Unravelling early onset of atherosclerosis in young asymptomatic individuals using physiological parameters - A way forward

Bhaskar Sai Vardhan; Manisha Kar; Sushil Chandra Mahapatra

doi:10.4103/2395-2113.251357

STUDENT CORNER

Year : 2018 | Volume : 4 | Issue : 1 | Page : 81-85

Unravelling early onset of atherosclerosis in young asymptomatic individuals using physiological parameters - A way forward

Bhaskar Sai Vardhan¹, Manisha Kar², Sushil Chandra Mahapatra³
¹ MBBS Student, Department of Physiology, All India Institute of Medical Sciences, Bhubaneswar, India
² Associate Professor, Department of Physiology, All India Institute of Medical Sciences, Bhubaneswar, India
³ Professor & Head, Department of Physiology, All India Institute of Medical Sciences, Bhubaneswar, India

Date of Submission	27-Apr-2018
Date of Acceptance	15-Jun-2018
Date of Web Publication	1-Feb-2019

Correspondence Address:
Manisha Kar
Associate Professor, Department of Physiology, All India Institute of Medical Sciences, Bhubaneswar
India

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/2395-2113.251357

Abstract

Introduction: India is burdened with 25% of cardiovascular disease-related deaths. CHD manifests almost 10 years earlier on an average in Indian subcontinent. Objectives: to study the early onset atherosclerosis in young, asymptomatic individuals using physiological parameters. Material & Method: 31 young, asymptomatic males of age group of 21- 40 yr participated in this cross-sectional, observational study. The basic characteristics and anthropometric measurements of the subjects were obtained. Baseline blood pressure was recorded and Mean Arterial Pressure (MAP), pulse pressure (PP) were calculated. The arterial stiffness was assessed by recording central systolic blood pressure (central SBP), central diastolic blood pressure (central DBP) and augmentation index by arteriography. Ankle-brachial index was also measured. The data were presented as median (range). Results: 31 male subjects of 21-40 years of age participated in the study. Participants were grouped into lower age group [group A (21-30 yr), n=14] and higher age group [group B (31-40 yr), n=17]. More subjects (71.14%) of group B were in overweight-pre-obese-obese group than in group A (64.69%). Considering waist-hip ratio (WHR), more subjects of group A (94.11%) had low estimated health risk than group B (85.71%). Interestingly, SBP of 11.8% and DBP of 5.9% subjects of group A were higher, but none had higher SBP and DBP in group B as per JNC 8 criteria. The lower limit of central SBP and DBP were slightly more in group B than group A. Augmentation index value was within normal range in both groups. Ankle Brachial Index (ABI) of 14.3% of subjects of group B was indicative of mild to moderate degree of peripheral vascular disease. Conclusion: The important findings in this study have significance in practice as atherosclerosis eventually leads to serious consequences such as an MI or Stroke.

Keywords: Atherosclerosis, Mean Arterial Pressure, Ankle Brachial Index

How to cite this article:
Vardhan BS, Kar M, Mahapatra SC. Unravelling early onset of atherosclerosis in young asymptomatic individuals using physiological parameters - A way forward. Indian J Community Fam Med 2018;4:81-5

How to cite this URL:
Vardhan BS, Kar M, Mahapatra SC. Unravelling early onset of atherosclerosis in young asymptomatic individuals using physiological parameters - A way forward. Indian J Community Fam Med [serial online] 2018 [cited 2021 Jan 24];4:81-5. Available from: https://www.ijcfm.org/text.asp?2018/4/1/81/251357

Introduction

The incidences of cardiovascular disease related death and disability are increasing in developing countries at alarming pace.^[1] India alone is burdened with 25% of CVD- relateddeaths.^[2] Most of CVD sufferers are in productive age group in India and that imposes tremendous socioeconomic burden and devastating consequences over the coming years.^[3] Though manifestation of CVD occurs after 40 years of age, atherosclerotic changes begin early in life as demonstrated by necropsy studies.^[4] It was reported that CHD manifests almost 10 years earlier on an average in Indian subcontinent in comparison to rest of the world.^[5] Therefore, it is the need of the day to develop effective tools to identify young individuals who are otherwise asymptomatic but at risk of developing CVD for timely prevention and treatment at early stage.

