From the Guidelines
Demand ischemia and coronary artery disease (CAD) are distinct cardiac conditions, with demand ischemia being a supply-demand mismatch problem and CAD representing a structural limitation in coronary blood flow. The management of these conditions differs, with demand ischemia focusing on treating the underlying condition causing increased cardiac demand or decreased oxygen supply, and CAD treatment typically involving antiplatelet therapy, statins, beta-blockers, and possibly revascularization procedures like angioplasty or bypass surgery 1. Key differences between demand ischemia and CAD include:
- Demand ischemia often shows diffuse ST-segment depression without regional patterns on ECG, while CAD typically presents with more localized changes corresponding to specific coronary territories.
- Both conditions can cause troponin elevation, but the pattern and context differ.
- Understanding this distinction is crucial for appropriate management, as treating only the coronary disease without addressing the underlying cause of demand ischemia may not resolve the patient's condition. In patients with stable ischemic heart disease (SIHD), the decision to perform revascularization should be based on the presence of significant ischemia or symptoms that persist despite optimal medical therapy, as recommended by recent clinical practice guidelines 1. The use of fractional flow reserve (FFR) analysis can help identify patients who may benefit from revascularization, with an FFR ≤0.80 indicating a potential benefit from revascularization 1. Overall, the management of demand ischemia and CAD requires a comprehensive approach that takes into account the underlying pathophysiology and individual patient characteristics, with the goal of improving outcomes and quality of life.
From the Research
Demand Ischemia vs CAD
- Demand ischemia refers to a condition where the heart's oxygen demand exceeds its supply, often due to increased heart rate, blood pressure, or contractility 2, 3.
- Coronary artery disease (CAD) is a condition where the coronary arteries become narrowed or blocked, reducing blood flow to the heart and leading to ischemia 4, 5.
- The key difference between demand ischemia and CAD is that demand ischemia is a functional imbalance between oxygen supply and demand, whereas CAD is a structural obstruction of coronary blood flow 3, 5.
Treatment and Management
- Beta-blockers and calcium channel blockers are effective in reducing myocardial oxygen demand and improving oxygen supply in demand ischemia 2.
- Exercise training (ET) can increase coronary blood flow and reduce myocardial infarction and angina in CAD patients 4.
- The role of beta-blockers in CAD has been questioned in recent years, and additional large-scale randomized clinical trials are needed to evaluate their effectiveness in current clinical practice 6.
Pathophysiology
- Myocardial ischemia is characterized by an imbalance between myocardial oxygen supply and demand, causing cardiac dysfunction, arrhythmias, myocardial infarction, and sudden death 3.
- The coronary circulation matches blood flow with oxygen requirements by coordinating the resistances within microvasculature, where the endothelium plays an important role by liberating several vasodilator substances 3.
- Impaired endothelial regulation is involved in the pathogenesis of a wide variety of cardiovascular diseases and is an important therapeutic target 3.