|Year : 2016 | Volume
| Issue : 1 | Page : 28-32
Pattern of ankle brachial index among adults in Sagamu South-West Nigeria
Oluseun O Adeko1, Adekunle Joseph Ariba1, Oluranti B Familoni2, Olatunde Odusan2, Sanya B Osalusi2
1 Department of Family Medicine, Olabisi Onabanjo University Teaching Hospital, Sagamu, Ogun State, Nigeria
2 Department of Internal Medicine, Olabisi Onabanjo University Teaching Hospital, Sagamu, Ogun State, Nigeria
|Date of Web Publication||13-Jan-2016|
Oluseun O Adeko
Department of Family Medicine, Olabisi Onabanjo University Teaching Hospital, Sagamu, Ogun State
Source of Support: None, Conflict of Interest: None
Background: The ankle-brachial index (ABI) is a ratio of Doppler recorded ankle and brachial systolic blood pressure. ABI value of <0.9 is diagnostic of peripheral arterial disease (PAD) and is associated with increased risk of cardiovascular morbidity and mortality. ABI is a simple and noninvasive tool that can be used in primary care as part of cardiovascular risk assessment.
Objectives: To determine the pattern of ABI, the prevalence of PAD, and the risk factors for low ABI.
Subjects and Methods: Four hundred subjects aged 50 years and above were selected by systematic random sampling. Their demographic data and cardiovascular risk factors were assessed, and their ABI was measured. ABI value of ≤0.9 was taken as low ABI indicating PAD while a value >1.3 was taken as high ABI indicating arterial calcification.
Results: Two hundred and eighty-eight (72.0%) of the participants had normal ABI, 99 (24.8%) had low ABI indicating PAD, and 13 (3.3%) had high ABI. The prevalence of low ABI increased from 4.9% between 50 and 59 years to 25.3% and 58.7% between 60 and 69 and ≥70 years, respectively. The risk factors for low ABI were age (P = 0.00), history of hypertension (P = 0.03), and diabetes mellitus (DM) (P = 0.00).
Conclusion: 24.8% of the participants had low ABI indicating PAD. The prevalence of PAD increases by 5–10 folds after the fifth decade of life. Low ABI was associated with advancing age, DM, and hypertension.
Keywords: Ankle brachial index, diabetes mellitus, hypertension, peripheral arterial disease
|How to cite this article:|
Adeko OO, Ariba AJ, Familoni OB, Odusan O, Osalusi SB. Pattern of ankle brachial index among adults in Sagamu South-West Nigeria. Nig J Cardiol 2016;13:28-32
|How to cite this URL:|
Adeko OO, Ariba AJ, Familoni OB, Odusan O, Osalusi SB. Pattern of ankle brachial index among adults in Sagamu South-West Nigeria. Nig J Cardiol [serial online] 2016 [cited 2019 Aug 21];13:28-32. Available from: http://www.nigjcardiol.org/text.asp?2016/13/1/28/173856
| Introduction|| |
Adverse cardiovascular events such as myocardial infarction and stroke are emerging as major causes of morbidity and mortality worldwide. These events may occur in individuals who have no clinical record of cardiovascular disease (CVD) and the underlying pathology in most cases is atherosclerosis which is largely asymptomatic but may manifest as peripheral arterial disease (PAD). Atherosclerosis, if present in the periphery as PAD, is also likely in the cerebral and coronary vasculature. Ness and Aronow found that 68% of patients with PAD also had coronary artery disease. Patients with PAD even if asymptomatic, have an increased risk of future cardiac and cerebrovascular events, as well as being 6 times more likely to die within 10 years. The ankle-brachial index (ABI) had been demonstrated as the most effective tool in the early diagnosis of PAD. A reduced ABI indicates hemodynamic disturbances in the arterial supply to the lower limbs, which is strongly associated with atherosclerosis in the coronary and carotid arteries. It has thus been proposed as a biomarker of generalized atherosclerosis and cardiovascular risk. Having a low ABI ratio is an independent risk factor for CVD as it had been related to an increased incidence of mortality, myocardial infarction, and stroke. These increased relative risks were found to be independent of baseline CVD and risk factors, suggesting that the ABI might have an independent role in predicting cardiovascular events. Despite the simplicity and usefulness of the procedure, it is not widely used in clinical practice because most clinicians are not aware that a low ABI is a marker of cardiovascular risk, do not know how to perform the test and is perceived as a specialist test for use only by vascular surgeons and physicians. Therefore, this study was carried out to determine the pattern of ABI, the prevalence of PAD, and the risk factors for low ABI.
| Subjects and Methods|| |
A cross-sectional study was carried out at the General Out-patient Clinic of the Olabisi Onabanjo University Teaching Hospital (OOUTH) Sagamu, Ogun State South-West Nigeria. Four hundred subjects were selected by systematic random sampling, and the inclusion criterion was adult patients aged ≥50 years. Excluded from the study were patients with acute respiratory distress and clinical feature suggestive of deep venous thrombosis to prevent embolism while measuring ABI.
