Peripheral arterial disease screening
Peripheral arterial disease Microchapters
AHA/ACC Guidelines on Management of Lower Extremity PAD
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Synonyms and Keywords: Ankle-brachial index; ankle brachial index; ABI; ankle-arm index; ankle-brachial blood pressure index, ankle-arm ratio; Winsor index
A resting ankle brachial index (ABI) is the screening study of choice in a patient who has suspected lower extremity peripheral arterial disease. The ankle brachial index is an indicator of atherosclerosis and it provides prognostic information even in the absence of any symptoms of peripheral arterial disease. It is defined as the ratio of the ankle blood pressure divided by the highest brachial blood pressure. An ankle branchial index should be obtained if a patient has one or more of the following characteristics: 1) exertional claudication; 2) presence of nonhealing wounds; 3) age over 50 with a history of smoking or diabetes or 4) age over 65.
Ankle Brachial Index (ABI)
- The ABI is a screening test for the assessment of the presence of PAD. Studies in 2006 suggests that an abnormal ABI may be an independent predictor of mortality, as it reflects the burden of atherosclerosis.
- The blood pressure in the ankle is higher than that in the arms because the blood pressure wave gets amplified as it propagates away from the heart causing the systolic blood pressure to increase and the diastolic pressure to decrease. In fact, two factors are involved in the amplification of the blood pressure distally from the heart:
- Retrograde wave reflection from resistant distal arterioles that adds up to the antegrade blood pressure wave.
- Remodelling and increased stiffness of the blood vessels in the legs as evidenced by increased wall thickening and and unchanged inner radius, secondary to the increased hydrostatic pressure while walking.
- It should be noted that the ABI varies by age, ethnicity, gender, and height:
- The pressures in the posterior tibial artery and dorsalis pedis artery in the feet and the brachial artery at the elbow are estimated. A Doppler probe is used, through a device called the Pulse Volume Recorder (some variances may apply depending on the physician), to monitor the pulse while a sphygmomanometer (blood pressure cuff) is inflated above the artery. The cuff is deflated and the pressure at which the pulse returns is recorded. The blood pressures are measured after 10 minutes of rest.
- All patients with symptoms suggestive of PAD
- All patients more than 65 years old
- All patients more than 50 years old but less than 69 years old who are smokers or have diabetes
ABI Measurement at Rest
- The ABI is the ratio of the ankle to the highest brachial blood pressure and an ABI of greater than 0.9 is considered normal, suggesting that there is no significant peripheral vascular disease affecting the vessels of the legs.
- ABI should be measured in both legs in all new patients with PAD of any severity to confirm the diagnosis and establish a baseline.
Interpretation of the ABI Results at Rest
- 0.9 to 1.3: Normal
- 0.5 to 0.7: Moderate
- < 0.50: Severe
- ≥ 1.4: Poorly compressible vessels
- A value greater than 1.4 is considered abnormal, and suggests calcification of the walls of the arteries and noncompressible vessels, reflecting severe peripheral vascular disease.
ABI Measurement in Exercise Testing
- The exercise ABI is done by having the patient stand on their toes repeatedly. The ABI is rechecked after exercise. This test is done if the patient has symptoms with exercise. However, patients with peripheral artery disease can have normal ABI at rest; however, they show abnormal ABI measurements after stress exercise.
- During exercise, the systolic pressure increases causing an increase in the pressure difference beyond the diseased vessel. Hence, the ABI will decrease. An abnormal result is a drop of > 20% on ABI in one minute, despite a normal ABI at rest.
- Patients who can not tolerate the treadmill exercise can do the tip toe exercise as an alternative.
Interpretation of the ABI Results with Exercise
- 0.5 to 0.9: Mild
- 0.15 to 0.8: Moderate
- < 0.15: Severe
Evaluation of the Severity of the Arterial Occlusive Disease Based on the Tolerance to Exercise Testing
- Exercise tolerance less than 5 minutes: Moderate
- Exercise tolerance less than 3 minutes: Severe
- When the vessels are stiff, as in the case of diseases like diabetes, the ABI index is inaccurate in the evaluation of the severity of the arterial occlusive diseases.
- Toe-brachial index is a reliable alternative when the vessels are stiff and non compressible.
- The normal range for the toe-brachial pressure index is values more than 0.70.
Segmental Pressures Examination
- Segmental pressure examinations is basically applying the same ABI principle but on different parts of the extremities.
