Is pre-surgical test worth the risk?

USA Today (Society for the Advancement of Education), Feb, 1996

Tests for hidden heart problems that might arise in patients undergoing non-cardiac vascular surgery tend to cause more harm than good, researchers have found. In the U.S., about 170,000 people a year undergo the procedure, largely for the repair of clogged leg arteries.

A common strategy for treating patients in need of a leg artery repair is to perform a heart test first and then to fix any complication before going on to carry out the vascular surgery, explains Mark Hlatky, associated professor of health research and policy, Stanford University School of Medicine.

The heart test, called coronary angiography, involves releasing an X-ray-impermeable substance through a catheter to help capture on film the structure of the coronary arteries. Angiography can detect hidden heart problems, such as a clogged coronary artery, that would add to the risk of undergoing the vascular surgery. This cardiac risk then can be reduced substantially by successful coronary bypass surgery or coronary angioplasty, though these procedures carry their own dangers.

In analyzing the relative risks of various scenarios, Hlatky and his colleagues found that the benefit of identifying any heart problems likely to emerge during non-cardiac vascular surgery does not outweigh the risk of a patient suffering a heart attack or stroke as a result of coronary angio-graphy and the ensuing effort to repair an unmasked heart condition.

"At first, this doesn't seem to make sense," Hlatky notes. "How can patients who undergo the angiography, and then a coronary artery bypass, not be better off, considering that these procedures cut their cardiac risk during vascular surgery by one-half to two-thirds? The answer is that the use of pre-operative coronary angiography commits the patient to undergo two or three potentially risky procedures, rather than just one. We found the best strategy is to simply proceed with the originally planned vascular surgery, with more intensive monitoring in high-risk cases, rather than to routinely perform pre-operative coronary angiography."

In addition to holding implications for treatment, the finding suggests a flaw in the approach usually used by governments and other agencies to gauge hospital success rates. "Instead of focusing on risks due to individual procedures, raters should look at the bigger picture and consider the risks associated with the entire treatment strategy for the patient's condition - the risks of all of the procedures that go into that treatment. By focusing on individual procedures in isolation, raters tend to lose sight of the forest for the trees."