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| ORIGINAL ARTICLE |
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| Year : 2021 | Volume
: 7
| Issue : 1 | Page : 54-59 |
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A comparative assessment of the severity of coronary artery disease in patients with low ankle–Brachial index and normal ankle–Brachial index: An angiography-based cross-sectional observational-analytical study (CADLABI study)
Awadhesh Kumar Sharma1, Mohit P Kejriwal1, Santosh Kumar Sinha1, MM Razi1, Umeshwar Pandey1, Praveen Shukla1, Ramesh Thakur1, CM Verma1, Vinay Krishna2
1 Department of Cardiology, LPS Institute of Cardiology, GSVM Medical College, Kanpur, Uttar Pradesh, India
2 Department of Cardiothoracic Surgury, LPS Institute of Cardiology, GSVM Medical College, Kanpur, Uttar Pradesh, India
| Date of Submission | 17-Sep-2020 |
| Date of Decision | 24-Feb-2021 |
| Date of Acceptance | 12-Mar-2021 |
| Date of Web Publication | 24-Apr-2021 |
Correspondence Address:
Awadhesh Kumar Sharma
Department of Cardiology, LPS Institute of Cardiology, GSVM Medical College, Kanpur - 208 019, Uttar Pradesh
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/jpcs.jpcs_91_20
Objectives: The ankle–brachial index (ABI) is an efficient tool and an indicator of generalized atherosclerosis. Still, there is uncertainty regarding the severity of coronary artery disease (CAD) in patients having low ABI. The uniqueness of this study is that it is the first largest study done with the aim to determine the severity of CAD in the form of a number of involvements of coronary vessel in patients with low ABI. Materials and Methods: It is a hospital-based cross-sectional observational-analytical study. A total of 500 patients of suspected CAD were recruited. ABI was measured first and then all patients were sent for coronary angiography. Based on ABI values, patients were divided into two groups, i.e., Group A (patients with low ABI or ABI ≤0.9) and Group B (patients with normal ABI or ABI >0.9). Results: Twenty-three, i.e., 4.6% of patients had ABI <0.9. All patients having low ABI had CAD. In assessing CAD severity, it was reported that in Group A, triple-vessel disease (TVD) was present in 65.2% (P = 0.0001), double-vessel disease in 21.7% (P = 0.72), single-vessel disease in 8.6% (P = 0.06), and noncritical CAD in 4.3% (P = 0.9) as compared to Group B. In patients with Group A, 52.1% were smoker (P = 0.01), 69.5% have increased body mass index (P = 0.71), 43.4% have a history of hypertension (P = 0.73), and 60.8% were diabetic (P = 0.0005). Conclusion: CAD is widely prevalent almost in all patients with low ABI and more than half of these patients have TVD on angiographic assessment.
Keywords: Angiography, ankle–brachial index, atherosclerotic risk factors, coronary artery disease, peripheral artery disease
How to cite this article:
Sharma AK, Kejriwal MP, Sinha SK, Razi M M, Pandey U, Shukla P, Thakur R, Verma C M, Krishna V. A comparative assessment of the severity of coronary artery disease in patients with low ankle–Brachial index and normal ankle–Brachial index: An angiography-based cross-sectional observational-analytical study (CADLABI study). J Pract Cardiovasc Sci 2021;7:54-9 |
How to cite this URL:
Sharma AK, Kejriwal MP, Sinha SK, Razi M M, Pandey U, Shukla P, Thakur R, Verma C M, Krishna V. A comparative assessment of the severity of coronary artery disease in patients with low ankle–Brachial index and normal ankle–Brachial index: An angiography-based cross-sectional observational-analytical study (CADLABI study). J Pract Cardiovasc Sci [serial online] 2021 [cited 2023 May 28];7:54-9. Available from: https://www.j-pcs.org/text.asp?2021/7/1/54/314484 |
| Introduction | |  |
Cardiovascular diseases have been gaining importance in Asian countries in the last decade.[1] There is no doubt that coronary angiography is the gold standard test to detect coronary artery disease (CAD), but it is costly, invasive, and not widely available. The ankle–brachial index (ABI) may be an effective tool in primary health-care settings for the early diagnosis of cardiovascular diseases and an idea of its severity.[2],[3],[4],[5] This is the first largest study done with the aim to determine the severity of CAD in the form of a number of involvements of coronary vessel in patients with low ABI.
| Materials and Methods | | |
It is a hospital-based cross-sectional observational-analytical study done at a tertiary care, cardiac teaching center for a period of 1 year. A total of 500 patients were recruited for the study from both outdoor and indoor patient clinics based on different inclusion and exclusion criteria. Determination of sample size was done using the formula, n = z2pq/e2, here n = sample size, z = 1.96 at 95% confidence level, p = the prevalence of undiagnosed PAD in patients undergoing coronary angiography and taken maximum as 12.8%,[6] q = (1-p), and e = Absolute precision/margin of error (5%). On using the formula and above values, the calculated estimated sample size was 171. Due to availability of required patients and keeping in mind the accuracy of study findings and for the ease of calculations, a total sample size of 500 was taken.