The Appropriate Management Actions Following Screening with ABI
Shown below is a table summarizing the interpretation of the ABI values and the appropriate actions to be taken accordingly:
|ABI value||Interpretation||Action||Nature of ulcers, if present|
Vessel hardening from PVD
|Refer routinely||Venous ulcer|
use full compression bandaging
|1.0 - 1.2||Normal range||None|
|0.9 - 1.0||Acceptable|
|0.8 - 0.9||Some arterial disease||Manage risk factors|
|0.5 - 0.8||Moderate arterial disease||Routine specialist referral||Mixed ulcers|
use reduced compression bandaging
|Under 0.5||Severe arterial disease||Urgent specialist referral||Arterial ulcers|
no compression bandaging used
Prognosis Associated with Ankle Brachial Indexes (ABI)
- Normal ABI in the presence of symptoms: No change in the mortality rate
- ABI < 0.85: 10% five year mortality rate
- ABI < 0.4: 50% one year mortality rate
2012 AHA Guidelines for Measurement and Interpretation of the Ankle-Brachial Index (DO NOT EDIT)
Measurement of the ABI (DO NOT EDIT)
|"1. The Doppler method should be used to measure the SBP in each arm and each ankle for the determination of the ABI. (Level of Evidence: A) "|
|"2. The cuff size should be appropriate with a width at least 40% of the limb circumference. (Level of Evidence: B) "|
|"3. The ankle cuff should be placed just above the malleoli with the straight wrapping method. (Level of Evidence: B) "|
|"4. Any open lesion with the potential for contamination should be covered with an impermeable dressing. (Level of Evidence: C) "|
|Class III (No Benefit)|
|"1. The use of the cuff over a distal bypass should be avoided (risk of bypass thrombosis).(Level of Evidence: C)"|
Measurement of the Systolic Pressures of the 4 Limbs (DO NOT EDIT)
|"1. Each clinician should adopt the following sequence of limb pressure measurement for the ABI at rest: first arm, first PT artery, first DP artery, other PT artery, other DP artery, and other arm.(Level of Evidence: C "|
|"2. After the measurement of systolic pressures of the 4 limbs, if the SBP of the first arm exceeds the SBP of the other arm by >10 mm Hg, the blood pressure of the first arm should be repeated, and the first measurement of the first arm should be disregarded. (Level of Evidence: C) "|
Calculation of the ABI (DO NOT EDIT)
|"1. The ABI of each leg should be calculated by dividing the higher of the PT or DP pressure by the higher of the right or left arm SBP. (Level of Evidence: A) "|
|"2. When ABI is used as a diagnostic tool to assess patients with symptoms of PAD, the ABI should be reported separately for each leg. (Level of Evidence: C) "|
|"3. When the ABI is used as a prognostic marker of cardiovascular events and mortality, the lower of the ABIs of the left and right leg should be used as the prognostic marker of cardiovascular events and mortality. The exception to this recommendation is the case of noncompressible arteries. (Level of Evidence: C) "|
|"1. For any situation, when the ABI is initially determined to be between 0.80 and 1.00, it is reasonable to repeat the measurement. (Level of Evidence: B) "|
Use and Interpretation of the ABI in Case of Clinical Presentation of Lower-Extremity PAD (DO NOT EDIT)
|"1. In the case of clinical suspicion based on symptoms and clinical findings, the ABI should be used as the first line noninvasive test for the diagnosis of PAD. (Level of Evidence: A) "|
|"2. An ABI <0.90 should be considered the threshold for confirming the diagnosis of lower extremity PAD. (Level of Evidence: A) "|
|"3. When the ABI is >0.90 but there is clinical suspicion of PAD, post-exercise ABI or other noninvasive tests, which may include imaging, should be used. (Level of Evidence: A) "|
|"4. When the ABI is >1.40 but there is clinical suspicion of PAD, a toe-brachial index or other noninvasive tests, which may include imaging, should be used. (Level of Evidence: A) "|
|"1. It is reasonable to consider a post-exercise ankle pressure decrease of >30 mm Hg or a post-exercise ABI decrease of >20% as a diagnostic criterion for PAD. (Level of Evidence: A) "|
Interpretation of the ABI During Follow-Up (DO NOT EDIT)
|Class III (No Benefit)|
|"1. The ABI should not be used alone to follow revascularized patients. (Level of Evidence: C)"|
|"1. An ABI decrease of >0.15 over time can be effective to detect significant PAD progression. (Level of Evidence: B) "|
Interpretation of the ABI as a Marker of Subclinical CVD and Risk in Asymptomatic Individuals (DO NOT EDIT)
|"1. Individuals with an ABI <0.90 or >1.40 should be considered at increased risk of cardiovascular events and mortality independently of the presence of symptoms of PAD and other cardiovascular risk factors. (Level of Evidence: A) "|
|"1. The ABI can be used to provide incremental information beyond standard risk scores in predicting future cardiovascular events. (Level of Evidence: A) "|
|"1. Subjects with an ABI between 0.91 and 1.00 are considered “borderline” in terms of cardiovascular risk. Further evaluation is appropriate. (Level of Evidence: A) "|
Management of Patients With Peripheral Artery Disease (Compilation of 2005 and 2011 ACCF/AHA Guideline Recommendations) : A Report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines
|"1. The resting ABI should be used to establish the lower extremity PAD diagnosis in patients with suspected lower extremity PAD, defined as individuals with 1 or more of the following: exertional leg symptoms, nonhealing wounds, age 65 years and older, or 50 years and older with a history of smoking or diabetes.(Level of Evidence: B)"|
|"2. The ABI should be measured in both legs in all new patients with PAD of any severity to confirm the diagnosis of lower extremity PAD and establish a baseline.(Level of Evidence: B)"|
|"3. The toe-brachial index should be used to establish the lower extremity PAD diagnosis in patients in whom lower extremity PAD is clinically suspected but in whom the ABI test is not reliable due to noncompressible vessels (usually patients with long-standing diabetes or advanced age). (Level of Evidence: B)"|
|"4. Leg segmental pressure measurements are useful to establish the lower extremity PAD diagnosis when anatomic localization of lower extremity PAD is required to create a therapeutic plan. (Level of Evidence: B)"|
|"5. ABI results should be uniformly reported with noncompressible values defined as greater than 1.40, normal values 1.00 to 1.40, borderline 0.91 to 0.99, and abnormal 0.90 or less. (Level of Evidence: B)"|
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