.5x10-7 ). There was no significant evidence for quantile-specific heritability for factor VII (plinear trend  = 0.35), D-dimer (plinear trend  = 0.08), tPA (plinear trend  = 0.74), or von Willebrand factor (plinear trend  = 0.79).

CONCLUSION

Higher mean plasma PAI-1 antigen concentrations tend to accentuate genetic effects (quantile-dependent expressivity), which is consistent with the greater reported differences in PAI-1 concentrations between rs1799889 SERPINE1 (4G/5G) genotypes in patients with osteonecrosis, meningococcal sepsis, obesity, prior myocardial infarction, deep vein thrombosis, and polycystic ovarian syndrome than in healthy controls. It is also consistent with the greater increases in PAI-1 concentrations in 4G-allele carriers than 5G/5G homozygotes following fibrinolytic treatment, low-salt intake, and high saturated fat intake.

Von Willebrand factor in aortic or mitral valve stenosis and bleeding after heart valve surgery

OBJECTIVES

Low von Willebrand factor (VWF) increases the risk of bleeding. The objective was to assess the influence of VWF on bleeding after valvular surgery.

METHODS

We studied 82 consecutive patients in median age of 65.5 years with severe isolated aortic stenosis (AS, n = 62) or mitral stenosis (MS, n = 20), undergoing heart valve surgery in extracorporeal circulation. Preoperatively, we assessed VWF antigen (VWF:Ag) and activity (VWF:RCo), a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13), and fibrinolysis inhibitors.

RESULTS

Compared with AS, MS patients were more frequently female (80 vs. 55%, p = 0.045) with atrial fibrillation (AF) (80 vs. 8%, p < 0.0001), with no difference in age or comorbidities. Median postoperative drainage was 420 ml for AS, and 425 ml for MS (p = 0.37). Patients with AS had lower VWF:RCo (125.8 [88.5-160.8] vs. 188.0 [140.3-207.3] IU/dl, p = 0.003) and VWF:Ag (135.8 [112.0-171.2] vs. 191.7 [147.3-236.4] IU/dl, p = 0.01) than MS patients. Mean VWF:RCo/Ag ratio was 0.88 ± 0.17, with no intergroup differences. ADAMTS13 levels and activity were similar in both groups. In AS, both VWF:RCo and VWF:Ag correlated inversely with maximal (r = -0.39, p = 0.0003 and r = -0.39, p = 0.0004, respectively) and mean (r = -0.40, p = 0.0004 and r = -0.39, p = 0.0006, respectively) transvalvular pressure gradients. There was no difference in perioperative bleeding between patients following mitral and aortic valve surgery, and bleeding was not associated with VWF:Ag or VWF:RCo.

CONCLUSIONS

In severe AS, VWF levels and activity correlate inversely with transvalvular pressure gradients, and are lower than in severe degenerative MS, but do not affect blood loss after valvular surgery in extracorporeal circulation.

Cocaine use modifies the association between antiretroviral therapy and endothelial dysfunction among adults with HIV infection

Cocaine is commonly used among HIV-infected people and may worsen HIV disease progression. In addition, existing evidence suggests a link between antiretroviral regimens and endothelial dysfunction. This study aimed to examine whether the associations of antiretroviral therapy (ART) regimens with endothelial dysfunction may be modified by cocaine use in adults with HIV infection. Between 2003 and 2014, 466 HIV-positive participants residing in Baltimore, Maryland, were enrolled in a study investigating comorbidities associated with HIV/ART. The associations between various risk factors and endothelial dysfunction indicators were examined by robust regression models fitted for the overall subjects and cocaine subgroups, separately. Duration of nonnucleoside reverse-transcriptase inhibitor (NNRTI)-based therapy was negatively associated with plasma vWF:Ag levels in cocaine non-users (β = -.715, SE = .220, P < .05). However, cocaine users on longer-term NNRTI-based regimens had greater plasma endothelin-1 (ET-1) concentrations than their counterparts (β = .003, SE = .001, P < .05). In addition, current cigarette smoking was significantly positively associated with ET-1 concentrations in both cocaine non-users (β = .609, SE = .164, P < .05) and cocaine users (β = .331, SE = .086, P < .05). In conclusion, cocaine use modified the potential effects of NNRTI-based therapy on biomarkers of endothelial dysfunction. These findings suggested that reduction in cocaine use may improve endothelial function in HIV-infected cocaine users.

Von Willebrand factor revisited

Degenerative aortic valve stenosis is the most common valvular heart disease seen in developed countries. Since the implementation of transcatheter aortic valve replacement, there has been a surge of efforts to improve procedural technique as well as reduce mortality. Until recently, the mainstay method of assessment of valve implantation as well as paravalvular regurgitation has relied heavily on imaging techniques including transesophageal echocardiography and aortic root angiography. There has been a lot of scientific inquiry to identify biomarkers in the management of patients with aortic stenosis. von Willebrand factor activity and high molecular weight multimer level assessment has emerged as an excellent biomarker with intraoperative, point of care potential. These implications can both supplement imaging modalities as well as potentially serve as a more accurate assessment TAVR complications.

Coagulation, Fibrinolytic System Activation and Endothelial Dysfunction in Patients With Mitral Stenosis and Sinus Rhythm

Anticoagulation treatment can prevent systemic embolism in patients with mitral stenosis (MS) and atrial fibrillation (AF), but this treatment is under debate if patients are in sinus rhythm. The authors aimed to determine the hemostatic changes in patients with MS and sinus rhythm. Forty-six patients (28 in sinus rhythm and 18 in AF) with mitral stenosis were enrolled in this study. They studied systemic venous fibrinogen, D-dimer, antithrombin-III, tissue plasminogen activator (tPA), plasminogen activator inhibitor-I (PAI-I), von Willebrand factor (vWF), and platelet factor 4 (PF 4) in these patients. The patients were first classified according to their rhythm as sinusal and AF, and then according to the presence of left atrial spontaneous echo contrast (LASEC). Fibrinogen, D-dimer, antithrombin-III, vWF, and PF 4 levels were significantly greater in patients with MS and sinus rhythm or atrial fibrillation compared to the control group (p<0.05). Whether the rhythm was sinus or AF, fibrinogen, D-dimer, antithrombin-III, vWF, and PF 4 levels were significantly higher in patients with LASEC than in the control group (p<0.05). Only PF 4 was higher in the AF group than in those with sinus rhythm (p<0.05). As to plasminogen activator and PAI-I levels, only tissue plasminogen activator levels were found to be higher in the AF group than in those with sinus rhythm and the control group (p<0.05). In patients with mitral stenosis and sinus rhythm, if LASEC is present, coagulation activation, platelet activation, and endothelial dysfunction are similar in patients with AF, and anticoagulation should be considered in these patients.

Circulating Endothelial Cells and Platelet Microparticles in Mitral Valve Disease With and Without Atrial Fibrillation

Hypercoagulability in mitral valve disease (MVD), a cause of atrial fibrillation (AF) and stroke, is potentially due to endothelial damage/dysfunction (marked by circulating endothelial cells [CECs]), platelet activation (soluble P-selectin [sPsel], platelet microparticles [PMPs], and soluble CD40 [sCD40]), and oxidized low-density lipoprotein (oxLDL) cholesterol. We measured these variables in 24 patients with MVD as well as in 21 with MVD + AF and compared them with 20 healthy controls (HCs). The CECs and PMPs were measured by flow cytometry; sPsel, oxLDL, and CD40 by enzyme-linked immunosorbent assay. Compared with HCs, sPsel and PMPs were equally higher in MVD and MVD + AF; sCD40 and oxLDL were higher in MVD + AF than in HCs and MVD; and CECs were higher in MVD than in the HCs, with further increases in MVD + AF (all P < .001). We conclude that excess platelet activation is present in MVD regardless of AF, and that increased endothelial damage in MVD is greater when compounded by AF.

