Chest pain is the second most common symptom in the emergency room. Approximately 1 in 5 patients with chest pain are ultimately diagnosed with acute coronary syndrome (ACS). The vast majority of clinical guidelines have recommendations on how to manage ACS. However, it is more challenging to quickly and accurately rule out ACS in the emergency room, especially in patients with chest pain who are negative for ECG and troponin. Conventional AMI tests are mostly post-myocardial necrosis products, which often appear late and patients often lose the first aid time when positive. Ischemia-modified albumin (IMA) is a new and more desirable marker of ischemia, and it is the first myocardial ischemia marker approved for sale by the U.S. Food and Drug Administration (FDA). The ischemia-modified albumin level is measured using an albumin-cobalt binding assay as an indicator of early myocardial ischemia. Multiple studies have proved that IMA can reflect myocardial ischemic condition sensitively and is of great significance in the early diagnosis, risk stratification and guidance of treatment of acute coronary syndrome, and is currently a more ideal biochemical marker for detecting myocardial ischemia.
Clinical mechanism of IMA test.
IMA is a novel biochemical marker approved by FDA for the assessment of myocardial ischemia
IMA measures the degree of alteration of albumin in contact with ischemic tissue.
IMA is elevated in ischemia, but not in necrosis like other myocardial markers
IMA can be elevated within minutes of ischemia and can be maintained at high levels for several hours after ischemia has resolved.
Clinical significance of IMA test.
1. IMA is a sensitive indicator for detecting early myocardial ischemia, so it can detect acute myocardial ischemia earlier and predict the relative risk of cardiac events earlier.
IMA is a biomarker for the diagnosis of acute coronary syndrome (ACS), which is characterized by rapid onset, rapid changes, and uneven clinical presentation and risk, making early diagnosis difficult. Traditional biomarkers such as troponin (cTn), myoglobin (Myo), and creatine kinase isoenzyme (CK-MB) are only elevated when myocardial necrosis occurs, but by this time irreversible pathological damage has been inflicted on the patient. Therefore, there is an urgent need for an early sensitive biochemical index that can reflect myocardial ischemia for early diagnosis, and IMA is a research hotspot in recent years, opening a new path for the study of early diagnosis of ACS. the sensitivity of IMA for detecting myocardial ischemia in ACS patients is two times that of ECG and four times that of cTn.
2, IMA is a biochemical marker for detecting ischemia due to coronary spasm. ima is an ischemic marker, not a diagnostic marker of necrosis.
3, IMA can be used not only for the early diagnosis of ACS patients, but also as an indicator of coronary events, i.e., post-PCI. The IMA values of patients without collateral circulation are significantly higher than those with collateral circulation, and the increase in IMA values correlates with the severity of the lesion.
4. IMA values can be used as biochemical markers for early identification of acute stroke – the median level increases at the beginning of the cerebral hemorrhage attack.
Advantages of IMA testing.
The relationship between IMA and cardiac troponin (cTn).
1. scTn is released into the blood 6hr after myocardial necrosis, whereas IMA is released into the blood minutes after myocardial ischemia. Therefore, relying solely on cardiac markers such as cTn to make the diagnosis of ACS will be later than the actual course of ACS, and the diagnosis may be missed early.
2. cTn testing is retrospective, i.e., necrosis has already occurred. The benefit of the test is that it can prevent further myocardial damage from occurring.
3, If blood is collected at the same time as the disease occurs, cTn is not elevated and is of little diagnostic significance.
4. cTn elevation is not always the result of an acute event. For patients with ACS, the key to treatment is early detection, confirming the diagnosis of patients at high risk for myocardial ischemia, and taking aggressive interventions – not relying on cTn alone, as necrosis and ischemia together are important for the diagnosis of ACS.
Relationship between IMA and ECG.
ECG is the simplest, fastest and most cost-effective method to diagnose myocardial ischemia. ST-segment and T-wave changes are characteristic of myocardial ischemia and injury, but ECG is not sufficiently sensitive for diagnosis (about 35% for UA and 50% for AMI, with 10% of IMA patients being normal). The onset of ischemia is often transient, whereas ischemic ECG changes are in real time. Therefore, if there is no myocardial ischemia at the time of the ECG, the ECG is normal. Certain therapeutic measures may have some effect on ECG results, such as nitrates that may mask ischemic ECG changes and thus interfere with the diagnosis. IMA, on the other hand, has a rapid response and high diagnostic sensitivity for myocardial ischemia.
IMA and acute coronary syndrome.
(1) The positive rate of IMA for predicting the recent onset of acute myocardial injury is 94,4%.
(2) For the diagnosis of ACS, IMA has a fairly high sensitivity (>80%) but poor specificity; the combination of ECG and cTNs can improve the sensitivity of early diagnosis of ACS; the high negative rate of IMA can be used as an indicator for the exclusion of ACS
(3) IMA test can help to determine the poor prognosis of ACS patients.