Author + information
- Received March 12, 2001
- Revision received June 14, 2001
- Accepted July 12, 2001
- Published online November 1, 2001.
- Erik Jørgensen, MD*,* (, )
- Henning Kelbæk, MD*,
- Steffen Helqvist, MD*,
- Gunnar V.H Jensen, MD*,
- Kari Saunamäki, MD*,
- Jens Kastrup, MD*,
- Ole Havndrup, MD*,
- Henning Bundgaard, MD*,
- Jan Kyst Madsen, MD*,
- Michael Christiansen, MD†,
- Paal S Andersen, PhD† and
- Johan H.C Reiber, PhD‡
- ↵*Reprint requests and correspondence:
Dr. Erik Jørgensen, 2014 Cardiac Catheterisation Laboratory, Department of Cardiology, Rigshospitalet, Blegdamsvej 9, DK-2100 Copenhagen Ø, Denmark
This study aimed to clarify the role of the angiotensin-converting enzyme (ACE) gene polymorphism in the development of in-stent restenosis.
In-stent restenosis occurs after treatment of coronary artery stenosis in 12% to 32% of coronary interventions with stents. Experimental and clinical studies have suggested that the deletion/insertion (D/I) polymorphism of the ACE gene plays a role in this.
Quantitative coronary angiography before, immediately after and six months after stent implantation were compared in 369 patients, in whom D/I typing of the ACE gene was performed.
At follow-up we found no differences between the three genotypes in minimal lumen diameter (homozygotes with two deletion alleles in the ACE gene [DD], 2.20 mm; heterozygotes with one deletion and one insertion allele in the ACE gene [DI], 2.19 mm; and homozygotes with two insertion alleles in the ACE gene [II], 2.25 mm). The corresponding diameter stenoses were: DD: 25%, DI: 27%, II: 27% (p = NS), and the frequency of restenosis (>50% diameter stenosis) was: DD: 15.7%, DI: 11.0% and II: 16.4% (p = NS). Logistic regression analysis identified diabetes (odds ratio [OR]: 3.0, 95% confidence interval [CI]: 1.0 to 8.7), lesion length (OR: 1.1, 95% CI: 1.01 to 1.30) and minimal lumen diameter immediately after the intervention (OR: 0.3, 95% CI: 0.14 to 0.85) as predictors of in-stent restenosis. In a post hoc analysis of patients treated versus those not treated with an ACE-inhibitor antagonist or an angiotensin receptor antagonist, we found an increased frequency of in-stent restenosis in the DD genotypes (40% vs. 12%, p = 0.006).
The D/I polymorphism is not an independent predictor of coronary in-stent restenosis in general, but it may be of clinical importance in patients treated with ACE inhibitors or angiotensin receptor antagonists.
Percutaneous coronary intervention with stent implantation has proved efficient to reduce complications and restenosis compared with balloon angioplasty alone. The major drawback of this technique is intimal hyperplasia developed by migration and proliferation of cells derived from the vessel media, a cell growth process that causes significant in-stent restenosis in 12% to 32% of cases (1–6). The angiotensin-converting enzyme (ACE) stimulates smooth muscle cell proliferation (7), and the plasma concentration of the ACE is partly controlled by a deletion/insertion (D/I) polymorphism in the ACE gene on chromosome 17 (8). Angiotensin-converting enzyme inhibitors have, accordingly, been evaluated as prophylactic treatment against restenosis in several studies, but no positive effect has been shown (9–12). Restenosis after balloon angioplasty depends predominantly on elastic vessel recoil as opposed to in-stent restenosis, which depends mainly on neointimal growth (13–15). Thus, the significance of the D/I polymorphism of the ACE gene might increase with the rate of stent implantation. This study was undertaken to evaluate the role of the ACE gene polymorphism for the development of restenosis after coronary stenting.
Four hundred seventy-three patients, of which 99% were Caucasian Danes with coronary artery disease, were included in the Danish Randomized Multicenter Trial of Coronary Restenosis After Treatment with the NIR and the Palmaz-Schatz Stent (DANSTENT) study from April 1997 through January 2000 (16). The patients had one or more coronary stents implanted in coronary lesions. Most patients were treated electively for stable angina. Of the 473 patients, 93% had a follow-up coronary angiography performed six months after stent implantation. Patients scheduled to follow up in our lab were entered into this study and had a blood sample taken for genotyping at the time of the follow-up angiography. Thus, all 369 patients in this study had a follow-up angiogram done. The end points of the study were clinical and angiographic signs of in-stent restenosis. The study protocol was approved by our scientific ethics committee and conformed to the Declaration of Helsinki.
