SAN FRANCISCO – A postexercise ankle-brachial index measure provides useful, additional risk stratification to patients with peripheral arterial disease, according to a review of more than 2,800 patients tested at one U.S. center.
"Postexercise ABI [ankle brachial index], which is not routinely tested in most vascular labs, is a very effective tool to identify patients at risk of peripheral disease," Jason Strefling, D.O., said while presenting a poster at the annual meeting of the American College of Cardiology. "Resting ABI is a pretty sensitive test, but when you add exercise you can significantly increase the sensitivity," said Dr. Strefling, a cardiologist at Texas Tech University in Lubbock.
"Patients with diabetes or renal dysfunction can have an unusually normal resting ABI," but measuring a patient’s ABI a second time, after exercise, can better stratify patients who have some level of peripheral arterial disease (PAD), he said in an interview. "Postexercise ABI should probably be measured in all patients having their ABI measured, and on all PAD patients, but most vascular labs don’t do it." Patients with depressed ABIs both at rest and after exercise have the worst outcomes, but depressed exercise ABI with a normal rest ABI may identify patients with milder but nonetheless clinically significant PAD.
The exercise can be in the form of a treadmill protocol, or as simple as a few minutes of toe lifts, he said.
Dr. Strefling and his associates reviewed 2,842 patients seen at the vascular laboratory at the Cleveland Clinic during 2005-2009 who underwent both resting and postexercise ABI measurements. "A lot of vascular surgeons and cardiologists [at the Cleveland Clinic] order an exercise ABI," he explained. The ABI, the difference in systolic pressure between the ankle and arm, is measured with a handheld continuous wave Doppler ultrasound device and a blood pressure cuff. An ABI measurement of less than 0.90 is considered diagnostic of PAD. Dr. Strefling was on the Cleveland Clinic staff when he did this analysis.
The cohort included 1,383 patients with a normal ABI, greater than 0.9, at rest and post exercise, 479 with a normal rest ABI but a depressed ABI post exercise, 0.9 or less, and 980 patients with a low ABI at both measurements.
During follow-up of up to 5 years, the mortality rate was 9% in patients with both ABIs normal, 13% in patients whose ABI was only depressed post exercise, and 21% in patients with low rest and exercise ABIs, statistically significant between-group differences. The researchers reported a similar, statistically significant risk stratification pattern for the combined outcome of death, stroke, and myocardial infarction.
A third combined outcome – death, stroke, myocardial infarction, or lower extremity revascularization or amputation – had rates of 14% in patients with normal rest and exercise ABIs, 27% in patients with a normal rest ABI but reduced postexercise ABI, and 51% in patients with a low ABI on both measures, statistically significant differences. This combined endpoint was primarily driven by episodes of revascularization or amputation, Dr. Strefling noted.
No study results have yet documented the best way to manage patients with a normal resting ABI and a depressed exercise ABI, but Dr. Strefling suggested treating these patients with at least one antiplatelet drug and possibly two of these drugs (such as aspirin and clopidogrel), aggressive statin treatment, and other treatments for risk-factor modification.
Dr. Strefling said that he had no disclosures.
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