Definition of Ischemic Heart Disease
Ischemic heart disease is a pathophysiologic condition in which coronary blood flow is inadequate to meet myocardial oxygen demands, resulting from both obstructive epicardial coronary artery disease and non-obstructive mechanisms including microvascular dysfunction, vasospasm, and other functional coronary alterations. 1
Core Pathophysiology
Myocardial ischemia represents the fundamental underlying mechanism where inadequate coronary perfusion prevents the heart from sustaining cardiac performance sufficient to support the body across its full physiological range of activity. 1 This creates a cascade of pathophysiologic changes including:
- Left ventricular relaxation abnormalities 1
- Regional contractile impairment 1, 2
- Myocardial infarction 1
- Arrhythmias, including sudden cardiac death 1, 2
Multiple Etiologic Mechanisms
The critical clinical pitfall is assuming ischemic heart disease equals obstructive coronary artery disease—it does not. 1, 3 The condition encompasses:
Obstructive Causes
- Atherosclerotic plaque rupture or erosion 1
- Flow-limiting epicardial stenoses 1
- Coronary dissection 1
- Coronary embolism 1
Non-Obstructive Causes
- Coronary microvascular dysfunction (impaired vasodilation, microvascular spasm) 1
- Epicardial vasospasm 1
- Myocardial bridges 1
- Extramural microvascular compression 1
- Microembolization 1
- Hypercoagulable states 1
Clinical Presentations
The American College of Cardiology and Circulation guidelines now classify ischemic heart disease into two broad categories 3:
Acute Myocardial Ischemic Syndromes (AMIS)
- ST-elevation myocardial infarction (STEMI) 3
- Non-ST-elevation myocardial infarction (NSTEMI) 3
- Unstable angina 3
- Includes both obstructive and non-obstructive causes 3
Non-Acute Myocardial Ischemic Syndromes (NAMIS)
- Stable angina (predictable exertional chest discomfort relieved by rest or nitroglycerin) 3
- Asymptomatic ischemic heart disease 3
- Silent myocardial ischemia (occurs in 10-20% of stable coronary disease patients) 1, 4
Critical Clinical Considerations
Angina and ischemia do not necessarily coexist—absence of symptoms does not equal absence of risk. 1, 4 Silent myocardial ischemia occurs more commonly in patients with diabetes who have autonomic neuropathy and altered pain perception. 1, 4
A purely anatomical diagnostic approach using coronary angiography or CT angiography may fail to diagnose microvascular and vasospastic angina as treatable causes. 1 Patients with non-obstructive coronary arteries on imaging may be falsely reassured that ischemia is not present, leading to discharge from cardiology care and pursuit of costly non-cardiac evaluations rather than proper functional assessment of non-obstructive ischemic mechanisms. 1, 4
Epidemiologic Impact
Ischemic heart disease affects approximately 1 in 3 adults in the United States, with more than 13 million Americans having coronary artery disease and over 9 million with angina pectoris. 1 It was responsible for nearly 380,000 deaths in the United States in 2010 and is now the leading cause of adult heart failure. 2