Unstable rest angina with ST-segment depression. Pathophysiologic considerations and therapeutic implications

Area of Science:

• Cardiology
• Cardiovascular Physiology

Background:

• Rest angina with ST-segment depression has been traditionally attributed to increased myocardial oxygen demand.
• Recent findings necessitate a re-evaluation of this concept.

Purpose of the Study:

• To investigate the immediate cause of ischemia in patients experiencing rest angina with ST-segment depression.
• To identify the underlying mechanisms of flow reduction during rest angina.

Main Methods:

• Continuous hemodynamic and electrocardiographic monitoring before and during rest angina attacks.
• Thallium-201 scintigraphy performed during episodes of chest pain.

Main Results:

• Transient reduction in coronary blood flow was identified as the primary cause of myocardial ischemia in most cases.
• Coronary arterial spasm and/or platelet aggregation at atherosclerotic sites were implicated in flow reduction.
• A significant portion of patients did not exhibit increased blood pressure or heart rate preceding angina.

Conclusions:

• Rest angina with ST-segment depression is frequently caused by reduced coronary flow, likely due to spasm or aggregation, rather than solely increased oxygen demand.
• Therapeutic strategies for unstable rest angina should focus on preventing transient flow reductions and managing myocardial oxygen consumption.
• A combination therapy including long-acting nitrates, beta-blockers, calcium-channel blockers, and antiplatelet agents (aspirin or heparin) is recommended, with IV nitroglycerin for acute episodes.