Myocardial ischemia and angina pectoris: the clinical problem in patients.
The morbidity and mortality suffered by patients with coronary artery disease is probably caused by the development of myocardial ischemia. Angina pectoris occurs not only during stress but also at rest and at night. This suggests that myocardial ischemia may be caused by a variety of mechanisms. Ambulatory monitoring of ST segment changes was performed in 60 patients presenting with angina, positive ECG stress tests and coronary artery disease. 85% of ischemic ECG events were asymptomatic, 37% occurred with no increase in heart rate and 15% of episodes either lasted 20 minutes or more or fluctuated in severity. A controlled pilot study in ten patients showed that the combination of high dose propranolol and nifedipine produced a significant decrease in chest pain and episodes of ST depression. Radionuclide studies in 50 patients with angina and coronary artery disease have shown that stress (i.e., atrial pacing) produced different patterns of disturbed regional myocardial perfusion related to the patient's exercise capacity and eventually leading to a decrease in regional myocardial perfusion during the ischemic episode. St segment depression appeared only after the decrease in regional myocardial perfusion. These findings combined with past research suggest that patients with angina and coronary artery disease can suffer frequent asymptomatic disturbances of the regional myocardial perfusion. The frequency of these episodes and the time course for the recovery of the metabolic consequences mean that segments of ventricular myocardium may be constantly abnormal. The relative importance of changes in coronary tone and malfunction of platelets in the diseased coronary tree needs to be examined in clinical research. Pilot studies of antiplatelet agents have shown a significant beneficial effect on episodes of ischemia occurring at night and those occurring without any increase in heart rate. The techniques and observations in these patients with coronary artery disease all suggest that acute transient regional myocardial ischemia is caused by a variety of mechanisms. Further research using objective methods is required to discover the causes of ischemia and to rationalize treatment. f
D000787:Angina Pectoris / Q000175:diagnosis*; D002304:Cardiac Pacing, Artificial; D003326:Coronary Circulation; D003327:Coronary Disease / Q000175:diagnosis*; D004562:Electrocardiography; D006801:Humans