First Alert for Heart Attacks

Anne L. Fischer, anne.fischer@laurin.com

The symptoms of a heart attack frequently mimic the warning signs of other conditions. Often the only reliable tool for diagnosing a true myocardial infarction is a blood test that determines the level of cardiac-specific troponins. The problem, however, is that the enzyme level does not show a substantial increase until about four to six hours after the heart attack starts, and the reading does not reach its peak until 12 hours after that. The waiting period represents a valuable treatment window for limiting damage to the heart muscle. But now under study is a rapid test method that measures hundreds of markers in the blood.

At Massachusetts General Hospital in Boston and at the Broad Institute of MIT and Harvard in Cambridge, a group has developed a technique that can identify molecular markers released during a heart attack. The group took blood samples from 36 patients undergoing septal ablation, a technique that destroys tissue overgrowth in the heart and that induces many indicators of a spontaneous heart attack. Taking samples before and after patients underwent septal ablation allowed the researchers to observe the metabolic changes that occur when myocardial tissue is destroyed. Patients undergoing elective diagnostic coronary angiography served as negative controls, while those with spontaneous myocardial infarction served as positive controls. The results were published in the October 2008 Journal of Clinical Investigation.

The blood samples were analyzed using a method referred to by Dr. Robert Gerszten, a cardiologist at Massachusetts General Hospital and lead researcher, as liquid chromatography tandem mass spectrometry analysis. According to Gerszten, “We know that certain metabolites have an address, and we know where to find them.”

Unique to the setup was a robotic sample loader from Leap Technologies Inc. of Carrboro, N.C., which was connected to a triple quadrupole mass spectrometer from Applied Biosystems of Foster City, Calif. Although the study is relatively straightforward when examining the blood of a single individual, it becomes more complex when analyzing the potential variables among individuals. The mass spectrometry system assessed hundreds of metabolites in as little as 10 minutes, and it identified several metabolic changes that occurred right after the ablation process. These changes are observed also in patients who arrive at the emergency department after spontaneous heart attacks.

The purpose of the study was to find blood markers for reversible myocardial injury. The most successful treatments for heart attacks take place within hours of occurrence, so it’s important to determine whether a heart attack is happening or has just happened – as quickly as possible. The researchers intend to increase the breadth of their coverage by integrating more metabolic analyses into their platform. “We need to saturate all the known biological pathways,” Gerszten said.