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Biomedical subjects

F L Li-Saw-Hee

Publications and source records attributed to F L Li-Saw-Hee.

At least 19 recordsLinked to original sources
PubMed2003

Angiogenesis, thrombogenesis, endothelial dysfunction and angiographic severity of coronary artery disease.

BACKGROUND: Thrombogenesis, angiogenesis, and endothelial damage/dysfunction are components in the pathogenesis of atherosclerosis. OBJECTIVE: To investigate the relation of these variables to atherosclerotic disease severity and the possible interrelations between the three. METHODS: 111 patients attending for coronary angiography were studied (85 male, 26 female; mean (SD) age, 61.6 (10.0) years). Plasma concentrations of von Willebrand factor (vWf, a marker of endothelial damage/dysfunction), vascular endothelial growth factor (VEGF, associated with angiogenesis), soluble VEGF receptor Flt-1 (sFlt-1), and tissue factor (TF, a key component of coagulation) were measured by an enzyme linked immunosorbent assay. Following angiography, disease severity was assessed by the number of coronary vessels diseased (> 50% stenosis) and by a coronary atheroma score. RESULTS: All indices were raised in the patients compared with 34 healthy controls except sFlt-1, which was lower in the patients. No significant correlations were found between the coronary atheroma score and values of vWf (Spearman correlations: r = 0.21, p = 0.83), VEGF (r = 0.11, p = 0.27), or TF (r = -0.04, p = 0.68). However, there was an inverse correlation between plasma sFlt-1 and coronary atheroma score (r = -0.19, p = 0.049). The number of vessels diseased had no relation to any marker. Correlations were found between TF and VEGF (r = 0.25, p = 0.008) and between TF and sFlt-1 (r = 0.42, p < 0.001) in the patients. CONCLUSIONS: Despite evidence of abnormal angiogenesis (VEGF and sFlt-1), thrombogenesis (TF), and endothelial damage/dysfunction (vWf) in the patients with coronary artery disease, there was no correlation between VEGF, sFlt-1, vWf, or TF and angiographically defined disease severity.

Coronary Angiography↗
PubMed2002

Effects of enalapril and losartan on circulating adhesion molecules and monocyte chemotactic protein-1.

At least four independent studies in different clinical settings showed that angiotensin-converting enzyme inhibitors (ACE-Is) such as enalapril effectively decrease plasma levels of circulating adhesion molecules (cAMs). To examine whether this effect may be mediated by the decreased action of angiotensin, we compared the effects of enalapril with the direct angiotensin-II antagonist, losartan, on plasma levels of cAMs, and monocyte chemotactic protein-1 (MCP-1). In a randomized trial, we recruited 32 untreated patients (19 male, aged 59+/-13 years) with hypertension, who received either enalapril (mean dose 17 mg/day) or losartan (mean dose 77 mg/day) at equipotent doses. Enalapril decreased plasma levels of all cAMs after 8 weeks of treatment: cE-selectin levels decreased by 13% (P=0.007), intercellular adhesion molecule-1 (cICAM-1) by 15% (P=0.002) and vascular cell adhesion molecule-1 (cVCAM-1) by 19% (P=0.003). Similarly, enalapril decreased plasma levels of MCP-1 by 13% (P<0.001). Losartan did not significantly change cAM or MCP-1 plasma concentrations after 8 weeks of treatment: cE-selectin levels decreased by 3%, cICAM-1 by 5%, cVCAM-1 by 8%, whereas MCP-1 increased by 2% (all P=NS; not significant). The enalapril effect on percentage changes of cVCAM-1 was significantly different from losartan (P=0.0429). Eight weeks of antihypertensive treatment with enalapril but not losartan, significantly decreased plasma levels of cAMs and MCP-1 in hypertensive patients. The beneficial effects of ACE-Is on cAMs may have implications for atherogenesis and the reduction of cardiovascular events, which cannot be fully explained by their antihypertensive effects alone.

Aged↗
PubMed2002

Abnormal low-density lipoprotein subfraction profile in patients with untreated hypertension.

