When clot-busting drugs aren't working.

Researchers at the Washington University School of Medicine have developed blood tests that provide a quicker, safer way to identify heart attack patients who are not responding to clot-busting drugs. They reliably identify individuals who will need more invasive therapy to restore blood flow to the heart and do it within the time period when treatment is most effective.

When doctors administer the clot-dissolving drugs streptokinase or t-PA, they can count on them restoring blood flow promptly in about 50 or 75% of patients, respectively. Until now, however, an invasive X-ray imaging procedure called angiography had been the only reliable way to reveal reperfusion--the return of blood flow--in a blocked artery.

Angiography involves using a catheter to inject a special dye that highlights blood vessels on X-rays. The test is not always practical to perform during the early stages of an attack, and some hospitals do not have the necessary facilities, notes Dana R. Abendschein, research associate professor of medicine and of cell biology and physiology. "The advantage of the tests we have developed is that they can be done quickly while the patient is still being treated with a thrombolytic [clot-dissolving] agent to identify those patients who will require additional invasive measures to restore f low to the heart. Then we will be able to administer invasive therapy within the four-hour window that's available to minimize heart damage."

The investigators monitored 176 individuals for blood levels of two enzymes--MB creatine kinase (MB CK) and MM creatine kinase...