Ankle Brachial Index Measurement: What is it and why measure it? Mary O’Connor Cardiovascular Medical Science Liason Bristol Myers Squibb Guinness Storehouse 31 st March 2006

Ankle Brachial Index Measurement Non-invasive, rapid, quantitative measurement for assessing the arterial circulation 95% sensitivity, 99% specific An ABI ≤ 0.90 is diagnostic of PAD –Permits stratification of the severity of PAD Assess disease progression Predict cardiovascular and cerebrovascular mortality Mohler, E. Arch Intern Med. 2003;

How is Ankle-Brachial Index (ABI) measured? Measure ankle and brachial systolic pressures with Doppler Use highest arm and each ankle pressures 1,2 1. TASC Working Group. Int Angiol 2000; 19 (suppl): Vascular Disease Foundation, Available at: Ankle systolic pressure Brachial systolic pressure ABI =

Ankle Brachial Index Measurement

Calculation of the of Ankle Brachial Index Pre-Procedure: Position: Resting supine ≥ 5 minutes prior to the measurement Allay anxiety: explain procedure and reassure patient Allay anxiety: explain procedure and reassure patientEquipment: Handheld Doppler 5-10 MHz Ultrasound gel Sphygomanometer: anaeroid or mercury

Measurement of the Ankle Brachial Index Arms: Place BP cuff on arm, Palpate the brachial pulse Apply ultrasound gel Angle the doppler probe between 45-65° angle Inflate the BP cuff until signal abolished Deflate slowly until signal returns Record the pressure at which signal returns, then deflate cuff completely Take the highest of the 2 systolic brachial pressures Take the highest of the 2 systolic brachial pressures

Measurement of the Ankle Brachial Index Legs: Legs: Place cuff around leg just above the ankle Locate and record both the Posterior Tibial and Dorsalis Pedis systolic pressures in each limb Repeat the procedure as for arms Take the highest ankle systolic pressure in each limb for the ABI ratio Take the highest ankle systolic pressure in each limb for the ABI ratio

Brachial Systolic blood pressure –Right: 156/88 mmHg –Left: 160/92 mmHg –Right leg: DP: 160 mmHg DP: 160 mmHg PT: 154 mmHg PT: 154 mmHg 160/160 = /160 = 1.00 –Left leg: DP: 96 mmHg DP: 96 mmHg PT: 100 mmHg PT: 100 mmHg 100/160 = /160 = 0.63 The lowest ABI between both legs is the ABI that stratifies the patient’s risk DP: 160 mm Hg PT: 154 mmHg Right 156 mmHg Left 160 mmHg Diagnosis: moderate PAD in left leg ABI measurement DP: 96 mmHg PT: 100 mm Hg

How is Ankle-Brachial Index (ABI) measured? Right side Measurements Left side 156 Brachial Systolic Blood Pressure Dorsalis Pedis Posterior Tibialis Highest each ankle pressure Highest Brachial Pressure ABI0.63

Interpretation of ABI Normal ABI: ≥ 0.91 – ≤1.30 An ABI ≤ 0.90 is diagnostic of PAD –Mild PAD: –Moderate PAD: –Severe PAD or Critical Limb Ischaemia: ≤ 0.4 Non-compressible: ≥ 1.31 Hiatt, WR. NEJM. 2001; 344:

Limitations of the ABI Measurement Non-compressible arteries: ABI values  Refer for other noninvasive testing Bilateral brachial pressures –Difference of 20mmHg indicates arterial disease in upper extremity 2 Inability to localise arterial lesion accurately 1. Weitz et al. Circulation. 1996; 94: Ollin JW www.svmb.org/medpro/cme/p1/cme_part1.html

ABI to Monitor Disease Progression Changes in ABI +/ indicate disease re/progression 1 An improved ABI suggest enhanced perfusion via collateral vessels A deterioration in ABI suggests disease progression or decreased perfusion secondary to revascularization procedure problems 1. Mohler, E. Arch Intern Med. 2003; 163:

ABI to Assess Functional Capacity Decreasing ABI values are independently associated with impaired lower extremity functioning 1, 2 Lower ABI scores are associated with –Slower walking velocity 1, 2 –fewer blocks walked per week 1,2 –Lower hip abduction force 2 –Lower knee extension force 2 1. MeDermott et al, Circulation. 2000; 101: Vogt et al, Journal Am Geriatric Society. 1994; 42:

