Simple but unconventional tests, such as blood pressure measurement taken at the ankle, could spot people with otherwise unsuspected heart risks, new research shows.
Many people who seem to be at low risk of cardiac problems by conventional standards actually have subtle signs of future trouble, noted a team from Brown University in Providence, R.I.
Traditional screening, which assesses risk factors such as cholesterol, blood pressure and diabetes, "probably has only about 20 percent sensitivity in identifying people at high risk of sudden death," said study lead author Dr. Timothy P. Murphy, professor of diagnostic imaging at Brown. "When you filter out people who have had prior heart attacks and strokes, you are left with a large number of people who are supposed to be at lower risk. They are not considered candidates for intensive therapy to lower that risk. But two-thirds of heart attacks and sudden cardiac deaths occur in that group," he said.
The Brown researchers were expected to present their findings Tuesday at the annual meeting of the Society of Interventional Radiology, in San Diego.
In the study, Murphy's group examined data on more than 6,200 people in the 1999-2004 National Health and Nutrition Examination Survey (NHANES). The researchers pinpointed three unconventional indicators of future cardiac problems: an abnormal ankle brachial index (blood pressure taken at the ankle), elevated blood levels of a clotting factor called plasma fibrinogen, and high levels of C-reactive protein, a marker for inflammation.
While 91 percent of the NHANES group was at low or intermediate risk of cardiovascular problems by conventional standards (based on the long-running Framingham heart study), almost 45 percent of these people fared poorly on least one of the three more unconventional measurements, Murphy said.
Some 3.7 percent had a low ankle brachial index, indicating weaker blood flow to the legs. More than 17 percent had elevated levels of fibrinogen, the major protein of blood clots, and 37.9 percent had high levels of C-reactive protein.
All three of those conditions appeared to be associated with an increased risk of heart attack and sudden cardiac death, Murphy said. So, readings of all three may need to be part of a standard screening test, he said.
This study doesn't yet fully prove that point, because "we don't have longitudinal follow-up," Murphy stressed. "We want to follow these people for 10 years and see whether they have an event rate similar to that of a high-risk Framingham population."
Murphy is proposing just such a study. "Once we present these data, we want to get the study funded through the National Heart, Lung, and Blood Institute," he said. "We also are collecting data on a new population, which we can follow in a longitudinal study."
Meanwhile, the study "adds evidence that screening for the ankle brachial index should be done," Murphy said. "We will lobby Congress to get funding for screening the ankle brachial index. We hope to increase that screening in the primary care setting. It is not now routinely done."
The ankle brachial index test takes only about 15 minutes but is not usually done, because it is not covered by Medicare and other insurers, explained Dr. Rajoo Dhangana, a research fellow at Rhode Island Hospital and a member of the group that did the study.
The study results indicate that as many as two million Americans who would not be listed as high-risk by the Framingham rules would require further study because of an abnormal ankle brachial index, Dhangana said.
Another study expected to be reported on at the meeting found that major surgery was not always necessary for people with potentially fatal abdominal aortic aneurysms, a weakening of the main blood vessel leading from the heart.
Instead, the implantation of artery-opening tubes called stents proved effective in reducing the risk that the blood vessel might rupture, according to the study of 453 people with the condition. British physicians at Guy's and St. Thomas' Hospitals in London said that radiologists could guide the stent to the proper location.
There's more on the ankle brachial index at the Vascular Disease Foundation.
SOURCES: Timothy J. Murphy, M.D., professor, diagnostic imaging, Brown University, Providence, R.I.; Rajoo Dhangana, M.D., research fellow, Rhode Island Hospital, Providence, R.I.; March 10, 2009, presentations, Society of Interventional Radiology annual meeting, San Diego