Normal Peripheral Arterial Parameters in Young Healthy Black Africans in Tanzania

Abstract

Background: Functionally arteries play the role of supplying blood, oxygen, and nutrients to the peripheral tissues and organs to maintain normal physiological state. Compromised arterial function as a result of atherosclerosis may cause progressive arterial narrowing and eventually blockage. Routine peripheral arterial function (PAF) is primarily assessed by the Ankle Brachial Index (ABI) and can provide information on arterial status. Other parameters include, Toe Brachial Index (TBI) and Pulse Volume Waveform (PVW), both with internationally established reference values for normal and impaired arterial status. Several reports have shown discrepancies between the established ABI, TBI, and PVW normal reference values, with values obtained from different populations of healthy, disease-free individuals. Despite the availability of noninvasive peripheral arterial test (using ABI, TBI, and PVW) to assess PAF, and the increasing prevalence of peripheral arterial diseases (pad) assessment of PAF is not commonly done in our setup. Furthermore, data comparing ABI, TBI, and PVW from young PAD-free black Africans with internationally established reference values, are lacking. Due to this, we aimed to determine ABI, TBI, and PVW in a population of young, healthy, and PAD-free black Africans and compare the results with internationally established normal reference values. OBJECTIVE: To determine normal peripheral arterial parameters (ABI, TBI, and PVW) and compare with internationally established references, in young and healthy black Africans. Methodology: A cross-sectional study was conducted among first-year undergraduate students from Muhimbili University of Health and Allied Sciences (MUHAS). A total of 121 students volunteered to participate in the study (minimum 104). Data was collected using a standardized questionnaire for demographics, medical history and lifestyle, and other risk factors. We used an automated device to measure ABI, TBI, and PVW and compared the obtained value with the American Heart Association (AHA) reference. Anthropometric (height, body mass index (BMI), and waist to hip ratio (WHR) and cardiac (blood pressure (BP) and resting pulse rate (RPR)) parameters were measured and their effect on Peripheral Arterial Status/ parameters was elucidated using multiple linear regression. Data were expressed as mean ± standard deviation (SD), and as a median in interquartile ranges (IQR) for continuous and in frequency table for categorical data, respectively. Student t-test used to determine the difference between means and P-value of < 0.05 are considered statistically significant. Results A total of 121 undergraduate first-year students with a median age of 20(20,23IQR), were recruited. All maintained a relatively healthy lifestyle (fruit and vegetable intake and physical activity level of >600MET/min/week. They had a median body mass index of 21.5(19.72, 23.46 IQR) and all had no obvious symptoms and signs suggestive of PAD. Majority of study participants who met inclusion criteria had normal peripheral arterial parameters (ABI (81% right, 52.9%left), TBI (75.2% right, 66.1%left) and PVR (>86% toe,>96% ankle)).We found a significantly higher seated brachial blood pressure on the right when compared with the left (P <0.001). Likewise, a significantly higher Ankle Brachial Index (ABI) was found on the right side (1.06±0.08 right vs. 1.00±0.09 left) (P<0.0001). The overall mean Toe Brachial Index (TBI) was 0.77±0.11 and 0.74±0.14 on the right and left respectively, and did not differ significantly between the two sides. In general, males had higher brachial blood pressures and ABI than females. When compared to the AHA normal reference range the values for the lower limits of our population’s 95%confidence interval (right ABI =0.9 and left ABI=0.82) fell below the reference range (ABI=1.00-1.3) Conclusion and Recommendation Despite comparable values between our population mean ABI and TBI with that of AHA, interpretation of right and left ABI in healthy young black Africans, using established cut-offs should be done with caution, given the relatively lower values on the left. In addition, based on the findings of ABI and TBI being lower than established standards (AHA) for normal in apparently healthy young adults, lower values for ABI and TBI might not necessarily mean abnormalities in this age group. Further research to clarify these findings and confirm whether the lower limit of normal references in a population of healthy young adults should be lowered, is warranted.