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 Table of Contents  
ORIGINAL ARTICLE
Year : 2018  |  Volume : 6  |  Issue : 1  |  Page : 6-11

Correlation between carotid ultrasonography findings and SYNTAX score in South Asian patients with coronary artery disease: A single-center study


Department of Cardiology, King George's Medical University, Lucknow, Uttar Pradesh, India

Date of Web Publication27-Apr-2018

Correspondence Address:
Akshyaya Pradhan
Department of Cardiology, King George's Medical University, Lucknow - 226 003, Uttar Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/heartindia.heartindia_11_18

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  Abstract 


Objective: The objective of the study was to examine the correlation between the carotid ultrasound findings (i.e., carotid intima-media thickness [IMT] and plaque score) and complexity of coronary artery disease (angiographic SYNTAX score) in Indian patients with stable ischemic heart disease.
Materials and Methods: This was a hospital-based, prospective, consecutive comparative case series. The study population comprised 117 Indian patients with stable ischemic heart disease, who underwent carotid ultrasonography for the estimation of mean carotid IMT and plaque score and coronary angiography for the estimation of SYNTAX score. Groups comprising patients with low SYNTAX score (0–22; n = 88) and patients with intermediate (23–32) and high (≥33) SYNTAX score (n = 29) were compared for various demographic factors and carotid ultrasound findings.
Results: Patients with intermediate or high SYNTAX score had significantly higher prevalence of diabetes (51.7% vs. 15.9%), hypertension (89.7% vs. 30.7%), and hypercholesterolemia (100% vs. 31.8%) as compared to patients with low SYNTAX score (P < 0.001). Further, the mean IMT and plaque scores increased with increasing SYNTAX score. Patients with intermediate and high SYNTAX score had significantly higher mean IMT (1.1 ± 0.1 vs. 0.9 ± 0.1 mm) and plaques score (6.6 ± 1.2 vs. 1.9 ± 1.9 mm) as compared to patients with low SYNTAX score. Significant correlation between SYNTAX score and mean IMT (r = 0.73; P < 0.01) and plaque score (r = 0.68; P < 0.01) was observed.
Conclusions: Carotid ultrasound findings showed a significant correlation with the degree of complexity of coronary artery lesions.

Keywords: Carotid artery, coronary artery disease, intima-media thickness, plaque score, SYNTAX score


How to cite this article:
Vishwakarma P, Narain VS, Saran RK, Dwivedi SK, Sethi R, Chandra S, Pradhan A. Correlation between carotid ultrasonography findings and SYNTAX score in South Asian patients with coronary artery disease: A single-center study. Heart India 2018;6:6-11

How to cite this URL:
Vishwakarma P, Narain VS, Saran RK, Dwivedi SK, Sethi R, Chandra S, Pradhan A. Correlation between carotid ultrasonography findings and SYNTAX score in South Asian patients with coronary artery disease: A single-center study. Heart India [serial online] 2018 [cited 2018 Aug 20];6:6-11. Available from: http://www.heartindia.net/text.asp?2018/6/1/6/231339




  Introduction Top


Cardiovascular diseases are the most significant cause of morbidity and mortality in India. Coronary artery disease (CAD) remains the most alarming form cardiovascular disease, with a sharp increase in its prevalence in the Indian subcontinent. The prevalence of CAD in India is projected to be around 3%–4% in rural and 8%–10% in urban adults. Further, the incidence rate remains high with 47 million new CAD cases per year and mortality due to CAD in 2.3 million cases.[1],[2] CAD is a multifactorial disease resulting from the interaction of multiple risk factors with varying effect over a prolonged asymptomatic period. Hence, it is important to study the disease, i.e., atherosclerosis, rather than the risk factors. Although risk assessment and noninvasive testing are recommended before coronary angiography, the effectiveness of electrocardiogram, echocardiogram, exercise or pharmacologic stress tests, radionuclide scans, computed tomography scans, or other heart scans remains insufficient.[3],[4],[5] It has been reported that diagnostic yield of elective cardiac catheterization was 40%.[6] In this regard, several surrogate endpoint markers of disease course and disease response to intervention have emerged in recent years. Carotid ultrasound findings are significant surrogate markers.

