Study examines value of coronary artery scansA scientific statement describing the clinical merits of coronaryartery scans, a controversial technique that uses electron beamCT technology developed by Imatron of South San Francisco, CA,has raised
A scientific statement describing the clinical merits of coronaryartery scans, a controversial technique that uses electron beamCT technology developed by Imatron of South San Francisco, CA,has raised charges and countercharges about what the report means.
The 17-page American Heart Association study appears to givea mixed review to the imaging technique, which measures arterialcalcium to predict the probability of future heart disease. Itconcludes that a negative coronary artery scan using electronbeam CT produced by an Imatron ultrafast CT scanner does not meana patient is free of atherosclerosis, including unstable plaque.It finds, however, that the absence of calcium implies a low likelihoodof significant coronary obstruction and low risk of a cardiovascularevent within two to five years. A high calcium score may be consistentwith moderate to high risk of a cardiovascular event within twoto five years, it said.
The authors could not recommend the screening technique in lieuof stress testing for most patients with chest pain, except thosewith atypical chest pain. They recommended against the test forscreening individuals younger than 40.
The AHA statement was prepared by a 10-member committee chairedby Dr. Lewis Wexler, a professor of radiology at Stanford University,and published in the September issue of Circulation, the AHA'sjournal.
The way The Wall Street Journal interpreted the results, however,had Imatron officials scurrying to conduct damage control. A Sept.5 article in the newspaper noted that the AHA study found thatultrafast CT can measure coronary disease risk, but warned doctorsagainst using the test indiscriminately. It also quoted Wexler,who was less than kind to Imatron in his assessment of coronaryartery scans as a screening test for healthy men.
"I am not against it if you do it to accumulate data,"he told a WSJ reporter. "But to do it indiscriminately justto get calcium scores is just a waste in most cases."
Wexler's criticism figuratively cut to the heart of Imatron'sstrategy for its $2 million ultrafast CT scanners. The manufactureris beginning to find placements for the EBCT technology at imagingcenters formed by its own HeartScan subsidiary. HeartScan operatesfacilities in San Francisco, Houston, and Seattle, and is planninginstallations in at least six more cities (SCAN 7/17/96). Theiradvertising targets middle-aged men and touts coronary arteryscans as an inexpensive, noninvasive screening test.
Imatron fired off a news release disputing the newspaper's interpretationof the study and put its own spin on the results.
"Nowhere does the AHA `warn' doctors against using EBCTindiscriminately,'' said CEO Lewis Meyer. "EBCT has beendemonstrated to be effective in screening individuals over age40 with either known risk factors for or symptoms of coronaryartery disease." Meyer also faulted Wexler for sayingthat the medical community is still looking for ways to predictwhich asymptomatic patients will suffer a heart attack or acutechest pain. He claimed that the statement contradicted Wexler'sown report and the results of a study published in the June issueof Circulation. According to research conducted by cardiologistsat St. Francis Hospital in Roslyn, NY, Imatron's ultrafast CTscanner is more powerful than the best noninvasive test in predictingheart attacks, Meyer said.