The effect of atherosclerosis on the vasomotor response of coronary arteries to mental stress

Article Abstract:

Patients with coronary artery disease may have adequate blood flow to supply the heart muscle under average conditions, but increased demands for oxygen by the heart muscle during exercise may surpass the capabilities of the arteries partially blocked by atherosclerosis. It is well established that patients with coronary artery disease may also suffer angina in response to mental stress as well as the stress of exercise. It has generally been thought that the reaction to mental stress follows similar mechanisms, that is, the inability of the diseased arteries to supply adequate blood to the heart muscle when the heart is beating faster. However, imaging studies have now suggested that mental stress may be a two-edged sword. In addition to the increased oxygen demands resulting from increased work performed by the heart, there is also an indication that the diseased arteries themselves actually constrict in response to mental stress, compounding the problem. To explore the physiological basis for this phenomenon, a study was conducted with 26 patients with coronary artery disease. Angiography, an X-ray technique used to directly observe the size of the lumen within blood vessels, was used to monitor patient response to mental stress. In this study, the mental stress was induced by asking the patient to perform arithmetic calculations, and then interrupting the patient to frustrate his attempts to perform the task. The smooth portions of the coronary arteries (the healthy portions) were observed to either dilate or remain about the same in response to the mental stress; this is the normal physiological response. In contrast, the portions of the arteries affected by atherosclerosis actually constricted in many instances during the mental stress, an abnormal response having the effect of impeding blood flow at a time when it is needed more. These results suggest that the normal balance between artery relaxation and artery constriction is subverted by the atherosclerotic disease process. This local failure of artery dilation results in an abnormal response to mental stress. (Consumer Summary produced by Reliance Medical Information, Inc.)

Psychological aspects, Stress (Psychology)

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Coronary vasoconstriction: visible and invisible

Article Abstract:

Angina pectoris is characterized by chest pain that results when the demands of the heart muscle for oxygen are exceeded by the capacity of the coronary arteries to supply blood, the ischemic threshold. Clinical experience has shown that angina may result from exercise, but it also may result from mental stress. In the November 28, 1991 issue of The New England Journal of Medicine, researchers measured the response of the coronary arteries to mental stress. Heart patients were asked to perform arithmetic calculations while the researchers subjected them to interruptions and annoyances. Visual observation of the coronary arteries using angiography revealed that many of the smooth artery segments, regions of artery not affected by atherosclerosis, either dilated in response to the mental stress or remained about the same. In contrast, regions of the arteries that were already partially obstructed by atherosclerosis constricted in many patients during the mental stress. It should be emphasized, however, that the amount of constriction observed in this study is unlikely to be the cause of the heart muscle ischemia and the angina that is associated with mental stress. Narrowing of the vessels does not necessarily mean a decrease in blood flow, since the rate of blood flow can speed up to result in the same net flow. Far greater obstructions are required before a serious impairment of blood flow results. The net flow of blood into the heart muscle is the sum of the interaction of a variety of physiological factors. One possibility is that, while the effects of mental stress on the larger arteries may be easily observed, it may be that the smaller arteries are responsible for obstructing the adequate flow of blood. Many of the smaller arteries are too small to be visible on angiography. Heart disease is a very complex problem, and the more that is learned about the physiology of cardiovascular disease, the more complex it seems to become. (Consumer Summary produced by Reliance Medical Information, Inc.)

Editorial, Stress (Physiology)

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The effect of cholesterol-lowering and antioxidant therapy on endothelium-dependent coronary vasomotion

Article Abstract:

A combination of low density lipoprotein (LDL) cholesterol-lowering and antioxidant therapy may improve blood vessel dilator responses in the lining of the heart in patients with atherosclerosis of the heart and high cholesterol levels. Atherosclerosis is the irregular distribution of fat deposits in the medium and large arteries. In a study, 49 patients were randomly assigned to one of three therapies: an American Heart Association diet, lovastatin and cholestyramine to lower LDL levels, or lovastatin and probucol to lower LDLs and provide antioxidants. The researchers found that the LDL lowering and antioxidant treatment group showed the most improvement in blood vessel dilator (vasodilator) responses to acetylcholine that were dependent on the lining of the heart (endothelium). The contributions of LDL cholesterol-lowering and antioxidant therapy may not be separable based on study results. Probucol may be partly responsible, as was lovastatin, for improvement in endothelial vasodilator responses. The diet therapy had little to no effect on fat levels. The therapies were continued for one year.

Drug therapy, Antioxidants, Antioxidants (Nutrients), Anticholesteremic agents, Vascular endothelium

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