RVS key terms

Ratio of the higher systolic pressure at the ankle (dorsalis pedis or posterior tibial artery) to the higher brachial systolic pressure, used to screen for and grade lower-extremity arterial occlusive disease.

Systolic blood pressures measured with cuffs at multiple levels of the limb (high thigh, low thigh, calf, ankle) to localize and estimate the severity of arterial stenoses along the limb.

Air-plethysmographic tracing of limb volume change with each cardiac cycle, displayed as a waveform whose amplitude and contour reflect arterial inflow to the segment beneath the cuff.

Noninvasive optical technique that detects pulsatile changes in dermal blood volume using infrared light, commonly used for digital pressures, toe-brachial index, and venous reflux assessment.

Ratio of toe systolic pressure to brachial systolic pressure, used when ankle pressures are falsely elevated by medial calcinosis and to assess distal perfusion in critical limb ischemia.

Doppler mode that transmits and receives continuously, detecting flow at any depth along the beam but without depth discrimination; used for handheld pressure and waveform assessment.

Graphic display of blood flow velocities over time, whose shape (triphasic, biphasic, monophasic) and spectral broadening indicate the presence and severity of upstream or local arterial disease.

Damped arterial waveform with a prolonged, rounded systolic upstroke and low peak velocity, indicating a significant stenosis or occlusion proximal to the sampling site.

Combined B-mode imaging and pulsed Doppler that allows direct visualization of vessels and measurement of flow velocities, the primary noninvasive tool for carotid and peripheral arterial and venous evaluation.

Doppler mode that superimposes direction- and velocity-coded color on the B-mode image, used to rapidly identify vessels, detect flow disturbances, and guide spectral Doppler sampling.

Ambiguous color or spectral display that occurs when blood velocity exceeds the Nyquist limit of the pulse repetition frequency, causing flow to appear in the wrong direction or wrap around the scale.

Highest velocity recorded during systole at a sample site; an elevated PSV relative to adjacent segments suggests stenosis, and a PSV ratio is used to grade internal carotid artery disease.

Widening of the velocity spectrum caused by turbulent, nonuniform flow, commonly seen just distal to a stenosis and used as a qualitative sign of hemodynamic disturbance.

Retrograde venous flow lasting longer than a defined threshold after distal compression, indicating incompetent valves in the deep, superficial, or perforating veins.

Compression ultrasound study of the deep and superficial veins, assessing compressibility, spontaneous and phasic flow, augmentation, and reflux to diagnose thrombosis or valvular incompetence.

Organization of the aorta and its branches supplying the head, upper limbs, abdominal organs, and lower limbs, including the iliac, femoral, popliteal, and tibial arteries.

Ring of communicating arteries at the base of the brain linking the anterior and posterior circulations, providing collateral routes when a carotid or vertebral artery is occluded.

Division of the common carotid artery into the internal and external carotid arteries, usually near the level of the upper thyroid cartilage; the internal carotid has no cervical branches.

Arrangement of deep veins (femoral, popliteal, tibial), superficial veins (great and small saphenous), and perforating veins connected by valves that direct blood centrally against gravity.

Study of blood flow and pressure relationships, including Poiseuille's law, resistance, velocity profiles, and the Bernoulli principle used to interpret Doppler findings.

Relationship stating that flow through a tube varies directly with the pressure gradient and fourth power of the radius and inversely with length and viscosity, explaining the strong effect of vessel caliber.

Opposition to blood flow created mainly by small arterioles; changes in resistance alter downstream pressure and waveform contour, producing high- or low-resistance flow patterns.

Laminar flow moves in parallel layers with a smooth velocity profile, whereas turbulent flow is chaotic with spectral broadening; turbulence occurs at stenoses and bifurcations.

Dimensionless value relating inertial to viscous forces that predicts whether flow will remain laminar or become turbulent; higher values favor turbulence.

Chronic inflammatory disease in which lipid-rich plaques form in the arterial intima, narrowing the lumen and predisposing to thrombosis, embolism, and aneurysm formation.

Arterial insufficiency of the limbs, most often from atherosclerosis, producing claudication, rest pain, or tissue loss and detectable by reduced ankle-brachial index.

Severe limb hypoperfusion with rest pain, ulceration, or gangrene, typically with ankle pressure below 50 mmHg or toe pressure below 30 mmHg, threatening limb loss.

Narrowing of the internal carotid artery, usually at the bulb, that raises local peak systolic velocity and can cause transient ischemic attack or stroke through embolism or hypoperfusion.

Insufficient blood flow to the posterior circulation from vertebral or basilar artery disease, causing dizziness, diplopia, dysarthria, or drop attacks.

Formation of thrombus in a deep vein, commonly in the lower limb, that obstructs flow and risks pulmonary embolism; diagnosed by noncompressibility on duplex ultrasound.

Chronic failure of venous valves or calf pump function causing venous hypertension, edema, skin changes, and ulceration, confirmed by reflux on duplex or plethysmographic testing.

Abnormal focal dilation of an artery, such as the abdominal aorta or popliteal artery, that may enlarge, thrombose, embolize, or rupture and is monitored by ultrasound diameter measurements.

Compression of the popliteal artery by anomalous muscle or tendon anatomy during exercise, causing claudication in young patients and detectable by provocative duplex testing.

Blood-filled sac communicating with an artery through a defect in the vessel wall, often after catheterization, showing a characteristic to-and-fro neck flow on Doppler.

Episodic vasospasm of digital arteries triggered by cold or stress, producing color changes; evaluated with digital pressures, plethysmography, and occasionally cold provocation testing.

Compression of the subclavian artery, vein, or brachial plexus at the thoracic outlet, assessed with provocative maneuvers and duplex or plethysmographic testing of the arm.

Choosing probe frequency and footprint appropriate to vessel depth and body habitus; higher frequencies give better resolution but less penetration for deep structures.

The angle between the ultrasound beam and direction of blood flow, ideally 60 degrees or less; inaccurate angle correction causes velocity measurement error.

Correct patient positioning, exposure, and ergonomic practice during vascular studies, along with universal precautions and attention to patient comfort and fall prevention.

Knowledge of ultrasound bioeffects, output limits, and indications for contrast-enhanced vascular imaging, including patient screening and monitoring for adverse reactions.