C-Reactive Protein and Immunoglobulin-E Response to Coronary Artery Stenting in Patients with Stable Angina

Clinical Studies

Okan ERDOGAN,1 MD, Armagan ALTUN,1 MD, Cetin GUL,1 MD and Gultac OZBAY,1 MD

SUMMARY Recent reports indicate that inflammatory mechanisms play a crucial role in the pathogenesis of atherosclerosis and neointimal proliferation as well as coronary restenosis. To provide baseline data for further studies regarding stenting, restenosis and inflammatory response, we prospectively conducted a clinical study to investigate the time related response of plasma levels of immunoglobulin-E (IgE) and C-reactive protein (CRP) which are two different inflammatory markers mediated by different cytokines in stable patients who underwent elective coronary artery stenting. Thirteen consecutive stable patients who underwent coronary artery stenting were included in the study. Levels of IgE and CRP were determined pre- and poststent implantation on four consecutive days and at the end of the first as well as third month. Levels of these two markers were gradually elevated on postprocedure days while reaching peak values on the second and third days for IgE (initial 278 ± 335 IU/mL vs peak 350 ± 489 IU/mL, P = 0.01) and CRP (initial 0.5 ± 0 mg/dL vs peak 2.7 ± 3 mg/dL, P = 0.002), respectively. High levels gradually returned to baseline values determined at the end of the first and even third months after stent implantation implying an acute inflammatory reaction. Stent implantation seems not to cause any persistent and ongoing inflammatory response in the long term. (Jpn Heart J 2003; 44: 593-600)

Key words: C-reactive protein, Immunoglobulin E, Inflammation, Atherosclerosis, Stent

CORONARY artery stenting is one of the most effective means for the preven- tion of restenosis in atherosclerotic coronary artery segments.1,2) Recent reports indicate that inflammatory mechanisms play a crucial role in the pathogenesis of atherosclerosis and neointimal proliferation as well as coronary restenosis.3,4) C- reactive protein (CRP), an acute phase reactant, increases several fold within 24 to 48 hours after an inflammatory stimulus.5) Additionally, mast cells have also been implicated in the pathogenesis of coronary heart disease.6) Their number in the adventitia of coronary arteries increases with the progression of atherosclerosis. Higher mast cell counts are seen in coronary arteries containing both fresh

From the 1 Department of Cardiology, School of Medicine, Trakya University, Edirne, Turkey. Address for correspondence: Okan Erdogan, MD, Arseven Sitesi Villa Konutlari NO:2, D-100 Karayolu, Edirne, 22030, Turkey. Received for publication November 11, 2002. Revised and accepted January 9, 2003. 593 Jpn Heart J 594 ERDOGAN, ET AL September 2003 and organizing thrombi and lower counts are observed in association with fully organized thrombi.7) The best known immunologic stimulus leading to degranulation of human mast cells is their activation when the immunoglobulin E (IgE) molecules on their surfaces bind a relevant antigen.8) If mast cells are actively involved in atherosclerotic plaques, they must be activated by stent implantation which will cause stretching and overdilation of the diseased vessel wall. This reaction should be associated with an increased response of IgE which plays a predominant role in activation and degranulation of mast cells. Plasma levels of CRP after coronary artery stenting could also be a marker of the intensity of the inflammatory reaction. In light of the above-mentioned assumptions and to provide baseline data for further studies regarding stenting, restenosis, and the inflammatory response, we prospectively conducted a clinical study to investigate the time-related response of plasma levels of IgE and CRP, which are two different inflammatory markers mediated by different cytokines, in stable patients who underwent elective coronary artery stenting.