The subjects had their blood pressure checked using accoson mercury sphygmomanometer and was approximated to the nearest 5 mmHg. The height and weight were measured using health scale stadiometer calibrated to the maximum of 120 kg and 1.90 m with patients wearing light clothing and no footwear. The weight and height were approximated to the nearest 0.1 kg and 0.01 m, respectively. The ABI was measured using accoson mercury sphygmomanometer and handheld 10 MHz Doppler device with vascular probe (Huntleigh Healthcare Mini Dopplex Model No. 0900) as follows: With each subject in the supine position and after resting for 5 min, the brachial systolic pressure was measured by applying the cuff of the sphygmomanometer on the upper arm with the lower edge approximately 1 inch above the antecubital fossa. The brachial artery was palpated, and conductivity gel applied over it after which the tip of the probe of Doppler device was placed on it at 45–60° angles until clear arterial pulse sounds were heard. The cuff was inflated to the point that the pulse sounds disappeared and then went to 20 mmHg above that point. The cuff was deflated slowly at a rate of 5 mmHg, and the point at which the arterial pulse sounds resumed was taken as brachial systolic pressure. This procedure was repeated on the other arm. The systolic pressure in the ankle was measured by applying the cuff on the patient's leg approximately 2 inches above medial malleolus and the dorsalis pedis pulse was palpated. The gel was applied, and the tip of the Doppler probe was applied to the gel. The systolic pressure was measured following the same steps described for the arm. The same procedure was repeated for the other leg. The ABI was calculated by dividing the higher of the ankle systolic pressures by the higher brachial systolic pressure. Their demographic data, cardiovascular risk factors (hypertension, diabetes, and body mass index [BMI]) and ABI were collated with the aid of a questionnaire. Normal ankle brachial pressure index (ABI) was taken as 0.91–1.3 and ABI ≤0.9 was taken as abnormal and diagnostic of PAD. ABI of >1.3 was also considered abnormal as it indicates incompressibility of the artery as a result of calcification. However, due to poor correlation between calcification and severity of atherosclerosis, the ABI is generally unreliable in this situation. Hypertension was defined as self-reported physician diagnosis or blood pressure measurements >140/90 mmHg. Diabetes was defined as self-reported physician diagnosis or fasting blood glucose of ≥126 mg/dL. BMI was estimated by dividing kilograms of weight by height in meters squared and was categorized according to the classification system established by the National Institutes of Health. Overweight was defined as BMI ≥25 kg/m 2. The data were analyzed using Statistical Package for Social Sciences version 16 (SPSS Inc, Chicago IIinois, USA) and descriptive statistics was used to analyze and present the results. Chi-squared test was used to investigate the association between two categorical variables and for continuous variables the t-test was used. All analysis was done with P < 0.05 considered statistically significant.
This study was approved by the Health Research and Ethical Committee of the OOUTH Sagamu. Furthermore, informed written consent was obtained from all the participants.
| Results|| |
[Table 1] shows the sociodemographic characteristics of the subjects. The age range of the patients was between 50 and 86 years with a mean of 62.5 ± 9.29 years. There were 144 (36.0%) males and 256 (64.0%) females giving a male to female ratio of 1:1.8.
[Table 2] shows the cardiovascular risk factors of the subjects. One hundred and thirty (32.5%) of the subjects had hypertension while 60 (15.0%) had diabetes mellitus (DM).
[Table 3] displays the pattern of ABI and the prevalence of PAD. Two hundred and eighty-eight (72.0%) patients had normalABIindicating no PAD, 99 (24.8%) had low ABIindicating PAD and 13 (3.3%) patients had high ABI indicating arterial calcification. Therefore, using the ABI to diagnose PAD gave the overall PAD prevalence of 24.8%.
The patterns of ABI across the demographic and cardiovascular risks are shown in [Table 4]. The mean age of patients with low ABI and high ABI were 70.32 years and 72.00 years, respectively while the mean age of patients with normal ABI was 62.51 years. The prevalence of low ABI increased from 4.9% in the fifth decade to 25.3% and 58.7% in the sixth and seventh decade of life, respectively. Thirty-eight (33.4%) of the patients with low ABI had DM while only 14 (4.9%) of those with normal ABI had DM. Of the 99 patients with low ABI, 48 (48.5%) had hypertension while 77 (26.7%) of the patients with normal ABI had hypertension. In addition, 73 (73.7%) of the subjects with low ABI were overweight.
