Elsevier

The Lancet

Volume 353, Issue 9154, 27 February 1999, Pages 708-712
The Lancet

Articles
A1/A2 polymorphism of glycoprotein IIIa and association with excess procedural risk for coronary catheter interventions: a case-controlled study

https://doi.org/10.1016/S0140-6736(98)07257-2Get rights and content

Summary

Background

A five-fold increase in risk of stent thrombosis in carriers of A1/A2 (Leu33Pro) polymorphism of glycoprotein IIIa has been described. Whether this increased procedural risk applies to other coronary interventions is unknown. We investigated the role of A1/A2 polymorphism as a putative risk factor.

Methods

We genotyped 1000 consecutive patients with angiographically confirmed coronary-artery disease and 1000 controls matched for age and sex. 653 of the 1000 patients received interventions (271 coronary angioplasty, 102 directional coronary atherectomy, and 280 stenting) and were assessed for a 30-day composite endpoint of need for target-vessel revascularisation, myocardial infarction, and death.

Findings

The composite endpoint occurred in 41 (6·3%) patients. There was no evidence that the A2 allele was associated with excess procedural risk (relative risk 1·36 [95% CI 0·70–2·70], p=0·37). Nor, in subgroup analyses, did A2 predict events that complicated coronary angioplasty (1·17 [0·40–2·70]), directional coronary atherectomy (1·50 [0·30–8·70]), or stenting (1·45 [0·60–3·50]). Neither heterozygotes (A1/A2) nor homozygotes (A2/A2) were over-represented in any subgroup, including those with acute coronary syndromes, early disease manifestation (age <40 years), and histories of myocardial infarction.

Interpretation

A1/A2 polymorphism is not a major risk factor for 30-day adverse events that complicate coronary angioplasty, directional coronary atherectomy, or stenting. Furthermore, A1/A2 polymorphism has no apparent impact on more chronic processes such as atherogenesis of the coronary arteries.

Introduction

Glycoprotein IIIa is a 90 kDa integrin β3 subunit that is expressed on the cell surface of platelets. With the glycoprotein IIb it forms the glycoprotein IIb/IIIa complex, a Ca2+ -dependent, 1:1 heterodimer. Activation by agonists leads to conformational changes of glycoprotein IIb/IIIa, which enables adhesive proteins such as fibrinogen, von Willebrand factor, and vitronectin to bind at sites containing Arg-Gly-Asp sequences and mediate platelet aggregation.1, 2, 3 These properties suggest a pivotal role of glycoprotein IIb/IIIa in the formation of thrombi at the site of coronary-catheter interventions or of ruptured plaques in acute coronary syndromes. Three polymorphisms of glycoprotein IIb/IIIa have been identified. A1/A2 (Leu33Pro) is the most thoroughly investigated for its potential pathophysiological role in coronary artery disease.4 A five-fold increase in risk of stent thrombosis in carriers of this polymorphism has been reported.5 Whether the link between A1/A2 polymorphism and increased risk of adverse events applies to other coronary interventions, including coronary angioplasty and directional coronary atherectomy, has not been shown.

The role o of A1/A2 in the chronic multifactorial process of atherogenesis is also unclear. Some small studies have reported higher prevalence of A1/A2 polymorphism in subgroups of patients presenting with acute coronary syndromes or a history of myocardial infarction, but others have not confirmed these findings.6, 7, 8, 9 We investigated A1/A2 polymorphism as a risk factor for adverse events that complicate coronary interventions and corony-artery disease.

We used a matched case-control study design, with a multiple endpoint of seven genetic traits.

Between October, 1995, and January, 1997, we recruited 1000 consecutive white patients from the Berlin area who had been admitted for coronary angiography to the Charité University Medical Centre at the Humboldt University of Berlin. At the same time, we enrolled as controls a further 1000 patients who had no evidence of coronary-artery disease (history, physical examination, electrocardiography, and echocardiography) or any other cardiovascular disease, and who were matched for age and sex. All patients gave written consent and the study protocol was approved by the Charité Hospital ethics committee in 1994.

We defined coronary-artery disease as stenosis of 50% or more in a major coronary artery or in a major branch. We classified the severity by the number of affected arteries (one-vessel, two-vessel, or three-vessel disease). Experienced assessors, masked to patients' identity and outcome, reviewed the angiograms. They assessed vessel diameters by the caliper reading. We established a diagnosis of myocardial infarction by assessment of case notes against WHO criteria10 and by angiography.