BACKGROUND: Low-density lipoprotein (LDL) consists of a heterogeneous group of particles of varying size and electrophoretic mobility. A predominance of small, more mobile particles is a risk factor for cardiovascular disease. AIM: To investigate the hypothesis that untreated patients with essential hypertension in the absence of vascular disease may exhibit abnormalities of LDL subfractions. SETTING: Specialist hypertension clinic. DESIGN: Cross-sectional study. METHODS: Following disc polyacrylamide gel electrophoresis, the mean (LDL locus) and heterogeneity (LDL spread) of mobility was recorded in 41 patients (mean age 52.6 years, 24 men) presenting with untreated essential hypertension (in the absence of vascular disease or diabetes mellitus) and in 45 healthy controls (age 56.9 years, 22 men) recruited from primary-care lists. RESULTS: Although there were no significant differences in total, low- or high-density lipoprotein cholesterol concentrations, LDL locus was significantly greater in the hypertensive group: mean (95%CI) 36.7 (35.7-37.6) vs. 34.8 (34.1-35.5), p=0.002. LDL locus was significantly elevated even in hypertensives with triglyceride concentrations below the median (<1.25 mmol/l). LDL spread was also greater in the hypertensive group, but not significantly: 5.6 (5.2-6.0) vs. 5.5 (5.3-5.8), p=0.10. DISCUSSION: Hypertensive patients have a preponderance of smaller LDL subfractions. This dyslipidaemia is not readily detected by conventional lipid assays.

Cross-Sectional Studies↗
PubMed2001

Plasma levels of vascular endothelial growth factor and its soluble receptor (SFlt-1) in essential hypertension.

In this study of 27 untreated patients with uncomplicated essential hypertension, we report on elevated plasma levels of vascular endothelial growth factor and its soluble receptor Flt-1 compared with healthy controls; these increased levels are reduced by the treatment of hypertension. This raises the possibility that abnormal angiogenesis may contribute to the pathogenesis of complications related to hypertension and merits exploration in larger studies.

Antihypertensive Agents↗
PubMed2001

Effect of acute exercise on the raised plasma fibrinogen, soluble P-selectin and von Willebrand factor levels in chronic atrial fibrillation.

BACKGROUND: There is increasing evidence that chronic atrial fibrillation (AF) is associated with a prothrombotic or hypercoagulable state. HYPOTHESIS: This study was undertaken to determine whether short-term exercise in patients with chronic AF would shift the overall hemostatic balance toward a more prothrombotic state with a reduction in fibrinolytic potential. METHODS: We recruited 20 patients (13 men; mean age 65 years +/- 11 standard deviation [SD]) with chronic AF who were not treated with antithrombotic therapy and exercised them to exhaustion using a multistage treadmill exercise (standard Bruce) protocol. Blood samples were taken pre exercise, immediately after cessation of exercise, and at 20 min post exercise. The prothrombotic state was quantified by fibrinogen (an index of hemorheology and a coagulation factor), soluble P-selectin (sP-sel, marking platelet activation), von Willebrand factor (vWF, an index of endothelial dysfunction), and plasminogen activator inhibitor-1 (PAI-1, a regulator of fibrinolytic activity) levels. There were two groups of age- and gender-matched controls in sinus rhythm: (1) healthy controls, and (2) "hospital controls" who were patients with vascular disease. RESULTS: Baseline levels of vWf (p = 0.034) and fibrinogen (p < 0.0001), but not sP-sel (p = 0.075) were significantly elevated in patients with AF compared with both control groups in sinus rhythm. The PAI-1 levels were highest in the hospital control patients, but not in chronic AF (p = 0.041). Following treadmill exercise, achieving a mean metabolic equivalent of 4.9 METS (+/- 1.75 SD) and total exercise duration of 4.9 min (+/- 2 SD), there was a significant rise in plasma fibrinogen (repeated measures analysis of variance [ANOVA] p = 0.047) and a reduction in PAI-1 levels (p = 0.025) in patients with AF. There were no significant changes seen in vWf (p = 0.308) or sP-sel (p = 0.071) levels. No significant changes in these indices were seen in hospital controls (all p = not significant), despite a much longer duration of exercise with greater workload. CONCLUSION: Patients with chronic AF have increased vWf and fibrinogen levels compared with sinus rhythm. Exercise to exhaustion influences the hypercoagulable state in chronic AF, with a rise in plasma fibrinogen and possible increase in fibrinolytic activity. Nevertheless, acute exercise does not appear to have a significant influence on endothelial dysfunction or platelet activation in patients with AF.