Patient-prosthesis mismatch increases the mean platelet volume in patients with aortic valve replacement

PURPOSE

Patient-prosthesis mismatch (PPM) is defined when the ratio of the effective orifice area of the normally functioning prosthetic valve to the body surface area of the patient is <0.85 cm(2)/m(2). The aim of this study was to assess the measurements of the mean platelet volume (MPV) as an indicator of platelet activation in patients with PPM.

METHODS

A total of 109 patients with isolated aortic valve replacement (AVR) procedures with a mechanical prosthesis and a control group from a normal population of 102 people compatible in terms of age and sex were chosen for the study. The AVR group was subdivided into a PPM group (n = 41) and non-PPM group (n = 68). All patients and control participants underwent echocardiographic examinations, with simultaneous measurements of the serum MPV values.

RESULTS

The MPV measurements were significantly higher in the patients with AVR compared to the control group (8.97 ± 0.93 vs. 8.26 ± 0.14, p < 0.001). Higher results were also obtained in the patients with PPM compared to the non-PPM group (9.36 ± 0.61 vs. 8.73 ± 1.01, p < 0.001). The platelet counts were found to be similar in both groups (p > 0.05).

CONCLUSIONS

We have herein shown that the PPM patients had a significantly higher MPV compared to the patients with AVR without PPM and healthy subjects.

Do biologic markers predict cardiovascular end points in diabetic end-stage renal disease? A prospective longitudinal study

BACKGROUND

Diabetic patients on hemodialysis are at high risk of death from cardiovascular disease, and research has suggested that various biologic markers of inflammation, oxidative stress and hemostasis may give added value to clinical information for predicting cardiovascular event (CVE)-free survival. This information could be particularly important in evaluating this population for renal transplant, given the scarcity of organs. We hypothesized that in diabetic patients undergoing renal replacement therapy (RRT) these biologic markers would prove useful in predicting event-free follow-up in a prospective study.

METHODS

One hundred and fifty diabetic (76 type 1, 74 type 2) and 27 non-diabetic stable RRT patients were followed for 0.04-13.69 years for CVE (myocardial infarction, coronary arterial intervention, peripheral arterial bypass or amputation, cerebrovascular accident or carotid artery intervention), cardiac and all-cause mortality. Measured biologic markers of inflammation included the following: Il-6, C reactive protein, fibrinogen; of hemostasis: fibrinogen, plasminogen activator inhibitor (PAI), fibrinolytic activity, von Willebrand factor VII (vWF), platelet-selectin, viscosity and of oxidative stress: advanced glycated end products and antibody to oxidized low-density lipoprotein. For each, upper versus lower tertiles were compared for duration of event-free follow-up.

RESULTS

Cardiovascular events prior to study entry occurred in 51.3% of DM1, 54.0% of DM2 and 25.9% of DM0 patients. Subsequent cardiovascular events were noted in 31.6% of DM1, 45.9% of DM2 and 11.1% of DM0 patients. All mean levels of biologic markers at baseline were abnormal (P < 0.05).

CONCLUSIONS

In this RRT population, all biologic marker levels except PAI did not improve clinical prediction of events.

Increase in mean platelet volume in patients with myocardial bridge

AIM

Myocardial bridge is associated with atherosclerosis altered in shear stress and endothelial dysfunction. Mean platelet volume (MPV), a determinant of platelet activation, is shown to be related with atherosclerosis and endothelial dysfunction. In this study, we aimed to evaluate platelet function assessed by MPV in patients with myocardial bridge.

METHODS

Forty-two patients with myocardial bridge in the left anterior descending artery (LAD) and 43 age- and gender-matched healthy participants were included in the study. Myocardial bridging was defined as an intramyocardial systolic compression or milking of a segment of an epicardial coronary artery on angiography. For the entire study population, MPV was measured using an automatic blood counter.

RESULTS

The study population consisted of 42 patients with myocardial bridge (52.7 ± 10.2, 76.2% male) and 43 age- and sex-matched healthy control participants (52.1 ± 10.4, 74.4% male). Compared to the control group, MPV value was significantly higher in patients with myocardial bridge (8.9 ± 1.24 vs 8.3 ± 0.78; P = .01). Further, there were no significant differences between groups regarding hemoglobin level, platelet count, fasting blood glucose, and creatinine levels.

CONCLUSIONS

Our study findings indicated that myocardial bridge is associated with elevated MPV values. Our results might partly explain the increased cardiovascular events in patients with myocardial bridge.

Plasma von Willebrand factor as a predictor of survival in pulmonary arterial hypertension associated with congenital heart disease

Biomarkers have been identified for pulmonary arterial hypertension, but are less well defined for specific etiologies such as congenital heart disease-associated pulmonary arterial hypertension (CHDPAH). We measured plasma levels of eight microvascular dysfunction markers in CHDPAH, and tested for associations with survival. A cohort of 46 inoperable CHDPAH patients (age 15.0 to 60.2 years, median 33.5 years, female:male 29:17) was prospectively followed for 0.7 to 4.0 years (median 3.6 years). Plasma levels of von Willebrand factor antigen (VWF:Ag), tissue plasminogen activator (t-PA) and its inhibitor (PAI-1), P-selectin, reactive C-protein, tumor necrosis factor alpha, and interleukin-6 and -10 were measured at baseline, and at 30, 90, and 180 days in all subjects. Levels of six of the eight proteins were significantly increased in patients versus controls (13 to 106% increase, P < 0.003). Interleukin-10 level was 2.06 times normal (P = 0.0003; Th2 cytokine response). Increased levels of four proteins (t-PA, PAI-1, P-selectin, and interleukin-6) correlated with disease severity indices (P < 0.05). Seven patients died during follow-up. An average VWF:Ag (mean of four determinations) above the level corresponding to the 95th percentile of controls (139 U/dL) was independently associated with a high risk of death (hazard ratio = 6.56, 95%CI = 1.46 to 29.4, P = 0.014). Thus, in CHDPAH, microvascular dysfunction appears to involve Th2 inflammatory response. Of the biomarkers studied, plasma vWF:Ag was independently associated with survival.

Increased platelet activation and endothelial dysfunction in patients with atrial fibrillation immediately following percutaneous balloon mitral valvuloplasty

BACKGROUND

Immediately following percutaneous balloon mitral valvuloplasty (PBMVP), patients have a 3% risk of systemic thromboembolism.

HYPOTHESIS

We hypothesized that this may in part be due to an increase in hypercoagulability (as indicated by abnormal coagulation, platelet activation, and endothelial dysfunction) in such patients.

METHODS

We measured indices of platelet activation [soluble P-selectin (sPsel), ELISA], endothelial dysfunction [von Willebrand factor (vWf), ELISA], and coagulation (fibrinogen, modified Clauss) in 16 patients (15 women, mean age 59 +/- 10 years) with chronic atrial fibrillation admitted for PBMVP, and 16 healthy age- and gender-matched controls. Blood samples were obtained as follows: (1) peripheral venous samples prior to PBMVP, immediately following PBMVP, and 24 h after PBMVP; and (2) arterial samples prior to and immediately following PBMVP.

RESULTS

Patients with mitral stenosis and chronic atrial fibrillation demonstrated significantly higher mean levels of vWf [148 (SD 24) vs. 102 (SD 37); t-test, p < 0.001] and plasma fibrinogen [4.2 (SD 0.8) vs. 3.3 (SD 0.8); p = 0.003] at baseline than matched healthy controls. There was a nonsignificant trend toward lower median sP-sel levels in patients with mitral stenosis [64 (inter quartile range 47-91) vs. 109 (46-128); Mann-Whitney test, p = 0.08]. Following PBMVP, there was a significant increase in venous sP-sel levels immediately post procedure (paired Wilcoxon test, p = 0.03) and at 24 h afterward (p = 0.01). Arterial s-Psel levels correspondingly increased immediately post procedure (p = 0.008). There was a significant increase in mean venous (at 24 h) but not arterial vWf levels post PBMVP. There were no significant changes in mean venous or arterial plasma fibrinogen levels following PBMVP.