Aims and objectives of the study
The primary objective of the study was to assess the angiographic severity of CAD in patients with low ABI in comparison to patients having a normal ABI. The secondary objective was to determine the prevalence of PAD in suspected CAD patients undergoing coronary angiography and the epidemiological assessment of various atherosclerotic risk factors in those having a low ABI. [Figure 1]- The consortium diagram of the study design.
Eligibility criteria
Inclusion criteria
1. Patients with suspected CAD undergoing coronary angiography-suspected CAD were defined on the basis of symptoms suggestive of ischemia (angina) and/or positive results on noninvasive ischemia tests (exercise testing or stress echocardiography).
Exclusion criteria
- Patients with prior history of confirmed CAD, coronary artery bypass grafting, or percutaneous coronary intervention
- Patients with previous surgery or intervention for PAD
- Patients with deformity in upper and lower limbs
- Critically ill patients
- Patients with severe limb ischemia.
Patients attending the cardiology outpatient and indoor patient department satisfying the inclusion and exclusion criteria were enrolled. Written informed consent was obtained from all studied subjects. Other demographic, anthropometric parameters, and history of atherosclerotic risk factors such as diabetes mellitus (DM), hypertension (HTN), and smoking were obtained.
Atherosclerotic risk factors were described as follows:
- HTN: Systolic blood pressure (BP) ≥140 mmHg and/or diastolic BP ≥90 mmHg and/or receiving antihypertensive treatment[7]
- DM: Symptoms of DM plus random plasma glucose concentration ≥200 mg/dl or fasting blood glucose ≥126 mg/dl or 2-h GTT blood glucose ≥200 mg/dl or HbA1C ≥6.5% and/or use of glucose-lowering drugs[8]
- Smoking: Smoking was defined as the regular intake of tobacco products more than one time per day or the patient had a history of smoking in the last 30 days prior to the admission.[9]
Technique
ABI was measured prior to coronary angiography. ABI was derived from systolic BP measured in the arms and legs after 10 min of rest in a supine position with arms and legs straight and at rest. Manual cuffs were used for all BP measurements and arm circumference was determined during screening to select the appropriate cuff size consistent with the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC7) recommendations.[10],[11] The same cuff size was used for the lower leg. A straight wrapping technique was employed. Arm BPs and leg BPs were measured with an 8 MHz Doppler to detect pulses. One measurement was made at each of the four sites in the following order: right arm, right ankle, left ankle (dorsalis pedis, posterior tibialis), and left arm. Right ABI was calculated as the ratio of the higher right ankle pressures (dorsalis pedis or posterior tibialis) divided by the higher brachial pressure (right or left side) or, in case where right and left brachial pressures differed by >10 mmHg, the average of the right and left brachial pressures. Left ABI was calculated in a similar way. The lower ratio of either side was considered the participant's overall ABI. ABI ≤0.9 was considered as low. Based on ABI values, patients were divided into two groups, i.e., Group A (patients with low ABI or ABI ≤0.9) and Group B (patients with normal ABI or ABI >0.9). Then, all patients underwent selective coronary angiography via the radial/femoral approach with a 5F or 6F catheter. Three cardiologists evaluated each coronary angiography. CAD was defined as a luminal stenosis of >50% in the major coronary vessels. Coronary artery stenosis or CAD was evaluated visually and categorized as noncritical or nonsignificant if luminal stenosis <70% and significant if there was a stenosis >70%.[12] Angiographers made a subjective assessment of severity of CAD on the basis of number of coronary arteries involved. All the results were compared in both the groups.
