|Ahead of print publication
Study of Ankle–Brachial index among the patients of metabolic syndrome
Anusha Jawahar, Vishwanath Krishnamurthy, Ashwin Kulkarni, T Anil Kumar
Department of General Medicine, M.S. Ramaiah Medical College, Bengaluru, Karnataka, India
|Date of Submission||08-Oct-2021|
|Date of Decision||09-Dec-2021|
|Date of Acceptance||30-Dec-2021|
Department of Medicine, Ramaiah Medical College, Bangalore, Karnataka
Source of Support: None, Conflict of Interest: None
Background: Metabolic syndrome (MetS) refers to a group of conditions that are associated with increased cardiovascular risk. Ankle–brachial index (ABI) is a noninvasive, inexpensive way of assessing the blood flow in the lower limbs and may be useful as an indirect marker of subclinical atherosclerosis. Aim and Objective: To study and compare ABI values between patients with MetS and patients without MetS. Materials and Methods: A total of 98 patients attending the outpatient department between October 2018 and September 2020 were included in the study. They were categorized as MetS and non-MetS as per the National Cholesterol Education Program Adult Treatment Panel III guidelines. They were tested for ABI with a handheld Doppler. The ABI values were compared between the two groups. Results: Among 98 patients, 49 were cases and 49 as controls. ABI values were found to be 1.09 ± 0.12 among the cases and 1.22 ± 0.05 among the controls and were found to be statistically significant (P < 0.001). Conclusion: The patients with MetS had lower ABI compared with the patients who did not have MetS. ABI can be used as an indirect marker of atherosclerosis and can be used in routine clinical assessment for identifying patients at a higher cardiovascular risk.
Keywords: Ankle–brachial index, metabolic syndrome, peripheral artery disease
|How to cite this URL:|
Jawahar A, Krishnamurthy V, Kulkarni A, Kumar T A. Study of Ankle–Brachial index among the patients of metabolic syndrome. Med J DY Patil Vidyapeeth [Epub ahead of print] [cited 2022 Dec 7]. Available from: https://www.mjdrdypv.org/preprintarticle.asp?id=339951
| Introduction|| |
Metabolic syndrome (MetS), also known as “Syndrome X” refers to a group of conditions that includes abdominal obesity, elevated blood pressure, hyperglycemia, and dyslipidemia that is associated with an increased cardiovascular risk. Patients having MetS are at increased of developing complications such as acute myocardial infarction and cerebrovascular accidents. Early diagnosis and prompt intervention in the form of dietary and lifestyle changes along with pharmacological intervention were deemed necessary could help in preventing the abovesaid complications. MetS is a state of chronic inflammation and is characterized by increased inflammatory markers such as C-reactive protein, interleukin-6, and fibrinogen.
The main determinants of MetS were urbanization, geographical region to which participants belonged, and socioeconomical and cultural factors. Patients having MetS are at a higher risk of developing peripheral arterial disease (PAD)., A study done in Mumbai in 2010 by Sawant et al., with 548 participants demonstrated that 19.52% of the participants had MetS with the prevalence among men being double that of women.
Atherosclerotic disease of the lower limbs may reflect a similar process in the coronary and cerebral vasculature, which can cause myocardial infarction and stroke, respectively. The ankle–brachial index (ABI) is a noninvasive test and is cost-effective to detect any obstruction to the arterial blood flow in the lower limbs. It has a sensitivity of 95% and specificity of 99% in detecting peripheral vascular disease. ABI is also being used as a part of diabetic foot examination as advised by the American Diabetes Association. The cutoff for abnormal ABI is 0.9; however, it has been noted that subnormal ABI values ranging between 0.9 and 1.1 are also associated with symptoms of claudication.
This study was undertaken to compare the ABI values between patients with MetS and without MetS.
| Materials and Methods|| |
This is a hospital-based cross-sectional study conducted from October 2018 to September 2020. The study was conducted after approval from the institutional ethics committee (EC/PG-24/2018). The patients attending the medicine outpatient department who satisfied the inclusion and exclusion criteria during the study were included in the study. Simple random sampling method was used as the sampling technique. Informed consent was taken from all the patients. All patients were clinically evaluated and if found to satisfy the clinical parameters of MetS, that is the waist circumference and blood pressure, underwent biochemical screening and were considered cases (MetS). The National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) guidelines were used to identify patients with MetS.
The measurement of waist circumference: at a point midway between the costal margins and iliac crest. Blood pressure was measured on both arms in the sitting position after 5 min of rest. The systemic examination was done. According to the NCEP ATP III definition, MetS is diagnosed if three or more of the following five parameters are present: waist circumference over 40 inches (men) or 35 inches (women), blood pressure more than 130/85 mmHg, fasting triglyceride (TG) level more than 150 mg/dl, fasting high-density lipoprotein cholesterol level <40 mg/dl (men) or 50 mg/dl (women), and fasting blood sugar over 100 mg/dl. Only that at least three of five criteria are met.
Palpation of all the peripheral pulses was done. ABI was done in accordance with American heart association (AHA) guidelines by a radiologist with the use of a handheld Doppler. The diagnosis of PAD was done as per the AHA guidelines 2016, where ABI of <0.9 is considered PAD. ABI values between 0.9 and 1.10 are categorized as subnormal ABI values and above 1.4 are considered noncompressible arteries. The classification of ABI as per the AHA/American College of Cardiology 2016 guidelines. ABI >1.4 was considered noncompressible arteries, more than 1.1 was normal, 0.9–1.1 was borderline, and less than 0.9 was abnormal. Fasting lipid profile and fasting blood sugar were done.
