Associations between a polymorphism in the gene encoding glycoprotein IIIa and myocardial infarction or coronary artery disease

Association of human platelet alloantigens encoding gene polymorphisms with the risk of Coronary artery disease in Iranian patients

Background

Coronary artery disease (CAD) is characterized by narrowing/ blockade of coronary arteries that is mainly caused by atherosclerotic plaques. Considering the involvement of platelet abnormalities, such as defective aggregation and adhesion, in the cardiovascular-related disorders, genetic variations in human platelet alloantigens (HPA) have been implicated in the CAD susceptibility. Herein, we intended to determine the association of HPA-1 to -6, -9, and -15 biallelic polymorphisms with CAD in an Iranian population.

Methods

In this retrospective case–control study, 200 CAD subjects and 100 matched healthy individuals were enrolled. DNA samples were isolated from peripheral blood samples and genotyping of HPA polymorphisms was accomplished using polymerase chain reaction-sequence-specific primers.

Results

The alleles and genotypes of studied HPA polymorphisms were equally distributed among cases and controls and therefore no statistically significant differences were detected. Univariate analysis identified no association of combined haplotypes with CAD risk. However, multivariate analysis showed a positive association of the‌ HPA1b/2a/3b haplotype with CAD after adjustment for some covariates (including BMI, TG, LDL, FBS and blood pressure) that conferred a CAD susceptibility haplotype (P = 0.015; OR = 2.792; 95% CI 1.45–8.59).

Conclusions

Although alleles, genotypes, and haplotypes of HPA polymorphisms were not associated with CAD risk, HPA1b/2a/3b haplotype was found to be a dependent disease risk haplotype in Iranian population after correcting for confounding factors.

Platelet glycoprotein IIIa Leu33Pro gene polymorphism and coronary artery disease: A meta-analysis of cohort studies

Great interest has been focused in the last year on genetic predictors of cardiovascular risk. Glycoprotein IIb/IIIa (GP IIb/IIIa), fibrinogen receptor, is the final common pathway for aggregation and a key point for atherothrombosis. A single nucleotide polymorphism of IIIa subunit (Leu33Pro-PlA(1)/PlA(2) allele) has been suggested to increase aggregation and adhesion, however, contrasting reports have been reported so far on its effects on coronary artery disease (CAD). Aim of the current study was to perform a large meta-analysis including cohorts of patients undergoing coronary angiography in order to evaluate whether this polymorphism is associated with coronary artery disease. Literature archives (Pubmed, EMBASE, Cochrane) and main scientific sessions abstracts were scanned for data of consecutive cohorts of patients undergoing coronary angiography, where PlA genotype was assessed. Primary endpoint was the prevalence of CAD. Secondary endpoint was severity of CAD defined as prevalence of multivessel disease (≥2 vessels). Data from seven studies were extracted, including a final number of 6700 patients. Among them 1893 (28.3%) carried the PlA(2) polymorphism, 163 of them in homozygosis. Angiographically defined CAD was present in 3573 (74.3%) PlA(1)/PlA(1) patients and in 1430 (75.5%) PlA(2) carriers. PlA(2) polymorphism was not associated with an increased prevalence of coronary artery disease, (OR [95% CI] = 1.07 [0.95-1.21], p = 0.28, pheterogeneity = 0.39). Similar results were obtained for multivessel disease (OR [95% CI] = 1.07[0.95-1.20], p = 0.27, pheterogeneity = 0.12). Meta-regression analysis demonstrated a significant inverse relationship between the risk of CAD among the PlA(2) carriers and ageing (r = -0.044, (-0.09, -0.0008), p = 0.046). Present meta-analysis demonstrates that 33Leu → Pro substitution of GPIIIa does not influence the prevalence and extent of angiographically defined coronary artery disease in general population, although apparently playing a role among younger patients.

The PlA1/A2 polymorphism of glycoprotein IIIa as a risk factor for myocardial infarction: a meta-analysis

BACKGROUND

The PlA2 polymorphism of glycoprotein IIIa (GPIIIa) has been previously identified as being associated with myocardial infarction (MI), but whether this represents a true association is entirely unclear due to differences in findings from different studies. We performed a meta-analysis to evaluate whether this polymorphism is a risk factor for MI.

METHODS

Electronic databases (MEDLINE and EMBASE) were searched for all articles evaluating genetic polymorphisms of GPIIIa. For studies where acute coronary events were recorded in association with genetic analysis, pooled odds ratios (ORs) were calculated using fixed-effects and random-effects models. The primary outcome measure was MI, and a secondary analysis was also performed for acute coronary syndromes (ACS) more generally.

FINDINGS

57 studies were eligible for statistical analysis and included 17,911 cases and 24,584 controls. Carriage of the PlA2 allele was significantly associated with MI (n = 40,692; OR 1.077, 95% CI 1.024-1.132; p = 0.004) but with significant publication bias (p = 0.040). The degree of association with MI increased with decreasing age of subjects (≤45 years old: n = 9,547; OR 1.205, 95% CI 1.067-1.360; p = 0.003) and with adjustment of data for conventional cardiovascular risk factors (n = 12,001; OR 1.240, 95% CI 1.117-1.376; p<0.001). There was a low probability of publication bias for these subgroup analyses (all p<0.05).

CONCLUSIONS

The presence of significant publication bias makes it unclear whether the association between carriage of the PlA2 allele and MI is true for the total population studied. However for younger subjects, the relative absence of conventional cardiovascular risk factors results in a significant association between carriage of the PlA2 allele and MI.

Platelet glycoprotein IIIA PIA1/A2 polymorphism in young patients with ST elevation myocardial infarction and idiopathic ischemic stroke

It has been identified that platelet glycoprotein IIIa PIA1/A2 polymorphism plays an important role in atherothrombotic disease such as myocardial infarction and stroke, but results remain controversial. Here, we investigated whether the PIA2 allele is associated with ST myocardial infarction or idiopathic ischemic stroke in young individuals in two independent studies. In a case-control study 275 patients with ST elevation myocardial infarction ≤45 years of age and 278 controls were recruited. In a second study, 200 patients with idiopathic ischemic stroke ≤45 years of age and 200 controls were enrolled. In both studies cases and controls were matched by age and gender. The PIA1/A2 polymorphism was determined in all participants by a polymerase chain reaction-restriction fragment length polymorphism assay. There was a significant difference in the PIA1/A2 genotype distribution (P = 0.001) and allele frequency (P = 0.001), between ST elevation myocardial infarction and control groups, but not in the PIA1/A2 genotype distribution (P = 0.61) and allele frequency (P = 0.80), between idiopathic ischemic stroke. The allele PIA2 represented an independent risk for ST elevation myocardial infarction but not for idiopathic ischemic stroke. Hypertension, smoking, and family history of atherothrombotic disease were also associated with ST elevation myocardial infarction and idiopathic ischemic stroke. Our results suggest that PA2 allele represents a risk factor for ST elevation myocardial infarction in young Mexican individuals but not for idiopathic ischemic stroke.

