The Ankle-Brachial Index (ABI) and Pulse Volume Recording (PVR) are non-invasive tests that assess blood flow in the arteries of the limbs, primarily the legs. This procedure is a standard tool for detecting Peripheral Artery Disease (PAD), a condition where narrowed arteries reduce blood flow to the extremities. The ABI compares blood pressure between the ankles and the arms, providing a numerical ratio to indicate arterial health. The PVR records changes in limb volume to produce visual waveforms, which complement the pressure measurements by offering a qualitative assessment of blood flow dynamics.
Identifying the Need for ABI PVR Testing
The primary reason a healthcare provider orders an ABI/PVR test is to screen for or diagnose Peripheral Artery Disease. PAD is caused most commonly by atherosclerosis, the slow buildup of fatty plaque within the arterial walls, which restricts the flow of oxygen-rich blood, especially to the legs. This reduced circulation can lead to significant health issues, including non-healing wounds and an increased risk of heart attack or stroke.
A diagnosis may be prompted by classic symptoms, such as intermittent claudication—muscle pain, cramping, or fatigue in the legs that starts during exercise and subsides with rest. Other signs that warrant testing include numbness or weakness in the legs, one foot feeling noticeably colder than the other, and sores on the feet or legs that are slow to heal. The absence of a pulse or a weak pulse in the feet is also a physical indicator suggesting the need for evaluation.
Testing is also recommended as a screening measure for individuals who carry significant risk factors for PAD, even if they are asymptomatic. Major risk factors include increasing age (especially over 65, or over 50 with other risks), a history of smoking, diabetes, high blood pressure, or high cholesterol. Early diagnosis in these high-risk groups is important because PAD is often asymptomatic in its early stages.
Performing the Ankle-Brachial Index and Pulse Volume Recording
The ABI and PVR test is a non-invasive procedure that typically takes less than an hour to complete. The patient is asked to lie down in a supine position and rest quietly before the test begins. Blood pressure cuffs are wrapped around the upper arms and at various points on the legs, including the ankles, calf, and thigh.
The Ankle-Brachial Index portion of the test involves measuring systolic blood pressure in both the arms and the ankles. A Doppler ultrasound device is used to locate the pulse in the brachial artery of the arm and the posterior tibial and dorsalis pedis arteries in the ankle. The cuff is inflated until the pulse signal disappears, and the pressure is recorded when the pulse returns during cuff deflation, which represents the systolic pressure.
The Pulse Volume Recording (PVR) is performed concurrently or immediately after the ABI measurements. For this part, the cuffs on the leg are inflated to a lower, specific pressure. As blood flows beneath the cuff, slight changes in limb volume are detected as pressure changes, which are translated into a graphical waveform. This waveform provides a qualitative assessment of the pulse’s strength and shape at that segment of the limb.
Understanding the Test Results
Interpreting the ABI/PVR results involves analyzing both the calculated pressure ratio and the shape of the volume waveforms. The Ankle-Brachial Index is calculated by dividing the highest systolic blood pressure measured in the ankle by the highest systolic pressure measured in the arm. A normal ABI is between 1.00 and 1.40, indicating that the ankle pressure is equal to or slightly higher than the arm pressure.
An ABI value of 0.90 or lower is considered diagnostic for PAD. A ratio between 0.91 and 0.99 is often classified as borderline, suggesting an early sign of arterial disease. Values that fall between 0.41 and 0.90 suggest mild to moderate PAD, which correlates with reduced blood flow that can affect mobility. A severe PAD diagnosis is indicated by an ABI of 0.40 or less, signifying a high risk for non-healing wounds and tissue loss.
The PVR waveforms provide important complementary information, especially in cases where the ABI is misleadingly high. An ABI greater than 1.40 suggests that the arteries are stiff or calcified, a condition often seen in patients with long-standing diabetes. In these instances, the PVR waveforms become a more reliable indicator of flow because the arterial stiffness prevents the cuff from compressing the vessel for an accurate pressure reading.
Normal PVR results show a triphasic waveform, which has three distinct components: a sharp systolic upstroke, a rapid downstroke, and a small reflective wave during late diastole. As arterial disease progresses, the waveform changes, first becoming biphasic, and then monophasic. A monophasic waveform shows a blunted peak, a prolonged upstroke, and a loss of the reflective components. The combination of a low ABI and a monophasic PVR waveform confirms reduced blood flow and helps pinpoint the location of the arterial obstruction.