MUNICH—Neither pulse palpation nor an automatic oscillometric blood pressure device is a reliable substitute for Doppler determination of ankle-brachial index, according to a comparative study.
Experts agree that the ankle-brachial index (ABI) is an extremely useful screening test for peripheral artery disease and cardiovascular risk—and that it is underutilized in clinical practice. There has been considerable interest in pulse palpation and automatic oscillometric methods as alternatives to determining ABI using a Doppler device. The hope has been that these lower-cost, low-tech alternatives might boost the popularity of routine ABI screening in primary care. But they simply don't make the grade, Dr. Denis L. Clement indicated at the annual congress of the European Society of Cardiology. He cited a recent French study that compared the three methods of measuring ABI in 54 subjects.
The mean ABI by Doppler—the only validated method—was 1.03, well within what is generally considered normal. In contrast, the mean ABI in the same subjects as determined by pulse palpation by the same physicians was 0.85, which is supposed to indicate occlusive peripheral artery disease.
The automatic blood pressure device yielded a mean ABI of 1.09; however, both intra- and interobserver variability were unacceptably high for this method. The same was true for pulse palpation, according to the investigators (Int. J. Clin. Pract. 2008;62:1001–7).
Another recent technical development in ABI measurement involves using the lower rather than the higher of the two ankle pressure readings, continued Dr. Clement, emeritus professor of cardiology and angiology at the University of Ghent (Belgium).
The American Heart Association currently recommends measuring the systolic blood pressure of both the anterior and posterior tibial arteries of each leg, then using the higher of the two ankle pressures in calculating the ABI for each leg. But Dr. Christine Espinola-Klein and coworkers at Johannes Gutenberg University Mainz (Germany) have shown this method excludes a sizeable group of individuals at high risk for cardiovascular events. Better to use the lower ankle pressure reading, according to the investigators.
They followed 812 patients for a median of 6.6 years after undergoing ABI determination during hospitalization for chest pain. By the standard definition of ABI using the higher ankle pressure, 25% of patients had peripheral artery disease as defined by a baseline ABI below 0.9. Another 11% of patients had an ABI of less than 0.9 when the lower ankle pressure reading was utilized, but not by the standard definition; Dr. Espinola-Klein and coworkers called this the “suspected PAD” group.
During follow-up, 19% of patients experienced an MI, stroke, or cardiovascular death. The event rate was 28.4% in patients with baseline PAD as defined by ABI in the standard manner and was similar at 25% in those with suspected PAD based on the lower ankle pressure. Those without PAD according to the modified definition had a significantly lower 14.8% event rate (Circulation 2008;118:961–7).