Several prediction models have been proposed to estimate a 10-year risk of developing CVD in past decades. Framingham Risk Score (FRS) is one such prediction model to estimate risk for developing CVD. FRS predicts CHD using traditional risk factors namely age, diabetes, smoking, systolic blood pressure (SBP), treatment for hypertension, total cholesterol and high-density lipoprotein (HDL) cholesterol.^[6] The individuals are risk- stratified based on these models. However, considerable number of CVD events occurs in asymptomatic individuals who are otherwise stratified in intermediate or low risk strata. They may suffer from undiagnosed substantial atherosclerosis which itself is the main cause of CVD.^[7] Therefore, it is imperative to incorporate or modify risk factor that has an early predictive value in a given population. Enhanced peripheral blood pressure is a known cardiovascular risk factor. Although diastolic and mean arterial pressures are relatively constant, systolic pressure may be up to 40 mm Hg higher in the brachial artery than in the aorta. This occurs because of increase in arterial stiffness moving away from the heart.^[8] Increasingly, the importance of central blood pressure (Central BP) is recognized over and above peripheral blood pressure as a cardiovascular risk factor. Increased arterial stiffness will enhance pulsatile component of blood pressure, which in turn modulates atherosclerosis progression. Central BP waveform is a sum of a forward travelling wave, by and a reflected wave coming back from periphery. Central pulse pressure ≥50 mm Hg carries greatest risk of future cardiovascular event.^[9] Augmentation pressure is calculated as SBP (the peak of the observed wave) minus the peak of the forward waveform. Thus, Augmentation pressure represents additional SBP due to wave reflection.^[10] Ankle- brachial index (ABI) is defined as the ratio of systolic pressure of the ankle to that in the arm. It is another parameter to evaluate changes in the blood vessel and is utilized for measuring peripheral vascular disease. An abnormal low ABI (≤0.90) indicates the presence of peripheral artery disease, while an abnormally high ABI (≥1.40) is indicative of vascular calcification.^[11] ABI is documented as an indicator of generalised atherosclerosis because lower levels have been associated with higher rates of concomitant coronary and cerebrovascular disease, and with the presence of cardiovascular risk factors.^[12] A community-based study concluded that higher Augmentation Index, a measure of arterial stiffness and wave reflection was independently associated with a lower ABI. The results of this study added to the growing body of evidence linking measures of arterial stiffness/wave reflection to subclinical atherosclerotic vascular disease.^[13] To this end, the present study aims to determine early onset atherosclerosis in young, asymptomatic individuals using physiological parameters namely determination of SBP, DBP, MAP, PP, central blood pressure, augmentation index and ankle-brachial index. It was reported that measurement of the ankle brachial index may improve the accuracy of cardiovascular risk prediction beyond the Framingham Risk Score. Furthermore, it was suggested that development and validation of a new risk equation incorporating the ankle brachial index is warranted.^[14]

Material & Methods

The present study is a cross-sectional, observational, pilot study. The participants were young, asymptomatic males of age group of 21-40 yr. working with AIIMS Bhubaneswar as residents and administrative staff. Those subjects were included in the study who had no history of dyslipidemia, hypertension, diabetes and peripheral vascular disease.