Peripheral Arterial Disease Peripheral Arterial Disease is a manifestation of systemic atherosclerosis in which the arterial lumen of the lower extremities becomes progressively occluded by atherosclerotic plaque 1 it may be symptomatic or asymptomatic It is a distinct atherothrombotic syndrome 1. Criqui et al. In: Fowkes FGR, ed. Epideminiology of Peripheral Vascular Disease. New York, NY: Springer-Verlag; 1991:85096

5-year natural history of PAD 100 patients with asymptomatic PAD 100 patients with claudication who do not seek medical advice Local Events 100 patients diagnosed with claudication Systemic Events CHD15 Other cardiovascular and cerebrovascular 5 Non-cardiovascular 10 PLUS Major amputation 2 patients 10 to 20 non-fatal MIs or strokes Dormandy JA. Hosp Update 1991;April:314– deaths: Surgical revascularization 10 patients Worsening claudication 25 patients

Symptomatic PAD 10 year mortality for Patients with large vessel PAD: The risk of all cause mortality and death from CHD is more than 3 and 6 times respectively greater than in patients with no PAD 1 3 fold excess cardiovascular morbidity at baseline compared with control subjects of the same sex 2 1. Criqui et al. N Eng J Med. 1992; 326: Criqui et al. Drugs. 1991; 42 (supp 5): 16-21

Asymptomatic PAD Asymptomatic PAD associated with an increased risk of –atherothrombotic events ( MI and Stroke) 1, 2 –Impaired lower extremity functioning 3 –Internal artery carotid stenosis 4, 5 Patients with asymptomatic PAD have a risk factor and co-moribidity profile comparable to that of symptomatic patients 1 1. Hooi et al. Scand J Prim Health Care. 1998; 16: Criqui et al. Vasc Med. 1998; 3: McDermott et al. Circulation. 2000; 101: Simons et al. J Vasc Surg. 1999; 30: House et al. Cardiovascular Surgery. 1999; 7: 44-49

Risk of death is increased in patients with both symptomatic and asymptomatic PAD *Kaplan-Meier survival curves based on mortality from all causes. † Large-vessel PAD. Normal subjects* Asymptomatic PAD † Symptomatic PAD † Severe symptomatic PAD † Survival (% of patients) Year Criqui MH et al. N Engl J Med 1992; 326:

ABI as a Predictor of Cardiovascular Morbidity and/or Mortality Reduced ABI is a significant independent predictor of cardiovascular and coronary mortality Prognosis varies with multiple risk factors and/or severity of disease

ABI – inverse relationship with 5-year risk of cardiovascular events and death Dormandy JA, Creager MA. Cerebrovasc Dis 1999;9(Suppl 1):1–128 (Abstr 4). 10.2% relative risk increase per 0.1 decrease in ABPI (p = 0.041) ABPI Risk relative to ABPI

Resnick HE et al. Circulation 2004; 109: There is a strong two way association between decreased ABI and increased risk for cardiovascular death 1 Baseline ABI* Percent (%) <0.60 (n=25) <0.70 (n=21) 0.70-<0.80 (n=40) 0.80-<0.90 (n=130) 0.90-<1.0 (n=195) 1.0-<1.10 (n=980) All-cause mortality CVD mortality *Mean participant follow-up 8.3 years

Atherothrombosis is a Systemic Disease: Increase for Myocardial Infarction and Stroke as a Function of ABI Measurement 1 x Ankle-brachial index (ABI) index Dormandy JA, Creager MA. Cerebrovasc Dis 1999;9(Suppl 1):1–128 Shelley, E. Dept of Health & Children 2004

Referral to a Vascular Surgeon Primary Care Team –Not confident of making the diagnosis –Lack the resources to initiate & monitor best medical practice –Unacceptable symptoms despite a trial and adherence to best medical practice –Weak or absent femoral pulses –All Diabetic Patients Urgent: –Critical Limb Ischaemia/ Rest Pain –Ulceration or Gangrene –Suspected AAA / TIA / Amaurosis Fugax Burns et al, BMJ, 2003; 326:

Ankle Brachial Index Measurement-Key Learning Points ABI measurement single most valuable test for assessing the arterial circulation Simple, portable, inexpensive, non-invasive, rapid, quantitative measurement An ABI ≤ 0.90 is diagnostic of PAD Permits stratification of the severity of PAD Predicts cardiovascular and cerebrovascular mortality Should ideally be performed in the primary care setting