Newer Version of Heart Attack Blood Test a Game Changer?

Health Writer
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One of the most common symptoms worldwide that brings a patient to the emergency room is chest pain.  Many patients who present with this symptom are often kept for hours for observation, or are hospitalized overnight for evaluation, which can add to patients' anxiety as well as to healthcare costs. But a test that could identify “low-risk patients” who are likely experiencing something other than a heart attack could also provide peace of mind relatively quickly to patients while more efficiently releasing patients from emergency rooms. Troponin levels help doctors determine if a heart attack has occurred. A new study, which used a more sensitive version of the troponin blood test, may help doctors feel more confident in quickly ruling out a heart attack.

The current troponin test (also called cardiac troponin test) measures the levels of troponin T or troponin 1 proteins in the blood.  These proteins are released when there is damage to the heart muscle. Typically, the more damage to the heart muscle, the higher the levels of troponin.  The test is usually ordered when a doctor suspects that a patient may has had a heart attack, and results are usually available in about one hour. The test is typically repeated two more times over the course of several hours after the baseline test, since it can take time for the relevant proteins to be released in measurable quantities.

The test can also identify heart damage due to other causes, like trauma. Even a slight elevation in troponin can signal cardiac damage.  Very high levels usually indicate that a heart attack has occurred recently.  Levels can remain high for one to two weeks after a heart attack.  Non-cardiac causes that can raise troponin levels include pulmonary hypertension, long term kidney disease and very prolonged vigorous exercise.  In these cases, blood tests that measure certain cardiac markers will help rule out heart damage.

The cost of the test can be as low as $45 dollars up to $100 or more, depending on the laboratory.  It is important to recognize that a doctor will likely take a full history from the patient, order an EKG and troponin levels, and even if the troponin comes back as “normal” the doctor may still decide to keep the patient in the hospital for further evaluation**. (Conceivably a patient who is in the midst of having a heart attack, or who is in the early minutes or hours post-cardiac event,  may not have had enough cardiac damage to register an abnormal troponin level.**)

A recent study published in the journal The Lancet looked at a more sensitive version of the troponin blood test.  Levels of troponin were measured in 6,000 patients who presented with a complaint of chest pain to four hospitals in Scotland and the U.S.  The researchers found the patients with troponin levels less than 5 ng/L, were 1) at very low risk of having recently sustained a heart attack and 2) at low risk of having a heart attack in the next 30 days post-discharge.

In fact, two thirds of the subjects had levels in this range, and at one-year post-testing, they had three times lower the risk of heart attack and cardiac death compared to patients with a troponin level of 5ng/L or greater.

According to Dr. Jonathan Winograd, D.O., FAAEP, an emergency room physician at Bethesda Hospital West in Boynton Beach, Florida, the study results suggest that this newer, more sensitive troponin test could someday allow emergency room doctors to send many more “low-risk” patients home from the emergency room with fewer concerns regarding an impending heart attack. Still, Dr. Winograd cautioned that a person’s family and cardiac history, presenting symptoms and other variables might still require further monitoring, despite normal troponin levels.  And even if this newer version picks up lower levels, Dr. Winogradwas not clear from the study on how this more sensitive test is able to provide assurance of no evolving heart damage, if performed in the very early minutes or hours after the initial symptom of chest pain (It takes time for troponin levels to release after heart muscle damage occurs.)

Still, the newer test could be a game changer if further studies confirm its findings.

Another recent study suggests that certain patients who already have cardiac disease may experience mental stress induced ischemia, and therefore have higher levels of cardiac troponin.  Using the currently available troponin test can help doctors to identify these at-risk patients and intercept further cardiac damage by instigating more aggressive therapies.

In all these cases, meanwhile, Dr. Winograd notes that an accurate interpretation of the current troponin test, coupled with other considerations, is still reliant on the expertise of the doctor.

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