The subjects having history of chronic renal disease, chronic inflammatory condition, and suspected neoplasm were excluded from the study. 31 subjects participated in the study. The necessary ethical clearance was obtained from Institute Ethical Committee (IEC Reference no. IEC/AIIMS BBSR/STS_UG/2018-19/03). The subject information sheet was handed over to the participant and informed consent was taken from them. The data collection form as approved by Institute Ethics Committee was utilised to record information pertaining to relevant family history, anthropometric measurements such as height, weight, BMI, waist-hip ratio. The height was measured with the stadiometer following the standard protocol, weight was measured using weighing machine using the standard protocol. BMI was calculated as per the formula [wt in kg/ht² (in m)] using the parameters weight (kg) and height (m). The hip circumference was measured around the widest portion of the buttocks. The waist was measured as midpoint between lower margin of the last palpable rib and the top of the iliac crest. Afterwards the ration of waist and hip was calculated. The subjects were asked to report in Clinical Physiology Laboratory of Department of Physiology and were requested to refrain from tea, coffee 2-3 h before the test. After 15 min of rest in supine position, baseline blood pressure were recorded by mercury sphygmomanometer (Diamond, India) following standard protocol. Mean arterial blood pressure and pulse pressure were calculated from the recorded blood pressure data. The arterial stiffness was assessed by recording central aortic systolic and diastolic blood pressure and augmentation index by arteriograph [USCOM make BP + (cardioscope II), Australia]. Ankle-brachial index is the ratio of systolic pressure of the ankle to that in the arm. Accordingly, systolic pressure at brachium and ankle were measured using oscillometric blood pressure measuring equipment. The ABI value was determined by taking the higher pressure of the 2 arteries at the ankle (Posterior Tibial artery), divided by the brachial arterial systolic pressure. In calculating the ABI, the higher of the two brachial systolic pressure measurements was used.^[15] The data were entered in Microsoft excel sheet (Microsoft Excel 2013, Microsoft Corp., and Redmond, WA) and necessary calculations were done. Finally, the data were presented as median (range).

Results

Total 31 male subjects of age group of 21-40 years participated in the study. 7 participants gave the family history of myocardial infarction, hypertension and diabetes. The total number of participants were divided into two subgroups, group A (n=17) comprising of subjects of 21 to 30 years of age and group B (n=14) comprising of subjects of 31 to 40 years of age. The data are expressed as median (range). [Table 1] shows height, weight, BMI and waist-hip ratio of the participants. Waist-hip ratio (WHR) was also computed and cut-off value ≤ 0.9 was regarded as normal as per WHO criteria, 2000. These anthropometric indicators tell us about the obesity and atherosclerosis risk. [Table 2] shows the resting blood pressure, pulse pressure and mean blood pressure of the study subjects taken at the level of brachial artery. The percentage of subjects required pharmacological intervention as per JNC 8 criteria was shown in [Table 2]. Mean Blood Pressure (MBP) and Pulse Pressure (PP) of both groups were within normal limits. [Table 3] shows central blood pressure and augmentation index of the participating study subjects. Central systolic BP was lower than peripheral systolic BP in both groups. But central diastolic BP was little higher than peripheral diastolic BP in both groups. The lower limit of central systolic and diastolic blood pressure is slightly more in group B than group A. Ankle Brachial Index (ABI) was found to be within normal range in group A. But 14.3% of participants in group B were detected to suffer from mild to moderate grade of peripheral arterial disease which is a known cardiovascular risk factor.

Table 1: Height, weight, BMI and Waist-hip ratio of the participants

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Table 2: Resting Blood Pressure, Pulse Pressure and Mean Blood Pressure of the study subjects taken at the level of brachial artery

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Table 3: Central Blood Pressure, Augmentation Index and Ankle Brachial Index of the study subjects which correspond to the arterial stiffness status of an individual

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Discussion

Atherosclerosis begins at a quite early age, which is invariably associated with risk factors, and it is largely preventable.^[16] One of the major risk factor for developing atherosclerosis is hypertension because of which systolic and diastolic BP of both brachial artery and central artery have been measured in this study.^[17] Hypertension also has a higher risk for development of greater number of plaques as compared to normotensive individuals due to endothelial alterations which predispose the individual to various inflammatory processes and cholesterol deposition.^[18] Overweight and obesity are other major culprits.^[19] Therefore, height, weight, BMI and waist-hip ratio of the participating subjects have been measured in this study.