CONCLUSION

Patients with mitral stenosis and chronic atrial fibrillation have increased plasma levels of vWf and fibrinogen levels compared with healthy controls, suggesting increased endothelial dysfunction and coagulation at baseline in these patients. The increased levels of sP-sel immediately post procedure and at 24 h, in association with increased vWf levels at 24 h after PBMVP, are in keeping with an increase in platelet activation and endothelial dysfunction following PBMVP. These changes may contribute to the increased risk of thromboembolism following PBMVP and suggest the need for adequate antithrombotic therapy following PBMVP.

Von Willebrand factor, type 2 diabetes mellitus, and risk of cardiovascular disease: the framingham offspring study

BACKGROUND

Von Willebrand factor (vWF) is inconsistently associated with cardiovascular disease (CVD). This might be explained by associations of vWF with type 2 diabetes mellitus and insulin resistance.

METHODS AND RESULTS

We tested whether vWF predicted incident CVD in 3799 Framingham Offspring Study participants, and in particular, among those with type 2 diabetes mellitus or insulin resistance. During 11 years of follow-up, 351 participants developed CVD. In proportional hazards models (with adjustment for age, sex, blood pressure, smoking, body mass index, total and high-density lipoprotein cholesterol, and treatment with aspirin, insulin, antihypertensives, and lipid-lowering medications) with the lowest quartile of the vWF distribution as the referent, the hazard ratio (HR) for CVD was 0.94 in the second quartile, 0.98 in the third, and 1.32 in the highest (P=0.04 for trend). Additional adjustment for type 2 diabetes mellitus or insulin resistance (homeostasis model) partially attenuated the association (multivariable HRs for top quartile 1.28 and 1.21, respectively). We then stratified the models by diabetes status or the homeostasis model of insulin resistance distribution (top quartile versus lower 3 quartiles). vWF was associated with CVD among participants with diabetes mellitus (HR for top quartile relative to bottom 1.47, P=0.04 for trend) but not among nondiabetic participants (HR 1.15, P=0.5) and similarly among insulin-resistant (HR 1.50, P=0.01) but not insulin-sensitive (HR 1.02, P=0.9) participants.

CONCLUSIONS

Higher levels of vWF were associated with risk of CVD in people with type 2 diabetes mellitus or insulin resistance, which suggests that vWF may be a risk factor unique to these populations.

Increased von Willebrand factor in acute stroke patients with atrial fibrillation

Plasma level of von Willebrand factor (vWF) is a useful marker not only for endothelial dysfunction, but also for left atrial thrombogenesis. We measured plasma levels of vWF antigen and other coagulation and fibrinolysis markers in 183 consecutive patients with acute ischemic stroke and compared these data between patients with and without atrial fibrillation (AF). vWF correlated with severity, outcome, and infarct size and were significantly higher in the AF group than in the non-AF group. The positive correlations of vWF with plasmin-alpha2 plasmin inhibitor complex and soluble fibrin monomer complex, and higher levels of vWF in patients with than without spontaneous echo contrast, indicate thrombogenesis in the left atrium. Plasma levels of vWF may reflect thrombogenesis in patients with AF.

Alterations of von Willebrand Factor and Ristocetin Cofactor Activity During Atrial Fibrillation

The aim of this study was to assess the plasma levels of von Willebrand factor antigen and ristocetin cofactor activity, which are well-known markers of endothelial function, in atrial fibrillation (AF) with or without mitral stenosis (MS). Forty-two patients (16 patients with MS and AF [MS(+)AF(+)], 13 patients with nonvalvular AF [MS(−)AF(+)], and 13 patients with MS and sinus rhythm [MS(+)AF(−)]) were included. Von Willebrand factor antigen levels and ristocetin cofactor activities in all participants were assessed. Overall, von Willebrand factor antigen levels and ristocetin cofactor activities in the AF(+) patients were higher than in the AF(−) patients ( P = .003 and P = .002, respectively). Von Willebrand factor antigen levels and ristocetin cofactor activities in the 3 groups were found to be different ( P = .012 and P = .01, respectively). Von Willebrand factor antigen levels were similar between the MS(+)AF(+) and MS(−)AF(+) groups and were higher than that of the MS(+)AF(−) group. Ristocetin cofactor activity in the MS(−)AF(+) group was significantly higher than in the other 2 groups. The ristocetin cofactor activity and von Willebrand factor antigen levels were significantly higher in diabetic or hypertensive patients than in nondiabetic or normotensive patients. According to the results of this study, circulating von Willebrand factor antigen levels and plasma ristocetin cofactor activities are affected by the presence of AF, MS, and associated comorbidities including type 2 diabetes mellitus and systemic hypertension. Further studies are needed to assess the role of von Willebrand factor antigen and ristocetin cofactor activity in predicting vascular thrombotic events in AF, MS, systemic hypertension, and diabetes mellitus.

Acquired and Reversible von Willebrand Disease With High Shear Stress Aortic Valve Stenosis

BACKGROUND

Severe aortic valve stenosis is relatively more prevalent in patients with repeated bleeding episodes. The goal of the present study was to determine the effect of aortic valve replacement on von Willebrand factor levels in patients with aortic stenosis.

METHODS

von Willebrand factor levels were assessed by using immunoblotting electrophoresis techniques before and 1 month after surgery in 29 consecutive patients with severe aortic valve stenosis.

RESULTS

Eight of 29 patients reported episodes of bleeding, including three episodes of major bleeding, in the 6 months before surgery. None of the patients were receiving anticoagulation therapy. Although there was no difference in platelet count before and after surgery, von Willebrand factor levels were significantly greater at 1 month after surgery (p = 0.05) when compared with preoperative values. Further, von Willebrand factor levels were significantly lower in patients with aortic valve prosthesis mismatch than in those patients without this phenomenon (p < 0.05). Electrophoresis experiments showed a deficit in large multimers of von Willebrand factor preoperatively but not postoperatively, except for in those patients with aortic valve prosthesis mismatch.

CONCLUSIONS

In conclusion, valve replacement can result in increases in von Willebrand factor in patients with aortic valve stenosis.

Relation of the prothrombotic state to increasing age (from the Framingham Offspring Study)

A greater life expectancy has led to an increasing proportion of elderly patients. Increasing age is an important risk factor for cardiovascular disease, but the mechanism of risk is not well understood. Because thrombosis plays a key role in plaque development and the onset of acute coronary syndromes, the age-related increase in cardiovascular risk may be a result of a prothrombotic imbalance. The study aim was to examine the relation between age and thrombotic potential in the Framingham Offspring Cohort. Hemostatic factors previously associated with cardiovascular risk were measured in 3,230 patients (55% women) without evidence of cardiovascular disease who were participating in cycle 5 of the Framingham Offspring Study. The subjects were divided by age into decades. Advancing age was associated with a significant increase in fibrinogen and von Willebrand factor levels and measures of impaired fibrinolytic potential (plasminogen activator inhibitor and tissue plasminogen activator antigens). For men, the mean fibrinogen levels were 21% higher in those > or =70 years versus those aged <40 years (326 vs 268 mg/dl, p <0.001 for linear trend). The mean fibrinogen levels were 15% higher in older than in younger women (330 vs 286 mg/dl, p <0.001). The significant relations persisted after multivariate adjustment. In conclusion, advancing age is associated with elevated levels of hemostatic factors indicative of a prothrombotic state. Because these factors are also associated with endothelial dysfunction, these findings are consistent with an injurious effect of age on the endothelium. Measures to reduce thrombotic potential may be of particular value in the elderly, because they counter the prothrombotic state that develops with aging.