Adult↗
PubMed2001

Effect of antihypertensive therapy using enalapril or losartan on haemostatic markers in essential hypertension: a pilot prospective randomised double-blind parallel group trial.

To test the hypothesis that the hypercoagulable state in hypertension is significantly altered by anti-hypertensive therapy, we conducted a pilot prospective randomised double-blind trial of 40 untreated hypertensive patients (30 males, mean age 59 years) who were treated with either enalapril (10-20 mg per day) or losartan (50-100 mg per day) for 8 weeks. Thrombogenicity was assessed by measurement of plasma fibrinogen, soluble P-selectin (an index of platelet activation), plasminogen activator inhibitor 1 (PAI-1, an index of fibrinolysis) and von Willebrand factor (an index of endothelial dysfunction). Baseline von Willebrand factor alone was significantly higher in untreated hypertensive patients compared to controls (P<0.001). Following 8 weeks treatment with enalapril (mean dose 17 mg/day) or losartan (mean dose 77 mg/day), there was a significant reduction in mean blood pressure from 169+/-11/94+/-8 mmHg (baseline) to 147+/-14/84+/-7 mmHg (post-treatment) (P<0.001). However, there were no statistically significant changes in the levels of haemostatic markers (von Willebrand factor, fibrinogen, s-Psel and PAI-1). Our pilot study confirms previous observations of endothelial dysfunction in hypertensives. However, plasma fibrinogen and indices of platelet activation, fibrinolysis or endothelial dysfunction were not significantly affected by antihypertensive treatment with enalapril or losartan, despite satisfactory blood pressure control.

Angiotensin Receptor Antagonists↗
PubMed2001

Plasma von Willebrand factor, fibrinogen and soluble P-selectin levels in paroxysmal, persistent and permanent atrial fibrillation. Effects of cardioversion and return of left atrial function.

BACKGROUND: Atrial fibrillation is associated with increased risk of stroke and thromboembolism, possibly by conferring a prothrombotic or hypercoagulable state. However, it is unclear whether or not this differs in the clinical subgroups of chronic atrial fibrillation patients, that is, in those with paroxysmal, persistent or permanent atrial fibrillation. We therefore hypothesized that: (i) there are differences in the prothrombotic state between these patients; and (ii) reduction in indices of hypercoagulability would follow elective electrical cardioversion of persistent atrial fibrillation and the return of left atrial function. PATIENTS AND METHODS: We studied 69 patients with chronic atrial fibrillation: 23 with paroxysmal atrial fibrillation (16 males; mean age 65 years+/-SD 13); 23 with persistent atrial fibrillation (16 males; 65 years+/-13), with a mean duration of atrial fibrillation of 3 months (range 2 to 6 months); and 23 with permanent atrial fibrillation (16 males; 67 years+/-10). Blood results were compared to 20 age- and sex-matched healthy controls. The patients with persistent atrial fibrillation then underwent elective DC cardioversion, with Doppler echocardiographic examinations and bloods tests performed prior to cardioversion, and at 3 and 12 weeks afterwards. The prothrombotic state was quantified by measurement of plasma levels of fibrinogen, soluble P-selectin (an index of platelet activation) and von Willebrand factor (a marker of endothelial dysfunction). RESULTS: Permanent atrial fibrillation was associated with significantly raised levels of von Willebrand factor, soluble P-selectin and fibrinogen (all P<0.001); paroxysmal atrial fibrillation with significantly elevated levels of plasma von Willebrand factor (P=0.0067) and fibrinogen (P=0.0001) but not soluble P-selectin (P=0.472); and persistent atrial fibrillation with normal levels of fibrinogen, von Willebrand factor and soluble P-selectin when compared to healthy controls (all P=ns). Stepwise multiple regression analyses demonstrated that the presence of atrial fibrillation was an independent predictor of abnormal von Willebrand factor, fibrinogen and soluble P-selectin levels. Electrical cardioversion of the patients with persistent atrial fibrillation did not significantly alter levels of von Willebrand factor (P=0.766), soluble P-selectin (P=0.726) or fibrinogen (P=0.50) despite maintenance of sinus rhythm and a significant return of left atrial systolic function (as quantified by the presence of A wave on Doppler echocardiography) at 3 months. CONCLUSION: There were significant differences in the prothrombotic state when patients with paroxysmal and permanent atrial fibrillation are compared to matched patients with persistent atrial fibrillation or controls in sinus rhythm. Cardioversion of persistent atrial fibrillation did not significantly alter indices of hypercoagulability even after 3 months maintenance of sinus rhythm, despite the return of atrial systole.

