Myocardial ischemia. Prepared by: Dr. Nehad Ahmed. Study objectives. Understand the relationship between myocardial ischemia and angina. Distinguish among classic angina, unstable angina, variant angina and silent ischemia .
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Dr. Nehad Ahmed
Myocardial ischemia occurs when the blood ﬂowdemands of the heart exceed the blood supplied by the coronary arteries. The leading cause of myocardial ischemia is atherosclerosis or blockage of coronary arteries due to the accumulation of lipid plaques and/or thrombus
Under conditions of rest, myocardial oxygen supply and delivery of nutrients through the coronary arteries should match the metabolic requirements of the heart.
When the metabolic needs of the heart increase, the coronary blood ﬂow must increase accordingly .
With age and progressive occlusion of coronary arteries, smaller vessels may begin to carry a greater proportion of blood and provide an alternate means of perfusion for an area of myocardium.
Development of collateral circulation may reduce or delay the occurrence of symptoms from myocardial ischemia until the blockage is very progressed.
- Symptoms may remain “stable” for a number of years or progress in severity.
- Angina that occurs at rest.
- Requires intensive treatment and evaluation.
• Caused by vasospasm of the coronary arteries.
• Usually associated with coronary artery disease but may result from excess sympathetic activity.
• Frequently occurs at night, at rest or during minimal exercise.
• May be precipitated by stress, cold exposure or smoking.
Silent ischemia is a particularly dangerous form of myocardial ischemia as there is a lack of clinical symptoms, i.e., ischemia without angina.
Usually diagnosed by exercise stress testing or Holter monitoring
Ischemia — Inadequate blood ﬂow to a tissue or part of the body.
Hypoxia — Deﬁciency of oxygen in tissues.
Preload —The load on the heart at the end of diastole.
Afterload—The force that the contracting heart must generate to eject blood.