Risk factors for thromboembolic events in renal failure

OBJECTIVES

To determine whether prior thromboembolic events (TE) influence current measures of hemostasis, inflammation and oxidative stress in a population at high cardiovascular risk.

BACKGROUND

Renal failure patients demonstrate a remarkably elevated incidence of TE.

METHODS

Relationships between plasma test results and prior TE history were studied in 78 diabetic and 23 non-diabetic patients with renal failure. TE were defined as myocardial infarction, stroke or vascular surgery.

RESULTS

Markers for inflammation (interleukin (IL)-6, C reactive protein (CRP)), thrombosis (fibrinogen, low molecular weight (LMW) fibrinogen, factor VII, viscosity), fibrinolysis (fibrinolytic activity, plasminogen activator inhibitor (PAI)), endothelial/platelet activity (P-selectin, von Willebrand factor (vWf)) and oxidative stress (antibody to oxidized low-density lipoprotein (LDL), advanced glycated end products) were significantly different from a healthy control population. Dialysis patients with diabetes were twice as likely to have sustained a TE (58 vs. 30%, p = 0.032). Those patients in the total group with levels above the median for IL-6 (p = 0.045), and CRP (p < 0.017) were more likely to have sustained a TE than those with levels below the median. Those diabetic patients with levels above the median for CRP were more likely to have a prior history of TE (p < 0.021). For non-diabetic patients, levels above the median of IL-6 were associated with a prior history of TE (p = 0.027). Multiple correlations for factors of inflammation, hemostasis and oxidative stress indicate that these mechanisms are not independent of one another.

CONCLUSION

Prior TE was associated with markers of inflammation a relationship that may influence the interpretation of these tests which are strongly interrelated in patients at high cardiovascular risk.

Decreased platelet activation and endothelial dysfunction after percutaneous mitral balloon valvuloplasty

OBJECTIVE

This study was conducted to assess the changes in platelet activation and endothelial dysfunction in patients with mitral stenosis (MS) and sinus rhythm (SR) following percutaneous mitral balloon valvuloplasty (PMBV).

BACKGROUND

Systemic thromboembolism is a serious complication in patients with valvular heart disease, and its incidence is highest in those with mitral stenosis. A hypercoagulable state has also been reported in patients with mitral stenosis and sinus rhythm. A recent study has shown that patients with previous PMBV had a lower incidence of thromboembolism.

METHODS AND RESULTS

The study was conducted in 21 patients (two men, 19 women, mean age=34+/-6 years) with mitral stenosis and sinus rhythm (SR) who underwent percutaneous mitral balloon valvuloplasty and 17 healthy control subjects (two men, 15 women, mean age=33+/-6 years). Biochemical markers of platelet activity (beta thromboglobulin, BTG, and soluble P-selectin, sPsel) and endothelial dysfunction (von Willebrand Factor, vWF) were measured in both control subjects' and patients' serum samples taken immediately before PMBV and 24 h after PMBV procedure. All patients underwent successful PMBV. Significant improvement of mitral valve area, pulmonary artery pressure, mean mitral gradients, and left atrial diameter were achieved in all patients after PMBV. Compared with control subjects, patients with MS had higher plasma levels of BTG (66+/-26 ng/ml vs. 14+/-6 ng/ml, P<0.001), vWF (177+/-67 units/dl vs. 99+/-37 units/dl, P<0.0001), sPsel (226+/-74 ng/ml vs. 155+/-66 ng/ml, P<0.001). There was a significant reduction of plasma levels of BTG (66+/-26 ng/ml vs. 48+/-20 ng/ml, P=0.002), vWF (177+/-67 units/dl vs. 134+/-60 units/dl, P=0.001) and P-selectin (226+/-74 ng/ml vs. 173+/-71 ng/ml, P=0.008,) 24 h after PMBV.

CONCLUSION

We have shown that patients with severe MS and SR have increased platelet activation and endothelial dysfunction compared with control subjects and PMBV results in decreased platelet activity and improvement of endothelial injury.

Expression of the von Willebrand Factor in Atrial Endocardium is Increased in Atrial Fibrillation Depending on the Extent of Structural Remodeling

BACKGROUND

The incidence of stroke in patients suffering atrial fibrillation (AF) is increased when left atrial enlargement occurs. Recently, the platelet adhesive molecule, von Willebrand factor (vWF), located in the atrial endocardium, has been shown to be increased in patients with a variety of heart diseases compared with patients who have no cardiac problems.

METHODS AND RESULTS

We investigated the expression of vWF mRNA and protein in the endocardium as a possible prothrombotic alteration of AF in association with atrial structural remodeling. Atrial appendage specimens were obtained during either heart surgery or at an autopsy from AF patients with and without underlying heart disease. The immunohistochemical and in situ hybridization signals for vWF in the endocardium were well correlated and varied widely among the individual atrial appendages examined. The increased expression of vWF in the endocardium was associated with enlarged left atrial dimensions in mitral valvular disease or increased myocyte diameters in the underlying myocardium. Platelet adhesion/aggregation on the endocardium was always found under the fresh thrombi and was colocalized with strong vWF staining, but not necessarily with fibrinogen and/or fibrin staining.

CONCLUSIONS

Endocardial overexpression of vWF may occur during the process of atrial structural remodeling contributing to the thrombotic predilection of AF in association with underlying heart disease.

Relationship between plasma markers of endothelial cell integrity and the Framingham cardiovascular disease risk-factor scores in apparently healthy individuals

Separate reports have identified differences in plasma levels of the endothelial markers soluble E-selectin, von Willebrand factor (vWf) and soluble thrombomodulin in each of the major modifiable risk factors for atherosclerosis (smoking, hypertension and hypercholesterolaemia), and abnormal levels of some plasma markers predict various adverse cardiovascular events. However, it is unclear whether there is an increasing effect on the endothelium with a worsening risk-factor profile. We measured the three endothelial cell markers by enzyme-linked immunosorbent assay in the plasma of 200 subjects (mean age, 54 years; 58% men) free of the symptoms and clinical signs of atherosclerosis. Levels of the markers were then correlated with the Framingham coronary heart disease (CHD) and cerebrovascular disease (CVD) scores to help determine which (if any) may be useful as good laboratory predictors of future cardiovascular events in prospective epidemiological studies. vWf correlated with CHD (r(s) = 0.269, < 0.001) and CVD risk (r(s) = 0.331, P < 0.001), but soluble E-selectin correlated only with CHD risk (r(s) = 0.163, P = 0.021). We conclude that, of the three specific endothelial markers, vWf correlates most closely with the Framingham risk-factor prediction scores and therefore may be the better plasma endothelial marker of the future development of an atherothrombotic event.

Increased von Willebrand factor in the endocardium as a local predisposing factor for thrombogenesis in overloaded human atrial appendage

OBJECTIVES

We investigated immunoreactive von Willebrand factor (vWF), a platelet adhesion molecule, in the endocardial endothelium and its relationship to thrombogenesis in the human atrial appendage.

BACKGROUND

Intra-atrial thrombogenesis is generally thought to be induced by blood stasis in the atrial appendage involved with atrial fibrillation (AF). Little attention has been paid to alterations of the endocardial endothelium on which the thrombus develops.

METHODS

Atrial appendage tissue was obtained at heart surgery or at autopsy from AF and non-AF cardiac patients and from noncardiac patients. Immunohistochemistry for endothelial cell markers including vWF, CD31, CD34 and endothelial nitric oxide synthase (eNOS) and platelet glycoprotein Ib/IX or IIb/IIIa was performed and semiquantitatively graded.

RESULTS

In contrast to the apparent immunostaining for CD31, CD34 and eNOS, only focal or little immunoreactive vWF was seen in the endocardium of noncardiac patients. Immunoreactive vWF in the endocardial endothelium was increased in most cardiac patients, particularly in the left, but not in the right, atrial appendage of patients with mitral valvular disease, irrespective of whether AF was present. Platelet adhesion/thrombus formation in the endocardium was found in limited sites in which the overlying endothelium was deficient in eNOS and CD34. When warfarin-treated cases were excluded, there was a significant correlation between the immunohistochemical grade for vWF and the degree of platelet adhesion/thrombus formation in the endocardium.