Platelet glycoprotein IIIA PIA2 polymorphism is associated with ST elevation acute myocardial infarction in young Mexican population

Platelet membrane glycoprotein IIb/IIIa plays an important role in adhesion and platelet aggregation. Polymorphisms of genes in platelet activation and fibrinolysis have been associated with myocardial infarction (MI), however this has not been confirmed by others, and results are still controversial. The aim of this study was to determine the frequency distribution and association of polymorphism in the platelet glycoprotein GPIIIa PLA/A2 and the possible interaction with the 4G/5G in the plasminogen activator inhibitor genes with ST elevation acute myocardial infarction (STEAMI) in young Mexican subjects. A total of 254 unrelated patients with first STEAMI ≤45 years of age, who were admitted to a cardiovascular intense care unit and 254 healthy controls matched by age and gender were recruited from January 2006 and May 2011. The PIA1/A2 and 4G/5G polymorphism were determined in all participants by a PCR restriction based restriction endonuclease digestion. There was a difference in the PIA2 allele distribution between both groups (P = 0.001). Also, we found an increased percent of 4G allele in the group of patients compared to control group (P = 0.001). There was an increased risk for STEAMI in carries with the allele PIA2 and 4G (OR = 4.3, CI 95 % 1.7-6.5). The modifiable risk factors such: smoking, hypertension, family history of cardiovascular disease, and dyslipidemia were associated with myocardial infarction. This is the first study to evaluate the role of gene polymorphism in both the thrombotic and fibrinolytic pathways in young Mexican individuals with STEAMI and suggest a synergistic effect between PIA2 and 4G allele.

Platelet glycoprotein IIIa (platelet antigen 1/platelet antigen 2) polymorphism and 1-year outcome in patients with stable coronary artery disease

Platelet glycoprotein IIb/IIIa is a membrane receptor which plays a key role in coronary artery disease and thrombotic events. However, there is a considerable controversy regarding the clinical impact of glycoprotein IIIa platelet antigen 1 (PlA1)/platelet antigen 2 (PlA2) polymorphism as a risk factor for myocardial infarction. To evaluate the association between glycoprotein IIIa PlA1/PlA2 polymorphism and 1-year cardiovascular events occurrence in aspirin-treated patients with stable coronary artery disease. We prospectively included 188 postacute coronary syndrome patients (183 men) aged 59 ± 10 years and receiving aspirin (250 mg/day). The clinical outcome at 1 year was the composite end point of nonfatal myocardial infarction, stroke, recurrent unstable angina or cardiac death. Genotyping for PlA1/PlA2 polymorphism was conducted using PCR and restriction fragment length polymorphism analysis. The genotype distribution of glycoprotein IIIa PlA1/PlA2 polymorphism was PlA1/PlA1, 55.3%; PlA1/PlA2, 39.3% and PlA2/PlA2, 4%. Incidence of composite end point in homozygous PlA1/PlA1 carriers was significantly higher than in PlA2/PlA2 and PlA1/PlA2 patients [14.4 vs. 3.6% odds ratio 4.5 (1.2-16.6, 95% confidence interval); P = 0.012]. Multivariate analysis identified three strong predictive factors of cardiac death: age more than 65 years [odds ratio = 6.8, (1.4-34, 95% confidence interval); P = 0.018], ventricular ejection fraction less than 50% [odds ratio = 8.6, (1.7-42.6, 95% confidence interval); P = 0.008] and homozygous PlA1/PlA1 genotype [odds ratio = 8.8, (1.0-78.6, 95% confidence interval); P = 0.014]. Our results demonstrated that glycoprotein IIIa PlA1/PlA1 genotype carriers have a significantly increased risks of acute vascular ischemic events associated with a poor prognosis at 1 year. These postacute coronary syndrome patients might require an optimized secondary antithrombotic prophylaxis strategy.

Genetic regulation of platelet receptor expression and function: application in clinical practice and drug development

Understanding genetic contributions to platelet function could have profound clinical ramifications for personalizing platelet-directed pharmacotherapy, by providing insight into the risks and possible benefits associated with specific genotypes. This article represents an integrated summary of presentations related to genetic regulation of platelet receptor expression and function given at the Fifth Annual Platelet Colloquium in January 2010. It is supplemented with additional highlights from the literature covering (1) approaches to determining and evidence for the associations of genetic variants with platelet hypo- and hyperresponsive phenotypes, (2) the ramifications of these polymorphisms with regard to clinical responses to antiplatelet therapies, and (3) the role of platelet function/genetic testing in guiding antiplatelet therapy.

Platelet polymorphisms: frequency distribution and association with coronary artery disease in an Indian population

Platelets play a critical role in normal blood hemostasis and thrombus formation in myocardial infarction (MI). Several polymorphisms of genes involved in platelet activation and fibrinolysis have been reported to be associated with MI. The aim of the present study was to determine the frequency distribution and association of polymorphisms in these genes with coronary artery disease (CAD) among Indians. A case-control genetic association study was performed for polymorphisms in platelet glycoprotein receptors (GPIIb/IIIa [HPA1a/1b], GPIb-IX-V [VNTR], and GPIa/IIa [C807T]), fibrinogen β-chain (BclI), α-chain (Aα312), tissue plasminogen activator (tPA) [I/D] and plasminogen activator inhibitor-I (PAI-1) [4G/5G] in 473 healthy controls and 446 patients with stable and unstable angina. Genotyping was either by PCR-based restriction endonuclease digestion or allele-specific primers. The I allele frequency of the tPA I/D polymorphism was significantly higher in our patients (χ(2)=7.33, P<0.01) and no other polymorphisms varied significantly between patients and controls. Also, none of the polymorphisms seemed to affect the severity of the disease, the only exception being the mutant alleles of β chain of fibrinogen gene, which were significantly elevated in single vessel disease. This is the first study to evaluate the role of gene polymorphisms in both the thrombotic and fibrinolytic pathway in the Indian population and suggests that tPA I/D polymorphism confers CAD risk in our population.

Human platelet alloantigens HPA-1, HPA-2, and HPA-3 polymorphisms associated with extent of severe coronary artery disease

The contribution of human platelet antigen (HPA)-1 (GPIIb/IIIa), HPA-2 (GPIb/IX), and HPA-3 (GPIIb/IIIa) polymorphisms to the risk of coronary artery disease (CAD) was investigated in 341 CAD patients and 316 matched control subjects. HPA genotyping was performed by PCR-SSP. Regression analysis was employed in assessing the contribution of these variants to CAD risk. The frequency of HPA-1b (P = .009) and HPA-3b (P = .004) alleles, and HPA-1a/1b (P = .045), HPA-1b/1b (P = .007), and HPA-3b/3b (P = .008) genotypes were higher in patients than control subjects. No significant association was demonstrated between the HPA variants and 1-, 2- and 3-vessel disease. HPA-1b/2a/3b (Pc = .021) and HPA-1b/2b/3a (Pc = .002) haplotypes were positively associated with CAD, thereby conferring a disease susceptibility nature to these haplotypes. Multivariate analysis confirmed the positive association of HPA-1b/2a/3b (aOR = 3.72; 95% CI = 1.49-9.28), and in addition identified HPA-1b/2a/3a (aOR = 2.49; 95% CI = 1.06-5.86) to be positively associated with CAD, after adjusting for a number of covariates. Our results demonstrate positive association of HPA variants and specific HPA-1/HPA-2/HPA-3 haplotypes with CAD in Tunisians.

