Infectious agents, protein electrophoresis and immunoglobulin levels in patients with coronary artery ectasia

Abstract

Background

Although the mechanism of coronary artery ectasia (CAE) shares the common pathophysiologic steps resembling those of atherosclerosis, there are certain discrepancies or aspects incompatible with atherosclerosis. Therefore, we hypothesize that the pathophysiology of CAE might differ from that of atherosclerosis in terms of inflammatory parameters, infectious agents and the read out of protein electrophoresis.

Materials and methods

Seventy patients with coronary artery disease (CAD) and 30 patients with both CAD and CAE comprised the study populations. Blood samples were centrifuged for the measurement of IgG antibodies against C.pneumoniae and H.Pylori, alongside with total IgE, IgG levels and protein electrophoresis.

Results

There were not statistically significant differences between patients with and without CAE regarding the complete blood counting and routine biochemical laboratory parameters except hemoglobin levels. Among other studied laboratory parameters, IgE, Alpha 2 macroglobulin, Beta-1 globulin levels were found to be higher in patients with CAE + CAD than those of CAD alone. Logistic regression analysis by including the variables IgE, Hb, Alpha 2 macroglobulin, beta-1 globulin, and gender, revealed that Ig E (Odd ratio:1.004 85 % CI: 1.000–1.008, p = 0.01) and alpha 2 macroglobulin (Odds ratio: 9.41, 95 %CI: 1.69–52.28, p = 0.028) were independently and positively associated with the presence of CAE.

Conclusion

Independent association of serum IgE levels and alpha2 globulins with the presence of CAE underlines the divergent features of pathophysiology of CAE compared with atherosclerosis or CAD alone. Comparable activity of humoral immunity measured by IgG antibody against C.Pneumoniae, and H. Pylori has suggested that these infectious agents do not play an additional role in the pathogenesis of CAE.

1. Introduction

Pathophysiology of coronary artery ectasia (CAE) has gained an increasing interest in the last decades. Although the mechanism of CAE shares the common pathophysiologic steps resembling those of atherosclerosis, there are certain discrepancies or aspects incompatible with atherosclerosis.1, 2, 3, 4, 5, 6, 7 Common shared cardiovascular risk factors and histopathologic similarities have led to the assumption that CAE is a variant of atherosclerosis in the past years. However, this assumption has been neither proved nor disproved yet. Rather than elucidating the mechanism of atherosclerosis and CAE or dilating vascular disease per se, we aimed to figure out the possible discrepancies, in terms of pathophysiological steps of CAE and atherosclerosis. Accordingly, we hypothesized that pathophysiology of CAE might differ from that of atherosclerosis in terms of inflammatory parameters, infectious agents and the read out of protein electrophoresis. Therefore, we assessed and compared the levels of IgG antibody against Chlamydia pneumonia, and Helicobacter pylori, components of serum protein electrophoresis and plasma levels of total Ig G and Ig E.

2. Materials and methods

Study populations were recruited from those who underwent elective diagnostic coronary angiography. Patients with acute coronary syndromes, heart failure, moderate to severe valvular heart disease, hepatic failure, renal failure, malignancies, hematologic diseases, known autoimmune diseases including systemic lupus erythematosus, rheumatoid arthritis, hyper IgE syndrome and recent infection within past three months were excluded. Seventy patients with coronary artery disease (CAD) and 30 patients with both CAD and CAE comprised the study populations. All patients underwent transthoracic echocardiography examination before coronary angiography. Coronary angiography was performed either by the Judkins method through femoral artery access or right radial artery access. Patients with <50 % stenosis in coronary arteries were defined as non-CAD patients were not included in the statistical analysis. CAD was diagnosed according to the presence of more than 50 % stenosis in at least one main epicardial coronary artery.