CONCLUSIONS

Immunoreactive vWF in the endocardial endothelium was increased in overloaded human atrial appendage, which may be a local predisposing factor for intraatrial thrombogenesis.

Correlation between quantitative left atrial spontaneous echocardiographic contrast and intact fibrinogen levels in mitral stenosis

An association between left atrial spontaneous echocardiographic contrast (LASEC) and thromboembolic events has been recognized. However, the appearance of LASEC and the assessment of its intensity are gain dependent. To evaluate the relation between LASEC intensity and coagulation activity, 11 patients with mitral stenosis underwent transesophageal echocardiography with quantitative integrated backscatter assessment of LASEC. Right and left atrial blood samples were evaluated for concentrations of coagulation markers, including intact fibrinogen, fibrinopeptide A, D-dimer, prothrombin fragment 1+2, and thrombin-antithrombin III complex. The patients were found to have significantly higher mean left atrial concentrations compared with right atrial concentrations of thrombin-antithrombin III (28.46 +/- 21.05 versus 3.21 +/- 7.16 ng/mL, respectively; P =.001) and fibrinopeptide A (32.78 +/- 17.54 versus 7.42 +/- 8.27 nmol/L, respectively; P <.001). Intact fibrinogen levels were similar in both atria, and a strong, direct correlation existed between left and right atrial intact fibrinogen levels (r = 0.78, P =.005). Quantitative integrated backscatter of LASEC correlated directly with left atrial fibrinogen level (r = 0.78, P =.013) but not with markers of thrombin generation (thrombin-antithrombin III) or activity (fibrinopeptide A). Our results confirm that patients with mitral stenosis have evidence of a regional hypercoagulable state in the left atrium. However, the intensity of LASEC assessed by quantitative integrated backscatter correlates with both right and left atrial intact fibrinogen level, a systemic marker of coagulation.

The effect of vitamin C supplementation on coagulability and lipid levels in healthy male subjects

Although dietary intake and plasma levels of vitamin C have been inversely associated with cardiovascular disease, the mechanism through which it may exert its effect has not been fully explained. Since thrombosis plays an important role in the onset of cardiovascular disease, we investigated the effect of vitamin C on measures of hemostasis that have been associated with cardiovascular risk. The effect of vitamin C on lipid levels was also evaluated. In a randomized, placebo-controlled, crossover study, we determined the effect of 2 g daily of vitamin C supplementation on platelet adhesion and aggregation, levels of tissue plasminogen activator antigen, plasminogen activator inhibitor, fibrinogen, plasma viscosity, von Willebrand factor, and lipid levels in 18 healthy male volunteers with low normal vitamin C levels. No striking effects of vitamin C on the hemostatic measures were observed, although tissue plasminogen activator antigen levels were inversely related to Vitamin C levels. Von Willebrand factor levels were slightly higher with vitamin C, although within the normal range. Total cholesterol levels were 10% lower when subjects were receiving vitamin C compared to placebo (167+/-7 mg/dL vs. 184+/-7 mg/dL), P=0. 007), although the total cholesterol/HDL ratio was not significantly different. Higher levels of tissue plasminogen activator antigen, which in the present study were associated with lower vitamin C levels, have been shown in prospective studies to convey an increased risk of cardiovascular events. Further studies of the effect of vitamin C on hemostatic measures are required in higher risk populations or those with known cardiovascular disease.

Endothelial cell dysfunction correlates differentially with survival in primary and secondary pulmonary hypertension

BACKGROUND

Plasma von Willebrand factor antigen (vWF:Ag) has been used as a marker of endothelial perturbation in a number of vascular disorders. In this study, vWF:Ag was determined as an attempt to evaluate the severity of endothelial cell dysfunction in primary pulmonary hypertension (PPH) and congenital heart disease-associated pulmonary hypertension (CHD-PH) comparatively and to determine its impact on short-term survival.

METHODS AND RESULTS

Clinical, hemodynamic, and biochemical data were obtained from 11 patients with PPH and 24 with CHD-PH. Patient groups were similar in terms of age and pulmonary artery pressure. vWF:Ag was measured by electroimmunodiffusion. Patients were followed up for 1 year and at that time, data collected at the beginning of the study were subjected to univariate and multivariate analyses. vWF:Ag was increased in patients (normal reference value 87% +/- 23% activity, mean +/- SD), with higher levels in the PPH group (231% +/- 89%) in comparison with the CHD-PH group (127% +/- 68%) (P <.001). Multivariate analysis showed that survival was influenced by the underlying cause of pulmonary hypertension and vWF:Ag levels but not by patient age, sex, or pulmonary artery pressure. Seven of 10 nonsurvivors but only 4 of 25 survivors had PPH (P =.007). vWF:Ag was 255% +/- 90% in the nonsurvivor group and 121% +/- 54% in the survivors (P <.001).

CONCLUSIONS

Our findings suggest that short-term survival is related to the severity of endothelial cell dysfunction in pulmonary hypertension. In addition, exceedingly high vWF:Ag levels in PPH might reflect a particular pattern of endothelial cell dysfunction that could be associated with decreased short-term life expectancy in this disorder compared with secondary forms of pulmonary hypertension.

Improved glycemic control and platelet function abnormalities in diabetic patients with microvascular disease

Patients with diabetes mellitus have a variety of platelet and coagulation system dysfunctions. At least theoretically, these can contribute to microvascular complications. Intensive glycemic control has been demonstrated to decrease microvascular complications in type 1 diabetics. We studied 16 patients with type 1 diabetes mellitus (11 men and five women; mean age, 39 years) with albuminuria greater than 0.1 g/d and/or proteinuria greater than 0.3 g/d and a creatinine clearance rate higher than 30 mL/min. They received a regimen including three to four injections of insulin per day with or without a weekly infusion of intravenous insulin, and were evaluated for 6 months. We compared the plasma level of von Willebrand factor, platelet aggregation responses to adenosine diphosphate (ADP), epinephrine, and collagen, and platelet adhesion at the beginning of the study and at follow-up intervals. Glycemic control improved significantly. There were no significant differences in the platelet aggregation responses to ADP (1.59 +/- 0.34 v 1.88 +/- 0.23 mmol/L, P = .3; normal, 4.6 +/- 0.2), epinephrine (0.50 +/- 0.20 v 1.11 +/- 0.31 mmol/L, P = .06; normal, 7.6 +/- 1.5), or collagen (92.4 +/- 6.61 v 82.60 +/- 3.78 seconds, P = .6; normal, 79.1 +/- 3.1) or in platelet adhesion (126.31 +/- 16.95 v 195.08 +/- 30.2 platelets, P = .34; normal, 68.6 +/- 1.4). Baseline von Willebrand factor increased, but not significantly (166.38% +/- 10.6% v 142.72% +/- 14.73%, P = .21; normal, 102.0% +/- 6.0%). In type 1 diabetic patients with established microvascular complications of nephropathy, a statistically significant improvement in glycemic control did not improve the in vitro platelet function abnormalities. Improved glycemic control delays the progression of microvascular disease through mechanisms not measured by tests of platelet function.

Endothelin and von Willebrand factor as parameters of endothelial function in idiopathic dilated cardiomyopathy: different stimuli for release before and after heart transplantation?

BACKGROUND

Congestive heart failure (CHF) and heart transplantation (HTX) are characterized by endothelial dysfunction as indicated by elevation of markers of endothelial function, including endothelin and von Willebrand factor (vWF). However, previous studies included both patients with idiopathic dilated cardiomyopathy and ischemic heart disease; the latter condition shows endothelial dysfunction, per se. The 2 endothelial factors have different origin and may provide different information about endothelial dysfunction in CHF and after HTX caused by idiopathic dilated cardiomyopathy.