The glycoprotein IIIa gene polymorphism and the risk of myocardial infarction

The hemostatic platelet response of an individual may be influenced by the genetic profile of the platelet membrane glycoprotein (GP) receptors. The GP IIIa, as a part of von Willebrand factor and fibrinogen receptor, plays a central role in platelet aggregation. Polymorphism in GP IIIa has been extensively studied for its association with myocardial infarction or coronary artery diseases. To date, the role of GP IIIa polymorphism in genetic susceptibility to thrombotic disease still remains controversial. The results of case-control association studies vary, even with the same ethnic background, and the association was hardly found in studies with larger sample size, suggesting publication-bias toward positive findings. In meta-analysis, the GP IIIa Pl(A2) allele carriers did not show increased risk for myocardial infarction compared with Pl(A1/A1) homozygotes. The functional studies also showed conflicting results. In conclusion, GP IIIa Pl(A1/A2) polymorphism does not seem to have a major role either in determining the individual variance of platelet function or the risk of myocardial infarction according to the currently available data. Therefore, the genotype determination of GP IIIa Pl(A1/A2 )polymorphism may not be useful for risk assessment of myocardial infarction at this time. Nevertheless, the author can not completely exclude its possible role in coronary thrombosis after angioplasty or sudden cardiac death. Thus, further evaluation in larger prospective or multicenter studies is required to elucidate the role of GPs in cardiovascular system.

Polymorphisms of human platelet alloantigens HPA-1 and HPA-2 associated with severe coronary artery disease

OBJECTIVES

Insofar as platelet membrane glycoprotein (GP) polymorphisms were identified as potential risk factors for coronary artery disease (CAD), we investigated the contribution of human platelet antigen (HPA)-1 (GPIIb/IIIa) and HPA-2 (GPIb/IX) alleles and haplotypes to CAD pathogenesis.

METHODS

Study subjects comprised 247 middle-age CAD patients and 316 age-, gender-, and race-matched controls; HPA genotyping was performed by polymerase chain reaction with sequence specific primers.

RESULTS

The frequencies of HPA-1b (P<.001) and HPA-2b (P<.001) alleles and HPA-1a/1b (P<.001), HPA-1b/1b (P<.001), and HPA-2a/2b (P<.001) genotypes were higher in patients than control subjects. Select HPA haplotypes comprising the HPA-1b/2a (Pc=2.2 × 10(-4)) and HPA-1b/2b (Pc=.001) haplotypes which were positively associated, and the HPA-1a/2a (Pc=3.2 × 10(-5)) which was negatively associated with CAD, confer a disease susceptibility and protective nature to these haplotypes. Multivariate analysis confirmed the positive association of HPA-1b/2a [adjusted odds ratio (aOR)=3.63; 95% CI=2.42-5.43] and HPA-1b/2b (aOR=2.92; 95% CI=1.43-5.94) haplotypes with CAD, after adjustment for a number of covariates.

CONCLUSIONS

Our results suggest that HPA-1/HPA-2 haplotypes may be considered to be a major risk factor for CAD in middle-aged Tunisians.

Pharmacological inhibition of AMP-deaminase in rat cardiac myocytes

Because mutation of AMP deaminase 1 gene leading to reduced AMP deaminase activity may result in protection of cardiac function in patients with heart disease, inhibitors of AMP deaminase (AMPD) may have therapeutic applications. This study evaluated the effect of a specific inhibitor of AMP deaminase 3-[2-(3-carboxy-4-bromo-5,6,7,8-tetrahydronaphthyl)ethyl]-3,6,7,8-tetrahydroimidazo [4,5-d][1,3]diazepin-8-ol (AMPDI) on the isolated human enzyme and on nucleotide catabolism in rat cardiomyocytes. AMPDI effectively inhibited isolated human AMPD with an IC(50) = 0.5 micro M. AMPDI was much less effective with isolated cardiomyocytes (IC(50) = 0.5 mM). AMPDI is a very effective inhibitor of AMPD that despite lower efficiency in the cell system examined could be useful for in vivo studies.

The PlA1/A2 polymorphism of glycoprotein IIIa and cerebrovascular events in hypertension: increased risk of ischemic stroke in high-risk patients

OBJECTIVE

The platelet GPIIIa plays a pivotal role in platelet aggregation. Previous studies showed an association between the GPIIIa Pl(A1/A2) polymorphism and coronary thrombosis, while there is only contrasting evidence about its role in stroke. We explored the possibility that this polymorphism represents a risk factor for stroke in hypertensive patients.

METHODS

We studied two populations. In loco, we genotyped 140 hypertensive control individuals and 28 hypertensive patients with ischemic stroke. Furthermore, we performed an analysis of previously published data of 451 Sardinian hypertensive patients, already characterized and genotyped.

RESULTS

Association analysis revealed that the Pl(A2) distribution was similar between hypertensive patients with and without stroke, but when considering a more homogeneous population of high-risk hypertensive patients, defined according to ESH/ESC 2003 guidelines, we observed that the frequency of the Pl(A2) allele was higher among stroke versus nonstroke patients (stroke, 46.4%; nonstroke, 22.6%; P = 0.01). The multiple regression analysis taking into account this polymorphism among other factors known to contribute to ischemic stroke confirmed the Pl(A2) allele as an additive risk factor for stroke (B = 0.986, Wald = 4.943, P < 0.03), increasing the risk of stroke by 2.9 (95% confidence interval = 1.23-6.85, P < 0.02). Similar results were obtained in the Sardinian population: in hypertensive patients with three or more risk factors, Pl(A2) increases the risk (odds ratio = 2.8, 95% confidence interval = 1.3-6.0, P < 0.001) and is an additive risk factor for stroke (B = 1.073, Wald = 6.920, P < 0.01).

CONCLUSIONS

Our data suggest that the Pl(A2) polymorphism is a genetic determinant of ischemic stroke in a selected high-risk hypertensive population.