Coronary artery ectasia (CAE) is defined as the abnormal dilatation of the epicardial coronary artery exceeding 1.5 times the normal adjacent coronary artery segments.⁸ Isolated local post-stenotic dilatation of coronary arteries was not considered as coronary artery ectasia. Patients with isolated coronary artery aneurysms, namely saccular (transverse diameter exceeding its longitudinal diameter) or fusiform (longitudinal diameter exceeding its transverse diameter) coronary aneurysm were not included in the study. Presence of CAE was confirmed by at least two orthogonal angiographic views by two blinded cardiologists. Routine hematologic and biochemical analysis were performed before scheduling the coronary angiography. Blood samples were taken into tubes from the antecubital veins of patients who were enrolled in the study after performing coronary angiography. Blood samples were allowed to clot at room temperature then centrifuged at 1500 rpm for 5 min then serum kept at deep freeze (−20 C $°$) to be used for the measurement of IgG antibodies against C.pneumoniae and H.Pylori, total IgE, IgG levels and protein electrophoresis.

Serum protein electrophoresis was performed by using the Helena automated capillary protein electrophoresis system (Helena Bioscience Europe). Human serum IgE and IgG levels were measured by using immunoturbidimetry method (Roche Diagnostics). The IgG antibodies against C.Pneumoniae and H.Pylori were measured by enzyme linked immunoassay (ELIA) kits (Immunolab).

The following clinical and demographic parameters were recorded: age, hypertension (known hypertension treated with antihypertensive drugs, two or more blood pressure recordings greater than 140/90 mmHg), diabetes mellitus (known diabetes treated with diet or drugs or both; or a fasting serum glucose of more than 126 mg/dl), and hypercholesterolemia (known, treated hypercholesterolemia or fasting or non-fasting total serum cholesterol concentrations higher than 200 mg/dl). Current cigarette smoking was defined as active smoking within the past 12 months. The study was conducted in accordance with the Declaration of Helsinki. The study protocol has been reviewed and approved by the local ethics committee ((2017-KAEK-120)/2019–14) and all patients have given informed consent. The abstract of the paper has been presented as a poster in the Congress of European Society of Cardiology in 2021 in London⁹.

3. Statistical analysis

Continuous variables were presented as mean ± standard deviation, and categorical variables were presented as percentage. Continuous variables were compared by Un-paired t and categorical variables were compared by using Chi-square and Fishers’ exact t test where appropriate. To assess the possible association of CAE with gender, IgE, Alpha 2 macroglobulin, Beta-1 globulin and hemoglobin levels which were found to have a p value less than 0.10, were included in the logistic regression analysis. A p value less than 0.05 was considered to be statistically significant. Statistical analyses were performed by using SPSS 15.0 Statistical Package Program for Windows (SPSS Inc, Chicago, Illinois, USA).

4. Results

The baseline clinical and laboratory parameters are presented in Table 1. There were not statistically significant differences between patients with and without CAE regarding the complete blood counting and routine biochemical laboratory parameters except hemoglobin levels which was found to be significantly higher in patients with concomitant CAE and CAD than those with CAD only (13.42 ± 1.83 gr/dL vs 14.3 ± 1.65 gr/dL respectively p = 0.03). The distribution of single vessel, two vessel and three vessel diseases regarding the obstructive CAD were comparable between two groups (Table 1). Moreover, Gensini score of patients with CAD alone did not differ from those with concomitant CAD + CAE (33 ± 32 vs 27 ± 28 respectively p = 0.24). Serum protein electrophoresis revealed that Alpha-2 macro globulins (0.84 ± 0.35 vs 0.70 ± 0.26 p = 0.026, Fig. 1) and beta-1 globulins (1.25 ± 2.35 vs 0.63 ± 15 p = 0.025) were significantly higher in patients with CAE than those without CAE (Table 2). The other protein electrophoresis measures, namely alpha1 globulin, beta-1 globulin, and gamma globulin were comparable between two groups. Neither the seropositivity rate, nor the specific IgG antibodies againts C.pneumoniae and H.Pylori were statistically different between two groups (Table 3). In contrast to total Ig G (1208 ± 513 vs 1157 ± 344 p = 0.55 respectively), IgE leves (312 ± 618 vs 91 ± 105, p = 0.03 respectively, Fig. 2) were found to be significantly higher in patients with concomitant CAE and CAD compared to those with CAD alone. In terms of atherosclerotic burden, there was no statistically significant correlation between the Gensini score, and IgG antibody against H. Pylori (r = 0.048, p = 0.66) and C. Pneumoniae (r = −0.12 p = 0.27) regarding the whole study population. On the other hand, logistic regression analysis with the variables IgE, Hb, Apha 2 macroglobulin, beta-1 globulin, and gender, revealed that Ig E (Odd ratio:1.004 85 % CI: 1.000–1.008, p = 0.01) and alpha 2 macroglobulin (Odds ratio: 9.41, 95 %CI: 1.69–52.28, p = 0.028) were independently and positively associated with the presence of CAE (Table 4).

