New Testing Strategy Could Help Diagnose Heart Attacks in an Hour

Using a highly sensitive blood test, emergency room doctors may someday be able to rule in or rule out heart attack within an hour

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Symptoms of heart attack account for about 10% of emergency room visits, and a new algorithm using highly sensitive blood tests may help emergency department doctors diagnose the condition in an hour, potentially speeding necessary treatment and easing overcrowding in the emergency department, a new study finds.

The test measures levels of troponin, a substance released in the blood indicating cell death and a heart attack. Older tests for troponin required that patients be repeatedly tested for as many as six to 12 hours, since circulating levels of the substance may not rise immediately. Using the newer, more sensitive test, however, researchers from University Hospital Basel in Switzerland were able to rule in or rule out a heart attack in 77% of patients within about an hour of their arriving at the emergency department with chest pain.

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Researchers led by Dr. Tobias Reiclin studied 872 emergency patients with acute chest pain. The scientists developed the algorithm — which included a measure of a patient’s initial troponin level and the change in that level an hour later — using blood tests from 436 patients, then validated the test in the other 436. Additional data, such as the patients’ age, gender, electrocardiogram results and the time since onset of the symptoms, were also included in the algorithm.

Using the algorithm, researchers ruled out heart attack in 259 patients (60%) — no patient who had actually had a heart attack was included in this group. Seventy-six patients, or 17%, were ruled in, and the new testing method worked with 97% specificity. One hundred and one patients, or 23%, were categorized in the “observational zone”; later, 8% of these patients would be diagnosed with heart attack. Taken together, the algorithm allowed for a definite diagnosis — either rule in or rule out — in an hour in 77% of patients.

The 30-day survival rate was 99.8% for patients without a heart attack, 98.6% for patients placed under observation and 95.3% for patients who underwent a heart attack.

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“The use of this algorithm seems to be safe, significantly shortens the time needed for rule-out and rule-in of [heart attack], and may obviate the need for prolonged monitoring and serial blood sampling in three of four patients with chest pain,” the authors conclude in the study.

More than 5 million people arrive at the nation’s emergency departments each year with chest pain, leading to at least $6 billion in health care costs. Considering that only about 1.6 million of such patients actually suffer from heart attack, a quick and sensitive test to diagnose these patients could save the medical system significant time and money.

However, the authors acknowledge that the new, highly sensitive troponin tests aren’t ready for prime time; since they may identify other heart conditions besides heart attack — troponin is also associated with heart failure, pulmonary embolism (clots in the lungs), sepsis and stroke — more studies need be done before the test is ready for widespread use.

“It is important to realize that high-sensitivity troponins are not just a test to ‘rule in’ or ‘rule out’ [heart attack],” Dr. Robert Glatter, an emergency physician at Lenox Hill Hospital in New York City, told HealthDay. “Instead, they are a valuable tool to risk-stratify patients with chest pain who may have a number of potentially lethal [conditions].”

Such tests could be useful as one tool in a cardiologist’s armamentarium, but they shouldn’t trump other diagnostic measures or clinical exams of patients, experts said.

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The study was published online in the journal Archives of Internal Medicine.

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