PIA1/A2 polymorphism of the platelet glycoprotein receptor IIb/IIIIa and its correlation with myocardial infarction: an appraisal

Platelet glycoprotein (GP) IIb/IIIa is a membrane receptor for fibrinogen and von Willebrand factor. There is considerable controversy regarding the clinical role of the GPIIb/IIIa PIA1/A2 as a risk factor for myocardial infarction. A summative analysis is performed on the recent previous reports on the GPIIb/IIIa PIA1/A2 and its correlation to myocardial infarction. The metanalysis was performed to assess the correlation between the pattern of GPIIb/IIIa PIA1/A2 polymorphism and myocardial infarction. From 7 available case-control reports, 553 patients and 1,059 controls are evaluated. The overall frequencies of PIA2 allele for the patients and controls are 0.249 and 0.221, respectively. According to this study, 49.4% of subjects with PIA2 allele have myocardial infarction while 39.5% of subjects without PIA2 allele have cerebrovascular disease. From overall risk estimation, the subjects with PIA2 alleles have a 1.1 times higher risk to have myocardial infarction. According to this analysis, it is proposed that the pattern of GPIIb/IIIa PIA1/A2 polymorphism does not represent a useful marker of increased risk for myocardial infarction. In addition, the lack of association between the pattern of GPIIb/IIIa PIA1/A2 polymorphism and ethnicity of the patients was demonstrated in this study.

Stromelysin-1 promoter 5A/6A polymorphism is an independent genetic prognostic risk factor and interacts with smoking cessation after index premature myocardial infarction

OBJECTIVE

To evaluate the prognostic roles of multiple polymorphisms and smoking cessation for premature myocardial infarction (MI).

METHODS

We studied 170 patients with MI onset before the age of 45 years (range 27-45 years, 84% men) and analyzed the traditional risk factors and several candidate genes' associations with their subsequent coronary events.

RESULTS

Follow-up data were available for a total of 162 individuals (95.3%) with the other 38 individuals (4.7%) being lost-to-follow-up premature MI patients. During a mean period of 4.43 years' follow-up, diabetes mellitus (DM), hypertension, hypercholesterolemia and Killip's status > or =II were more frequent among patients with subsequent cardiac events (all P-values <0.05). The frequency of 5A allele of stromelysin-1 gene was significantly higher among event group (P = 0.01). Smoking cessation after MI, use of beta-blocker or angiotensin-converting enzyme inhibitor (ACEI) could improve outcome (all P-values <0.05). After multivariate analysis, we found that DM was an independent risk factor for survival [Hazard ratio (HR) 2.45, P = 0.01]. Successful smoking cessation and therapy with ACEI could have a protective effect (HR 0.33 and 0.09, P = 0.01 and <0.01, respectively). The stromelysin-1 5A gene polymorphism was also an independent survival predictor (HR 2.51, P = 0.03). In addition, smoking cessation could significantly modify the risk, especially among patients with 5A allele polymorphism (HR 6.75 vs. 1.50).

CONCLUSION

We thus conclude that the stromelysin-1 gene polymorphism alone or in combination with smoking cessation can influence the prognosis after index premature MI.

Genetics of platelet glycoprotein receptors: risk of thrombotic events and pharmacogenetic implications

Platelet aggregation and coronary thrombosis have a central role in the development of acute coronary syndromes and myocardial infarction (MI). Therapies aimed at inhibiting platelet aggregation have shown great benefit in individuals with coronary disease or with multiple risk factors for coronary disease. Genetic variation in platelet surface receptors mediating thrombus formation has been suggested to be associated with platelet hyperreactivity, with increased risk of MI and possibly with the benefit received from various antithrombotic drug treatments. This review focuses on discrepancies and their likely explanations in studies on platelet glycoprotein genetics. Current knowledge on important issues concerning coronary event phenotypes and pharmacogenetics is analyzed. Possible future applicability of these data to patient treatment is also discussed.

Platelet glycoprotein Ia C807T, Ib C3550T, and IIIa Pl(A1/A2) polymorphisms and ischemic stroke in young Taiwanese

Platelet plays a pivotal role in the pathogenesis of thrombotic cardiovascular diseases. Recently, the polymorphism of platelet glycoprotein (GP) genes has been reported to be associated with an increased risk for ischemic stroke. The purpose of this study is to evaluate the association between platelet GP genetic variants and ischemic stroke in young Taiwanese. We conducted a case-control study in 157 young ischemic stroke patients recruited between September 2001 and March 2003 and 157 age- and sex-matched controls. The genotypes of platelet GP Ia C807T, GP Ib C3550T, and GP IIIa Pl(A1/A2) polymorphisms were analyzed by polymerase chain reaction-restriction fragment length polymorphism. Student's t-test, chi-square test, and logistic regression modeling were used for data analyses. The GP Ia C807T CC, CT and TT genotype frequencies were similar between patients (50.3%, 43.9%, 5.7%) and controls (53.5%, 38.9%, 7.6%; p=0.58). There were no significant differences in GP Ib C3550T CC and CT genotype distributions between patients (91.1%, 8.9%) and controls (91.7%, 8.3%; p=0.84). Of all subjects, none carries GP IIIa Pl(A2) mutation. In conclusion, platelet GP Ia C807T and GP Ib C3550T polymorphisms in our population are less common compared with Caucasians, and GP IIIa Pl(A1/A2) genetic mutation is not found, and all of them are not associated with ischemic stroke in young Taiwanese.

Association of the platelet glycoprotein receptor IIIa (PlA1/PlA1) genotype with coronary artery disease in Arabs

The PlA2 allele (heterozygotes or homozygotes) resulting from a genetic polymorphism in the glycoprotein IIIa gene has been proposed as a potential genetic factor linked to platelet hyperaggregability and increased risk of coronary artery disease (CAD). Such an association could only be established in some ethnic groups. There were no previous reports investigating the distribution of this allele and its possible link to CAD in Arabs. We used the polymerase chain reaction and allele-specific restriction digestion for determining the prevalence of this allele in 509 healthy blood donors (BD) and 451 angiographically confirmed CAD patients of Arabic ethnic background. For the BD group (n = 509), 70.7% were homozygous PlA1/PlA1, 26.9% were heterozygous PlA1/PlA2 and 2.4% were homozygous PlA2/PlA2. Within the CAD group (n = 451), 77.2% were homozygous PlA1/PlA1, 19.5% were heterozygous PlA1/PlA2 and 3.3% were homozygous PlA2/PlA2. The PlA1 allele frequency was 0.84 and 0.87, and for the PlA2 was 0.16 and 0.13 for the BD and CAD groups, respectively. In conclusion, our results suggest that the PlA1/PlA1 genotype (P = 0.029) is associated with CAD in Saudi Arabs.

A2 Alelle of GpIIIa Gene Is a Risk Factor for Stroke Caused by Large-Vessel Disease in Males

Background and Purpose— Glycoprotein IIIa (GpIIIa) is a platelet membrane receptor for fibrinogen and von Willebrand factor. It plays a key role in platelet aggregation. Previous studies in stroke patients, without analysis based on specific subtypes of stroke cause, have not shown any link between GpIIIa A1/A2 polymorphism and stroke risk. We studied the significance of the GpIIIa gene A1/A2 polymorphism in stroke patients with different stroke causes.

Methods— We genotyped 92 patients with stroke caused by large-vessel disease (LVD stroke) and 184 matched controls; 103 patients with stroke caused by small-vessel disease (SVD stroke) and 206 controls; and 182 patients with cardioembolic stroke (CE stroke) and 182 controls (TOAST criteria). The GpIIIa A1/A2 polymorphism was analyzed by polymerase chain reaction followed by restriction enzyme digestion and electrophoresis.