Numerous studies have shown association between increase in the carotid intima-media thickness (IMT) and the incidental risk of CAD.[7],[8],[9],[10],[11] On the other hand, one study has reported that the existence of carotid plaque is more strongly associated with CAD risk than the IMT.[12] For the quantification of such plaques, the plaque score has been used, and several studies have also shown that the plaque score is associated with the presence of CAD.[13],[14],[15] Conversely, the complexity of CAD was not assessed in these reports. Previously, the SYNTAX trial demonstrated that the angiographic SYNTAX score, which represents lesion complexity, correlated with the prognosis among patients who underwent coronary revascularization.[16] However, there have only been a few previous studies that have assessed the association between the complexity of CAD and the carotid ultrasound findings. With this background, we aimed to examine the correlation between the carotid ultrasound findings (i.e. carotid IMT and plaque score) and angiographic SYNTAX score in Indian patients with stable ischemic heart disease.


  Materials and Methods Top


Study design and patient population

The study was a hospital-based, prospective, consecutive comparative case series on Indian patients, conducted at a tertiary care center over a period of 1 year. Patients admitted with a diagnosis of stable ischemic heart disease and who underwent coronary angiography and carotid ultrasonography studies were considered for enrolment. Patients were excluded if they aged <18 years, had acute coronary syndrome (within 6 months), had normal coronaries after coronary angiography, or did not give consent for the study.

Data collection

All enrolled patients underwent complete clinical examination along with 12-lead electrocardiogram, two-dimensional echocardiography, and routine biochemical evaluations for lipid profile, hemoglobin, urea, creatinine, and blood glucose levels. Subsequently, all patients underwent carotid ultrasonography for the evaluation of IMT and plaque score. During the same period, they underwent coronary angiography for SYNTAX score analysis.

Intima-media thickness

Color Doppler and pulse Doppler ultrasonography for both carotid arteries were performed in B-mode with an ultrasound scanner (Aloka ProSound Alpha 7, Hitachi Aloka-Medical America, Inc.) equipped with UST-5412 high-resolution linear array transducer. Patients were examined in the supine position with the head tilted backward. Probe was aligned to obtain and record a longitudinal image of the anterior and posterior walls. The high-resolution images of the far wall of the bilateral common carotid arteries (CCAs), internal carotid arteries, and carotid bulbs were obtained according to the recommendations of the American Society of Echocardiography Carotid IMT Task Force.[17] The IMT was defined as the distance between the leading edge of the lumen-intima echo and the leading edge of the media-adventitia echo. At least three measurements were taken over distal 1 cm length of the far wall of each CCA segment, and these measurements on both sides were averaged to obtain the mean IMT. In cases where plaque was present in the segment used for measuring the mean IMT, the plaque thickness was averaged into the mean IMT measurement.

Plaque score

Plaque was considered as focal IMT ≥1.1 mm. The plaque score was calculated by adding the maximal thickness of all plaques in millimeters on both sides. The length of plaques was not a factor in determining the plaque score.

SYNTAX score

All enrolled patients underwent diagnostic coronary angiography. Those with normal coronaries and nonsignificant lesions (<50% diameter stenosis) were excluded from the study. Based on the baseline diagnostic angiogram, each coronary lesion producing ≥50% diameter stenosis in vessels ≥1.5 mm was scored separately, and these scores were added together to provide the overall SYNTAX score, which was calculated using SYNTAX Score Calculator version 2.11 based on the SYNTAX score algorithm.[18] For the purpose of grading the SYNTAX score, they were classified as low (0–22), intermediate (23–32), and high (≥33).

Statistical analysis

Continuous data were summarized as mean ± standard deviation, while categorical variables were summarized as frequencies and percentages. Groups were compared by analysis of variance (ANOVA) using general linear models, and the analyses for between and within the groups were done by Tukey's honestly significance difference post hoc test. Groups were also compared by independent Student's t-test. Categorical groups were compared by Chi-square test. Correlations between variables were analyzed by the Spearman's correlation coefficient by rank. A two-sided (α = 2) P < 0.05 was considered statistically significant. All the data were analyzed using Statistical Package for the Social Sciences (IBM SPSS; Chicago, IL, USA) program, version 20.