Adult↗
PubMed2001

Dyslipidaemia in patients with malignant-phase hypertension.

Low-density lipoprotein (LDL) consists of a heterogeneous group of particles of differing size, density and electrophoretic mobility, smaller particles being more atherogenic. A high proportion of small LDL particles is an independent risk factor for cardiovascular disease. We hypothesized that patients with malignant phase hypertension (MHT), the most severe form of hypertension, would demonstrate a more atherogenic LDL subfraction profile than either non-malignant hypertension (NMHT) or normotensive controls. We compared 16 patients with MHT to 41 patients with untreated NMHT and 45 normotensive controls. LDL subfraction profile was measured by disc polyacrylamide gel electrophoresis using a validated scoring system to calculate the mean size (locus) and heterogeneity (spread) of LDL subfraction mobilities. A higher LDL locus indicates a greater proportion of small LDL subfractions. LDL cholesterol levels were similar in all three groups (p=0.23). High-density lipoprotein cholesterol (HDL-C) levels were significantly lower (p<0.001) and serum triglyceride concentrations significantly higher (p=0.02) in the MHT group, compared to normotensive controls. LDL locus was greater in the NMHT group than in the normotensive controls and intermediate in the MHT group (p=0.008). There was no significant difference in LDL spread (p=0.26). Serum triglyceride concentrations were not significantly higher after adjusting for confounding variables. MHT is associated with an abnormal lipid profile, characterized by low HDL-cholesterol concentration. This dyslipidaemia may be partly responsible for the vascular complications and the poor prognosis of these patients.

Analysis of Variance↗
PubMed2000

Effect of degree of blood pressure on the hypercoagulable state in chronic atrial fibrillation.

To investigate the hypothesis that higher levels of blood pressure would further promote the hypercoagulable state in atrial fibrillation (AF) by increasing the degree of hemostatic abnormalities, we studied 82 consecutive patients with chronic nonvalvular AF who were not taking antithrombotic therapy. Patients with AF had higher levels of plasma fibrin D-dimer, von Willebrand factor, and fibrinogen than controls in sinus rhythm, and no differences between tertiles of either systolic, diastolic, or mean blood pressure were found, suggesting other mechanisms may be contributing to the hypercoagulable state in AF.

Aged↗
PubMed2000

Matrix metalloproteinase-9 and tissue inhibitor metalloproteinase-1 levels in essential hypertension. Relationship to left ventricular mass and anti-hypertensive therapy.

To test the hypothesis that the activity of enzymes degrading the extracellular matrix in hypertensive patients are abnormal, and that the treatment of hypertension will normalise these abnormalities, we measured the serum levels of metalloproteinase MMP-9, and its inhibitor, tissue metalloproteinase inhibitor (TIMP-1). Thirty-two patients with untreated hypertension (BP 168/96) had significantly lower levels of both MMP-9 and TIMP-1 when compared to 24 matched normotensive controls (BP 123/80) (P<0.001). There was no significant correlation between MMP-9 and TIMP-1 levels (P>0.2). In the patients, there were no significant correlations observed between left ventricular mass, Doppler V(E)/V(A) ratio (an index of diastolic function), blood pressure, left ventricular mass index and either MMP-9 or TIMP-1 levels (all P=NS). Levels of MMP-9 and TIMP-1 were not significantly altered after 2 months of antihypertensive treatment of 29 patients despite mean blood pressure falling from 170/96 to 143/85 mmHg (P<0.001). Correspondingly, there were also no significant alterations in indices of diastolic function and left ventricular mass. Our study suggests that the proteolytic activities of MMP-9 and TIMP-l are depressed in hypertensive patients and were not significantly affected by short-term antihypertensive treatment. The relationship between collagen metabolism in hypertensive subjects, especially in those with cardiac hypertrophy, and the effects of treatment needs to be further explored in larger trials over a longer period of time.