Results— The genotype distribution of the GpIIIa gene in patients with LVD stroke (A1/A1, 63%; A1/A2, 34.8%; A2/A2, 2.2%) differed significantly from their controls (A1A1, 79.3%; A1/A2, 20.1%; A2/A2, 0.6%). The distribution of the GpIIIa A1/A2 polymorphism in patients with SVD stroke and CE stroke was similar to that of their controls. In contrast to females with LVD stroke, we found that males with LVD stroke presented with an overrepresentation of at least 1 A2 allele of the GpIIIa gene when compared with their controls (39.7% versus 23.0%; P =0.003). Conditional logistic regression analysis showed that possession of at least 1 A2 allele of the GpIIIa gene was an independent risk factor for LVD stroke in males (OR, 2.51; 95% CI, 1.21 to 5.20).

Conclusion— A2 allele of the GpIIIa gene is an independent risk factor for LVD stroke in males.

The platelet polymorphism PlA2 is a genetic risk factor for myocardial infarction

OBJECTIVES

Platelet glycoprotein (GP) receptor IIb/IIIa plays a key role in the development of myocardial infarction (MI), and Pl(A2) is a polymorphism in the gene encoding this receptor. The prevalence of Pl(A2) shows pronounced geographical variation and has to our knowledge not been presented for a Scandinavian population before. Platelets from Pl(A2)-positive individuals show increased aggregability compared with platelets from Pl(A2)-negative individuals, and Pl(A2) genotypes might be associated with MI. The purpose of this study was to investigate the relation between the Pl(A2) polymorphism and MI in a large Scandinavian population.

DESIGN

Case-control study. We included patients with angiographically verified CAD with and without previous MI and a group of healthy individuals matched for age, race, and sex.

RESULTS

We studied the frequency of Pl(A2) in 1191 healthy individuals and 1019 patients with coronary artery disease (CAD). Amongst these patients, 529 subjects had suffered an MI previously. Pl(A2) was present in 28% of healthy individuals, 28% of patients with CAD but no MI, and in 35% of patients with CAD and MI. The difference between healthy individuals and MI patients was significant (P = 0.002). Furthermore, a graded relationship between the number of Pl(A2) alleles and the risk of MI was seen (P = 0.011). Associations between Pl(A2) and traditional cardiovascular risk factors as well as mean platelet volume were investigated. We found a significant interaction between Pl(A2) and serum cholesterol.

CONCLUSION

In our Scandinavian study population the common platelet polymorphism Pl(A2) is significantly associated with an increased risk of MI, but not of CAD. Clinically, typing for Pl(A2) might have implications for antiplatelet therapy of patients with MI.

Role of platelet glycoprotein polymorphisms in cardiovascular diseases

Atherothrombosis is the leading cause of death in western countries. Major complications of atherothrombotic disease, which are responsible for a large burden of morbidity and mortality, are acute coronary syndromes, ischemic stroke, and peripheral occlusive disease. Plaque rupture, platelet adhesion, aggregation, and thrombosis may lead to unstable angina and may progress to myocardial infarction as well as to ischemic stroke. Platelet membrane glycoprotein receptors mediate crucial reactions in acute thrombosis and chronic processes of atherogenesis. The platelet glycoprotein GP IIb/IIIa, which is the most abundant platelet receptor, also represents the drug target of a novel class of anti-platelet drugs, which includes abciximab, tirofiban, and eptifibatide. The genes encoding the three major platelet glycoprotein receptors (GP Ib/IX/V, GP Ia/IIa, and GP IIb/IIIa) are subject to considerable genetic variability. This paper reviews how polymorphisms in the platelet glycoprotein receptors affect platelet function, susceptibility to atherothrombosis and its major complications including myocardial infarction, stroke, and complications following percutaneous coronary interventions, and individual variability of drug response. Recent data on platelet glycoprotein receptor polymorphisms as modifiers of drug action and as predictors of drug response offer the perspective of individualized drug treatment. Prospective studies will show whether this approach is useful or not. As the data reviewed here show clearly, future clinical trials should routinely take into account genetic susceptibility factors and modifiers, both for study design and for predefined patient stratification.

Overestimation of genetic risks owing to small sample sizes in cardiovascular studies

We sought evidence of publication bias to explain conflicting findings in studies of angiotensin-converting enzyme deletion polymorphism (ACE D) and glycoprotein IIIa PlA2 (PLA2) polymorphism and the risk of myocardial infarction. Factor 5 Leiden (F5L), a well-established thrombotic risk factor, served as an internal comparison. We conducted systematic reviews of published studies involving ACE D, PLA2, F5L and relevant outcomes, searching medline (January 1990 through February, 2001), bibliographies, and meta-analyses. Random effects pooled odds ratios (95% confidence interval) for cardiovascular outcomes were as follows: PLA2 (n = 13,167 subjects): 1.13 (1.02, 1.26); ACE D (n = 42,140 subjects): 1.22 (1.11, 1.35); and F5L (n = 27,277 subjects): 4.43 (3.65, 5.38). However, funnel plots of ACE D and PLA2, but not F5L, showed an inverse relationship between sample size and odds ratios for ACE D (p = 0.02) and PLA2 (p = 0.04) but not F5L (p = 0.65) by Egger's test for potential publication bias. Despite research-based genotyping of over 50,000 subjects, the overall risk for myocardial infarction as a result of PLA2 and ACE D remains doubtful. Our study provides a clear example of how publication of underpowered studies can spuriously implicate polymorphisms as genetic risk factors.

A meta-analysis of studies on the association of the platelet PlA polymorphism of glycoprotein IIIa and risk of coronary heart disease

The Pl(A2) polymorphism of the glycoprotein IIIa subunit of the fibrinogen receptor (GPIIb-IIIa) has been reported by some studies to be associated with an increased risk of coronary thrombosis. Following the first paper on the subject in 1996, a large number of studies have investigated the relationship between this polymorphism and coronary thrombosis, either at the epidemiological or at the cellular and molecular levels. The cellular and molecular studies have shown in a consistent manner that this polymorphism increases platelet responsiveness. In contrast, epidemiological studies have generated inconsistent results regarding the clinical impact of Pl(A2). We consider 12 epidemiological studies that investigate the link between presence/absence of this polymorphism and presence/absence of coronary heart disease. Each is a case-control study that reports an odds ratio. The studies are not directly comparable because they differ greatly in their patient pools and also in the way the data are analysed. We present several meta-analyses of these 12 studies. The simplest one is based on a standard frequentist random effects model with a normal distribution for the study effects (the per-study population log-odds ratios). We also consider a Bayesian version of this model, with a diffuse prior for the mean and variance of the normal distribution of the study effects. The conclusions from both of these analyses is about the same, and is that there is evidence that the Pl(A2) polymorphism is associated with an increased risk of coronary heart disease. A look at the reported log-odds ratios across studies suggests that the study effects do not come from a symmetric distribution. For this reason, we also consider semi-parametric priors for the distribution of the study effects. These priors are specifically designed for this kind of meta-analysis, and are based on a certain class of mixtures of Dirichlet priors. They can be designed to concentrate most of their mass around the family of normal distributions, but still allow for any other distribution. The semi-parametric Bayesian model continues to give evidence of an association between the Pl(A2) polymorphism and the risk of coronary heart disease.