METHODS

We investigated plasma endothelin and vWF, the relation between these 2 factors, and determinants of endothelin and vWF plasma levels in 32 healthy controls, 25 patients with CHF, and 22 patients who had HTX; both conditions were caused by idiopathic dilated cardiomyopathy.

RESULTS

Plasma endothelin was elevated in CHF (6.8 +/- 3.4 pg/mL) and after HTX (6.1 +/- 2.1) compared with healthy controls (4.0 +/- 1.0, P <.0001 for both). VWF was also elevated in CHF (1.6 +/- 0.6 U/mL) and after HTX (2.6 +/- 1.0) compared with healthy controls (1.0 +/- 0.5, P <.0001 for both). VWF was increased after HTX compared with CHF (P <.001), in contrast to similar endothelin levels in CHF and after HTX. Plasma endothelin and vWF correlated in both CHF (r = 0.65, P <.001) and HTX (r = 0.66, P <. 001) but not in controls. In CHF, New York Heart Association functional class was an independent determinant of vWF (P <.0001) and furosemide dose of endothelin (P <.0001). In cardiac transplant recipients, plasma albumin was an independent determinant of vWF (P <.01), and plasma sodium and furosemide dose were independent determinants of endothelin (P <.01).

CONCLUSIONS

Plasma endothelin and vWF were directly correlated in both CHF and after HTX caused by idiopathic dilated cardiomyopathy. However, the production of the 2 factors appeared to be stimulated by different mechanisms and provided different information about endothelial function, as indicated by the different determinants and different response to heart transplantation.

Circulating von Willebrand factor antigen as a predictor of short-term prognosis in pulmonary hypertension

STUDY OBJECTIVE

To determine the potential value of plasma von Willebrand factor antigenic activity (vWF:Ag) and other commonly measured clinical variables for predicting which patients with precapillary pulmonary hypertension would be unlikely to survive 1 year.

DESIGN

Prospective clinical study. The data obtained at the beginning of the study were analyzed at the end of the first year of follow-up.

PATIENTS AND METHODS

Forty patients aged 1.2 to 45 years (median, 24 years) entered the study. Eleven patients had primary pulmonary hypertension, and in the remaining ones, pulmonary vascular disease was associated with antiphospholipid syndrome (n = 1), collagen vascular disease (n = 1), schistosomiasis (n = 3), or congenital heart defects (Eisenmenger's syndrome) (n = 24). Plasma vWF:Ag was determined by electroimmunodiffusion, and the results were expressed as the percentage of activity.

RESULTS

Seven of 11 patients with primary pulmonary hypertension but only 4 of 29 patients with secondary pulmonary hypertension died during the follow-up period (p < 0.005). Initial vWF:Ag values were significantly higher in the nonsurvivor group in comparison with the survivors (256.6+/-85.3% and 132.0+/-59.3% activity, respectively; p < 0.0001). The likelihood of fatal outcome as a function of plasma vWF:Ag levels was estimated for primary and secondary pulmonary hypertensive patients using logistic regression analysis. Decreased life expectancy was significantly related to high vWF:Ag levels and an established diagnosis of primary pulmonary hypertension. A plasma vWF:Ag of >240% (p = 0.003) was 54% sensitive and 93% specific for identifying patients who were unlikely to survive 1 year, with an overall predictive value of 75%. No other variables correlated significantly with survival.

CONCLUSION

Plasma vWF:Ag seems to be a useful biochemical index for predicting short-term prognosis in patients with pulmonary hypertension. In contrast to hemodynamic and histopathological predictors of survival, vWF:Ag does not require invasive techniques to be determined. In light of the possibility of false-negative results, serial measurements should be performed over time in patients with vWF:Ag of <240%. This observation proved helpful in two patients in this study.

Abnormalities in circulating von Willebrand factor and survival in pulmonary hypertension

BACKGROUND

Changes in circulating von Willebrand factor (vWF) have been widely used for evaluating the severity of endothelial dysfunction in vascular disorders. In pulmonary hypertension, quantitative and structural abnormalities in circulating von Willebrand factor have been identified. We therefore hypothesized that these abnormalities could have prognostic implications.

PATIENTS AND METHODS

We studied 30 consecutive medically treated patients with primary (n = 11) or secondary precapillary pulmonary hypertension associated with congenital heart disease (n = 16) or schistosomiasis (n = 3). Plasma antigenic activity of vWF (vWF:Ag) was measured by electroimmunodiffusion. The relative concentration of low molecular weight vWF multimers (vWF:LMW/Total) was determined by Western immunoblotting. Results of initial evaluation were analyzed at the end of the first and third years of follow-up.

RESULTS

Baseline vWF:Ag activity (P <0.0002) and the vWF: LMW/Total ratio (P <0.005) were higher in patients who died during the first year than in survivors. All patients with vWF:Ag activity >250% or a vWF:LMW/Total ratio >70% died in the first year. All 7 patients with vWF:Ag activity <100% were alive at the end of 3 years of follow-up. A vWF:LMW/Total ratio >68% was 67% sensitive and 95% specific for 1-year mortality, with an overall predictive value of 80%. Both vWF:Ag levels and mortality were greater in the patients with primary pulmonary hypertension than in patients with secondary pulmonary hypertension.

CONCLUSION

Patients with pulmonary hypertension who have abnormalities in circulating vWF have reduced 1-year survival. This might affect decisions such as patient assignment to lung transplantation.

Pulmonary and systemic responses to exogenous endothelin-1 in patients with left ventricular dysfunction

Plasma levels of immunoreactive endothelin-1 (ET-1) are elevated in chronic heart failure (CHF) and have been reported to correlate closely with pulmonary hemodynamic measurements. We investigated the effects of exogenous ET-1 on the pulmonary vasculature in patients with left ventricular systolic dysfunction (LVD), with or without overt heart failure. ET-1 was infused at 1, 5, and 15 pmol/min into a distal pulmonary artery of 10 patients with LVD. Hemodynamics were measured by a thermodilution catheter and arterial line. Intravascular Doppler and local pulmonary angiography were used to assess local pulmonary blood flow in the first four patients. Systemic hemodynamic changes occurred with ET-1 infusion in a dose-dependent fashion. Mean arterial pressure (100 +/- 8-107 +/- 11 mm Hg; p < 0.01) and systemic vascular resistance (1,699 +/- 375-2,033 +/- 427 dynes/s/cm-5; p < 0.001) rose, whereas the cardiac index fell from 2.43 +/- 0.53 to 2.20 +/- 0.491/min/m2 (p < 0.002). However, mean pulmonary artery pressure (21 +/- 7 mm Hg) and pulmonary vascular resistance (151 +/- 43-147 +/- 43 dynes/s/cm-5) did not change. Exogenous ET-1, when infused into patients with LVD, causes systemic but not pulmonary vasoconstriction.

