Medical Pharmacology Chapter 9: Antianginal Drugs
Angina: Definition and Causes
Definition: Angina are those symptoms of myocardial ischemia that occur when myocardial oxygen availability is insufficient to meet myocardial oxygen demand.
Chest discomfort often described as heaviness, pressure, and squeezing. The sensation is localized typically in the sternal region.
Symptoms often last one to five minutes. Angina can radiate to the left shoulder, to both arms (ulnar surfaces of the forearm and hand), and can radiate to the neck, jaw, teeth, epigastrium and back.
In classical angina these symptoms often occur with exertion and are not due to sudden-onset vasospasm.
By contrast, in variant or Prinzmetal's angina which is caused by coronary vasospasm, reduction of coronary blood flow with angina may occur at rest.
Myocardial ischemia is usually caused by coronary vessel atherosclerosis. As the vessel lumen narrows blood flow is reduced.
Other causes that limit coronary blood flow include:
The extent of coronary vessel obstruction can vary as a function of vascular tone: ranging from spasm resulting in 90% obstruction to intermediate effects.
Coronary vasospasm that results in significant obstruction is a basis for Prinzmetal's variant angina.
If the plaque size results in less than about 50% reduction, sufficent coronary blood flow during exertion is liely still available and anginal symptoms are not present.
Timmis, A.D. In Pocket Picture Guides: Cardiology, Gower Medical Publishing, London, 1985, p.21
Raehl, C.L., and Nolan, P.E. Ischemic Heart Disease: Anginal Syndromes in Applied Therapeutics: The Clinical Use of Drugs (Young, L.Y., and Koda-Kimble, M.A., eds), Applied Therapeutics, Inc., Vancouver, 1995, p 13-3.