Association between the Pl(A) platelet glycoprotein GPIIIa polymorphism and extent of coronary artery disease

BACKGROUND

The Pl(A2) allele of the gene encoding for GPIIIa subunit of the platelet membrane receptor glycoprotein (GP) IIb/IIIa has been suggested as a significant risk factor for thrombotic complications of coronary artery disease (CAD). The aim of the current investigation was to investigate the association between Pl(A) GPIIIa polymorphism and the extent of angiographically confirmed CAD in patients from the north region of Poland.

METHODS

The study was performed in 397 male Caucasian patients. All subjects had significant coronary artery stenosis confirmed by elective coronary angiography. Screening for the Pl(A) GPIIIa genotypes was performed by polymerase chain reaction of genomic DNA, followed by NciI digestion and agarose gel electrophoresis.

RESULTS

The genotype distribution of the Pl(A) GPIIIa polymorphism in our study group was Pl(A1/A1)-75%, Pl(A1/A2)-24% and Pl(A2/A2)-1% with Pl(A1) and Pl(A2) allele frequencies of 0.87 and 0.13, respectively. The prevalence of the homozygous Pl(A1/A1) genotype among subjects with multiple-vessel CAD (two or three vessels with at least 50% stenosis) was significantly higher than in patients with single-vessel disease; the odds ratio of Pl(A2/A2) or Pl(A1/A2) patients for having multiple-vessel CAD was 0.46 (95% CI 0.27-0.77, P<0.01). The mean CAD score for Pl(A1/A1) patients was significantly higher in comparison to Pl(A2/A2) and Pl(A1/A2) patients (7.58+/-2.20 and 6.98+/-2.37, respectively, P<0.05).

CONCLUSIONS

Our results suggest, that the Pl(A1/A1) genotype of Pl(A) GPIIIa polymorphism is associated with more severe CAD in male Caucasian patients from the north region of Poland.

Evaluation of an antibody-based genotype classification of the platelet fibrinogen receptor (GPIIb/IIIa)

Platelet membrane glycoprotein (GP) IIb/IIIa is the central molecule in platelet adhesion and aggregation by high-affinity binding of fibrinogen. Polymorphism of the beta chain of the receptor, especially the GPIIIa-proline33 allele [HPA-1b, Zwb, PI(A2)], has been suggested to be associated with a variety of vascular diseases, such as coronary stenosis, myocardial infarction, cerebral ischemia, or venous thrombosis. Using clinical chemistry standards, we evaluate a flow cytometric whole-blood, antibody-based method to determine the genotype [PI(A1A1), PI(A1A2), PI(A2A)] versus polymerase chain reaction (PCR)-based DNA restriction fragment length analysis in 220 individuals. Both homozygous and heterozygous genotypes differ in the expression of binding sites for the monoclonal antibody, SZ21. Agreement between the two methods was achieved in 187 cases, which reflects a test validity of 85%, a sensitivity of 83.6%, and a specificity of 85.4%. We conclude that flow cytometry is reliable for classifying the PI(AX) genotype. The performance characteristics are easy, fast, and cheap (genomics by proteomics). These features make it suitable for screening patients and broad populations for the future risk of cardiovascular ischemic events.

Platelet glycoprotein IIIa Pl(a) polymorphism, fibrinogen, and platelet aggregability: The Framingham Heart Study

BACKGROUND

Recent data suggest that the Pl(A2) allele of the platelet glycoprotein IIIa receptor may be a genetic risk factor for cardiovascular disease. We previously reported that the Pl(A2) allele was associated with increased platelet aggregability, as indicated by lower epinephrine threshold concentrations. Paradoxically, however, it has been reported that Pl(A2)-positive platelets have reduced fibrinogen binding. Because fibrinogen mediates platelet aggregability, we hypothesized that plasma fibrinogen levels may interact with Pl(A) genotype in modulating platelet aggregability. Methods and Results-- Glycoprotein IIIa Pl(A) genotype, fibrinogen level, and platelet aggregability were ascertained in 1340 subjects enrolled into the Framingham Offspring Study. Platelet aggregability was evaluated by the Born method. Higher fibrinogen levels were associated with increased epinephrine-induced aggregation (P=0.002) and a trend for ADP-induced aggregation (P=0.07). The fibrinogen effect was genotype specific, however, in that the increase in platelet aggregability with higher fibrinogen was present for the Pl(A1/A1) genotype (P=0.0005 and P=0.03 for epinephrine- and ADP-induced aggregation, respectively) but not for the Pl(A2)-positive genotype (P>0.90).

CONCLUSION

Higher fibrinogen levels were associated with increased platelet aggregability. However, the association between fibrinogen and platelet aggregability was genotype specific. This interaction may be responsible for the conflicting findings regarding Pl(A) genotype and platelet aggregability. Further study of this gene-environment interaction may provide insight into cardiovascular disease risk.

Sudden cardiac death, genes, and arrhythmogenesis: consideration of new population and mechanistic approaches from a National Heart, Lung, and Blood Institute workshop, Part II

This is Part II of a 2-part article dealing with malignant ventricular arrhythmias, which are the leading mechanism of death in common cardiac diseases. Genetic population studies directed at discovering common proximal sources of inherited molecular risk most directly linked to arrhythmia initiation and propagation would appear to have considerable potential in helping reduce cardiovascular mortality.

Correlation of polymorphisms to coagulation and biochemical risk factors for cardiovascular diseases

Currently, the established risk factors for cardiovascular disease (CVD) are largely environmental in nature. Conflicting studies have suggested that mutations in specific coagulation genes may also provide a genetic basis for CVD risk. We reviewed clinical studies that examined the role of single nucleotide polymorphisms in coagulation and platelet factors, and a biochemical factor to determine if specific genotypes are correlated with patients with a history of arterial thrombotic diseases (acute coronary syndromes or stroke). A meta-analysis was performed on studies for factors II (G20210A variant), V Leiden (G1691A), VII (R353Q), glycoprotein (GP) IIIa receptor (PI(A1/A2)), and methylenetetrahydrofolate reductase (MTHFR, C677T). There was no correlation for factor II or factor V polymorphisms to coronary artery disease (CAD) in 5,607 and 5,431 patients studied, respectively. There was also no correlation for factor II variants and stroke in 3,451 patients studied. For factor V, statistical significance was achieved for the G1691A variant on 3,399 patients with stroke (odds ratio [OR] 1.43, 95% confidence intervals [CI] 1.03 to 1.97). The GP IIIa PI(A1/A2) genotype was associated with increased risk for CAD in 7,920 patients (OR 1.12, 95% CI 1.01 to 1.24), but not for 1,855 patients who had a stroke (OR 0.80, 95% CI 0.62 to 1.04). The combined RQ and RR genotypes of factor VII R353Q were correlated to a reduced risk for CVD in 2,574 patients (OR 0.78, 95% CI 0.65 to 0.93), whereas the QQ genotype had offered more protection (OR 0.53, 95% CI 0.27 to 1.03). The TT homozygous variant of MTHFR was associated with CAD risk in 5,644 patients studied (OR 1.30, 95% CI 1.11 to 1.52) but not for 3,075 patients with stroke. This study shows that for some genes, further studies are unnecessary, whereas for others, no more enrollments are needed. The impact of certain genotypes must be examined in relation to other established risk factors and potentially new therapeutic strategies.