Table 1.

Clinical characteristics of patients.

	CAD (n = 74)	CAD + CAE (n = 30)	P value
Age (years)	62 ± 11	62 ± 11	0.95
Gender (male)	54 %	70 %	0.07
Diabetes Mellitus	25 %	34 %	0.29
Hypertension	28 %	31 %	0.66
Smoking	28 %	25 %	0.74
White Blood Cell (/mm3)	8.7 ± 2.0	8.9 ± 2.5	0.65
Hemoglobin (g/dL)	13.42 ± 1.83	14.3 ± 1.65	0.03
Platelet Count (x103/mm3	254 ± 73	251 ± 70	0.82
C-reactive protein (mg/dL)	2.53 ± 3.91	2.74 ± 3.58	0.24
Glucose	144 ± 66	123 ± 44	0.158
LDL-Cholesterol (mg/dL)	139 ± 45	136 ± 41	0.77
Triglyceride (mg/dL)	198 ± 127	230 ± 164	0.33
Creatinin (mg/dL)	0.96 ± 0.31	0.89 ± 0.20	0.32
Aspartate Aminotransferase (AST)	18 ± 8	21 ± 10	0.15
Gensini score	35 ± 33	27 ± 28	0.24
Single vessel disease	14 (19 %)	6 (20 %)	0.94
Two vessel disease	37 (50 %)	14(47 %)	0.92
Three vessel disease	23 (31 %)	10(33 %)	0.97
Distribution of CAE
LAD		20 (67 %)
LCx		16 (53 %)
RCA		25 (83 %)
Number of ectatic vessels
Single vessel		6 (20 %)
Two vessel		17 (57 %)
Three vessel		7 (23 %)

Fig. 1.

Boxplot view of Apha-2 globulin levels in patients with combined CAE and CAD and in patients with CAD alone.

CAD: coronary artery disease, CAE: coronary artery ectasia.

Table 2.

Serum proteins and IgE, IgG levels in patients with CAE.

	CAD	CAD + CAE	P value
Albumin (g/dL)	4.07 ± 0.63	4.14 ± 0.94	0.69
Alpha-1 globulin (g/dL)	0.31 ± 0.08	0.29 ± 0.9	0.34
Alpha-2 globulin (g/dL)	0.70 ± 0.26	0.84 ± 0.35	0.026
Beta-1 globulin (g/dL)	0.63 ± 0.15	1.25 ± 2.35	0.025
Beta-2 globulin (g/dL)	0.17 ± 0.08	0.16 ± 0.05	0.58
Gamma globulins (g/dL)	1.10 ± 0.73	1.05 ± 0.48	0.71
IgE (IU/dL)	91 ± 105	312 ± 618	0.03
IgG(IU/dL)	1157 ± 344	1208 ± 513	0.55
Total protein concentration (g/dL)	6.95 ± 1.11	7.12 ± 1.49	0.44

Table 3.

Comparison of serpositivity and IgG antibody levels in patients with concomittant CAD + CAE and in those with CAD alone.

	Patients with CAD + CAE	Patients with CAD	P value
C. Pneumonia	47 %	52 %	0.77
	2.56 ± 2.19	2.05 ± 1.32	0.14
H. Pylori	37 %	57 %	0.25
	3.68 ± 3.12	3.79 ± 2.96	0.87

Fig. 2.

Boxplot view of IgE levels in patients with combined CAE and CAD and in patients with CAD alone.

CAD: coronary artery disease, CAE: coronary artery ectasia.

