myocardial ischemia
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Introduction
A condition in which oxygen delivery to & waste removal from the myocardium falls below normal levels with oxygen demand exceeding supply. As a consequence, the metabolic machinery of myocardial cells is impaired leading to various degrees of diastolic (relaxation), then systolic (contractile) dysfunction. If not reversed within 30 minutes, myocardial ischemia generally results in myocardial infarction. Ischemia is usually diagnosed indirectly through techniques that demonstrate reduced myocardial blood flow or its consequences on contracting myocardium.
Etiology
- focal or diffuse coronary spasm
- coronary artery plaque instability
- platelet & fibrin thrombi
- abnormal resistance of intramyocardial vessels
Pathology
- stenosis > 95% to cause ischemia at rest
- factors of myocardial oxygen consumption
- temporal sequence of events
- ischemia
- diastolic dysfunction
- regional wall motion abnormalities
- ECG changes
- pain
- molecular pathology:
- miR-1 is overproduced in ischemic cardiac muscle
Clinical manifestations
- see angina & myocardial infarction