Indications for coronary angioplasty were in accordance with American Heart Association/American College of Cardiology guidelines.11 Angioplasty was performed by standard techniques. Indications for directional coronary atherectomy followed commonly accepted criteria, with target lesions located in the proximal sections of the three major coronary branches. Predilation was used to facilitate passage of the catheter. Similar to the Balloon vs Optimal Atherectomy Trial protocol,12 postprocedural angioplasty at low inflation pressures (3040 mm Hg) was done to lessen residual stenosis to less than 20%. Elective indications for stent implantation were new lesions (lesion length <30 mm; vessel diameters ≥2·75 mm), restenosis, venous-bypass graft lesions, and residual stenosis after coronary angioplasty or directional coronary atherectomy of 30% or more. Bail-out procedures were done in type-D2→F dissections and for flow deterioration of at least one thrombolysis in myocardial infarction (TIMI) degree after angioplasty, atherectomy, and in cases of acute vessel occlusion (TIMI flow grades 0 and 1). Stents were inserted with use of high inflation pressures (>9120 mm Hg) and balloons were slightly oversized by visual estimate of the angiogram. We gave patients aspirin and 10 000 units of heparin before intervention and, as required, repeated doses of heparin 2500 units to maintain activated clotting times of more than 250 s. Stent patients also received 500 mg oral ticlopidine after the procedure and for 4 weeks. 100 mg aspirin was continued indefinitely in all patients. Sheaths were removed after 4–8 h.

We assessed adverse events by the 30-day composite clinical endpoint need for target-vessel revascularisation, myocardial infarction, and death. All patients with suspected ischaemia underwent immediate recatheterisation, which permitted diagnosis of vessel occlusion at the site of the target lesion.

Triglycerides, total cholesterol, and HDL cholesterol were determined by enzymatic methods and, LDL cholesterol, apoA1 and apoB by immunoturbidimetric assays (Tina-quant; Boehringer, Mannheim).

Leucocytes were collected from venous blood samples by sedimentation in a hypo-osmolar buffer. DNA was isolated by standard three-step phenol/chloroform proteinase K extraction, or automatically in a 341A DNA-extractor (Applied Biosystems, Weiterstadt, Germany). DNA was dissolved overnight at 55°C in 10 mmol/L Tris, 1 mmol/L edetic-acid buffer (pH 8·0), and stored at 4°C until further analysis. Primers were designed according to the sequence of Fitzgerald and colleagues.13 A 252 bp fragment out of exon 2 of the glycoprotein IIIa gene was amplified with 0·5 units AmpliTaq (Perkin Elmer, Weiterstadt, Germany), 0·2 mmol/L deoxynucleotides, 0·2μmol/L downstream primer GP-3 5′-CTCCTGACTTACAGGCCCTG, 0·2 μmol/L upstream primer GP-4 5′-CACCTGCTTCAGGTCTCTCC, and 1·5 mmol/L magnesium chloride in a final volume of 25 μL. The PCR conditions were 35 cycles for 1 min at 94°C, 30 s at 63°C, and 30 s at 72°C in a 9600 or 9700 thermocycler (Perkin Elmer, Foster City, USA). PCR efficiency was checked on a 2% agarose gel for 20 min at 120 V. We digested 12·5 μL of the amplified product overnight with 90 units MspI (New England Biolabs, Schwalbach, Germany) in a final volume of 25μL at 37°C. Fragments were separated on a 3·5% NuSieve (FMC, Rockland, ME, USA) 3:1 gel for 60 min at 80 V.

Values are expressed as median (25th and 75th percentiles). We compared continuous values with the Mann Whitney U test, and genotype frequencies by X2 test or Fisher's exact test. We applied ANCOVA to calculate the relation between genotypes and clinical variables. To identify determinants for the 30-day clinical adverse events, we used logistic-regression models that included established atherogenic risk factors, procedural risk factors that complicate coronary interventions, and A1/A2 polymorphism. We calculated the relative risk of the composite endpoint by odds ratios and 95% CIs. We used SPSS software (version 7·5) for all analyses. We set the odds ratio at 1·5, probability exposed (controls) 25%, control per case 1, α=0·05/7=0·007 (Bonferroni-adjusted), power 1, β=0·80. On this basis, the required sample size was 1000 per group. Based on the assumption of an A2 frequency of 26·5% and sample size of 1000, α=0·05.

Section snippets

Results

The two groups differed significantly for prevalence of diabetes, hypercholesterolaemia, hypertension, and smoking status (table 1). Genotypes were not available for 24 cases and 29 controls.

Coronary interventions were performed in 653 cases: 271 underwent coronary angioplasty, 102 directional coronary atherectomy, and 280 stenting (table 2). The 30-day composite endpoint of target-vessel revascularisation, myocardial infarction, and death was reached by 41 (6·3%) patients (table 3). Among

Discussion

We have shown that A1/A2 polymorphism of the glycoprotein IIIa gene is not a major risk factor for 30-day adverse events that complicate coronary interventions. Nor was there an association between the frequency of A1/A2 and A2/A2 and the risk for developing acute coronary syndromes. Carriers of homozygous mutations are at no higher risk than heterozygotes for coronary-artery disease. Finally, among controls not on lipid-lowering medication, mutation homozygosity was associated with higher HDL

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