Table 4.

Logistic regression analysis for associates of coronary artery ectasia.

Variables	Odds ratio	95 % confidence interval	P value
Hemoglobin	1.18	0.82–1.69	0.37
Gender (Male)	1.39	0.43–4.48	0.57
Apha-2 globulin	9.41	1.69–52.28	0.028
Beta-1 globulin	0.055	0.001–4.10	0.18
IgE	1.004	1.000–1.008	0.010

5. Discussion

The association of atherosclerosis and infectious agents such as C.pneumoniae and H.Pylori has been a research interest for decades and has remained a challenging issue with its positive and negative evidences.10, 11, 12, 13, 14 In contrast to the situation in atherosclerosis, infectious etiology has not been assessed systematically in the pathophysiology of CAE. There is little evidence about the contribution of infectious agents on ectasia formation. Adiloglu et al¹⁵ have found that patients with CAE have higher levels of antibodies against C. pneumonia infection compared to controls. They did not find such a relationship in terms of H. pylori infection.¹⁵ They also have comparable IgG seropositivity against C.pneumoniae. However, atherosclerotic coexistence in CAE has not been clearly defined.

In our current study we have not demonstrated any significant correlations between the IgG levels against C.Pneumoniae, H.Pylori and atherosclerotic burden measured by Gensini score. Moreover, we have not found any significant differences between the patients with CAE + CAD and patients with CAD alone, regarding both IgG antibody levels and rate of seropositivity against C.pneumoniae and H. Pylori. Although our study design did not aim to evaluate the pathophysiological association between infectious agents and atherosclerosis, our findings support the idea that presence of CAE has no influence on the IgG antibody levels against C.Pneumoniae and H.pylori. In other words, IgG antibodies against C. Pneumoniae and H. Pylori do not have any distinctive role in the pathogenesis of atherosclerosis and CAE. Moreover, although we had a limited number of patients, lack of correlation between the antibody levels and atherosclerotic burden measured by Gensini score is against the infectious pathophysiology of atherosclerosis.

Higher levels of immunoglobulin E in patients with cardiovascular diseases and their association with ischemic heart disease have been well documented and reviewed in literature.16, 17, 18, 19 Unfortunately, the presence of CAE has never been mentioned in the studies evaluating the association of IGE and atherosclerosis. Even though our data does not directly allow us to address the underlying mechanisms of IgE in CAE, it supports the fact that an IgE mediated mechanism is more rigorously involved in the pathogenesis of CAE than in those with atherosclerosis. IgE has known to be the key element mediating allergic reactions in which it activates mast cells. By activating other immune cells such as monocytes and macrophages, IgE is involved in the pathogenesis of atherosclerosis or vascular wall pathology by allergy related mechanisms.17, 18, 19 Mast cell derived proteases, mainly chymase and tryptase have been supposed to play an important role in destabilization of atherosclerotic plaque and formation of arterial aneurysm.²⁰ It has been recently shown that IgE contributes to formation of aortic aneurysm by acting on not only mast cells but also on CD4⁺ T cells and macrophages.^21,22 Likewise, Freeman et al has reported increased frequency of coronary artery aneurysm up to 37 %, in patients with hyper immunoglobulin E syndrome at young ages.²³ An indirect evidence for the association of IgE with aneurysmal vascular disease has been revealed in patients with asthma and abdominal aortic aneurysm. An allergy related pathophysiology has been supported by the documentation of increased risk of abdominal aortic aneurysm in patients with allergic asthma, which is characterized by high levels of IgE.^24,25 Moreover, deficiency of IgE has shown a protective role against the formation of abdominal aortic aneurysm.²⁶

Accordingly, independent positive association of IgE with the presence of CAE suggests that there exists an IgE and mast cell mediated mechanism involved in the pathogenesis of CAE or aneurysm. This mechanism might be different than that of atherosclerosis and may show variations from those in atherosclerosis. Understanding the precise role of IgE or allergic mechanisms on the pathophysiology of CAE might promote further proposals not only for the development of disease but also for the medical treatment of CAE or aneurysmal diseases. Given the mortality and morbidity burden of CAE even in the absence of severe CAD, IgE mediated or antiallergic treatment approaches may reveal potential benefits in clinical practice. Unfortunately, it should be declared as a limitation of our study that we were not able to get detailed and definite allergic history of patients neither from the individual self-report nor from the data base records which would improve our argument and highlight the association between IgE mediated mechanism and coronary artery ectasia.

