Definition
Criteria for acute myocardial infarction
Types
Reinfarction
Myocardial infarction redefined—a consensus document of The Joint European Society of Cardiology/American College of Cardiology Committee for the redefinition of myocardial infarction (2000) [1]
Biochemical markers for detecting myocardial necrosis:
The following are biochemical indicators for detecting myocardial necrosis:
1. Maximal concentration of troponin T or I exceeding the decision limit (99th percentile of the values for a reference control group), on at least one occasion during the first 24 h after the index clinical event
2. Maximal value of CK-MB (preferably CK-MB mass) exceeding the 99th percentile of the values for a reference control group on two successive samples or maximal value exceeding twice the upper limit of normal (ULN) for the specific institution on one occasion during the first hours after the index clinical event
Values for CK-MB values should rise and fall; values that remain elevated without change are almost never due to MI. In the absence of availability of a troponin or CK-MB assay, total CK (greater than two times the upper reference limit) or the B fraction of CK may be employed, but these last two biomarkers are considerably less satisfactory than CK-MB
2007 Universal Definition of myocardial infarction [2]
The term myocardial infarction should be used when there is evidence of myocardial necrosis in a clinical setting consistent with myocardial ischemia. Under these conditions anyone of the following criteria meets the diagnosis for myocardial infarction:
1. Detection of rise and/or fall of cardiac biomarkers (preferably troponin) with at least one value above the 99th percentile of the URL together with evidence of myocardial ischemia with at least one of the following:
(a) Symptoms of ischemia
(b) ECG changes indicative of new ischemia [new ST-T changes or new LBBB (LBBB)]
(c) Development of pathological Q waves in the ECG
(d) Imaging evidence of new loss of viable myocardium or new regional wall motion abnormality
2. Sudden, unexpected cardiac death, involving cardiac arrest, often with symptoms suggestive of myocardial ischemia, and accompanied by presumably new ST elevation, or new LBBB, and/or evidence of fresh thrombus by coronary angiography and/or at autopsy, but death occurring before blood samples could be obtained or at a time before the appearance of cardiac biomarkers in the blood
Type 1: spontaneous MI related to ischemia due to a primary coronary event such as plaque erosion and/or rupture, fissuring, or dissection
Type 2: MI secondary to ischemia due to either increased oxygen demand or decreased supply, e.g., coronary artery spasm, coronary embolism, anemia, arrhythmias, hypertension, or hypotension
Type 3: sudden unexpected cardiac death, including cardiac arrest, often with symptoms suggestive of myocardial ischemia, accompanied by presumably new ST elevation, or new LBBB, or evidence of fresh thrombus in a coronary artery by angiography and/or at autopsy, but death occurring before blood samples could be obtained or at a time before the appearance of cardiac biomarkers in the blood
≥ 20 % increase of the value in the second cardiac biomarker sample 3–6 h following the immediate measurement at the time of the suspected clinical signs or symptoms
3. For PCI in patients with normal baseline troponin values, elevations of cardiac biomarkers above the 99th percentile URL are indicative of periprocedural myocardial necrosis. By convention, increases of biomarkers greater than 3 × 99th percentile URL have been designated as defining PCI-related myocardial infarction. A subtype related to a documented stent thrombosis is recognized
4. For CABG in patients with normal baseline troponin values, elevations of cardiac biomarkers above the 99th percentile URL are indicative of periprocedural myocardial necrosis. By convention, increases of biomarkers greater than 5 × 99th percentile URL plus:
(a) Either new pathological Q waves or new LBBB
(b) Angiographically documented new graft or native coronary artery occlusion
(c) Imaging evidence of new loss of viable myocardiumHave been designated as defining CABG-related myocardial infarction
5. Pathological findings of an acute myocardial infarction
Type 4a: myocardial infarction associated with PCI
If cTn values are elevated prior to PCI and are not stable (or falling) for at least two samples 6 h apart, there are insufficient biomarker criteria to diagnose a periprocedural MI (PPMI)
If the baseline cTn values are elevated and are stable or falling, then a rise of ≥20 % (as with reinfarction) together with the features of the electrocardiogram or imaging can be applied
Type 4b: myocardial infarction associated with stent thrombosis as documented by angiography or at autopsy
Type 5: myocardial infarction associated with CABG
If a cTn assay is not available, CK-MB, as measured by mass assay, is considered the best alternative
2012 Third Universal Definition of myocardial infarction [3]
The term acute myocardial infarction should be used when there is evidence of myocardial necrosis in a clinical setting consistent with acute myocardial ischemia. Under these conditions any one of the following criteria meets the diagnosis for MI:
1. Detection of a rise and/or fall of cardiac biomarker values [preferably cardiac troponin (cTn)] with at least one value above the 99th percentile URL and with at least one of the following:
(a) Symptoms of ischemia
(b) New or presumed new significant ST segment-T wave (ST-T) changes or new LBBB
(c) Development of pathological Q waves in the ECG
(d) Imaging evidence of new loss of viable myocardium or new regional wall motion abnormality
(e) Identification of an intracoronary thrombus by angiography or autopsy
2. Cardiac death with symptoms suggestive of myocardial ischemia and presumed new ischemic ECG changes or new LBBB, but death occurred before cardiac biomarkers were obtained, or before cardiac biomarker values would be increased
Same MI types as the 2007 Universal Definition of Myocardial Infarction with the addition of Type 4c MI