The risk factors associated with low ABI are shown in [Table 5]. The risk factors that were found to have statistically significant association with low ABI were age, history of hypertension, and DM.
| Discussion|| |
The prevalence of PAD using ABI value of ≤0.9 has been reported in the literature to be in the range of 3.9–26.2% depending on the population studied., In this study, the prevalence of PAD using ABI value of ≤0.9 was 24.8% which was within the reported range. Findings from the present study revealed a direct relationship between low ABI and age. With increasing age, the prevalence of low ABI increased from 4.9% in the fifth decade to 25.3% in the sixth decade and 58.7% in the seventh decade and above. In order words, from the fifth to seventh decade the prevalence of low ABI increased by more than tenfold. In addition, the mean age for low ABI was 70.32 years (±8.6) while the mean age for normal ABI was 62.51 years (±6.5). The result from this study shows that age had a statistically significant relationship with low ABI (P = 0.00).
These findings are consistent with results from other studies. In a study of 646 subjects aged 45–80, the prevalence of low ABI increased with age from <5% in 55–59 years age group to 20% in 70–74 years age group and almost 35% in 75–80 years age group. Also, in the PAD study (PERART/ARTPER) study of 3786 participants aged 49 years and above, the mean age for low ABI was 70.70 years while the mean age for normal ABI was 64.11 years similar to the finding in this study. Similarly, the impact of age on ABI was demonstrated in a study in Ogbomoso among the diabetics where it was found that the prevalence of low ABI was 44.1% between 50 and 59 years while it was 85.7% between 80 and 89 years. Abnormally high ABI of >1.3 was found in 3.3% of the studied population and shows a linear relationship with age and higher prevalence among the subjects with diabetes. The abnormally high values of ABI in these situations has been said to result from arterial calcification which renders the artery incompressible. This has been established as one of the limitations of ABI requiring toe brachial index to make a diagnosis of PAD.,
Findings from this study also revealed a statistically significant association between low ABI and other risk factors for atherosclerosis namely: DM and hypertension. The prevalence of DM among those with low ABI was 33.4% compared to 4.9% in those with normal ABI. Previous studies have noted this relationship between low ABI and DM. In the National Health and Nutrition Examination Survey (NHANES), report, 26% of subjects with low ABI were identified as having DM while in the Multi-Ethnic Study of atherosclerosis study 26% of women and 27.5% of men with low ABI had DM., In the study by Mlacak et al. the prevalence of DM in those with low ABI was 28.8%. The prevalence of hypertension in low ABI was 48.5% and 38.5% in high ABI compared to 26.7% in subjects with normal ABI. The findings from various studies gave different results depending on the population studied. In the PAD (PERART/ARTPER) study which was a community-based study the prevalence of hypertension was 11.9% among the subjects with low ABI while 86.0% was reported in the Framingham study of elderly subjects with a mean age of 81 years., Although overweight had been recognized as a risk factor for atherosclerosis, its relationship with abnormal ABI has not been firmly established due to inconsistent results from various studies.,, In the present study, the prevalence of overweight in those subjects with low ABI was 73.7%. This is similar to the study by Mlacak et al. where the prevalence was 72.7%. Similar results were reported in the PARTNERS study, NHANES report and in the Korean study of Kweon et al.,, However, while Mlacak et al. and Kweon et al. reported no statistically significant relationship between overweight and low ABI; the PARTNERS study and NHANES reported statistically significant relationship. While the result of the association of BMI, a measure of general obesity with abnormal ABI may be inconclusive, waist-to-hip ratio, a measure of central obesity had been found to have a statistically significant relationship with abnormal ABI in most studies., It had been established that an increased waist-to-hip ratio over the median value doubled the prevalence of low ABI.
This is a descriptive study which did not permit the establishment of a causal relationship between various cardiovascular risk factors and abnormal ABI.
| Conclusion|| |
Given the finding that increasing age on its own is associated with abnormal ABI, its measurement should be included as part of the cardiovascular evaluation of patients aged 60 years and above irrespective of the presence of cardiovascular risk factor. In addition, patients with hypertension and DM should have their ABI measured as part of their cardiovascular risk assessment.
We acknowledge the assistance rendered by CNO Adekanbi of the General Out-patient Clinic of OOUTH and the Resident Doctors in the Department of Family Medicine.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]