Involvement of Catecholamines in Coronary Spasm Under Stressful Conditions

Abstract

Since the early recognition that coronary arteries may go into spasm, provoking angina pectoris and myocardial infarction (1), it is becoming clear that coronary artery spasm plays an important role in the genesis of ischemic heart disease (2,3,4). In half the people who die of coronary disease the first symptom is sudden death, presumably due to cardiac arrhythmia. Although the occurrence of coronary spasm can be seen to explain cardiac arrhythmias and sudden death in individuals under stressful situations (5) the mechanisms of coronary spasm under conditions of stress are poorly understood (6,7). In view of the fact that circulating levels of catecholamines are markedly elevated under a wide variety of stressful conditions, it is possible that these hormones are involved in increasing the tone of coronary vessels under stress. Therefore in this report we wish to review some of the experimental data obtained by employing isolated perfused rat heart preparations (8,9) which identify the mechanisms of coronary spasm in stress-induced heart disease. Because of the crucial role played by calcium in muscle contraction as well as the therapeutic usefulness of calcium antagonistic drugs in coronary artery disease, the discussion will be focussed on issues relating to the involvement of calcium in coronary artery spasm. The differences between changes in coronary vessel tone in acute stress and chronic stress will also be highlighted.