Statistical analysis
Statistical quantitative data were analyzed using the two-sample t-test between percent/Mann–Whitney U-test for comparisons of data between the different patient groups. For qualitative variables, the Chi-square test/Fischer's exact test was applied. P < 0.05 was considered significant. The statistic calculator software system was used for the statistical analysis.
| Results | | |
In this study, 500 patients were evaluated, of which 23 (4.6%) patients had ABI <0.9. The mean age of study subjects was 55 ± 10.5 years with a range from 23 to 90 years. Maximum patients in Group A were of age group 51–70 years, i.e., 13 (56.5%). The same distribution was seen in Group B (P = 0.562). In analyzing sex distribution among the studied population, it was seen that out of total patients, 368 (73.6%) were male and 132 (26.4%) were female [Table 1]. In Group A, 21 (90.9%) patients were male and two, i. e., 9.1%, were female. hence there was a high prevalence of vascular atherosclerotic phenomenon with male sex in Group A (P = 0.001). Out of 23 patients in Group A with low ABI, 7 (30.4%) had a normal Body mass index (BMI), 12 (52.2%) had high BMI, and 4 (17.4%) were obese. These results were similar to patients having a normal ABI (P = 0.568). Out of the total studied population, 147 patients, i.e., 29.4%, were smoker. In Group A, 12 patients, i.e., 52.1%, were smokers, while in Group B, 135 patients, i.e., 28.3%, were smoker (P = 0.01). In Group A, 10 (43.4%) patients had a history of HTN, while in Group B, the number was 224 (46.96%) (P = 0.74). On analyzing other atherosclerotic risk factors, it was reported that 14 (60.8%) patients were suffering from diabetes mellitus (DM) in Group A, while in Group B, the number was 130 (27.2%) (P = of 0.001) [Table 2] and [Figure 2]. Postcoronary angiographic analysis of these patients revealed that triple-vessel disease (TVD) was present in 15 (65.2%) patients in Group A, while it was present in 127 (26.6%) patients in Group B (P = 0.0001). Double-vessel disease (DVD) involvement was present in 5 (21.7%) in patients Group A and 119 (24.9%) in Group B (P = 0.72). The single-vessel disease (SVD) was present in 2 (8.6%) in Group A, while 124 (25.9%) in Group B (P = 0.06). Noncritical disease was present in 1 (4.3%) in Group A, while 22 (4.6%) in Group B (P = 0.9). Normal coronaries were present in 85 (17.8%) patients in Group B, while in Group A, all patients had CAD (P = 0.02) [Table 3] and [Figure 3]. At an established cutoff value of ABI ≤0.9, the sensitivity, specificity, positive predictive value, and negative predictive value to predict CAD were 5.54%, 100%, 100%, and 17.82%, respectively [Table 4]. Hence, though ABI of ≤0.9 had a low sensitivity to predict CAD, a high specificity shows that if ABI is ≤0.9, there is a very high likelihood of having CAD in our patient population of suspected CAD. | Figure 2: Prevalence of atherosclerotic risk factors among both the groups. Group A – ankle–brachial index <0.9, Group B- ankle–brachial index >0.9.
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 | Figure 3: Angiographic assessment of CAD severity. Group A – ankle–brachial index <0.9, Group B – ankle–brachial index I >0.9.
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| Discussion | | |
This was the first largest study emphasizing and testing the role of ABI as a noninvasive tool for the early detection, assessing severity and timely prevention of CAD. Till date, the ABI is used to detect the presence of PAD. Since PAD is considered a coronary heart disease risk equivalent,[13] the ABI is also considered as a simple tool to identify those at risk of major adverse cardiovascular events. However, its validity was still unclear and not studied in a large population more so in developing countries. Fuethermore, there is uncertainty regarding the severity of CAD in patients having low ABI. In the present study, we had tried to search out the possibility of applying ABI as a noninvasive testing tool in a population at risk for CAD, especially in intermediate-risk profile patients to assess the severity of CAD so that timely preventive measures can be applied to halt the progression. According to the present study, the prevalence of low ABI or PAD in suspected CAD patients undergoing coronary angiography is 4.6%. The values of low prevalence of positive ABI (ABI <0.9) were almost similar with one Japanese study, i.e., 5%,[14] The baseline prevalence of PAD was 7.6% in Mediterranean population-based cohort of total 3786 subjects >49 years with 9-year follow-up with low cardiovascular risk in Spain (ARTPER cohort).[15] Although the prevalence of PAD is in single digit, when we segregate these patients and analyze them, we observed that almost 100% of these patients had CAD. In other words, finding low ABI had a very high specificity to detect CAD in intermediate-risk profile patients. Moreover, ABI measurement should be part of vascular risk assessment in patients with an intermediate cardiovascular (CV)-risk profile to predict future cardiovascular risk. ABI had high specificity but low sensitivity as a screening tool for detecting subclinical atherosclerosis.