The Value Of Ankle Brachial Index In Predicting And Diagnosing Atherosclerosis Diseases

Introduction and ObjectiveAtherosclerotic diseases are the main cause of mortality worldwide. Atherosclerosis is a systemic disease,it not only affect coronary artery,but also affect peripheral large artery.Peripheral artery disease(PAD)is an important manifestation of systemic atherosclerosis.Defined as equivalent dangerous disease to coronary heart disease(CHD),PAD is associated with cardiovascular disease(CVD)and increased the risk of CVD and mortality.Moreover,PAD is a drastic factor in predicting cardiac and cerebral vessels event including myocardial infarction,stroke,mortality,etc.. Among most of the examination methods on PAD assessing,ankle-brachial index (ABI)measurement is a simple,quick and non-invasive screening test,and is very charming now.ABI is the ratio of the ankle to brachial systolic blood pressure,and has been publicly considered as one of the commonly used and utility non-invasive measurements of PAD diagnosis.Recently,the American College of Cardiology and the American Heart Association(ACC/AHA)guidelines recommended an ABI≤0.90 as the criterion for the diagnosis of PAD.However,this cut-off point was based on research in European and American populations and there has not been a report about whether the threshold value differs between races.In addition,there are no reports on the threshold value of ABI in detecting PAD in Asian and especially in Chinese patients. Among all the patients with cardiac and cerebral vessels diseases risk factors,which with or without cardiac and cerebral vessels diseases,the associated risk factor, morbidity and therapeutic rate to PAD and the relationship between ABI and atherosclerotic diseases has not been investigated systematically by epidemiological methods in China.The aim of the present study was to prospectively evaluate the relationship between ABI and the incidence rate of cardiac and cerebral vessels diseases,and to identify if ABI can be a simple non-invasive screening test for high-risk group of atherosclerotic diseases.At the same time,this study further to evaluate prospectively the sensitivity and specificity of ABI with conventional digital subtraction angiography(DSA)as the reference standard in the assessment of lower extremity arteries,and to research the threshold value of ABI screening test in diagnosing PAD in Chinese population.Materials and MethodsThe present study included:(1)To obtain data on the epidemiology, co-morbidities and risk factor profile of PAD,we evaluated the clinical significance of ABI as an indicator of PAD in Chinese patients with high cardiovascular(CV)risk; (2)To evaluate prospectively the sensitivity and specificity of ABI with conventional DSA as the reference standard in the assessment of lower extremity arteries,and(3)To research the threshold value of ABI screening test in diagnosing periphery arterial disease(PAD).Materials:(1)5,646 Chinese patients over 50 years of age with two or more CV risk factors who attended the inpatient department in Tongji University Hospitals(Shanghai)and Beijing University Hospital(Beijing)were sequentially enrolled in the study.All subjects were inpatients from the Departments of Cardiology, Coronary Care Unit,Intensive Care Unit,Endocrinology,Renal Disease,Neurology, etc.,and were admitted to the hospital because of hypertension,hyperlipidemia, diabetes,stroke,acute coronary syndrome,renal disease,vascular disease,and so on. Measurements were carried out after a 5-min rest in the supine position with the upper body as fiat as possible.The investigators were specifically trained for 1 week to perform ABI measurements under standardized conditions.The Vascular Profiler-1000(Model BP203RPEⅡ,From PWV/ABI,OMRON Colin Medical Instruments,Tokyo,Japan),which has been approved by the US Food and Drug Administration,was used to obtain blood pressure(BP)in all 4 extremities.ABI was calculated as the ratio of the ankle Systolic blood pressure(SBP)to the brachial SBP on the homolateral side.PAD was defined as an ABI＜0.9 in either leg.The results were compared between the ABI≥0.9和ABI＜0.9 group.Multivariable logistic regression analyses were performed to identify factors associated with PAD;(2)A total of 383 consecutive patients(245 men and 138 women,mean age 64.1±11.7 years)inpatient department in Tongji University Hospitals(Shanghai)and Shengjing Hospital of China Medical University(Shenyang)underwent conventional DSA,ABI measurement,and questionnaire survey.Receiver operator characteristics(ROC)analysis was performed to assess possible threshold values that predict PAD in Chinese patients,including area under the curve,sensitivity,specificity,positive and negative likelihood ratios(LR+, LR-).ResultsA total 5,263 patients were analyzed,52.9%male,mean age67.3 years,mean body mass index(BMI)24.2kg/m2,mean systolic/diastolic blood pressure(SBP/DBP) 139.0/80.7mmHg.The prevalence of PAD in the total group of patients was 25.4%,and the prevalence was higher in female than in male(27.1%vs 23.9%;odds ratio [OR]:1.64).patients with PAD were older than those without PAD(72.3±9.9 years vs.65.6±11.7 years;OR:1.06),and more frequently had diabetes(43.3%vs.31.3%; OR:2.02),coronary heart disease(CHD)(27.0%VS.18.8%;OR:1.67),stroke(44.4%vs. 28.3%;OR:1.78),lipid disorders(57.2%vs.50.7%;OR:1.30)and a smoking habit (42.7%vs.38.6%;OR:1.52).The Ors for the PAD group compared with the non-PAD group demonstrated than these conditions were inversely related to ABI.Statin, angiotensin-converting anzyme-inhibitor and antiplatelet agents were only used in 40.5%,53.6%and 69.1%of PAD patients,respectively.And conventional DSA used as gold standard in defining≥50%luminal stenosis for the diagnosis of lower extremity PAD.So in this cohort the morbidity of PAD was 7.57%.When DSA was used as the golden standard in defining≥30%luminal stenosis for the diagnosis of lower extremity PAD,the morbidity was 17.0%.When DSA was used as the golden standard in defining≥50%luminal stenosis for the diagnosis of lower extremity PAD,the sensitivity,specificity,LR+and LR- ratios of different cut-off points of the ABI were as follows:at a cut-off point of 1.05,sensitivity 100%,specificity 37.9%,LR+1.61;LR-0.23; at a cut-off point of 0.95,sensitivity 93.1%,specificity 85.0%,LR+6.21;LR-0.08; at a cut-off point of 0.90,sensitivity 79.3%,specificity 91.0%,LR+ 8.81;LR-0.23; at a cut-off point of 0.58,sensitivity 41.4%,specificity 100.0%,LR-0.59.DSA used as a gold standard in defining lesions≥50%the area under the ROC curve was 0.953(95%CI 0.920,0.985).The mean ABI were 1.08,1.05,0.99,0.66,0.55 and 0.54 respectively in 1,2,3,4,5,6 grade stenosis in lower extremity.The greater the stenosis of the artery of the lower extremity,the lower the ABI value.Conclusions(1)The data demonstrated that the high prevalence and low treatment of PAD in Chinese patients at high CV risk.(2)A lower ABI was associated with age,female sex, BMI,TC,HDL-C,CRE,uric acid,coronary atherosclerosis heart disease,diabetes, stroke,and smoking.(3)ABI measurement is an accurate and reliable non-invasive alternative to conventional DSA in the assessment of lower extremity arteries in patients with peripheral arterial disease.And(4)a cut-off 0.95 of ABI is the threshold value in detecting PAD in Chinese population.