Plasma levels of von Willebrand factor antigen in acute bronchitis and in a normal population

von Willebrand factor (vWF) is a large glycoprotein secreted predominantly by endothelial cells in both the systemic and pulmonary circulations and has a central role in the formation of the platelet plug. It has been put forward as a possible marker of endothelial cell injury, but is not ideal in that it is not specific for either the pulmonary or systemic circulation and may be released as part of the acute phase response from otherwise healthy endothelial cells. We undertook two studies (i) to assess within-subject to assess within-subject variation in plasma von Willebrand factor antigen (vWF:Ag) levels over time and to assess between-subject variation in a healthy patient population, and (ii) as part of a descriptive study of acute bronchitis, to assess whether plasma vWF:Ag levels altered in such a common and minor insult. A random sample of patients aged 45-74 years were taken from a local general practice. vWF:Ag levels were measured on three occasions, and spirometry was performed. The descriptive study was undertaken on patients in the general practice diagnosed with acute bronchitis without pre-existing pulmonary disease. Plasma vWF:Ag was measured on presentation and 14 and 42 days later. In 219 randomly selected patients the mean plasma vWF:Ag was similar at all three visits, the within-subject standard deviation being 0.09 U ml(-1) and 1.12 U ml(-1) respectively). There was no correlation between plasma vWF:Ag and C-reactive protein on presentation. We conclude that there is relatively little variation in an individual's plasma vWF:Ag level but that levels increase significantly with age. The observed elevation occurring with acute bronchitis is a true phenomenon; the absence of an associated acute phase response suggests that endothelial cell injury is the mechanism for the rise. These observations are important in the context of vWF as a marker of endothelial cell damage, as a common and supposedly minor insult such as acute bronchitis may markedly raise plasma levels.

Thrombosis and Hemostasis in Cardiology: Review of Pathophysiology and Clinical Practice (Part I)

The adverse consequences of thrombosis are per haps nowhere more evident than in clinical cardiology. Throm bosis and hemostasis are primary issues in the management of patients with atrial fibrillation, prosthetic heart valves, severe left ventricular dysfunction, and coronary artery disease. Clini cal trials have defined a crucial role for anticoagulation with warfarin in patients with atrial fibrillation to reduce the inci dence of stroke. Anticoagulation with warfarin and aspirin in combination offers significant protection from systemic emboli in patients with mechanical prosthetic valves, without a sub stantial increased risk of hemorrhage. The risk of systemic emboli may also be reduced by anticoagulation in patients with severe left ventricular dysfunction. Disturbance of the normal balance of hemostasis is a major factor in the pathophysiology of coronary artery disease. Antiplatelet therapy, antithrombin agents, anticoagulants, and fibrinolytic agents have been used to prevent and treat acute coronary thrombosis and to prevent reocclusion following thrombolysis and interventional therapy. Guidelines are presented for antithrombotic therapy in the prac tice of clinical cardiology.

Fluid Shear Stress Modulates von Willebrand Factor Release From Human Vascular Endothelium

Fluid shear stress generated by blood flow on arterial wall may play a role in the process of atherosclerosis, not only affecting the mass transport phenomena that take place in blood, but also by modulation of synthesis and secretion of humoral factors released by vascular endothelium that mediate platelet-vessel wall interactions. The present study was designed to investigate whether shear stress, induced by laminar flow, modulates von Willebrand factor (vWF ) release from cultured human umbilical vein endothelial cells (HUVEC) and whether this physical stimulation can affect vWF synthesis. Monolayers of HUVEC were exposed to laminar flow of varying magnitude (from 2 to 12 dynes/cm2) using a cone-and-plate device. The release of vWF in cell supernatant and in extracellular matrix by cells exposed to flow or maintained in static conditions was evaluated by enzyme-linked immunosorbent assay. HUVEC exposed to laminar flow released higher amounts of vWF into the cell supernatant within few hours of exposure and vWF secretion was dependent on shear stress magnitude. vWF released in extracellular matrix was also higher in cell monolayers exposed to shear than in static controls. vWF mRNA expression in HUVEC was not affected by exposure of cells to laminar flow, indicating that shear-induced vWF release reflected enhanced secretion without de novo protein synthesis. Immunofluorescence studies showed that the release of vWF is due to exocytosis from Weibel-Palade bodies, the storage organelles of vWF. These data indicate a novel mechanism by which local hemodynamic shear forces modulate endothelial cell function and may play a role in development of arterial thrombotic events.

Fluid Shear Stress Modulates von Willebrand Factor Release From Human Vascular Endothelium

Fluid shear stress generated by blood flow on arterial wall may play a role in the process of atherosclerosis, not only affecting the mass transport phenomena that take place in blood, but also by modulation of synthesis and secretion of humoral factors released by vascular endothelium that mediate platelet-vessel wall interactions. The present study was designed to investigate whether shear stress, induced by laminar flow, modulates von Willebrand factor (vWF ) release from cultured human umbilical vein endothelial cells (HUVEC) and whether this physical stimulation can affect vWF synthesis. Monolayers of HUVEC were exposed to laminar flow of varying magnitude (from 2 to 12 dynes/cm2) using a cone-and-plate device. The release of vWF in cell supernatant and in extracellular matrix by cells exposed to flow or maintained in static conditions was evaluated by enzyme-linked immunosorbent assay. HUVEC exposed to laminar flow released higher amounts of vWF into the cell supernatant within few hours of exposure and vWF secretion was dependent on shear stress magnitude. vWF released in extracellular matrix was also higher in cell monolayers exposed to shear than in static controls. vWF mRNA expression in HUVEC was not affected by exposure of cells to laminar flow, indicating that shear-induced vWF release reflected enhanced secretion without de novo protein synthesis. Immunofluorescence studies showed that the release of vWF is due to exocytosis from Weibel-Palade bodies, the storage organelles of vWF. These data indicate a novel mechanism by which local hemodynamic shear forces modulate endothelial cell function and may play a role in development of arterial thrombotic events.

Von Willebrand factor and soluble E-selectin in hyperlipidaemia: relationship to lipids and vascular disease

Our objective was to determine whether endothelial cell products von Willebrand factor and soluble E-selectin are related to serum lipids, lipoprotein (a), and vascular disease in patients with hyperlipidaemia. In order to achieve our aim, blood samples were obtained for four experiments from 1) 160 patients (49 with symptomatic vascular disease) with hypercholesterolaemia and an equal number of age and sex matched controls; 2) 31 patients who were studied serially before and after successful resolution of their hypercholesterolaemia; 3) 15 patients with hypertriglyceridaemia; and 4) 20 controls, half of whom consumed a lipid-rich breakfast. von Willebrand factor and soluble E-selectin were measured by enzyme linked immunosorbent assay (ELISA) using commercial reagents. In experiment (1) von Willebrand factor was increased in the patients with hypercholesterolaemia (P=0.0077) and was higher still in patients with vascular disease (P<0.0001). Soluble E-selectin was not influenced by hypercholesterolaemia or vascular disease. The correlation of von Willebrand factor with total and LDL cholesterol (both P<0.001) remained after both age and blood pressure were controlled. Experiment (2) showed that serial studies in patients over an average of 7 months a reduction in total cholesterol was associated with a reduction in von Willebrand factor (r=0.51, P=0.002). Experiment (3) demonstrated that von Willebrand factor was not increased in patients with hypertriglyceridaemia (median 8.9 mmol/L), and in experiment (4) a lipid-rich breakfast taken by fasted, healthy controls produced an increase in serum triglycerides (P<0.01) but did not influence von Willebrand factor over an 8 hour period. We conclude that von Willebrand factor, but not soluble E-selectin, is raised in hypercholesterolaemia and therefore may be a potential indicator of endothelial cell physiology in subjects with, or at risk of, atherosclerotic vascular disease.