[16],[17] In the present study, at an established cutoff value of ABI ≤0.9, the sensitivity, specificity, positive predictive value, and negative predictive value to predict CAD were 5.54%, 100%, 100%, and 17.82%, respectively. Hence, though ABI of ≤0.9 had a low sensitivity to predict CAD, a high specificity shows that if the ABI is ≤0.9, there is a very high likelihood of having CAD in our patient population of suspected CAD. In a meta-analysis of nine studies by Doobay et al., they found that the sensitivity and specificity of a low ABI to predict incident coronary heart diseases were 16.5% and 92.7%, for incident stroke were 16.0% and 92.2%, and for cardiovascular mortality were 41.0% and 87.9%, respectively.[5] In the present study, our aim was to determine the relationship of a low ABI with the angiographic severity of CAD in the form of number of coronary arteries involved. On angiographic assessment of these patients, it was found that 100% of the patients with ABI <0.9 had CAD. On assessing severity of CAD in these patients with low ABI, it was reported that TVD was present in 65.2% (P = 0.0001), DVD in 21.7% (P = 0.72), SVD in 8.6% (0.06), and noncritical CAD in 4.3% (P = 0.9). On analyzing the results, it was observed that the presence of TVD was more in low ABI group and it was statistically significant as compared to patients having a normal ABI, while there was no statistically significant difference in the occurrence of DVD, SVD, and noncritical disease among the two groups. There were a limited number of studies correlating low ABI with the severity of CAD in the form of number of coronaries involved, but those available were suggestive of increased severity of CAD with low ABI. Multivessel involvement seems to be part of generalized vascular atherosclerosis.[18],[19]
ABI can be affected by various anthropometric and epidemiological parameters, such as age, sex, height, weight, and BMI as per the review of the literature. Cross-sectional and longitudinal population studies indicate that the ABI decreases with age, probably because of the increased prevalence and progression of PAD.[20],[21],[22] In our study too, the majority of the patients having low ABI, i.e., 56.5%, belonged to 51–70 years' age group. Among both sexes, low ABI was significantly more common in male as compared to female. These findings were similar to a previous study on 200 subjects by Premanath and Raghunath which showed that the ABI test was positive in 12 males (10%) and six females (7.5%).[23] In many other population studies too, similar sex differences in ABI have been reported.[24],[25],[26],[27],[28],[29] Among participants without traditional CVD risk factors in the San Luis Valley Diabetes Study,[30] the average ABI was 0.07 less in women than in men. In our study, no significant association between BMI and low ABI value was seen which was similar to one study, which did not find a significant association between BMI and prevalent low ABI.[31] In contrary to our results, the multi-ethnic study of atherosclerosis (MESA) result showed that baseline obesity was associated with the development of new-onset low-ABI measurements over a mean four-year follow-up, as well as mean ABI decreases over time.[32] These findings need future studies in terms of calculating other parameters for obesity like waist circumference to rule out central obesity and its correlation with ABI. As per the literature, BMI itself is not an appropriate criterion to define obesity. ABI values <0.9 in the present study were significantly associated with the presence of various atherosclerotic risk factors. The significant association between low ABI and cardiovascular risk factors such as smoking habits and diabetes is consistent with the findings of previous studies. DM is a very strong independent risk factor for critical limb ischemia and amputation, as well as incident CAD in the population studies.[33] Low ABI was found to be more prevalent in patients with DM. These results were similar to the present study. Smoking of tobacco products in any form was one of the most important risk factors for both PAD and CAD. In the present study, the prevalence of current smoking habits was significantly higher in a low ABI group. In few previous studies too, a direct correlation was found between smoking, low ABI, and CAD.[34],[35],[36]
| Conclusion | | |
On the basis of the findings of the present study, we conclude that CAD is widely prevalent almost in all patients with low ABI and more than half of these patients have TVD on angiographic assessment. ABI is a simple, reproducible, cost-effective, noninvasive, and precise screening tool to identify individuals at high risk for CAD.
Ethics clearance
Institutional Ethics Committee of LPS Institute of Cardiology, GSVM Medical College, Kanpur, issued ethical clearance in a meeting held on 06.08.2018 via letter no 562/2018/LPSIC/Off.
Acknowledgments
The authors like to thank senior cath lab technician Mr. Vinod Sharma, Sister Usha Nigam, and all the members of the nursing staff of our cath lab, for their indispensable commitment.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4]
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