Type 1: spontaneous myocardial infarction. Spontaneous myocardial infarction related to atherosclerotic plaque rupture, ulceration, fissuring, erosion, or dissection with resulting intraluminal thrombus in one or more of the coronary arteries leading to decreased myocardial blood flow or distal platelet emboli with ensuing myocyte necrosis. The patient may have underlying severe CAD but on occasion nonobstructive or no CAD
Type 2: myocardial infarction secondary to an ischemic imbalance. In instances of myocardial injury with necrosis where a condition other than CAD contributes to an imbalance between myocardial oxygen supply and/or demand, e.g., coronary endothelial dysfunction, coronary artery spasm, coronary embolism, tachy-/bradyarrhythmias, anemia, respiratory failure, hypotension, and hypertension with or without LVH
Type 3: myocardial infarction resulting in death when biomarker values are unavailable. Cardiac death with symptoms suggestive of myocardial ischemia and presumed new ischemic ECG changes or new LBBB, but death occurring before blood samples could be obtained before cardiac biomarkers could rise or in rare cases cardiac biomarkers were not collected
≥20 % increase of the value in the second cardiac biomarker sample 3–6 h following the immediate measurement at the time of the suspected clinical signs or symptoms
3. PCI-related MI is arbitrarily defined by elevation of cTn values (>5 × 99th percentile URL) in patients with normal baseline values (≤99th percentile URL) or a rise of cTn values ≥20 % if the baseline values are elevated and are stable or falling. In addition, either:
(a) Symptoms suggestive of myocardial ischemia, or
(b) New ischemic ECG changes, or
(c) Angiographic findings consistent with a procedural complication, or
(d) Imaging demonstration of new loss of viable myocardium or new regional wall motion abnormalityare required
4. Stent thrombosis associated with MI when detected by coronary angiography or autopsy in the setting of myocardial ischemia and with a rise and/or fall of cardiac biomarker values with at least one value above the 99th percentile URL
Type 4a: myocardial infarction related to PCI. Myocardial infarction associated with PCI is arbitrarily defined by elevation of cTn values >5 × 99th percentile URL in patients with normal baseline values (≤99th percentile URL) or a rise of cTn values ≥20 % if the baseline values are elevated and are stable or falling. In addition, either (i) symptoms suggestive of myocardial ischemia, or (ii) new ischemic ECG changes or new LBBB, or (iii) angiographic loss of patency of a major coronary artery or a side branch or persistent slow- or no-flow or embolization, or (iv) imaging demonstration of new loss of viable myocardium or new regional wall motion abnormality is required
Type 4b: myocardial infarction related to stent thrombosis. Myocardial infarction associated with stent thrombosis is detected by coronary angiography or autopsy in the setting of myocardial ischemia and with a rise and/or fall of cardiac biomarker values with at least one value above the 99th percentile URL
5. CABG related MI is arbitrarily defined by elevation of cardiac biomarker values (>10 × 99th percentile URL) in patients with normal baseline cTn values (≤99th percentile URL). In addition, either
(a) New pathological Q waves or new LBBB, or
(b) Angiographic documented new graft or new native coronary artery occlusion, or
(c) Imaging evidence of new loss of viable myocardium or new regional wall motion abnormality
Type 4c: myocardial infarction related to restenosis. ≥50 % stenosis at coronary angiography or a complex lesion associated with a rise and/or fall of cTn values > 99th percentile URL and no other significant obstructive CAD of greater severity following: (i) initially successful stent deployment or (ii) dilatation of a coronary artery stenosis with balloon angioplasty (<50 %)
Type 5: myocardial infarction related to CABG. Myocardial infarction associated with CABG is arbitrarily defined by elevation of cardiac biomarker values >10 × 99th percentile URL in patients with normal baseline cTn values (≤99th percentile URL). In addition, either (i) new pathological Q waves or new LBBB, or (ii) angiographic documented new graft or new native coronary artery occlusion, or (iii) imaging evidence of new loss of viable myocardium or new regional wall motion abnormality
If a cTn assay is not available, the best alternative is CK-MB (measured by mass assay)
The 2012 MI categories are similar to those from 2007, but the threshold for a Type 4a, PCI-related MI, increased from >3 × 99th percentile of the upper reference limit (URL) to >5 × 99th percentile, and the threshold for a Type 5 CABG-related MI increased from >5 × 99th percentile URL to >10 × 99th percentile URL. These thresholds are arbitrary. The Third Universal Definition of MI also defined a Type 4c MI due to restenosis as ≥50 % stenosis at coronary angiography or a complex lesion associated with a rise and/or fall of cTn values exceeding the 99th percentile URL and no other significant obstructive coronary artery disease of greater severity following either (i) an initially successful stent deployment or (ii) dilatation of a coronary artery stenosis with balloon angioplasty (<50 %) [3].
The definition of periprocedural MI (PPMI) remains controversial. Further study is needed to determine whether PPMIs (and particular thresholds) contribute to the prediction of death or MI (as do Type 1 MIs) when considered with pre-procedure risk estimates, atherosclerotic burden, and procedural complexity [4]. In 2013, the Society for Cardiovascular Angiography and Interventions (SCAI) published a definition for “clinically relevant” MI after both PCI and CABG procedures that uses higher thresholds than the 2012 Universal Definition of MI and CK-MB instead of cTn as the preferred biomarker [6]. In patients with normal baseline CK-MB and without ACS, SCAI recommends defining a clinically relevant PPMI as a peak CK-MB measured within 48 h of the procedure ≥10× the local laboratory ULN or in the absence of CK-MB measurements, a cTn (I or T) ≥70× ULN (or by CK-MB ≥5× ULN or cTn ≥35× ULN plus the development of new pathological Q waves in ≥2 contiguous leads or new persistent left bundle branch block [LBBB]) [6].
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