An inexpensive new blood test developed by Texas researchers could improve the treatment of heart attacks and save as much as $4 billion in medical costs each year by quickly identifying which patients who show up at emergency rooms with symptoms are actually having attacks.
The test, already available to hospitals, could speed the treatment of heart attack patients and reduce the use of potentially hazardous clot-busting drugs on patients who have symptoms but turn out not to be in the midst of an attack.
Only 10 percent of the 5 million patients who enter emergency rooms each year with symptoms are having heart attacks. Nonetheless, a majority of them are admitted to expensive intensive care units as a precautionary measure. Determining whether they are having attacks can require 12 to 24 hours, by which time the damage from attacks is complete.
In contrast, the new test, developed at Baylor College of Medicine, can identify victims in less than two hours, offering opportunity to minimize permanent damage to heart tissues, the team reports today in the New England Journal of Medicine.
"Had this test been used as a screening test, we could have reduced our coronary care admission rate by 70 percent," said Dr. Peter R. Puleo, a Baylor cardiologist.
"If this turns out to be as good as they say it is, it will give an enormous economic and patient-care benefit," said Dr. Pravin Shah of California's Loma Linda Medical Center, a member of the American Heart Association's Council on Clinical Cardiology. "At the present time, emergency room physicians tend to play it extra safe, largely for medico-legal reasons."
The new test meshes well with the current debate about minimizing health care costs, said Dr. George Sopko, a cardiologist at the National Heart, Lung and Blood Institute. "With the test, one can eliminate quite a few unnecessary hospitalizations and therefore reduce the cost, as well as using existing health care facilities more appropriately.
"What I like about the test is that it can be used in just about every hospital. . . . It's fairly simple, it can be done fast and it should be helpful for physicians."
Physicians can diagnose about half of heart attack victims by measuring electrical activity in the heart with an electrocardiogram, or EKG. Those patients display a peculiar wiggle, called a Q wave, in their EKG that is unique to heart attack victims.
For others, the EKG reveals little. In those cases, physicians must rely on a detailed clinical history and blood tests. The most useful test looks for the presence of an enzyme called CK-MB that leaks into blood from damaged heart tissues. Existing tests for CK-MB take five to six hours and are no more than 50 percent accurate in diagnosing heart attacks.
Because of this lag time in diagnosis, many patients with chest pain are admitted to intensive care units by physicians practicing what Loma Linda's Dr. Shah calls "defensive medicine." Previous studies have shown that the cost of this excess hospitalization is about $4 billion.
The new test developed by Dr. Robert Roberts and his colleagues at Baylor can detect an unusual form of CK-MB produced in heart attacks at the extremely low concentrations present shortly after a heart attack. The test has been approved by the Food and Drug Administration for monitoring heart attack victims.
Dr. Roberts, Dr. Puleo and their colleagues studied 1,110 patients who came to the emergency room of Ben Taub General Hospital in Houston with heart symptoms, testing blood for CK-MB every 30 to 60 minutes for at least six hours.
They found that it was 93.9 percent accurate in identifying those patients who had heart attacks, compared with only 48 percent for the conventional CK-MB test. It was 96.2 percent accurate in identifying those who were not having a heart attack.