There are documentary evidence which helps to postulate that hypertension predisposes to and accelerates atherosclerosis partly because of synergy between elevated blood pressure and other atherogenic stimuli to induce oxidative stress on the arterial wall.^[20] The resting brachial artery pressure in both groups is in normal range of 120/80 mmHg or below but ironically the highest systolic and diastolic BP was recorded from younger age group. It may be due to family history, early use of tobacco, consumption of alcohol or due to overweight. Arteries are permanently exposed to a basal stretch, which is related to mean BP, and to a pulsatile stretch owing to pulse pressure (PP). Cyclic changes in the intramural tension have been recognized an important factor in the pathogenesis of atherosclerosis and acute coronary syndromes.^[21] Therefore, in the present study, mean blood pressure and pulse pressure of the subjects were being measured. The mean blood pressure of individuals of both the groups was falling in normal range of 70 to 110 mmHg. A minimum of 65 mmHg of mean blood pressure is sufficient to ensure enough perfusion of organs. The range was quite large in lower age group. The inference from this is inconclusive. The pulse pressure was almost similar in both the groups. Since persistent elevated pulse pressure over 100 mmHg is considered significant, which neither of the groups of individuals show, therefore it is not much of any significance.

Relations of brachial and central pressures to carotid artery hypertrophy (intimal-medial thickness and vascular mass), extent of atherosclerosis (plaque score), and incident cardiovascular events were examined in the Strong Heart Study. Among 3520 participants, central and brachial pulse pressures were more strongly related to vascular hypertrophy and extent of atherosclerosis than were systolic pressures.^[22] So, in the present study central systolic and diastolic blood pressure were measured. The average central systolic and diastolic blood pressure seem to be in normal range even though there are no specific guidelines, which particularly state the threshold value for central BP. A point to be noted here is that the lower limit of central systolic and diastolic blood pressure are slightly more in upper age group (31-40 years) than younger age group which may signify the aging process of the artery making it more stiff with time. Central pulse pressure ≥50 mm Hg imposes greatest risk of future cardiovascular event. The Augmentation Index of individuals of both the groups was around 50%. But the upper and the lower limits are very extremely separated in the younger age group (21-30 years). In Korean population, reference value for peripheral AI (%) was reported for ≤39 yr as 81.2 % and for 40-49 yrs., 89.2%.^[10] Not much information about the reference values of this parameter are available for the population of India, especially Odisha as it may vary from population to population for which this data may be of significance. Since Ankle-Brachial pressure index is an indicator of peripheral arterial disease whose incidence increases with age, thereby it is evident in this study population that the older age group had relatively lower ABI slightly below 0.9. BMI of both groups on an average is around 25 or below which is normal according to WHO Asian criteria. This is still not a very reliable indicator because it does not tell us about what percentage of body is fat as cited in the Y-Y paradox of a WHO published article.^[23] The normal waist- hip ratio should be below 0.90 in men but there were many deviations from this. The subjects of 31-40 years were with slightly higher values indicating more abdominal adiposity.

Conclusion

The study overall indicated many parameters which are relevant in knowing the risk of developing atherosclerosis in otherwise young asymptomatic individuals. The important findings in this study as stated above have significance in practice as atherosclerosis is the silent disguised process, which eventually lands up in serious deadly consequences such as an MI or Stroke. The importance in knowing the risk factors and controlling it is the key to prevent such unforeseen events, which is a debilitating burden to the family members and the welfare of the society. At this juncture, it is of paramount importance to create awareness regarding self-health check up so that the risk factors can be detected early.

Acknowledgment

The first author, Mr. Bhaskar Sai Vardhan Pentakota, MBBS student, AIIMS Bhubaneswar is a recipient of ICMR STS award of 2017.

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