So the major limitation of the stress test approach, is that it needs a high grade stenosis as an indicator of heart attack risk. Thus, over the last 20 years or so, newer approaches in research, have increasingly focused on IMT to detect plaque at earlier stages of progression, before the artery lumen becomes severely stenosed, or compromised. not protruding into the artery lumen sufficiently to produce enough stenosis (usually less than 50%, average 20% by some IVUS studies) to be detectable by stress test methods. Recent (late 1990's) clinical studies have shown, that the vulnerable plaques which produce most myocardial infarctions are commonly present within many regions of the coronary (surface of the heart) arteries, yet are typically relatively flat, i.e. What most laypersons do not realize, is that stress tests do not detect atheromata (accumulations of macrophages overloaded with membranes containing cholesterol and other fats, within the walls, not lumens, of arteries) present throughout the heart or other body arteries, nor do they reveal the Vulnerable Plaques, which are the cause of most Heart Attacks or Myocardial Infarctions. Less severe stenoses are automatically compensated for, by vasodilation (widening or relaxing) of the ventricular arterioles during exercise, and do not usually produce enough of an imbalance of relative blood flow, to be detectable by stress test methods. hardening of the arteries, or arterial disease) and these High Grade Stenoses are the usual cause for both "stable" or reproducible exercise-related Angina (chest pain) and for "positive" stress tests. those greater than 75% occlusion, are usually the result of advanced Atherosclerosis (i.e. severe narrowing) of the larger coronary (surface of the heart) arteries can be detected. Blood flow imbalances within the heart muscle of the other three heart chambers are not detected this way. This is important because the Left Ventricle of the heart performs the greatest amount of work involved in pumping blood around the body. if it is "positive") are an indication of marked imbalances of relative blood flow to different portions of the Left Ventricular muscle tissue of the heart. These tests do not assess Emotional stress, or other connotations of the term stress. As an exercise test, the results can also reflect overall physical fitness. (December 2006)Ī Cardiac Stress Test is a medical test performed to evaluate arterial blood flow to (and indirectly the amount of oxygen that will reach) the myocardium (heart muscle) during physical exercise, compared to blood flow while at rest. All or part of this article may be confusing or unclear.
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