Coronary artery lesions
Lesion complexity at baseline was characterized by standard angiographic morphology criteria (17). One lesion per patient was analyzed in this study, and only de novo lesions located in native coronary arteries were included. The length of the lesion should not exceed 28 mm (to be covered maximally by two stents). Ostial and heavily calcified lesions were excluded.
Coronary angiography was acquired according to quantitative coronary angiography (QCA) guidelines before and immediately after angioplasty and six months later. Patients were positioned with the index lesion in the isocenter of the X-ray system (C-arm, Integris System, Philips Medical Systems, Best, the Netherlands), with the image intensifier close to the chest of the patient. The lesion was visualized in two different projections when possible, with a minimum of foreshortening and a minimal overlap of side branches after intracoronary administration of 0.2-mg nitroglycerin. Identical projections were used before and after coronary intervention and at the six-month follow-up angiography. The angiograms were saved on compact or laser discs. The coronary angiograms were analyzed by QCA by an independent core laboratory (Heart Core B.V., Leiden, the Netherlands) (18,19). The core laboratory had no access to clinical or genotype data.
Determination of the ACE D/I genotype
DNA was extracted from blood, and the D/I polymorphism of the ACE gene was determined by polymerase chain reaction amplification of intron 16 of the ACE gene using primers. All tests apparently homozygous for the D-allele were controlled for misclassification as previously described (20,21). The analyzing laboratory (Department of Clinical Biochemistry, Statens Serum Institut, Copenhagen, Denmark) had no access to clinical or angiographic data.
Coronary stenting technique
Lesions were predilated with a 20-mm long balloon of a diameter close to the reference diameter of the vessel. A 15-mm Palmaz-Schatz (Johnson and Johnson Interventional Systems, Warren, New Jersey) or a 16-mm NIR stent (Medinol Ltd., Tel Aviv, Israel) was hand crimped onto the balloon and implanted with high pressure (>12 atms). When two stents were implanted, an overlap of approximately 2 mm was intended. If necessary, high-pressure postdilation was performed with a noncompliant balloon. Intracoronary ultrasound imaging was discouraged.
Study end points and clinical decision making
The primary end point of the study was coronary restenosis defined as a diameter stenosis >50% of the index lesion at follow-up angiography. In addition, we analyzed other lesion-specific parameters including minimal lumen diameter, diameter stenosis and late lumen loss defined as the difference between the minimal lumen diameter immediately after stent implantation and that at six-month follow-up. We recorded the rate of ischemia driven target lesion revascularization defined as reangioplasty of the study segment together with >50% diameter restenosis in combination with angina pectoris or a pathologic exercise test. In case of an angiography performed 0 to 4 months after stent implantation leading to revascularization of the target vessel, the angiogram was evaluated by the core lab. If no significant restenosis was observed, a repeat angiography was performed at six months. If a coronary angiography was performed more than four months after stent implantation, the six-month angiography was waived. The decision to perform target lesion revascularization was left to the discretion of the investigator at the time of reinvestigation.
Median values and 5th and 95th percentiles were used as descriptive statistics for continuous variables. Whenever index lesion measurements were available in two different projections, we used the average values. Statistical analysis was performed using the chi-square test (discrete variables) and Kruskal-Wallis test (continuous variables). Logistic regression models were used to study the risk of restenosis. We used SAS procedures for statistical analysis (Freq, Npar1way, Univariate and Logistic; SAS version 8.0; 1998, SAS Institute, Cary, North Carolina).
Patients in the DANSTENT study belonged to a low-risk cohort. In 473 patients, there were a total of three deaths at six-month follow-up. One patient died of lung cancer, and two suffered a cardiovascular death. The average age of the 369 patients (24% women) in this study was 59 years (range: 40 to 77 years). There were no differences in baseline characteristics between the total DANSTENT cohort and the patients in this study, and the restenosis rates were 12.6% and 13.8%, respectively, with no difference between patients with or without genotyping (p = 0.1). The frequency of the D-allele of the ACE genotype was 0.55, and the frequencies of the DD, DI and II genotypes were 29%, 53% and 18%, respectively. The ACE genotype distribution was, thus, in Hardy-Weinberg equilibrium and comparable to those of previous reports (20,21). The clinical, angiographic and procedural baseline characteristics were comparable among the three groups (Table 1).
