What is the detection process for Myocardial Infarction (MINCA)?

MINOCA Detection: Diagnostic Process

MINOCA detection requires a three-step algorithmic approach: (1) confirm acute myocardial infarction with elevated troponin plus clinical evidence of ischemia, (2) document non-obstructive coronary arteries (<50% stenosis) on angiography, and (3) systematically exclude alternative diagnoses through cardiac magnetic resonance imaging and, when indicated, intracoronary imaging. 1

Step 1: Confirm Acute Myocardial Infarction

The first detection criterion requires documentation of both biochemical and clinical evidence of myocardial infarction 1:

Biochemical Criteria

• Cardiac troponin elevation >99th percentile upper reference limit with a documented rise or fall pattern on serial measurements 1
• A single elevated value is insufficient; serial troponin assessment demonstrating dynamic changes is essential 1

Clinical Evidence (At Least One Required)

• Symptoms of myocardial ischemia (chest pain, dyspnea, diaphoresis) 1
• New ischemic ECG changes (ST-segment or T-wave abnormalities) 1
• Development of pathological Q waves 1
• Imaging evidence of new loss of viable myocardium or new regional wall motion abnormality in a pattern consistent with ischemic cause 1
• Identification of coronary thrombus by angiography or autopsy 1

Step 2: Document Non-Obstructive Coronary Arteries

Angiographic confirmation must demonstrate absence of obstructive disease, defined as no coronary artery stenosis ≥50% in any major epicardial vessel 1:

Angiographic Categories Included

• Normal coronary arteries (no angiographic stenosis) 1
• Mild luminal irregularities (stenosis <30%) 1
• Moderate atherosclerotic lesions (stenosis 30-49%) 1

Critical pitfall: Additional careful review of the angiogram may be required to ensure accurate assessment of stenosis severity, as visual estimation can underestimate disease 1

Step 3: Systematic Exclusion of Alternative Diagnoses

MINOCA is a working diagnosis that requires active exclusion of non-ischemic causes 1, 2:

Immediate Assessment of Left Ventricular Function

• Perform LV wall motion assessment promptly in the acute setting using either LV angiography (if renal function permits) or echocardiography 1, 2
• Regional wall motion abnormalities may indicate epicardial causes or specific alternative diagnoses 1

Cardiac Magnetic Resonance Imaging (Class I, Level B Recommendation)

• CMR is mandatory in all MINOCA patients without an obvious underlying cause 1, 2
• CMR identifies the underlying cause in up to 87% of MINOCA cases, differentiating between Takotsubo syndrome, myocarditis, or true myocardial infarction 1, 2
• CMR serves as the gold standard for detecting myocardial infarction patterns and excluding non-ischemic myocardial injury 2, 3

Intracoronary Imaging When Indicated

• Consider intravascular ultrasound (IVUS) or optical coherence tomography (OCT) when thrombus, plaque rupture or erosion, or spontaneous coronary artery dissection (SCAD) are suspected 1
• Intracoronary imaging detects pathological alterations not visible on conventional angiography, including plaque disruption, coronary dissection, and coronary thromboembolism 1, 4

Exclusion of Non-Cardiac Causes

The following alternative diagnoses must be systematically excluded 1:

• Pulmonary embolism: Exclude with D-dimer testing, BNP, and/or CT pulmonary angiography as appropriate 1
• Sepsis 1
• Myocarditis (now formally excluded from MINOCA definition per updated AHA criteria) 1
• Takotsubo syndrome (now formally excluded from MINOCA definition) 1
• Supply-demand mismatch conditions: hypertensive crisis, tachyarrhythmias, severe anemia, cardiac contusion 1

Traffic Light Diagnostic Algorithm

The European Society of Cardiology recommends a structured "traffic light" approach 1:

• Red (immediate alternative diagnosis): Conditions requiring no further MINOCA workup—myocarditis, Takotsubo syndrome, pulmonary embolism identified on initial testing 1
• Yellow (working diagnosis): Initial MINOCA diagnosis requiring further investigation with CMR and potentially intracoronary imaging 1
• Green (final MINOCA diagnosis): Confirmed after systematic exclusion of alternatives, with underlying mechanism identified when possible 1

Undetermined Cases

Despite optimal workup, the cause of MINOCA remains undetermined in 8-25% of patients, termed "myocardial infarction of unknown/unclear causes" 1. In these cases, treatment should target the most probable mechanisms: vasospastic angina, coronary plaque disruption, and thromboembolism 1, 2.

Key Distinction: Myocardial Infarction vs. Injury

The detection process fundamentally distinguishes myocardial infarction from myocardial injury by requiring clinical evidence of ischemia 1, 5. Troponin elevation alone is non-specific and can result from either ischemic or non-ischemic mechanisms; the presence of ischemic clinical features (symptoms, ECG changes, imaging findings) differentiates true MINOCA from other causes of troponin elevation 1, 5.