Platelet polymorphisms in thrombotic disorders

Plaque rupture and/or endothelial damage lead to exposure of von Willebrand factor (VWF) and collagen which facilitate the adhesion of circulating platelets via glycoprotein (GP) GPIb-IX-V and integrin alpha2 beta1, respectively, to the damaged vessel wall. This process activates the platelets and leads to a conformational change of a second integrin alphaIIb beta3 that facilitates fibrinogen binding and platelet aggregation. Thrombin generated at the blood-plaque interface converts fibrinogen to fibrin, which stabilizes thrombus growth. Therefore, any genetic differences that might alter surface expression or activity of these receptors could influence the risk for adverse outcome as a result of the hemostatic process. In the last five years, there has been a rapid accumulation of literature concerning the relationship between genetic variations in platelet glycoproteins and risk for coronary heart disease. In this study, we have presented a comprehensive review of the impact of platelet receptor polymorphisms and thrombotic risk.

Effect of the Pl(A2) alloantigen on the function of beta(3)-integrins in platelets

The polymorphism responsible for the Pl(A2) alloantigen on the beta(3)-component of beta(3)-containing integrins is reported to be a risk factor for coronary thrombosis. This study examined the effect of Pl(A2) on the function of beta(3)-integrins using platelets from subjects homozygous and heterozygous for Pl(A1) and Pl(A2). There was overlap in the distribution of the dissociation constant (K(d)) and maximum fibrinogen binding (B(max)) values for fibrinogen binding to alpha(IIb)beta(3) on platelets from Pl(A1) and Pl(A2) homozygotes and Pl(A1)/Pl(A2) heterozygotes. However, whereas there was no statistical difference in these values for the Pl(A1) homozygotes and Pl(A2) heterozygotes, the K(d) for the Pl(A2) homozygotes was significantly lower than that for the Pl(A1)/Pl(A2) heterozygotes, but was not statistically different from that for the Pl(A1) homozygotes. No differences were detected in ADP sensitivity between platelets from Pl(A1) homozygotes and Pl(A1)/Pl(A2) heterozygotes, in the IC(50) for RGDS inhibition of fibrinogen binding to alpha(IIb)beta(3), in the alpha(v)beta(3)-mediated adhesion of platelets to osteopontin and vitronectin, and in the phorbol ester-stimulated adhesion to fibrinogen of B lymphocytes expressing alpha(IIb)beta(3) containing either the Pl(A1) or the Pl(A2) polymorphism. Finally, no differential effects of Pl(A2) on turbidometric platelet aggregation, platelet secretion, or platelet thrombus formation were found as measured in the PFA-100. Because no differences were detected in the ability of beta(3)-integrins to interact with ligands based on the presence or absence of the Pl(A2) polymorphism, the results suggest that factors unrelated to beta(3)-integrin function may account for the reported association of the Pl(A2) allele with coronary thrombosis.

Genetics of arterial prothrombotic risk states

Coronary artery disease is a leading cause of death worldwide and the largest killer of men and women in the United States. The pathophysiology of myocardial infarction is multifactorial, and numerous physiologic systems converge to dictate the formation of the two fundamental lesions, thrombosis and atherosclerosis. In this review we address genetic aspects of arterial thrombosis and the key thrombotic factors that have been associated with the increased risk for its development. Specifically, we consider components of coagulation, fibrinolysis, and platelet adhesive receptors, and we review the genetic epidemiology and in vitro laboratory data regarding their risk for the acute coronary syndromes. In combination with traditional risk factor assessment, in the near future these inherited markers can be used to manage patients with vascular disease through a better utilization of invasive or expensive diagnostic testing, as well as pharmacologic intervention.

The GPIIIa (beta3 integrin) PlA polymorphism in the early development of coronary atherosclerosis

The GPIIIa (beta3 integrin) is an integral part of two glycoprotein receptors - the GP(IIb/IIIa) fibrinogen receptors in platelets and the GP(V/IIIa) vitronectin receptors in endothelium and vascular smooth muscle cells (vSMC). The PlA polymorphism of the gene for GPIIIa (beta3 integrin) has been suggested to play an important role in the progression of coronary artery disease (CAD) and in coronary thrombosis. Whether the action of the PlA polymorphism is due to differences in platelet aggregability or function of the vSMC and endothelial GPIIIa is not known. The association of the PlA polymorphism with the early, non-complicated atherosclerosis and CAD was studied in the Helsinki Sudden Death Study (HSDS) comprising two independent, autopsy series of altogether 700 middle-aged Caucasian Finnish men (33-70 year) suffering sudden out-of-hospital death. The burden of complicated lesions was greater in men with the A2 allele (heterozygotes or homozygotes for A2) (P=0.01) compared with PlA1/A1 homozygotes in the entire series. To further estimate the role of platelet-independent GPIIIa receptors, we excluded all cases with coronary thrombosis and thrombus-overlaid complicated lesions. In this subset of men, fibrous coronary lesions were more frequent (OR 2.9; P<0.01) in the coronary arteries of PlA1/A1 homozygotes compared with men with the PlA2 allele. Moreover, men with the PlA1/A1 genotype also had more stenotic coronary arteries (P<0.05) compared with men with the A2 allele at this early, non-complicated stage of atherosclerosis. The findings of this study suggest that Pl(A1/A1) homozygotes may be prone to early atherosclerosis and more rapid progression of stable CAD whereas carriers of the PlA2 allele are more prone to thrombotic complications. We hypothesize that the PlA polymorphism may account for the early atherosclerosis by affecting the function of endothelial and vSMC GP(V/IIIa) receptors, whereas the PlA polymorphism on platelet GP(IIb/IIIa) receptors may play a major role in coronary thrombosis.

Meta-analysis of the association of platelet glycoprotein IIIa PlA1/A2 polymorphism with myocardial infarction

This meta-analysis examined all the published reports up to October 1999 that studied the association between PlA2 polymorphism of platelet glycoprotein IIIa gene and myocardial infarction. The PlA2 polymorphism was not found to be associated with an increased risk of myocardial infarction, either overall or in selected subgroups, which were patients with premature disease onset (age < or = 60 years), first acute myocardial infarction, and patients who were men, women, and exclusively Caucasian.