The frequency of ischemia-driven revascularization of the study lesion at follow-up after stent implantation did not differ between the three groups (homozygotes with two deletion alleles in the ACE gene [DD]: 15%, heterozygotes with one deletion and one insertion allele in the ACE gene [DI]: 10%, homozygotes with two insertion alleles in the ACE gene [II]: 13%, p = NS). Quantitative coronary angiography at follow-up revealed a 13% restenosis rate for the whole cohort with no differences in reference diameter, minimal lumen diameter, diameter stenosis or frequency of restenosis between the three groups, and there were no differences in late loss, net gain or loss index (Table 2). The cumulative distribution curves of the minimal lumen diameter before and after stent implantation and at follow-up were rather similar between the three groups of patients (Fig. 1). A logistic regression analysis showed no influence of ACE genotype and treatment with ACE inhibitors or angiotensin receptor antagonists on in-stent restenosis, and no interaction was found between ACE genotype and treatment with ACE inhibitors or angiotensin receptor antagonists. The only significant predictors of in-stent restenosis were a history of diabetes, lesion length before stent implantation and minimal lumen diameter immediately after stent implantation (Table 3).
The patients receiving ACE inhibitors or angiotensin receptor antagonists had more hypertension, diabetes, three-vessel disease, reduced left ventricular ejection fraction and long lesions than those who did not receive these drugs. This subset of patients treated with an ACE inhibitor/angiotensin receptor antagonist also had a tendency towards more in-stent restenosis, increased late loss, percentage of stenosis and target lesion revascularization at six-months follow-up. Patients on ACE inhibitor/angiotensin receptor antagonist treatment with the DD genotype of the ACE gene had a significantly higher in-stent restenosis rate than those without this treatment (Table 4).
ACE gene testing and clinical relevance
Restenosis after percutaneous coronary interventions has represented a large clinical problem since the introduction of balloon angioplasty, and it remains the major drawback of this technique even after the introduction of stent implantation (2–6). Drugs with anti-inflammatory and antiproliferative effects, drug-eluting stents and brachytherapy are currently the most promising new techniques to prevent in-stent restenosis (22–25). However, toxicity, drug interaction, long-term efficacy and costs have to be assessed to evaluate the potentials for routine therapy of these modalities. Thus, a test that could identify patients with increased risk of developing in-stent restenosis would be helpful. To our knowledge, this study is the first to address the ACE gene polymorphism and coronary in-stent restenosis issue using QCA analysis performed by an independent core laboratory. The results of our study, in which the rate of coronary in-stent restenosis was relatively low, showed that the D/I polymorphism of the ACE gene had no clinical relevance as a predictor of in-stent restenosis.
ACE gene polymorphism and in-stent restenosis
Amant et al. (26)studied the D/I polymorphism of the ACE gene in 171 patients who underwent percutaneous transluminal revascularization with stent implantation for suboptimal balloon results in most cases. In the 146 patients (85%) who had a six-month follow-up angiography, a significantly greater late lumen loss was demonstrated in patients with the D-allele, whereas the diameter stenosis and restenosis rate only tended to be higher in this group of patients. Ribichini et al. (27)examined 176 patients of whom 20% had angiographic restenosis six months after stent implantation. In addition to a higher late lumen loss, patients with the D-allele of the ACE genotype had a higher frequency of in-stent restenosis. In that study, in which no patients were on ACE inhibitor treatment, an association between the ACE plasma concentration levels and the rate of in-stent restenosis was suggested.
In 1,850 unselected patients undergoing percutaneous transluminal coronary angioplasty (PTCA) and stent implantation for a variety of indications, Koch et al. (28)found no association between the D/I polymorphism of the ACE gene and in-stent restenosis. The frequency of in-stent restenosis in the latter study was rather high (33%), as was the percentage of the patients treated with ACE inhibitors (DD: 54.3%, DI: 52.3%, II: 49.1%). In addition, there were significant differences in several baseline parameters between the ACE genotype groups. In the DD genotype group, there was a higher frequency of elderly, female and diabetic patients and more patients with unstable angina and multivessel disease. Although not directly comparable because of differences in patient characteristics and methodology, the results of our study confirm those of Koch et al. (28).
