Clinical Vascular Examination and Physiologic Testing

6.1Clinical assessment and indications

Peripheral artery disease (PAD) prevalence rises from approximately 5% in middle-aged adults to more than 18% among the oldest groups in high-income cohorts Criqui 2015. It shares major atherosclerotic risk factors with coronary and cerebrovascular disease, predominantly smoking, diabetes mellitus, hypertension, and dyslipidaemia.

Evaluation begins with a targeted history and structured bedside examination. Symptomatic presentation ranges from classic intermittent claudication to atypical exertional symptoms, walking impairment without recognized claudication, rest pain, or tissue loss. History assessment evaluates walking distance, pace, grade, reproducibility, relief with rest, prior interventions, and whether symptoms are limited by hip, knee, back, or pulmonary disease ACC/AHA 2024 · McDermott 2001.

Clinical examination features include:

• Dependent rubor, pallor on elevation, and trophic skin changes.
• Ulceration, tissue loss, deformity, and temperature asymmetry.
• Assessment of bilateral femoral, popliteal, dorsalis-pedis, and posterior-tibial pulses, and auscultation for femoral bruits.
• Identification of conditions that render arteries noncompressible, particularly advanced age, diabetes, and end-stage renal disease ACC/AHA 2024 · NICE CG147.

Targeted resting physiologic testing is indicated when history or examination suggests PAD, and as case finding for adults aged 65 years and older, or aged 50 years and older with a history of diabetes or smoking. Population-wide testing in asymptomatic adults without atherosclerotic risk factors is not indicated AHA/ACC 2016 · AUC PVUS 2012.

Men aged 65 to 75 years with any smoking history receive concurrent one-time abdominal ultrasound screening for abdominal aortic aneurysm, defined as an aortic diameter >= 3.0 cm USPSTF 2019.

6.2Ankle-brachial index and interpretation

The resting ankle-brachial index (ABI) is calculated by dividing the highest ankle systolic pressure (dorsalis pedis or posterior tibial) by the higher of the two brachial systolic pressures. Measurements are obtained supine using a manual Doppler, assessing both arms and both ankles AHA 2012 · NICE CG147.

Bilateral arm pressure measurement is mandatory. An interarm systolic pressure difference of >= 10 mmHg is associated with PAD. A difference of >= 15 mmHg indicates high cardiovascular risk and is associated with subclavian stenosis, cerebrovascular disease, and increased all-cause mortality. Using the higher brachial pressure prevents false elevation of the ABI by occult proximal upper-extremity disease AHA 2012 · Clark 2012.

Diagnostic categories for the resting ABI are defined as follows:

• 1.00 to 1.40: Normal.
• 0.91 to 0.99: Borderline.
• <= 0.90: Abnormal, diagnostic of PAD.
• > 1.40: Noncompressible, indicating medial arterial calcification and an unreliable index AHA 2012.

An abnormal ABI (<= 0.90) and a high ABI (> 1.40) are both associated with approximately doubled 10-year all-cause and cardiovascular mortality compared to the normal range Fowkes 2008. Both values establish high systemic risk and warrant secondary prevention targeting smoking cessation, body mass index, physical activity, diet, total cholesterol, blood pressure, and fasting plasma glucose AHA 2010.

6.3Physiologic rescue and localisation testing

When the resting ABI is nondiagnostic, unreliable, or discordant with symptoms, secondary physiologic tests confirm the diagnosis and localise disease.

Chronic limb-threatening ischaemia (CLTI). Diagnosis is clinical and haemodynamic, not symptomatic alone. Ischaemic rest pain is supported by an ankle systolic pressure < 50 mmHg or a toe pressure < 30 mmHg; with tissue loss the thresholds rise to an ankle pressure < 70 mmHg or a toe pressure < 50 mmHg, reflecting the higher perfusion demand for wound healing. A transcutaneous oxygen tension (TcPO2) < 30 mmHg supports CLTI when ankle and toe pressures are noncompressible or unreliable ACC/AHA 2024 · GVG 2019.

Toe-brachial index (TBI). Digital arteries are less prone to medial calcification. A TBI <= 0.70 supports the diagnosis of PAD and serves as the primary rescue test when the resting ABI is > 1.40, or when borderline (0.91 to 0.99) in symptomatic patients ACC/AHA 2024 · AHA 2012.

Exercise ABI. Provocation testing unmasks haemodynamic fall absent at rest. It is indicated for symptomatic patients with a normal (1.00 to 1.40) or borderline (0.91 to 0.99) resting ABI. Using a standardized treadmill protocol, a post-exercise ankle systolic pressure drop of >= 20% or an ABI decrease of >= 20% from baseline indicates exercise-unmasked PAD AUC PVUS 2012 · AHA 2012.

Segmental pressures and waveforms. Multilevel cuffs (high-thigh, low-thigh, calf, ankle) localise disease prior to anatomic imaging. An adjacent-cuff systolic pressure gradient of >= 20 mmHg indicates haemodynamically significant disease at the intervening segment. Pulse-volume recordings provide morphological waveform data that complement pressure readings, particularly when noncompressible vessels yield falsely elevated segmental pressures. High-thigh cuff artefact and bilateral inflow disease can confound interpretation ACC/AHA 2024 · AUC PVUS 2012.

6.4Diagnostic logic and imaging selection

Anatomic imaging is a revascularization planning tool, not a first-line diagnostic reflex. It is pursued once physiologic testing confirms PAD and the severity of symptoms or tissue loss warrants intervention ACC/AHA 2024.

For revascularization candidates, duplex ultrasound and computed tomography angiography (CTA) are first-line modalities. Magnetic resonance angiography (MRA) is used when renal function or cumulative radiation exposure precludes CTA. Catheter angiography is reserved for concurrent endovascular intervention or when noninvasive imaging fails to resolve the anatomy ACR 2022.

1. Measure the resting ankle-brachial index first, substituting the toe-brachial index when the ankles are noncompressible (suspected medial calcification).
2. Obtain segmental pressures with Doppler waveforms or pulse-volume recordings to localise the level of disease.
3. Add exercise or post-occlusive testing when resting indices are normal but symptoms persist.
4. Proceed to duplex ultrasound, then to cross-sectional CTA or MRA or catheter angiography, only when intervention is planned.

Physiologic testing logic and rescue pathways

6.5Areas of controversy

Thresholds for segmental limb pressure gradients vary among accredited vascular testing facilities; while >= 20 mmHg is the standard criterion for a haemodynamically significant lesion, some laboratories validate and use a >= 30 mmHg threshold to prioritize diagnostic specificity AUC PVUS 2012 · IAC 2025.

Exercise ABI relies heavily on protocol standardization. Standardised treadmill protocols (e.g., Gardner-Skinner) are well validated, but timing of post-exercise measurement and the use of alternative provocation strategies (such as reactive hyperaemia or active pedal plantarflexion for patients with severe limitations) can alter the magnitude of the measured haemodynamic drop AUC PVUS 2012.

Nomenclature frameworks remain in transition. Historical classification languages, particularly TASC II lesion categories and the term "critical limb ischemia", permeate historical reports but are superseded by contemporary diagnostic pathways, physiologic thresholds, and current society guidelines ACC/AHA 2024 · TASC II (2007).