There’s a reason why a troponin test can be negative for quite a while after a heart attack.
There’s two ways to ensure a heart attack doesn’t get missed.
A heart attack can get missed if the patient, whose troponin test turned up negative, decides to leave the emergency room before the second test is taken.
This actually happens. These patients are playing with some serious fire. Though it can be aggravating to have to wait around for the second troponin draw to be taken, it can also save one’s life.
When a heart attack cuts off blood flow, and therefore oxygen, to cardiac muscle, it’s called an ischemic heart attack.
“If the ischemia does not resolve, heart tissue will eventually die, causing a heart attack (myocardial infarction),” says Christopher J. Hanifin, PA-C, who has been a physician assistant in open heart surgery with Cardiothoracic Surgery of South Bend in South Bend, IN.
Hanifin explains, “Only when the heart tissue actually begins to die will cardiac enzyme tests begin to become positive.
“A patient could therefore have hours and hours of ischemic pain and their blood tests would remain negative.
“There are two strategies to try to avoid missing a myocardial infarction in these cases.
“The first is to repeat cardiac enzymes tests several times over the course of hours to see if levels are rising. Even if levels remain in the normal range, a rising level is a signal of trouble.”
The wait time between troponin tests is usually from four to six hours. Three consecutive tests showing NO upward trend are very reassuring to physicians.
“A second strategy is to perform stress testing prior to discharging a patient,” says Hanifin.
“In stress testing, the patient exercises [treadmill or stationary bike] while their cardiac function is observed.
“If a patient has an area of the heart that does not have a good blood supply, stress testing will often cause that area to become ischemic, leading to symptoms and changes that can be detected by ultrasound, ECG or nuclear medicine testing.
“Many hospitals now have chest pain units where patients can be admitted for a short stay while their chest pain is being evaluated.”
If a patient can’t exercise due to, for example, a recent knee replacement surgery, then a drug is used that makes the heart think the body is being exercised. This mode of testing yields results as accurate as the exercise stress tests.
Once a troponin test is taken, the results can be ready within 15 minutes.
Christopher J. Hanifin, PA-C, is currently Department Chair and Assistant Professor, Department of Physician Assistant, Seton Hall University,
Lorra Garrick has been covering medical, fitness and cybersecurity topics for many years, having written thousands of articles for print magazines and websites, including as a ghostwriter. She’s also a former ACE-certified personal trainer.