Aged↗
PubMed2000

A cross-sectional and diurnal study of thrombogenesis among patients with chronic atrial fibrillation.

OBJECTIVES: First, we sought to determine whether there is diurnal variation in hemostatic factors related to thrombogenesis and hypercoagulability among patients with chronic atrial fibrillation (AF). Second, we sought to determine whether levels of soluble thrombomodulin (sTM), a marker of endothelial function, or soluble P-selectin (sP-sel), an index of platelet activation, are altered in patients with AF as compared with subjects in sinus rhythm. BACKGROUND: Atrial fibrillation is associated with an increased risk of stroke and thromboembolism and is known to confer a hypercoagulable state, with abnormalities of thrombosis, platelet activation and endothelial cell function. Many cardiovascular events, such as acute myocardial infarction, have thrombosis as an underlying process, and they undergo diurnal variation. METHODS: Fifty-two patients (45 men, mean [+/- SD] age 66 +/- 6 years) with chronic AF, none of whom received antithrombotic therapy, were studied. Baseline levels of fibrinogen, sP-sel, sTM and von Willebrand factor (vWF) were compared to those levels in matched healthy control subjects in sinus rhythm. In a subgroup of 20 patients, five venous blood samples were collected through an indwelling cannula at 6-h intervals from 12 PM to 12 PM the following day and were analyzed for the same markers. RESULTS: Patients with chronic AF had higher plasma sP-sel, sTM, vWF and fibrinogen levels as compared with control subjects in sinus rhythm. Significant correlations were found between fibrinogen and sP-sel in patients with AF (r = 0.567 [Spearman], p < 0.001) and in control subjects (r = 0.334, p = 0.016). There was no significant diurnal variation in plasma levels of sP-sel, sTM, vWF or fibrinogen over the 24-h study period (repeated measures analysis of variance, p = NS). CONCLUSIONS: There is no circadian or diurnal variation in the hypercoagulable state seen in AF, as assessed by plasma fibrinogen and markers of platelet (sP-sel) and endothelial function (vWF and sTM). The persistent hypercoagulable state, together with the loss of diurnal variation in various hemostatic markers, in chronic AF may contribute to the high risk of stroke and thromboembolic complications in these patients.

Aged↗
PubMed2000

Effects of fixed low-dose warfarin, aspirin-warfarin combination therapy, and dose-adjusted warfarin on thrombogenesis in chronic atrial fibrillation.

BACKGROUND AND PURPOSE: Recent clinical trials have established that adjusted-dose warfarin (international normalized ratio [INR] 2.0 to 3.0) is highly effective in the reduction of ischemic stroke in patients with nonvalvular atrial fibrillation (AF). We hypothesized that the introduction of fixed low-dose warfarin alone or in combination with aspirin (300 mg) could normalize hemostatic markers, namely plasma fibrin D-dimer (an index of thrombogenesis), plasminogen activator inhibitor-1 (PAI-1, an index of fibrinolysis), fibrinogen, and von Willebrand factor (vWf, an index of endothelial dysfunction), in a manner comparable to adjusted-dose warfarin (target INR 2.0 to 3.0). METJODS: Sixty-one patients with AF (44 men, mean+/-SD age 64+/-19 years) who were not receiving any antithrombotic therapy were prospectively randomized into 1 of 3 treatment groups: warfarin (2 mg) (n=23; group 1), combination 1 mg warfarin plus 300 mg aspirin (n=21; group 2) or combination 2 mg warfarin plus 300 mg aspirin (n=17; group 3). Subjects from all 3 AF groups were matched for sex, age, and blood pressure. Blood samples were taken for sequential measurements for changes in plasma fibrin D-dimer, PAI-1, fibrinogen, and vWf before and at 2 and 8 weeks after randomization (phase 1). All patients were subsequently offered adjusted-dose warfarin therapy (phase 2), and an additional blood sample was taken 6 weeks later. RESULTS: When pretreatment results were compared with those from 60 age- and sex-matched healthy control subjects in sinus rhythm, there were significant elevations in levels of fibrinogen (P=0.025), vWf (P<0.0001), and fibrin D-dimer (P<0.0001) in patients with AF compared with control subjects. There were no significant changes in the levels of various indices measured after 2 and 8 weeks of therapy in all 3 groups, except for an increase in PAI-1 level (P=0.024) in group 3. After 6 weeks of therapy with dose-adjusted warfarin (INR 2.0 to 3.0), there was a significant decrease in plasma fibrinogen (P=0.023) and fibrin D-dimer (P=0.0067) levels. There were no significant changes in the levels of PAI-1 (P=0.198) or vWf (P=0.33). CONCLUSIONS: The present results confirmed that high levels of vWf, fibrinogen, and fibrin D-dimer levels were present in patients with AF compared with control subjects. Moreover, the introduction of 300 mg aspirin plus low-dose warfarin (1 mg/d), low-dose warfarin alone (2 mg/d), or 300 mg aspirin plus low-dose warfarin (2 mg/d) did not significantly reduce any of the hemostatic markers studied (except PAI-1 levels), whereas conventional full-dose warfarin (INR 2.0 to 3.0) significantly reduced levels of fibrin D-dimer and fibrinogen. These results are in keeping with the disappointing ineffectiveness of low-intensity warfarin therapy, aspirin-warfarin combination, and ultralow-dose warfarin therapy in the recent prematurely terminated clinical trials and the established benefits of conventional adjusted-dose anticoagulation therapy.