  Results Top


Baseline characteristics

During the study period, 138 patients satisfied the inclusion criteria. Of them, 21 patients had normal coronary angiogram and were excluded. The remaining 117 patients constituted study sample. The baseline characteristics of these patients are described in [Table 1]. In brief, the mean of age of study sample was 57.7 ± 9.9 years; 82 (70.8%) were male. Among risk factors, 24.8% were diabetic, 45.3% had hypertension, and 41.9% were current smokers. Mean total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, and triglyceride levels were 207 ± 40, 159 ± 42, 38.2 ± 6.2, and 138 ± 46 mg/dL, respectively. Mean IMT and plaque score were 0.9 ± 0.2 and 3.0 ± 2.7 mm, respectively. The low (0–22), intermediate (23–32), and high (≥33) SYNTAX score were noted in 88 (75.2%), 17 (14.5%), and 12 (10.3%) patients, respectively.
Table 1: Patient characteristics

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Group comparison

For the purpose of comparison, the sample was grouped as those having low SYNTAX score (Study Group 1; n = 88, 75.2%) and those having intermediate or high SYNTAX score (Study Group 2; n = 29, 24.8%). The demographic characteristics and their distribution in the two study groups are shown in [Table 2]. There was no significant difference in mean age or gender distribution of the two study groups. However, patients with higher SYNTAX score had significantly higher number of diabetics (16 vs. 51%; P < 0.001) and hypertensive patients (30 vs. 89.6%; P < 0.001). Further, patients with higher SYNTAX score had significantly higher prevalence of raised total cholesterol and LDL cholesterol and reduced HDL cholesterol, higher mean blood glucose levels, and lower mean estimated glomerular filtration rate (eGFR) as compared to that in patients with lower SYNTAX score (P ≤ 0.005 for each). Duration of angina symptoms and left ventricular ejection fraction also differed significantly in the two study groups. Further, patients with higher SYNTAX score had higher mean IMT (0.9 ± 0.1 vs. 1.1 ± 0.1 mm; P < 0.001) and higher mean plaque score (1.9 ± 1.9 vs. 6.6 ± 1.2; P < 0.001) as compared to those with low SYNTAX score.
Table 2: Comparison of baseline characteristics between groups

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Correlation between intima-media thickness and SYNTAX score

The mean IMT increased with increasing SYNTAX score. It was 0.9 ± 0.2 mm in low SYNTAX score category while 1.1 ± 0.9 and 1.2 ± 0.1 mm in intermediate and high SYNTAX score category, respectively [Figure 1]a. The observed difference in various SYNTAX score categories was significant between groups (f = 49.28 and P < 0.001; ANOVA). Intergroup analysis of mean IMT also showed significant difference when compared within individual SYNTAX score categories using Tukey's test. In addition, the Pearson's correlation coefficient analysis showed a positive correlation between mean IMT and SYNTAX score (r = 0.73; P < 0.01) [Figure 2]a.
Figure 1: Between Groups: P<0.001 (ANOVA); Low vs. Intermediate groups: P<0.001 (post-hoc Tuckey's test); Low vs. High groups: P<0.001 (post-hoc Tuckey's test); Intermediate vs. High groups: P=0.025 (post-hoc Tuckey's test)

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Figure 2: Correlation between SYNTAX score and (a) mean intima-media thickness; (b) mean plaque score

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Correlation between plaque score and SYNTAX score categories

The mean plaque score also increased gradually with increasing syntax score [Figure 1]b. It was least in low SYNTAX category (1.9 ± 1.9 mm) and was maximum in high SYNTAX score category (7.1 ± 1.5 mm). The observed difference in various SYNTAX score categories was significant between groups (f = 78.66 and P < 0.001; ANOVA). Intergroup analysis of mean plaque score also showed significant difference in low versus intermediate SYNTAX score patients and also in low versus high SYNTAX score patients (P < 0.001 for each pair). However, the difference observed in intermediate versus high SYNTAX score groups was not significant. In addition, the Pearson's correlation coefficient analysis showed a positive correlation between mean plaque score and SYNTAX score (r = 0.68; P < 0.01) [Figure 2]b.

Logistic regression analysis

Logistic regression analysis showed that only IMT and plaque score were identified to be significantly contributing to complex CAD (intermediate or high SYNATX score) (P < 0.01 for each) [Table 3].
Table 3: Logistic regression analysis of Complex CAD (intermediate or High SYNTAX score)

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  Discussion Top


Atherosclerosis is a global vascular phenomenon, and the presence of atherosclerosis in one vascular bed mandates an active search for its manifestation elsewhere. In the present study, we aimed to correlate carotid ultrasonography findings with the degree of complexity of coronary artery lesions.

