Crushing, unrelenting chest pain leads millions of people to their local Emergency Center (EC) each year. Because cardiovascular disease is the number-one killer in the United States, people are wise to seek emergency medical care if they think they are having a heart attack (known medically as “myocardial infarction”). However, after an extensive protocol — lasting six to ten hours — most people learn that they do not have a heart problem. Instead they are suffering from one of a myriad of other problems, including esophageal spasm or acid redux, which present like myocardial problems.
Because many illnesses present as possible acute myocardial infarction, the first step in the EC is to “rule out MI.” That is, emergency doctors try to first rule out myocardial infarction as the cause of the patient’s chest pain. For decades, one of two tests for specific enzyme levels has been part of the protocol. Now a faster and more reliable indicator has been found.
Overlake doctors such as Chief of Staff and Pathologist Dave Nordine and Emergency Center Medical Director Jack Ciliberti, are excited about a new biomarker for acute coronary syndromes. Triponin I, a relatively new, early biomarker, is found only in cardiac muscle. Its existence in the patient’s blood indicates that heart injury has taken place.
“Historically, elevations of one of two types of enzyme totals were used to indicate myocardial damage,” said Dr. Nordine. “Unfortunately, these enzymes are also found in non-cardiac muscle and are nonspecific for myocardial damage.”
Dr. Ciliberti explained further: “Troponin I is the only marker that is absolutely heart specific. With the two commonly used enzyme tests, doctors aren’t positive if the elevated readings are caused by heart, liver, brain or renal disease. Another positive factor is that Troponin I levels stay elevated for as much as 10 days after injury to the heart. Here’s why that’s important. Let’s say a patient has some fleeting chest pain over the period of a week or so. She hasn’t had a major heart attack, but damage to her heart has taken place. Finally, the pains brought her to the EC. Since even microscopic damage releases Troponin I, we can tell immediately that the patient is suffering from myocardial infarction, and we can treat her for myocardial infarction before the ‘big one’ hits. It’s major knowledge about a patient’s condition gained at an important time.”
In his search to give Overlake cardiologists the best tools available, Nordine started looking at Triponin I in parallel with more traditional studies such as the two enzyme tests mentioned above, EKGs and patient observation.
“The characteristics of an ideal marker are that it is cardiac specific,” said Dr. Nordine, “it rises soon after the injury occurs, is elevated over a sustained period, is easy to measure over a broad range and the assay has a quick turn-around time.”
Nordine is excited about Troponin I because the specific isoforms are found only in myocardial muscle and is released early following myocardial injury. The test results are available within 20 minutes.
Nordine completed a retrospective study to compare the clinical performances of the two commonly-used tests of enzyme levels. From October 1, 1997, to February 29, 1998, 978 patients arrived at the Overlake Emergency Department with chest pain. Of those, 886 — 85 percent — were ruled out for acute myocardial infarction. Test comparisons for the biomarker and the two enzymes, show 100 percent accuracy for Troponin I, 96.7 and 93.5 percent for the two enzyme tests.
While Drs. Nordine and Ciliberti and their colleagues continue to look forward to the development of the perfect marker for acute mycardial infarction, the recommendation has been made to replace the older enzyme tests with Troponin I in the “rule-out MI” panel.