Are Coronary Artery Disease and Ischemic Heart Disease the Same?
No, coronary artery disease (CAD) and ischemic heart disease are not the same—CAD is one specific cause of ischemic heart disease, but ischemic heart disease encompasses a much broader spectrum of conditions that includes both obstructive epicardial coronary disease and multiple non-obstructive mechanisms of myocardial ischemia. 1
Understanding the Critical Distinction
Ischemic Heart Disease: The Broader Umbrella Term
Ischemic heart disease represents the final common pathway of inadequate myocardial oxygen supply relative to demand, regardless of the underlying mechanism. 1 This occurs when coronary flow cannot sustain cardiac performance across the full physiological range of activity, leading to symptoms, impaired quality of life, myocardial damage, and major adverse cardiovascular events. 1
The term encompasses:
- Obstructive epicardial coronary artery disease (the traditional focus) 1
- Coronary microvascular dysfunction 1
- Vasospastic disorders 1
- Ischemia with non-obstructive coronary arteries (INOCA) 1
- Myocardial infarction with non-obstructive coronary arteries (MINOCA) 1
- Non-coronary causes including demand ischemia from conditions like severe anemia, hypotension, or tachyarrhythmias 2, 3
Coronary Artery Disease: A Subset
CAD specifically refers to atherosclerotic disease of the epicardial coronary arteries, typically involving obstructive stenoses. 1 While CAD is the most common and well-recognized cause of myocardial ischemia, focusing solely on epicardial coronary obstruction represents a significant limitation in understanding the full spectrum of ischemic heart disease. 1
Why This Distinction Matters Clinically
The Diagnostic Pitfall
A purely anatomical approach using invasive coronary angiography or coronary CT angiography may fail to diagnose microvascular and/or vasospastic angina as treatable causes of symptoms. 1 Patients without obstructive coronary lesions are often falsely reassured that ischemia is not present and discharged from cardiology settings, leading to pursuit of costly non-cardiac evaluations rather than proper investigation of non-obstructive causes of myocardial ischemia. 1
Treatment Implications Differ by Mechanism
Treatment strategies must be tailored to the specific pathophysiologic mechanism causing ischemia, not just the presence or absence of epicardial stenosis. 1
- Obstructive CAD: Optimal medical therapy and revascularization when indicated 1
- Non-obstructive mechanisms: Treatment guided by identification of functional alterations causing ischemia 1
- Demand ischemia (Type 2 MI): Address underlying precipitant (control heart rate, maintain adequate blood pressure, treat anemia, etc.) 2
Evolving Nomenclature
Current Terminology Confusion
Multiple competing classification systems exist across international guidelines, creating confusion in clinical practice. 1
The terminology has evolved inconsistently:
- American College of Cardiology/American Heart Association previously used "stable ischemic heart disease (SIHD)" 1
- ACC/AHA 2023 guidelines now use "chronic coronary disease (CCD)" 1
- European Society of Cardiology 2019 guidelines introduced "chronic coronary syndromes (CCS)" 1
- All these terms still perpetuate the restrictive focus on "coronary" and "disease" 1
Proposed New Framework
The 2024 Circulation guidelines propose a binary classification of "acute myocardial ischemic syndromes (AMIS)" and "non-acute myocardial ischemic syndromes (NAMIS)" to better encompass all pathophysiologic mechanisms. 1, 3 This more inclusive nomenclature moves away from the restrictive terms "coronary" and "disease" to better capture the multiple causes of myocardial ischemia, including both obstructive and non-obstructive mechanisms. 1
Key Clinical Takeaways
When evaluating patients with suspected ischemic heart disease, clinicians must look beyond epicardial coronary stenosis. 1
Critical considerations include:
- 10-20% of stable CAD patients experience silent myocardial ischemia, so absence of angina does not equal low cardiovascular risk 1
- A sizeable percentage of patients with Type 2 MI develop MINOCA, where diagnosis is based on functional criteria (troponin rise/fall) rather than anatomical coronary obstruction 1
- Myocardial ischemia can result from multiple precipitants including tachycardia, hypotension, hypoxemia, anemia, and elevated ventricular filling pressures—all without epicardial coronary obstruction 2
The principal target structure affected by ischemia is the myocardium and cardiac myocyte, regardless of whether the cause is obstructive CAD or another mechanism. 1 Therefore, equating ischemic heart disease solely with coronary artery disease neglects important treatable causes of myocardial ischemia and limits diagnostic and therapeutic approaches. 1