MIAMI BEACH — Several diagnostic tests complement the ankle-brachial index for diagnosing peripheral artery disease in patients with intermittent claudication.
For patients with suspected arterial disease but a normal ankle-brachial index of more than 0.9, segmental limb pressure, pulse volume recording, and an exercise treadmill test can help refine the diagnosis, Dr. Michael R. Jaff said at the 18th International Symposium on Endovascular Therapy.
Once peripheral artery disease (PAD) is diagnosed, three noninvasive methods can provide anatomic information prior to contrast angiograph: Doppler ultrasound, MR angiography, and CT angiography.
Both pulse volume recording and segmental limb pressure recording help gauge the severity of PAD, and they can localize the site of an occlusion or stenosis. These methods also are useful in patients who have atypical exertional limb symptoms. But like ankle-brachial index, they're less reliable in patients with calcified arteries, they can't distinguish between stenosis and occlusion, and severe inflow disease makes infrainguinal lesions hard to identify. Pulse volume recording is well suited to track changes in the severity of PAD. Sequential limb pressures are obtained by using a panel of pressure cuffs placed on the thigh, calf, ankle, and foot as well as on the arm, said Dr. Jaff, director of the vascular diagnostic laboratory at Massachusetts General Hospital in Boston.
Patients with atypical exertional symptoms are good candidates for assessment by a treadmill test. A treadmill test also is useful for measuring the functional impact of peripheral artery disease, evaluating the impact of treatment, and unmasking occult angina or coronary disease. The standard treadmill protocol for suspected peripheral artery disease is a maximum of 5 minutes walking at 2 miles per hour on a simulated 12% grade. This requires a programmable treadmill.
For anatomic information, Doppler ultrasound is notable as a relatively inexpensive test compared with MR and CT. It's also painless and risk free, and can both predict the ideal access for intervention and assess the adequacy of revascularization therapy over time.
MR angiography is fast and gives excellent visualization of the entire arterial tree as well as soft tissue and solid organs. The contrast used is not iodine based and there is no radiation exposure. A recently published comparison of MR angiography and Doppler ultrasound in 61 consecutive patients showed that MR angiography had a higher positive predictive value than did Doppler ultrasound for assessing vascular anatomy. MR angiography can't be used in patients with cardiac defibrillators or pacemakers, it's hard to use in patients who are claustrophobic or very obese, and it tends to overestimate the severity of stenoses, said Dr. Jaff.
CT angiography is even faster than MR, and provides high resolution images of the entire arterial tree, as well as soft tissue and solid organs. But it uses iodinated contrast, and requires significant radiation exposure and prolonged breath holding by the patient. In addition, calcification obscures vascular lumens, and correlation of the images with contrast angiography has not been established.