Classification of Ischemic Heart Disease
Ischemic heart disease is fundamentally classified into two major categories: acute presentations (acute coronary syndromes) and chronic/stable presentations (stable ischemic heart disease), with the most recent 2024 nomenclature proposing the terms "acute myocardial ischemic syndromes" (AMIS) and "non-acute myocardial ischemic syndromes" (NAMIS) to better encompass both obstructive and non-obstructive causes. 1
Primary Classification Framework
Acute Presentations (Acute Coronary Syndromes)
The acute category encompasses conditions caused by unstable plaque rupture with acute thrombosis: 1
ST-Elevation Myocardial Infarction (STEMI) - characterized by complete coronary occlusion with ST-segment elevation on ECG and elevated cardiac biomarkers 1, 2
Non-ST-Elevation Myocardial Infarction (NSTEMI) - partial coronary occlusion with elevated troponin but without ST-elevation 1, 2
Unstable Angina (UA) - myocardial ischemia without detectable myocardial necrosis and normal troponin levels 1, 2
Critical distinction: Unstable angina patients must be further risk-stratified into high, intermediate, and low-risk categories based on clinical features, ECG changes, and cardiac biomarkers. 1
Risk Stratification for Unstable Angina
High-risk features (requiring immediate transfer to emergency department or coronary care unit): 1
- Prolonged ongoing rest pain (>20 minutes)
- Pulmonary edema likely due to ischemia
- New or worsening mitral regurgitation murmur
- Transient ST-segment changes ≥0.5 mm with rest angina
- Elevated cardiac troponin (TnT or TnI ≥0.1 ng/mL)
- Sustained ventricular tachycardia
Intermediate-risk features: 1
- Prior MI, peripheral or cerebrovascular disease, or CABG
- Prolonged rest angina (>20 minutes) now resolved
- Age >70 years
- T-wave changes or pathological Q waves on ECG
- Slightly elevated troponin (0.01-0.1 ng/mL)
Low-risk features (addressed in stable IHD guidelines): 1
- New-onset angina within 2 weeks to 2 months
- Increased angina frequency, severity, or duration
- Angina provoked at lower threshold
- Normal or unchanged ECG
- Normal cardiac markers
Chronic/Stable Presentations
The chronic category includes: 1
Stable Angina - predictable chest discomfort with exertion, relieved by rest or nitroglycerin, reflecting gradual progression of obstructive CAD 1
Asymptomatic IHD - patients with known coronary disease who become symptom-free with appropriate therapy 1
Ischemic Equivalents - atypical presentations such as dyspnea or arm pain with exertion rather than classic angina 1
Emerging Comprehensive Classification (2024)
The most recent Circulation guidelines propose a paradigm shift to more inclusive terminology: 1
Acute Myocardial Ischemic Syndromes (AMIS)
This encompasses all acute presentations including traditional ACS categories (STEMI, NSTEMI, unstable angina) plus recognition of non-obstructive causes. 1
Non-Acute Myocardial Ischemic Syndromes (NAMIS)
This replaces competing terms like "stable CAD," "stable ischemic heart disease," "chronic coronary syndromes," and "chronic coronary disease" with unified nomenclature. 1
Key advantage of this classification: It explicitly includes both obstructive epicardial coronary disease AND non-obstructive pathogenetic mechanisms including: 1
- Coronary microvascular dysfunction
- Vasospastic disorders
- Non-coronary causes of myocardial ischemia
- Ischemia and MI with non-obstructive coronary arteries (INOCA/MINOCA)
Myocardial Infarction Type Classification
MI is further subclassified by mechanism: 2, 3
Type 1 MI - atherosclerotic plaque rupture, ulceration, fissure, or erosion with intraluminal thrombus 2
Type 2 MI - myocardial necrosis from supply-demand mismatch without plaque rupture (e.g., hypotension, severe anemia, tachyarrhythmias, coronary vasospasm) 2, 3
Clinical Presentation-Based Classification
Chest pain characteristics determine initial categorization: 1
Typical angina - substernal chest discomfort with radiation to neck/jaw/arms, precipitated by exertion, relieved by rest or nitroglycerin 1
Atypical angina - meets only 2 of the 3 typical criteria 1
Noncardiac chest pain - meets 1 or none of the typical criteria 1
Important Clinical Pitfalls
Do not assume all IHD is obstructive coronary disease. The restrictive focus on "coronary" and "disease" terminology has historically neglected microvascular dysfunction, vasospasm, and other non-obstructive mechanisms that cause genuine myocardial ischemia and infarction. 1
Low-risk unstable angina overlaps with stable IHD management. These patients can be managed using stable IHD guidelines rather than requiring acute coronary syndrome protocols. 1
Type 2 MI requires different management than Type 1. The absence of acute plaque rupture means the focus shifts to correcting the underlying supply-demand mismatch rather than urgent revascularization. 2, 3