Elevated circulating levels of von Willebrand factor and D-dimer in patients with heart failure and mechanical prosthesis

To test the hypothesis of association between heart failure and altered haemostatic balance in patients with a mechanical valve prosthesis, comparisons were made between 20 patients with mitral valve replacement and stable chronic heart failure (group A), 20 with the same prosthesis but satisfactory haemodynamics (group B) and 20 age-matched controls (group C). The left ventricular ejection fraction was significantly highest (p < 0.001) in group A. The pulmonary artery systolic pressure was also highest in group A (p < 0.001), without significant difference between groups B and C. Two group A patients had a transient ischaemic attack. The D-dimer plasma concentrations and the antigenic and biologic von Willebrand factor activities were significantly greatest in group A. Significant correlation was found between the plasma concentrations of these activities and pulmonary artery systolic pressure and between D-dimer and ejection fraction. Platelet-activating factor was detected only in six group A patients. The observed relationship between haemostatic factors and heart failure in patients with mechanical heart-valve prosthesis advocates careful evaluation of von Willebrand factor and D-dimer in order to prevent embolic events in such cases.

von Willebrand factor and its relevance to cardiovascular disorders

In the past decade the importance of the vascular endothelium in cardiovascular pathophysiology has become more apparent. One substance that is synthesised by and stored in endothelial cells is von Willebrand factor (vWF). When released, vWF seems to mediate platelet aggregation and adhesion to the vascular endothelium. Because the release of vWF is increased when endothelial cells are damaged, vWF has been proposed as an indicator of endothelial disturbance or dysfunction. The availability of such an index of endothelial dysfunction may have clinical value, because measurement of such a marker can be a non-invasive way of assisting in diagnosis or as an indicator of disease progression. The known association between vWF, thrombogenesis, and atherosclerotic vascular disease also suggests that high concentrations of vWF may be an indirect indicator of atherosclerosis and/or thrombosis. In addition, high vWF concentrations have prognostic implications in patients with ischaemic heart disease and peripheral vascular disease.

Heparin causes platelet dysfunction and induces fibrinolysis before cardiopulmonary bypass

BACKGROUND

Platelet dysfunction and increased fibrinolysis are the most important etiologic factors in the hemostatic defect observed following the institution of cardiopulmonary bypass. This study examined the effects of heparin per se, administered before the institution of cardiopulmonary bypass, on platelet function and fibrinolysis.

METHODS

Sampling was performed in 55 patients undergoing cardiac operations before and 5 minutes after the routine administration of heparin, before the institution of cardiopulmonary bypass.

RESULTS

Heparin administration resulted in a significant prolongation of the bleeding time (from 6.3 +/- 2.1 to 12.6 +/- 4.9 minutes; p < 0.00001), a significant reduction in the level of shed blood thromboxane B2 (from 1,152 +/- 669 to 538 +/- 187 pg/0.1 mL; p = 0.00002), and an increase in the plasma levels of plasmin (from 11.8 +/- 9.7 to 125.4 +/- 34.8 U/L; p < 0.0001) and D-dimer (from 571.3 +/- 297.1 to 698.5 +/- 358.6 micrograms/mL; p = 0.05). There were no significant differences before and after heparin administration in the plasma levels of fibrinogen, plasminogen, tissue plasminogen activator, antiplasmin, antithrombin III, and von Willebrand factor.

CONCLUSIONS

Heparin, independent of cardiopulmonary bypass, causes both platelet dysfunction and increased fibrinolysis. The use of an alternative anticoagulant or a lower dose of heparin in conjunction with heparin-coated surfaces might improve the hemostatic balance during open heart operations.

Coagulation activity is increased in the left atrium of patients with mitral stenosis

OBJECTIVES

This study investigated the hemostatic status of the right and left atria in patients with mitral stenosis.

BACKGROUND

Systemic thromboembolism is a serious major complication in patients with mitral stenosis. However, the pathogenesis of thromboembolism in mitral stenosis is not fully understood.

METHODS

We determined the plasma levels of biochemical markers for platelet activity (platelet factor 4 and beta-thromboglobulin) and status of thrombin generation (fibrinopeptide A and thrombin-antithrombin III complex) and fibrinolysis (D-dimer and plasmin-alpha 2-plasmin inhibitor complex) in specimens of blood obtained from the peripheral vein and right and left atria of 12 consecutive patients with mitral stenosis who were undergoing percutaneous mitral valvuloplasty.

RESULTS

Plasma levels of platelet factor 4, beta-thromboglobulin, D-dimer and plasmin-alpha 2-plasmin inhibitor complex in the patients did not differ significantly between the right and left atria, whereas levels of fibrinopeptide A and thrombin-antithrombin III complex in the left atrium were significantly higher than those in the right atrium (fibrinopeptide A in the left and right atria 19.35 +/- 4.64 and 6.31 +/- 0.75 ng/ml [mean +/- SE], respectively, p < 0.02; thrombin-antithrombin III complex in the left and right atria 11.45 +/- 2.29 and 3.98 +/- 0.60 ng/ml, respectively, p < 0.01). Levels of fibrinopeptide A and thrombin-antithrombin III complex in the left atrium did not correlate with mean transmitral gradient, dimension of the left atrium or reciprocal of the mitral valve area. Peripheral blood plasma levels of von Willebrand factor antigen were significantly higher in the patients than in an age-matched control group of normal subjects (168 +/- 25% and 99 +/- 7%, respectively, p < 0.05) but showed no difference in the peripheral blood and right and left atria of the patients.

CONCLUSIONS

The coagulation system is activated in the left atrium of patients with mitral stenosis even during anticoagulation.

Relationship between hemostatic abnormalities and neuroendocrine activity in heart failure

Thromboembolism is an important complication of heart failure. To test the hypothesis that heart failure may be associated with hemostatic dysfunction, we studied hemostatic function in 21 patients with stable chronic heart failure and related these measures to the severity of heart failure as assessed by clinical evaluation, neuroendocrine activation, radionuclide ventriculography, and cardiopulmonary exercise testing. Plasma and blood viscosity were elevated; all patients showed evidence of platelet activation, and many had elevated plasma concentrations of fibrinopeptide A, D-dimer, and von Willebrand factor. The plasma concentrations of these variables were poorly interrelated and related poorly to the severity of heart failure. Plasma concentrations of angiotensin II and endothelin were correlated, and the latter was also correlated with the plasma concentration of von Willebrand factor. Patients with chronic heart failure have hemostatic abnormalities that may predispose them to thromboembolic events and may be in part due to neuroendocrine activation.

Shear-dependence of endothelial functions

Endothelial cells are subjected to shear forces which influence important cell functions. Shear stress induces cell elongation and formation of stress fibers, increases permeability, pinocytosis and lipoprotein internalization, is involved in the formation of atherosclerotic lesions, increases the production of tissue plasminogen activator, and enhances von Willebrand factor release and hence platelet aggregation. It decreases adherence of erythrocytes and leukocytes, and increases the release of prostacyclin, endothelium derived relaxing factor, histamine and other compounds, but decreases erythropoietin secretion. The mechanism of signal transduction to the endothelial cell is not known exactly; shear-sensitive ion channels seem to be involved. It is concluded that a better understanding of shear-dependent endothelial functions will influence pathophysiologic concepts and therapeutic interventions.

The relationship of arterial compliance with endothelial-derived proteins of the hemostatic system

Cardiovascular risk factors associated with hypertension include alterations in arterial compliance and an increased tendency to thrombosis. In this study we examined the relationship between arterial compliance and endothelial derived components of the hemostatic system: von Willebrand factor (vWF) and tissue plasminogen activator (t-PA). Ten males (4 normal and 6 untreated hypertensives, 41 +/- 12 years) were studied. Compliance of proximal (large vessel) and distal (small vessel) arteries was measured by intraarterial pulse wave analysis; left ventricular wall thickness by echocardiography; and vWF and t-PA by immunoassay of plasma obtained before and immediately after maximum treadmill exercise. Baseline t-PA and vWF correlated inversely with distal compliance (r = -0.74, p = 0.01; r = -0.56, p = 0.09). Exercise strengthened the relationship between vWF and both distal compliance (r = -0.56 to r = -0.86) and proximal compliance (r = -0.44 to r = -0.70). Moreover, post-exercise levels of vWF and t-PA were each significantly related to left ventricular posterior wall and septal thickness. Of note, these protein concentrations correlated more strongly with arterial compliance and left ventricular wall thickness than with blood pressure. Thus, arterial compliance and left ventricular wall thickness appear to be more powerful than blood pressure as predictors of the endothelial release of vWF and t-PA in response to exercise. These findings indicate that some of the key cardiac and arterial characteristics of hypertension might be linked to increased endothelial reactivity to hemodynamic stress.