Those patients who did not fulfill the clinical parameters of MetS were considered controls. Patients with ABI values higher than 1.4, smokers and patients with chronic kidney disease were excluded from the study.
Sample size estimation
Heubel et al. study (2018) has observed that the ABI among the control group was 1.10 ± 0.09 and among the MetS group was found to be 1.02 ± 0.15 which was found to be statistically significant. In the present study, expecting a similar result with 80% power, 95% confidence level, and 0.58 effect size, the study requires a minimum of 49 participants in each group. Data were entered into Microsoft Excel datasheet and the analysis was carried out using SPSS 22 (PASW Statistics for Windows, Chicago). Categorical data were represented in the form of frequencies and proportions. The Chi-square test or Fisher's exact test (for 2 × 2 tables only) was used as test of significance for qualitative data. Continuous data were represented as mean and standard deviation. Independent t-test was used as test of significance to identify the mean difference between two quantitative variables. Correlations were performed with Pearson correlation coefficient. P < 0.05 was considered statistically significant after assuming all the rules of statistical tests. Statistical software SPSS version 22 (IBM SPSS Statistics, Somers NY, USA) was used to analyze data.
| Results|| |
A total of 98 patients were included in the study. Forty-nine patients were diagnosed with MetS (cases) as per the NCEP ATP III guidelines and 49 patients did not have MetS (controls). The mean age among cases was 53.5(±11.17) years and among controls was 53.63 (±10.42) years (P = 0.832). Among the cases, 33 (67.3%) of patients were males and 16 (32.7%) were females. Among the patients with MetS, 37 (42.9%) were diabetics and 23 (20.4%) were hypertensives. Among the patients without MetS, 4 (3%) were diabetics and 3 (2%) were hypertensives. Among the patient with MetS, the mean waist circumference was 104.71 (±9.62) and the mean waist circumference without MetS was 82.23(±4.55) (P < 0.001). Among the patients with MetS, mean fasting blood sugar was 192.80 mg/dl (±63.41), and among controls was 107.39 mg/dl ± 16.90 (P < 0.001). Among the cases, the mean TG was 209.5 mg/dl (±88.05) and among controls, it was 115.5 mg/dl (±21.96) (P < 0.001). The comparison between the various parameters of MetS between the cases and controls is summarized in [Table 1]. ABI among cases was 1.095 (±0.125) and among controls was 1.221 ± 0.0.05(P < 0.001) [Table 2]. ABI had a negative correlation with TG levels with an r-value of −0.296 which was statistically significant (P = 0.039). ABI also had a negative correlation with the waist circumference which was statistically significant (r = −0.312, P = 0.029) [Table 3].
|Table 1: Baseline characteristics and comorbidities among cases and controls|
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| Discussion|| |
MetS is rapidly growing as an epidemic in India. As an ethnic group, Indians are predisposed to develop abdominal obesity which is an independent predictor of cardiovascular diseases. ABI can indicate the condition of the vasculature and indirectly reflect the process of atherogenesis.
In the above study, it was observed that among the patients of MetS, mean ABI was subnormal as compared to the controls. The mean ABI obtained in the present study falls under the category of borderline ABI as termed by the AHA. As per these guidelines, patients with borderline resting ABI need to undergo treadmill exercise ABI to evaluate for PAD. The subnormal ABI values are associated with impairment in functional state and well-being such as decline in walking speed. This was similar to the results seen in the study by Heubel et al. where the mean ABI in the patients with MetS was 1.02 ± 0.15 and among the controls, it was 1.10 ± 0.09.
A study by Mostaza JM et al. found that patients with a lower ABI had a 3-fold greater rate of carotid stenosis and 1.6-fold increased rate of silent myocardial infarction as compared to the general population. In the Rotterdam coronary calcification study, it was observed that patients who had borderline or subnormal ABI values had a greater degree of subclinical coronary atherosclerosis as compared to the participants with normal ABI >1.20. The get ABI study group was another study conducted where individuals over the age of 60 years were screened using the ABI and it was noted that participants who had borderline ABI values were at a 25% increased risk of developing coronary syndromes than participants whose ABI was greater than 1.1., The Edinburgh Artery study done revealed that patients with a low ABI had higher carotid intimal thickness, thus indicating that ABI acts as an indirect marker for subclinical atherosclerosis.
It was observed in the study that ABI had a negative correlation with TG levels and with the waist circumference, which was statistically significant. This is in concordance with the study conducted by Vidula H and et al., where there was a strong correlation between waist circumference and TG levels and incidence of PAD. These associations remained statistically significant even after adjusting for inflammatory biomarkers. Rest all other correlations were not found to be statistically significant.
The findings of our study were concordant with the study conducted by Suárez C et al. which stated that the prevalence of low ABI is observed in about 27% of patients with MetS who do not have any cardiac disorders. The age, renal dysfunction, and current tobacco use were the factors associated with lower ABI. The findings of the present study were comparable with the study by Schmolling et al., which demonstrated that lower ABI was found in patients with diabetes mellitus and physical inactivity. MetS was associated with PAD. This study has recommended the measurement of ABI in patients with MetS.
Hence, our study concludes that MetS is associated with low ABI values. The parameters most significantly associated with the ABI are increased waist circumference and elevated TG levels. Limitations of the study were that the sample size was small-and long-term follow-up of the patients was not done.
| Conclusion|| |
The above study shows that MetS is associated with subnormal ABI values which can act as an indirect marker of subclinical atherosclerosis not just in the lower limbs but in any vascular bed. Inclusion of the ABI as a routine clinical assessment in patients who have MetS will help in identifying patients at a risk of cardiovascular disease. It can help to start early intervention in the form of therapeutic diet and lifestyle modifications along with pharmacological intervention.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]