In every
year More than 7 million people visit emergency departments with chest pain in the US,which sometimes,
but not always, indicates heart attack. Now, a new test can reduce the stress
of waiting and wondering by providing a fast and accurate assurance of heart attack .
The new test may indicate when chest pain is not a heart attack.cardiac troponin test is a blood
test The high sensitivity that can
measure low levels of troponin, a protein released from the heart during a heart
attack. The test can quickly and safely rule out a diagnosis of heart .
Basically, Electrocardiograms (ECGs) are used in the evaluation of
patients with chest discomfort but can be normal or not diagnostic in patients
with a myocardial infarction. Thus, blood will be obtained to detect for any heart damage that can be indicated by
abnormal protein levels in the blood
cell. The specific proteins that are the subjects of these blood tests
include:
- Creatine kinase (CK)
- Creatine kinase-MB (CKMB)
- Myoglobin
- Cardiac troponin I or cardiac troponin T
These proteins are normally present
within the heart cells and are released into the blood after a heart attack.
Their presence in the blood can indicate heart damage. However, some of these
proteins (CKMB, CK, and myoglobin) are also found in other muscles.
A newer blood test (for detecting
cardiac troponin) is both more specific and more sensitive for heart damage. Cardiac
troponins are found only in the heart. Depending on the hospital, either
troponin I or troponin T is measured; in general, both work equally well. The guidelines
recommend that several measurements be obtained within a period of 8 to 12
hours after admission in the hospital. Because there is a lag from the onset of
heart damage to appearance of troponin in the blood, serial monitoring is
important to avoid missing a heart attack.
Scientists
found that the new test could detect far lower levels of troponin in the blood
than, and they wanted to know if detecting troponin levels of less than 5 ng/L
or less in patients with chest pain would predict that the patient was not at
risk of a heart attack.
The
probability that patients were not at risk of heart attack or subsequent death
from a heart condition after 30 days was evaluated through reference to a range
of troponin concentrations.
A troponin
threshold of less than 5 ng/L identified 61% of patients at very low risk of
heart attack, with a negative predictive value of 99.6%, regardless of any
prior complaint or condition. A year later, the same patients still had a three
times lower risk of heart attack and cardiac death than those who had troponin
levels of 5 ng/L or higher.
Lead author
Dr. Aroop Shah, from the University of Edinburgh in the UK, comments that until
now, there has not been a quick way to rule out a heart attack within emergency
departments.
He says:
"We
have identified a cardiac troponin concentration below which patients are at
very low risk of heart attack either during the admission or in the ensuing 30
days. These patients are therefore potentially suitable for immediate and safe
discharge from the emergency department. These findings could dramatically
reduce unnecessary hospital admissions and provide substantial cost savings for
health care providers."
Earlier this
year, the BHF showed that the same test could double diagnosis rates of heart
attacks in women. They found that using different criteria for a positive test
improved diagnosis rates so that 1 in 5 women were diagnosed.
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