The major protein of serum measured by protein electrophoresis is albumin, and followed by other components labeled alpha1, alpha2, beta1, beta2 and gamma globulin. Albumin, the largest peak, lies closest to the positive electrode. The next five components (globulins) are labeled alpha1, alpha2, beta1, beta2, and gamma. The alpha1-protein fraction is comprised of alpha1-antitrypsin, thyroid-binding globulin, and transcortin. Ceruloplasmin, alpha2-macroglobulin, and haptoglobin contribute to the alpha2-protein band. Both the alpha1 and alpha2 components are increased as an acute-phase reactant. Beta-1 zone comprises proteins like transferrin, and beta2 contains beta-lipoprotein and C3, C4 complements. Components of serum proteins measured by protein electrophoresis are usually diagnostics of hepatic diseases, nephrotic syndrome, immunologic, oncologic, hematologic diseases, and monoclonal gammopathies.^27,28 Beyond their disease specific changes in plasma, they are also increased as acute phase reactants. In this regard independent association of alpha globulins with CAE can be assumed to be a reflection of increased inflammatory state in patients with CAD + CAE compared to those with CAD alone. However, this association needs to be evaluated further to assess precise role of subcomponents of alpha globulins, namely ceruloplasmin, alpha2 macroglobulin, and haptoglobin. Ceruloplasmin mainly functions as a copper carrier and exhibits ferroxidase activity, haptoglobin as a carrier of free hemoglobin and alpha2 macroglobin as protease inhibitor and carrier of zinc in a less extent.²⁸ Given the extracellular matrix remodeling activity in CAE, alpha2 macroglobulin might deserve particular attention due to its modulating role on protease activity. Although we have found higher levels of alpha2 globulin and beta1 globulin in patients with CAE + CAD compared with CAD alone, only the alpha2 globulin has shown independent association with CAE. It is noteworthy that we have found comparable levels of hsCRP in patients with CAE coexisted with CAD and CAD alone. Although literature evidences are in favor of higher hs CRP levels in patients with CAE, several studies have reported comparable levels of hs CRP in patients with CAE, CAD and normal coronary arteries.^2,29, 30, 31

In conclusion, we have shown for the first time that serum IgE levels and alpha2 globulin have shown an independent association with the presence of CAE in patients with CAD. Beyond this association it underlines the divergent features of pathophysiology of the CAE compared with atherosclerosis or CAD alone. Comparable activity of humoral immunity measured by IgG antibody against C.Pneumoniae, and H. Pylori has suggested that these infectious agents do not play an additional role in the pathogenesis of CAE.

Key messages.

• ●The mechanism of coronary artery ectasia shares the common pathophysiologic steps resembling to those of atherosclerosis
• ●There are certain discrepancies or aspects in the pathophysiology of coronary artery ectasia, incompatible with atherosclerosis
• ●IgE mediated mechanisms are likely to be involved more rigorously in the pathogenesis of coronary artery ectasia than in those with atherosclerosis
• ●Independent association of alpha globulins with coronary artery ectasia can be a reflection of increased inflammatory state.

Authorship

Each author gave substantial contribution in acquisition analysis and data interpretation. Each author had a part in preparing article for drafting and revising it critically for important intellectual content. Each author gave final approval of the version to be published.

Authors contributions

Conception and design: Gulay Yetkin, Ertan Yetkin, Didem Tascioglu; Acquisition, analysis and interpretation of data: Ertan Yetkin, Gulay Yetkin, Bilal Cuglan; Selcuk Ozturk, Drafting the article: Ertan Yetkin; Revising it critically for important intellectual content: Ertan Yetkin, Kenan Yalta.

Funding

This study has been supported by Society of Vascular and Molecular Cardiology.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.