Ankle Brachial Index Measurement: What is it and why measure it?

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

2. 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; 2306-2314

3. Ankle systolic pressure Brachial systolic pressure How is Ankle-Brachial Index (ABI) measured? • Measure ankle and brachial systolic pressures with Doppler • Use highest arm and each ankle pressures1,2 ABI = 1. TASC Working Group. Int Angiol 2000; 19 (suppl): 5-34. 2. Vascular Disease Foundation, 2003. Available at:http://www.vdf.org/ABI.htm.

4. Ankle Brachial Index Measurement

5. 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 Equipment: Handheld Doppler 5-10 MHz Ultrasound gel Sphygomanometer: anaeroid or mercury

6. 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 highestof the 2 systolic brachial pressures

7. Measurement of the Ankle Brachial Index 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 highestankle systolic pressure in eachlimbfor the ABI ratio

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

9. How is Ankle-Brachial Index (ABI) measured?

10. Interpretation of ABI • Normal ABI: ≥ 0.91 – ≤1.30 • An ABI ≤ 0.90 is diagnostic of PAD • Mild PAD: 0.70- 0.90 • Moderate PAD: 0.41-0.69 • Severe PAD or Critical Limb Ischaemia: ≤ 0.4 • Non-compressible: ≥ 1.31 Hiatt, WR. NEJM. 2001; 344: 1608-1621

11. Limitations of the ABI Measurement • Non-compressible arteries: ABI values 1.311 Refer for other noninvasive testing • Bilateral brachial pressures • Difference of 20mmHg indicates arterial disease in upper extremity2 • Inability to localise arterial lesion accurately 1. Weitz et al. Circulation. 1996; 94: 3026-3049 2. Ollin JW. www.svmb.org/medpro/cme/p1/cme_part1.html 2000

12. ABI to Monitor Disease Progression Changes in ABI +/- 0.15 indicate disease re/progression1 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: 2306-2314

13. ABI to Assess Functional Capacity • Decreasing ABI values are independently associated with impaired lower extremity functioning1, 2 • Lower ABI scores are associated with • Slower walking velocity1, 2 • fewer blocks walked per week1,2 • Lower hip abduction force2 • Lower knee extension force2 1. MeDermott et al, Circulation. 2000; 101:1007-1012 2. Vogt et al, Journal Am Geriatric Society. 1994; 42: 923-929

14. 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 plaque1 • 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

15. 5-year natural history of PAD 100 patientswith claudication who do notseek medical advice 100 patients with asymptomatic PAD 100 patients diagnosedwith claudication Local Events Systemic Events Worsening claudication25 patients 10 to 20 non-fatal MIs or strokes PLUS Surgical revascularization 10 patients 30 deaths: • CHD 15 • Other cardiovascular and cerebrovascular 5 • Non-cardiovascular 10 Major amputation 2 patients Dormandy JA. Hosp Update 1991;April:314–318.

16. 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 PAD1 • 3 fold excess cardiovascular morbidity at baseline compared with control subjects of the same sex2 1. Criqui et al. N Eng J Med. 1992; 326: 381-386 2. Criqui et al. Drugs. 1991; 42 (supp 5): 16-21

17. Asymptomatic PAD • Asymptomatic PAD associated with an increased risk of • atherothrombotic events ( MI and Stroke)1, 2 • Impaired lower extremity functioning3 • Internal artery carotid stenosis4, 5 • Patients with asymptomatic PAD have a risk factor and co-moribidity profile comparable to that of symptomatic patients1 1. Hooi et al. Scand J Prim Health Care. 1998; 16: 177-182 2. Criqui et al. Vasc Med. 1998; 3: 241-245 3. McDermott et al. Circulation. 2000; 101: 1007-1012. 4. Simons et al. J Vasc Surg. 1999; 30: 519-525 5. House et al. Cardiovascular Surgery. 1999; 7: 44-49

18. Risk of death is increased in patients with both symptomatic and asymptomatic PAD 100 Normal subjects* 75 Asymptomatic PAD† 50 Survival (% of patients) Symptomatic PAD† 25 Severe symptomatic PAD† 0 0 2 4 6 8 10 12 Year *Kaplan-Meier survival curves based on mortality from all causes.†Large-vessel PAD. Criqui MH et al. N Engl J Med 1992; 326: 381-386.

19. 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

20. 2.5 2.0 1.5 1.0 0.0 0.2 0.4 0.6 0.8 1.0 ABPI ABI – inverse relationship with 5-year risk of cardiovascular events and death 10.2% relative risk increaseper 0.1 decrease in ABPI (p = 0.041) Risk relative to ABPI Dormandy JA, Creager MA. Cerebrovasc Dis 1999;9(Suppl 1):1–128 (Abstr 4).

21. There is a strong two way association betweendecreased ABI and increased risk for cardiovascular death1 70 60 All-cause mortality CVD mortality 50 40 Percent (%) 30 20 10 0 <0.60 (n=25) 1.0-<1.10 (n=980) 0.90-<1.0 (n=195) 0.60-<0.70 (n=21) 0.70-<0.80 (n=40) 0.80-<0.90 (n=130) *Mean participant follow-up 8.3 years Baseline ABI* Resnick HE et al. Circulation 2004; 109: 733-739.

22. Atherothrombosis is a Systemic Disease: Increase for Myocardial Infarction and Stroke as a Function of ABI Measurement1 2.5 x 2.2 2.0 1.5 1.0 1.0 0.8 0.6 0.4 0.2 Ankle-brachial index (ABI) index • Shelley, E. Dept of Health & Children 2004 Dormandy JA, Creager MA. Cerebrovasc Dis 1999;9(Suppl 1):1–128

23. 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: 584-588

24. 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