Glycoprotein IIIa Pl(A1/A2) polymorphism and sudden cardiac death

OBJECTIVES

We studied the association of the Pl(A1/A2) polymorphism with coronary thrombosis, myocardial infarction (MI) and sudden cardiac death (SCD) in autopsied victims of sudden death.

BACKGROUND

Sudden cardiac death is one of the leading symptoms of coronary heart disease in early middle age. Platelet glycoprotein (GP)IIb/IIIa fibrinogen receptors play a key role in coronary thrombosis and MI. Pl(A1/A2) polymorphism of the gene for GPIIIa has been previously studied in hospital MI patients. Significance of the Pl(A1/A2) polymorphism in victims of SCD is not known.

METHODS

The Pl(A1/A2) polymorphism was studied in the Helsinki Sudden Death Study comprising 700 autopsied middle-aged white Finnish men (33 to 70 years, mean 53 years) who suffered sudden or violent out-of-hospital death.

RESULTS

Prevalence of the A2 allele decreased with age in the series. This decrease was observed among victims of SCD (n = 281) but not in men who died violently (n = 258) or of other diseases (n = 127). Of SCD victims below 50 years, 39.7% were carriers of the A2 allele compared with 28.3% among men under 50 who died of other causes (odds ratio [OR] 2.5, p = 0.01). Men with acute fatal coronary thrombosis (n = 39) were more often (OR 3.4, p < 0.01) carriers of the A2 allele than were men (n = 242) with SCD in the absence of acute coronary thrombosis (48.7% vs. 24.4%, respectively). In addition, men with MI and recent or old thrombosis (n = 67) were more often (OR 3.6, p = 0.005) carriers of the A2 allele than were men (n = 123) with MI in the absence of thrombosis (44.8% vs. 20.3%, respectively). These associations were especially strong in men under 60.

CONCLUSIONS

Our results suggest that the A2 allele of the Pl(A1/A2) polymorphism of GPIIIa is a major risk factor of coronary thrombosis and may be one important predictor of SCD in early middle age.

Platelet glycoprotein polymorphisms as risk factors for thrombosis

Both blood platelets and genetics contribute to the development of acute ischemic arterial diseases. A careful analysis of the various clinical association studies supports a modest increased risk for coronary artery disease events in carriers of the PIA2 polymorphism of GPIIIa. Investigations with both platelets and stable cells lines have shown the PIA2 polymorphism is prothrombotic. Only a handful of studies have been performed for platelet GPla (integrin alpha2) and GPIb-IX-V, but there is support for the 807 T/C polymorphism of GPIa and the met145 and VNTR B/C genotype of GPIbalpha as risk factors in younger age groups. And isolated reports suggest other platelet polymorphisms (GPIIb, FcgammaRIIa, P-selectin, alpha2 adrenergic receptor, transforming growth factor [TGF]beta) are risk factors for arterial disease or produce a prothrombotic phenotype. Platelet glycoprotein polymorphisms should be added to the list of genetic risk factors for arterial thrombosis, particularly in younger patients and women.

Prevention of coronary heart disease. Part II. Secondary prevention, detection of subclinical disease, and emerging risk factors

The prevention of CHD should be a major priority among primary care physicians and subspecialists who have any dealing with the cardiovascular system. There is ample evidence from epidemiologic studies for the impact of specific risk factors on CHD events. There is also ample evidence from observational studies and clinical trials that interventions of lifestyle and pharmacologic therapy can decrease morbidity and mortality from CHD before or after the first event. It behooves the physician who wishes to practice good medicine to understand the pathophysiologic roles of the risk factors and the evidence from epidemiologic studies and clinical trials for their association with cardiovascular disease. It is important to determine the efficacy of interventions, both lifestyle and pharmacologic, in modifying CHD risk. To be effective in doing so, the practicing physician has to have the motivation to determine target goals for risk factor modification in each patient, to understand the patient's own motivations in modifying risk factors, and to define clearly with the patient the expectations of such interventions. Although there are guidelines for risk factor modification in modification of cholesterol and in hypertension, the periodic renewal of these guidelines reflects the changing concepts of risk and its modification. A cardiovascular risk factor intervention categorization is presented in Table 12. The physician must be convinced that such intervention is beneficial to the patient, cost-effective, and thus fulfills the expectations of medical practice. The practice of medicine in the evaluation and treatment of coronary heart disease has always been challenging and stimulating. The prevention of CAD disease should ultimately provide the greatest accomplishment.

Polymorphism of platelet glycoprotein IIb and risk of thrombosis and restenosis after coronary stent placement

Both glycoprotein (GP) IIb and IIIa of platelet fibrinogen receptor are polymorphic proteins. Unlike GPIIIa, there is little information about the clinical significance of the GPIIb polymorphism. We designed this prospective study to assess whether patients with the human platelet antigen (HPA)-3 polymorphism of GPIIb are more susceptible to developing thrombosis and restenosis after coronary stent placement. We included 2,178 consecutive patients with coronary artery disease who underwent intracoronary stent implantation, 789 (36.2%) with HPA-3a/a, 1,023 (47.0%) with HPA-3a/b, and 366 (16.8%) with HPA-3b/b genotype. The incidence of stent thrombosis was 1.7% in HPA-3a/a, 1.7% in HPA-3a/b, and 1.6% in HPA-3b/b patients (p = 0.999). The incidence of stent restenosis was 37.3% in HPA-3a/a, 36.2% in HPA-3a/b, and 34.6% in HPA-3b/b patients (p = 0.724). Event-free survival 1 year after stent placement was 76.1% for HPA-3a/a, 76.5% for HPA-3a/b, and 76.4% for HPA-3b/b patients (p = 0.968). We conclude that the HPA-3 polymorphism of platelet GPIIb is not associated with an increase in the risk of thrombosis and restenosis over 1 year after coronary stent placement. These data indicate that unlike the HPA-1 polymorphism of GPIIIa, the HPA-3 polymorphism of GPIIb may not serve as a useful genetic marker for the risk assessment of patients treated with intracoronary stenting.

Coagulation abnormalities and cardiovascular disease

In patients with excessive venous thrombosis, genetic defects predisposing to thrombosis can be found in 60-80%. Increased plasma levels of coagulation proteins such as fibrinogen and plasminogen activator inhibitor-1 (PAI-1) are associated with an increased risk of myocardial infarction. However, despite the presence of polymorphisms that regulate plasma levels of factor VIII, PAI-1, and fibrinogen the association between common polymorphisms of these coagulation protein and ischemic cardiac disease remains ambiguous. Up to 10% of the population have defects that predispose them to excessive venous thrombosis. In spite of the essential role of thrombosis in coronary ischemic syndrome, no convincing evidence has implicated the two most common venous hypercoagulable states in ischemic heart disease. Pathogenic polymorphisms in the platelet fibrinogen and collagen receptors remains an area of intense research interest. Finally, it has been shown that lipoproteins can act as mediators of coagulation processes.