Peripheral Arterial Disease (PAD)
How can peripheral arterial disease (PAD) be diagnosed?
When a patient is suspected to have PAD, the doctor will evaluate him/her in two aspects:
- Establish the diagnosis of PAD by examine its severity and anatomic status;
- Checking the risk factors of PAD and other associated cardiovascular diseases.
There are several tests for doctors to determine the diagnosis of PAD:
- Physical Examination: Doctor will check the pulses in the legs by palpation, then observe the colour, temperature and hair of the legs, and check if there is any poor wound healing that may be signs of PAD.
- Resting Ankle-brachial Index (ABI): ABI is used to measure and compare the blood pressure at the ankle and in the arm while the patient is at rest. It could help establish the diagnosis of PAD, and assess the severity of the disease. In cases when the arteries are non-compressible, the specially designed toe cuffs can be used to measure the blood pressure in the toes, and use the toe-brachial index (TBI) instead.
- Exercise ABI: This is a sensitive measure for confirming PAD in patients with normal resting ABIs. During exercise, the peripheral resistance will reduce while the blood flow will increase, which will create a pressure gradient across the stenotic segment. This will also cause the ABI to decrease because the increase in the blood pressure in the arms is not matched by the increase in the legs. (ABI is a functional assessment of the arterial status of the legs. It can give and idea on whether the patient is having PAD and its severity, however it cannot tell which arteries are narrowed or occluded.)
- Duplex Ultrasound Scan: This test uses sound waves to provide imaging that can measure the flow velocities of blood in the blood vessel; with the addition of colour flow imaging, it can also localize the narrowed region. The findings sometimes can be affected by other structures around the arteries, limiting its efficacy.
- Computer Tomography Angiography (CTA) and Magnetic Resonance Angiography (MRA): These tests are non-invasive procedures that are widely used in diagnosing the anatomic location and degree of narrowing of PAD. The difference is CTA is using X-rays technology to provide detail imaging while MRA is using magnetic field and pulses radio wave energy. Those results are essential for patients who are planning to undergo endovascular and surgical intervention.
- Digital Subtraction Contrast Angiogram (DSA): This test is invasive bust accurate. It involves direct puncture of the artery followed with injection of contrast into the circulation. The images of the arteries are visualized under X-ray machine. Due to its invasiveness, it is nowadays performed only during endovascular intervention to define the detailed vascular anatomy before the operation.
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