The present study was designed as a prospective, consecutive, comparative case series study. It involved 117 patients of stable ischemic heart disease who underwent carotid ultrasonography for the estimation of mean carotid IMT and plaque score followed by coronary angiography for the estimation of SYNTAX score. Patients with low SYNTAX score (0–22) comprised Study Group 1 (n = 88) and patients with intermediate (23–32) and high (≥33) SYNTAX score comprised Study Group 2 (n = 29). These two groups were compared for various demographic factors and carotid ultrasound findings.

Among demographic characteristics, patients with higher SYNTAX score had higher proportion of diabetics and hypertensive patients. These patients also had significantly higher prevalence of elevated total cholesterol and LDL cholesterol and reduced HDL cholesterol. These findings correlate with the established fact that cardiovascular risk factors play an important role in the pathogenesis as well as progression of atherosclerosis, leading to increased complexity of coronary lesions. Moreover, we observed that the study group with higher SYNTAX score had significantly lower mean eGFR and lower left ventricular ejection fraction as compared to study group with higher SYNTAX score. Patients with higher SYNTAX score also displayed significantly longer history of angina as compared to patients with low SYNTAX score.

The principal finding of our study is that carotid ultrasound findings correlate with the complexity of CAD. The mean IMT increased with increasing syntax score; it was 0.866 ± 0.145 mm in low SYNTAX score category, while 1.082 ± 0.088 and 1.213 ± 0.055 mm in intermediate and high SYNTAX score category, respectively. Further, the group-wise comparison revealed that patients with higher SYNTAX score displayed higher value of mean IMT as compared to those with low SYNTAX score. When compared among different pairs of SYNTAX score categories, the mean IMT differed significantly for each pair.

In our study, the mean plaque score also increased gradually with increasing SYNTAX score; it was least in low SYNTAX category (1.875 ± 1.922 mm) while being maximum in high SYNTAX score category (7.08 ± 1.51 mm). The group-wise comparison also revealed that plaque score of patients with higher SYNTAX score was significantly higher. When compared among different pairs of SYNTAX score categories, plaque score differed significantly in low versus intermediate SYNTAX score patients and also in low versus high SYNTAX score patients. However, the difference observed in intermediate versus high SYNTAX score category was not significant.

Our study also showed a significant positive correlation between SYNTAX score and mean carotid IMT (r = 0.73) and mean plaque score (r = 0.68). In addition, a logistic regression analysis was performed in our study to identify the contributory factors to complex CAD as manifested by high or intermediate SYNTAX score. We found that only mean IMT and plaque scores were significantly contributing to the higher SYNTAX score.

A previous report showed that the SYNTAX score independently predicted major adverse cardiovascular and cerebrovascular event outcomes in CAD patients who underwent stent implantations.[19] Therefore, the SYNTAX score is a useful tool to risk stratify the prognosis in patients with extensive CAD undergoing percutaneous coronary intervention. Several studies have established that carotid ultrasound findings can predict life time risk of cardiovascular events.[20],[21],[22] We believe that noninvasive testing provides information on lesion complexity that is important for decision-making by cardiologists. Therefore, investigation of the correlation between the carotid ultrasound findings and the SYNTAX score is meaningful. Carotid ultrasonography is a cheap, noninvasive, easy to use, and universally available test. On the contrary, invasive coronary angiography, though gold standard for CAD, is invasive, costly, time-consuming, and nonuniversal. For a resource-poor and middle-income country like ours with a massive population burden, the positive correlation of a simple test, i.e., carotid ultrasonography with invasive coronary angiography, must bring a cheer for the public health administrators. The findings of the study can have potential and far-reaching implications for screening and management of atherosclerotic cardiovascular disease in population as a whole.

Our study has few limitations. Patients enrolled in our study were suspected to have ischemic heart disease. These patients may have relatively higher risk than the healthy population. Therefore, it is not clear whether our results will aid in screening the general asymptomatic population. In addition, the finding that age is not an independent predictor may have been affected by this selection bias. It should also be noted that the sample size was small and enrolled patients showed relatively low SYNTAX scores. Keeping these in view, it may not be possible to generalize the findings observed in this study to the general population these without caveats.


  Conclusions Top


In patients with stable ischemic heart disease, carotid ultrasound findings correlate with the degree of complexity of CAD. The mean IMT and plaque score increases with increasing SYNTAX score. Patients with intermediate and high SYNTAX score have higher mean IMT and plaque score as compared to patients with low SYNTAX score. It can be inferred that carotid ultrasonography can reliably predict complexity of underlying CAD and thus can help prognosticate the CAD patients.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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