METHODS Study population: Our study group consisted of 13 consecutive patients with chronic stable angina pectoris (Canadian Cardiovascular Society, Class II-III) who fulfilled the inclusion criteria and underwent successful coronary artery stenting procedures in elective conditions. All patients had at least 1-vessel coronary artery disease involvement defined as a 70% reduction of the luminal dia- meter in major epicardial arteries. Patients with acute coronary syndromes (myocardial infarction and unstable angina within 2 months), significant valvular heart disease, myocarditis, cardiomyopathies, hepatic and renal disease, acute infec- tion, collagenosis, malignancy, anti-inflammatory drug usage, any history of hay fever; asthma, allergic rhinitis or eczema; allergy to grasses, house dust, cats or dogs; asthma, allergic rhinitis or eczema in parents and positive skin allergy test results were excluded from the study. Biochemical tests and study design: Plasma CRP (mg/dL) and IgE (IU/mL) levels were determined before and after stent implantation on days 1, 2, 3, and 4 and at the end of the first and third month. Preprocedure CRP levels of all patients were normal (≤ 0.5 mg/dL). Plasma samples were immediately analyzed for CRP concentration that was determined with a nephelometric system (Behring Nephelometer 100 Analyser, Marburg, Germany). The normal upper reference value for CRP with this method is up to 0.5 mg/dL. Due to technical difficulty in quantitatively analyzing CRP concentrations less than 0.5 mg/dL, values less than this cutoff level were taken as 0.5 mg/dL in further calculations and compar- isons. Screening for allergy was conducted using an Immulite Allergy Food Panel FP5E (Diagnostic Products Corporation, Los Angeles, CA, USA) which is a Vo l 4 4 No 5 INFLAMMATION AND CORONARY ARTERY STENTING 595 chemiluminescent enzyme-labeled immunoassay designed for clinical use with the Immulite automated immunoassay analyzer for the qualitative detection of IgE antibody specific serum to a panel of food allergens: F1 (egg white), F2 (milk), F3 (codfish), F4 (wheat), F13 (peanut), and F14 (soybean). Patient serum was then analyzed with an Immulite AlaTop Allergy Screen (Diagnostic Products Corporation) for the detection of IgE antibodies specific to inhalant allergens in serum. Both tests were intended for in vitro diagnostic use as an aid in the differ- ential diagnosis of IgE-mediated allergic disorders and atopic allergy. Both tests were sufficiently sensitive and specific (99.1% and 95.7%, respectively) to be able to qualitatively differentiate IgE-mediated allergic status.9) Only patients with negative test results were included in the study. IgE determination was performed using an Immulite total IgE system (Diagnostic Products Corporation) which is a solid phase, two-site chemiluminescent immunometric assay. For cre- atine kinase MB (CK-MB) venous blood samples were obtained immediately before and one day after the procedure. Plasma samples for CK-MB were analyzed with commercially available immunochemical tests. Angioplasty and stent procedures were performed using conventional techniques. Only one stent was implanted in each patient. Medtronic AVE and Bestent 9-18 mm (n = 5), Cordis Crown and LP 12-18 mm (n = 4), and Jomed Jostent 12-19 mm (n = 4) stents were used. All stents were overdilated at high pressures. The type of angiographic lesion was determined according to ACC/AHA criteria.10) Procedural success was defined as residual stenosis < 30% in the worse of two orthogonal views, as assessed by quantitative analysis and normal runoff of the contrast medium in the stented vessel, and absence of death, myocardial infarction, and the need for further revascularization procedures during the hospital stay. Statistical analysis: Data are presented as the mean ± SD. Two-way Friedman repeated-measures analysis of variance was used for comparison of repeated variables in one particular group and the Wilcoxon signed-ranks test was used for post hoc analysis of differences between two continuous variables in the same group. Statistica for Windows (version 4.3) was used for statistical tests and analysis. A P < 0.05 was considered statistically significant.

RESULTS The clinical characteristics of all study patients who underwent coronary artery stenting are presented in Table I. All patients underwent successful stent implantation without any demonstrable complications. The patients were closely followed through a three-month period for ensuing symptoms and coronary events. Only two patients complained of recurrent angina during the follow-up period. One with a left anterior descending coronary artery stent underwent coro- Jpn Heart J 596 ERDOGAN, ET AL September 2003 nary artery bypass surgery, and the other with a right coronary artery stent was medically treated for in-stent restenosis. As shown in Table II, the mean prepro-

Table I. Clinical and Angiographic Characterisics of the Study Patientsa

Patients (n)13

Men (%) 92 Age (years) 58 ± 8 Risk factors Diabetes (%) 0 Hypertension (%) 62 Smoking (%) 54 Hypercholesterolemia (%) 54 Family History (%) 15 History of old MI (%) 43 Total C (mg/dL) 221 ± 53 LDL-C (mg/dL) 136 ± 44 HDL-C (mg/dL) 45 ± 10 Triglyceride (mg/dL) 183 ± 115 Ejection fraction (%) 64 ± 12 Coronary angiography One-vessel disease (%) 69 Two-vessel disease (%) 23 Three-vessel disease (%) 8 Stented vessel LAD (%) 54 RCA (%) 38 CX (%) 8 Lesion type Type A (%) 69 Type B (%) 31

a Values are presented as mean ± SD.; MI = myocardial infarction; C = cholesterol; LAD = left anterior descending artery; RCA = right coronary artery; CX = left cir- cumflex artery.

Table II. Demonstration and Comparison of Pre-and Postprocedure CRP and IgE Mean Plasma Concentrationsa

CRP (mg/dL) P value IgE (IU/mL) P value

Preprocedure 0.5 ± 0 278 ± 335 Postprocedure Day 1 1.4 ± 0.9 0.003 303 ± 368 0.01 Day 2 2.6 ± 1.9 0.002 350 ± 489 0.01 Day 3 2.7 ± 3 0.002 348 ± 422 0.009 Day 4 1.6 ± 1.8 0.01 321 ± 363 0.02 One month 0.7 ± 0.5 NS 251 ± 303 0.03 Three months 0.5 ± 0 NS 256 ± 322 0.002

a Data are presented as mean ± SD.; NS = not significant; P values between pre- and postprocedure CRP and IgE mean levels Vo l 4 4 No 5 INFLAMMATION AND CORONARY ARTERY STENTING 597 cedure CRP and IgE plasma levels increased markedly after the procedure and reached a peak value on day 3 for CRP and day 2 for IgE. Plasma concentrations of both CRP and IgE gradually returned to preprocedural levels during the first month and remained stable even at the third month after the procedure.

