What is Ischemic Heart Disease (IHD)?
Ischemic heart disease is a condition where myocardial oxygen supply fails to meet myocardial oxygen demand, resulting in inadequate blood flow to the heart muscle. 1
Definition and Pathophysiology
IHD represents an imbalance between myocardial oxygen supply and demand, encompassing a broader clinical spectrum that includes both symptomatic and asymptomatic conditions. 2 This occurs when coronary flow is inadequate to permit or sustain cardiac performance at a level sufficient to support the body over its full physiological range of activity. 1
The disease can result from:
- Coronary artery obstruction due to atherosclerosis (most common) 1
- Non-obstructive coronary causes including coronary vasospasm, microvascular dysfunction, and other pathophysiological mechanisms 1
- Conditions increasing oxygen demand such as hyperthyroidism, severe hypertension, hypertrophic cardiomyopathy, or aortic stenosis 1
- Conditions decreasing oxygen supply including anemia, hypoxemia, polycythemia, or hypergammaglobulinemia 1
Epidemiologic Burden
IHD affects approximately 1 in 3 adults in the United States, with more than 13 million Americans having coronary artery disease and over 9 million experiencing angina pectoris. 1 The disease was responsible for nearly 380,000 deaths in the United States in 2010, with an age-adjusted mortality rate of 113 per 100,000 population. 1 The economic burden is substantial, totaling $156 billion in direct and indirect costs in 2008. 1
Clinical Manifestations
Typical Angina
Typical angina presents with three cardinal features: 1
- Substernal chest discomfort with characteristic quality and duration
- Provoked by exertion or emotional stress
- Relieved by rest or nitroglycerin within 30 seconds to several minutes
Patients commonly describe the discomfort as "squeezing," "griplike," "suffocating," or "heavy"—rarely as "sharp" or "stabbing"—and it typically does not vary with position or respiration. 1
Atypical Presentations
Women and elderly patients frequently present with atypical symptoms including sharp chest pain, nausea, vomiting, or midepigastric discomfort rather than classic angina. 1 Some patients describe tightness, pressure, or discomfort rather than frank pain. 1
Silent Ischemia
A sizeable proportion of ischemic episodes occur without angina, particularly in patients with diabetes who have autonomic neuropathy and altered pain perception. 1
Clinical Categories
IHD encompasses both acute and chronic presentations:
Unstable angina is defined as new onset, increasing in frequency/intensity/duration, or occurring at rest. 1 Patients with high or moderate short-term risk require prompt emergency department transfer. 1
Stable angina has a short-term prognosis comparable to low-risk unstable angina and can be evaluated safely in an outpatient setting. 1
Risk Factors
Major modifiable risk factors include: 1
- Smoking
- Hyperlipidemia
- Diabetes mellitus
- Hypertension
- Obesity or metabolic syndrome
- Physical inactivity
Non-modifiable risk factors include: 1
- Family history of premature IHD (onset in male first-degree relative before age 55 or female before age 65)
- History of cerebrovascular or peripheral artery disease
Prognostic Implications
The extent and severity of coronary artery disease remain very significant predictors of long-term outcomes. 1 Five-year survival rates range from 93% for single-vessel disease with 50-74% stenosis to 59% for three-vessel disease with ≥95% proximal left anterior descending artery stenosis. 1
Evolving Nomenclature
Recent guidelines have introduced the terms Acute Myocardial Ischemic Syndromes (AMIS) and Non-Acute Myocardial Ischemic Syndromes (NAMIS) to better reflect the multiple pathophysiological causes of myocardial ischemia beyond obstructive coronary disease alone. 1 This nomenclature acknowledges that myocardial ischemia can occur with or without obstructive coronary arteries. 1