Aged↗
PubMed1999

Indexes of hypercoagulability measured in peripheral blood reflect levels in intracardiac blood in patients with atrial fibrillation secondary to mitral stenosis.

Systemic thromboembolism is a major complication in patients with mitral stenosis, especially in those who have atrial fibrillation (AF). It has been suggested that there may be increased regional left atrial coagulation activity in such patients, despite normal systemic coagulation activity on peripheral blood sampling. Our aim was to investigate whether there were significant differences between intracardiac versus peripheral indexes of hypercoagulability in 25 patients (5 men; mean age 60 years) with mitral stenosis who were undergoing percutaneous balloon mitral valvuloplasty and who were all in chronic AF. Two days after halting warfarin therapy, intracardiac (right and left atria) and peripheral (venous and arterial) blood samples from patients were obtained and compared with levels in matched healthy controls in sinus rhythm. Thrombogenicity was assessed by levels of fibrin D-dimer, fibrinogen, indexes of platelet activation (soluble P-selectin and beta thromboglobulin [betaTG]) and indexes of endothelial dysfunction (soluble thrombomodulin [sTM] and von Willebrand factor [vWF]). There were no statistically significant differences in the various markers between the femoral vein and artery, left and right atria, and between the femoral vein and both atria (all p = NS). Plasma fibrinogen, vWf (both p <0.005), and D-dimer (p = 0.011) were significantly higher and levels of sP-selectin and sTM were lower (both p <0.005) in patients when compared with controls. There was no significant difference in plasma betaTG levels. Our results suggest that there is no significant variation in indexes of thrombogenesis, platelet activation, and endothelial dysfunction between left atrium, right atrium, and the peripheral artery or vein. Peripheral samples therefore do reflect atrial coagulation, platelet, and endothelial activities.

Atrial Fibrillation↗
PubMed1999

Atrial fibrillation, thromboembolism and antithrombotic therapy.

Atrial fibrillation is the commonest sustained disorder of cardiac rhythm and is associated with increased risk of stroke and thromboembolic events. Warfarin (dose-adjusted to a target INR of 2.0-3.0) has been well established to reduce this risk of stroke by 68% (95% CI 50-79%), while aspirin provides a risk reduction of 21% (95% CI 0-38%). Nevertheless, warfarin confers a risk of bleeding and the inconvenience of regular monitoring checks, while aspirin seems effective only for certain low-risk subgroups. Thus there have been strenuous efforts to improve thromboprophylaxis in atrial fibrillation, by using low-intensity anticoagulation regimens, combination antiplatelet therapy and refinement of risk stratification strategies. Attempts at using a low-intensity, fixed-dose warfarin regimen have, however, been disappointing. For now, a strategy of risk stratification should be adopted to identify highest risk patients with atrial fibrillation who would benefit from anticoagulation.

Aged↗
PubMed1998

Digoxin revisited.

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Anti-Arrhythmia Agents↗