DISCUSSION Our study has unequivocally demonstrated that coronary artery stenting caused an intense inflammatory response, as was shown by increased plasma levels of CRP and IgE which are secreted by different cytokine pathways and cells, after stent implantation compared to baseline levels. Inflammation may have an important pathophysiologic role in a variety of coronary conditions. Activated macrophages secrete interleukin-1 and 6 which are powerful stimuli for production of CRP by the hepatocytes.11) CRP has also been shown to be an independent risk factor in atherosclerotic disease. It seems to reflect an inflammatory reaction of the arterial wall and might therefore indicate an ongoing inflammation-mediated atherosclerotic process.12-14) Previous studies showed that mast cells occur in the shoulder region of stable atherosclerotic plaques as well as at sites of plaque rupture.15,16) Mast cells have to be stimulated to secrete their neutral proteases. The immunologic stimulus leading to degranulation of human mast cells is their activation when the IgE molecules on their surfaces bind a relevant antigen.8) Activated T lymphocytes or macrophages which were found to be accompanied by mast cells at the sites of plaque erosion or rupture also seem to play a role in the pathway leading to degranulation of mast cells at the site of plaque rupture.17-19) Cytokines, like interleukin-4 and 13 that provide the first signal to B cells to switch to the production of the IgE isotype, are secreted by Th-2 cells that are also present in atherosclerotic plaques and play a major role in cytokine production and the inflammatory process.20) Secreted IgE molecules bind to mast cells and stimulate them to release histamine, leuko- trienes, and cytokines which further play major roles in perpetuating the inflammatory response and contraction of vascular smooth muscle cells.20,21) We sug- gested that if mast cells contribute to the pathophysiological process of atherosclerotic plaques, stretching and tearing of the plaque as well as the involved vessel segment by stenting will be responsible for mast cell activation and kindling of an intense inflammatory reaction. A simple way to detect a mast cell-mediated reaction is possible by demonstrating an increased level of IgE which is the signal turning the mast cells on. In accordance with this suggestion, our study clearly showed that the level of IgE markedly increased after stent implantation and gradually returned to baseline levels in a month. All study sub- jects involved in the study were thoroughly scrutinized subjectively and objec- Jpn Heart J 598 ERDOGAN, ET AL September 2003 tively for any allergic disorder that might falsely elevate the blood level of IgE though stool examinations for parasites could not be performed. There was no suspicion of any external factor that might be responsible for the elevated level of IgE other than an acute inflammatory reaction caused by stent implantation. In addition, our study group consisted of patients with stable angina and normal baseline CRP levels. The increase in CRP after stent implantation observed in our study is likely to be caused by the inflammatory stimulus of the coronary intervention itself. However, the intensity and persistence of the inflammatory response might be variable and unpredictable due to the different degree of stent- induced arterial damage and individual susceptibility. This intense inflammatory reaction persists throughout the four days after stent implantation and gradually declines over time. This means that the inflammatory response related to stent implantation seems to be an acute reaction rather than a chronic stimulus against a metallic object, namely the stent. Two previous studies investigating the role of CRP in coronary artery stenting demonstrated a similar response curve like we observed in our study.22,23) However, both studies investigated CRP levels for only five days after stent implantation and long term data about the CRP response are lacking regarding the persistence of inflammation against stenting. If high CRP or IgE levels persist for days or months, it might be related with ongoing intense inflammation as a reaction to the stent and possible neointimal muscle cell proliferation, in other words in-stent restenosis. We investigated two different markers for inflammation which are secreted by different cytokines and cells in order to better clarify the reaction against stent implantation. The peak value of IgE occurred a day earlier than CRP and gradually subsided along with CRP over several days. The importance of our study is that it showed for the first time the long term behavior of the CRP response to stenting; second, the role of mast cell activation supported by evidence of high IgE levels after stent implantation; third, the increase in CRP and IgE levels during the short term period and normalization thereafter in the long term reflects that the stent itself is not responsible for an ongoing inflammatory process; fourth, acute short term increases in these markers may or may not be indicators for neointimal cell proliferation and restenosis that should be elucidated by further studies; fifth, anti-inflammatory drugs, anti- histaminics, or mast cell stabilizators suppressing this acute short term inflammatory reaction to stent implantation might have some beneficial effect in decreas- ing the restenosis rate. A limitation of our study may be the small number of patients, although this limitation seems not to be a major factor affecting the results and end points of the study. The other limitation is that we could not use the high sensitive CRP method in our study. This method may provide more pre- cise determination of CRP. Vo l 4 4 No 5 INFLAMMATION AND CORONARY ARTERY STENTING 599

Conclusions: The present study has revealed that coronary artery stenting is responsible for acute increases in CRP and IgE levels during the first several days and gradual decreases during the first month and even at the third month after stent implantation implying an acute inflammatory reaction. Our study provides not only baseline data for further larger prospective studies about the relationship between stent restenosis and inflammatory response, but also sheds some light on the inflammation-mediated reaction to coronary artery stenting.

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