The conflicting findings in studies evaluating the influence of the D/I polymorphism on the development of coronary in-stent restenosis might be caused by ethnic differences in the expression of the D/I polymorphism and interactions with other genes or lifestyle factors, as has been suggested for myocardial infarction and restenosis after balloon angioplasty (20,29).
ACE inhibitor treatment and restenosis
Although animal studies have suggested a role of ACE inhibitors, large, randomized trials of ACE inhibitor treatment after coronary artery balloon angioplasty have found no effect on the development of restenosis (9–11). However, the formation of restenosis after balloon angioplasty is a complex process involving both recoil of the vessel and cell migration/proliferation, whereas in-stent restenosis is almost solely a result of neointimal growth (13–15). Angiotensin-converting enzyme inhibitors and angiotensin receptor antagonists, which are drugs widely used in patients with ischemic heart disease, were taken by 15% of patients in our study (Table 4). A post hoc analysis was performed to evaluate the potential of these drugs in reducing in-stent restenosis. Unexpectedly, a strong tendency towards higher in-stent diameter stenosis, late loss and frequency of restenosis was found in drug-treated patients. This may be explained by a higher frequency of risk factors such as diabetes, hypertension and longer coronary artery lesions in these patients (Table 3). Thus, a possible preventive effect of ACE inhibitors and angiotensin receptor antagonists on development of in-stent restenosis did not outweigh the impact of these risk factors, and, accordingly, an accelerating effect on in-stent restenosis of these drugs cannot be ruled out (Table 4).
DD genotype, ACE inhibitors and restenosis
In our subanalysis of patients on ACE inhibitors or angiotensin receptor antagonists, an increased rate of in-stent restenosis was confined to the DD genotype group suggesting a protective role of the I-allele. However, this kind of post hoc analysis should be evaluated with extreme caution, and further studies are needed to evaluate this issue. On the other hand, a randomized study by Okamura et al. (30)demonstrated that DD genotype patients treated with imidapril (an ACE inhibitor) compared with control subjects had a higher restenosis rate after balloon angioplasty. In addition, a recent randomized, double-blind, placebo-controlled study by Meurice et al. (31)of 91 DD genotype patients treated with the ACE inhibitor quinapril reported an increase in late lumen loss in the quinapril-treated patients.
Predictors of restenosis
Regression analysis of our data also showed that a history of diabetes, the lesion length before stent implantation and the minimal lumen diameter immediately after stent implantation are significant, and clinically relevant, independent predictors of in-stent restenosis (32–36). In the regression analysis, we found no independent impact of the DD genotype (Table 3). This finding does not exclude a small independent effect of the ACE gene polymorphism, but this is of no apparent clinical relevance.
Study limitations and implications
Given the limited size of our study, the findings that patients in the DD genotype group treated with ACE inhibitors or angiotensin 2 receptor antagonists have an increased rate of in-stent restenosis should not lead to an immediate change in established indications and clinically well motivated prescribing of these drugs after PTCA. However, taken together with the results of other studies, our findings underscore the need for a large trial to answer these questions definitively.
The ACE D/I genotype was not an independent predictor of in-stent restenosis, and, in general, there is no reason to test for this polymorphism when planning percutaneous coronary interventions with stent implantation. In patients treated with ACE inhibitors or angiotensin receptor antagonists, the rate of in-stent restenosis was increased, particularly in those with a DD genotype. This finding requires further study.
We thank chief research assistant Ms. Lene Kløvgaard for her enthusiastic and invaluable participation and managing director Mr. Anton van Weert, PhD, and his staff at Heart Core B. V. for their assistance in performing the quantitative coronary angiography analyses.
☆ The DANSTENT study was supported by grants from Boston Scientific Nordic AB and from Johnson & Johnson AB (Division Cordis, Sweden).
- angiotensin-converting enzyme
- Danish Randomized Multicenter Trial of Coronary Restenosis After Treatment with the NIR and the Palmaz-Schatz Stent
- homozygotes with two deletion alleles in the ACE gene
- heterozygotes with one deletion and one insertion allele in the ACE gene
- homozygotes with two insertion alleles in the ACE gene
- percutaneous transluminal coronary angioplasty
- quantitative coronary angiography
- Received March 12, 2001.
- Revision received June 14, 2001.
- Accepted July 12, 2001.
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