Radionuclide techniques in the diagnosis and assessment of occult coronary artery disease

Abstract

The diagnosis of coronary artery disease in the absence of symptoms is not an easy task. It is possible that the lack of symptoms is due to the presence of haemodynamically significant coronary artery disease that is entirely silent, yet it is possible that the lack of symptoms is due to the mild and hence, haemodynamically insignificant nature of the coronary stenosis. Such patients are therefore, not expected to produce abnormalities in any of the traditional forms of screening tests, such as exercise electrocardiography, thallium-201 imaging, and radionuclide angiography. These patients are, nevertheless, prone to sudden total occlusion of a coronary artery by a thrombus with the catastrophic results of massive myocardial infarction or sudden death. An argument can be made that patients with severe stenosis which results in a pressure drop across the lesion are protected by well functioning collaterals that are likely to develop and thus, protect the left ventricle in the event of thrombus occlusion of the diseased vessel. Therefore, paradoxically it appears that patients with less severe Stenosis who may not be diagnosed by non-invasive testing are at higher risk for sudden death or large infarctions than patients with more severe stenosis who are likely to be detected by exercise studies. Parenthetically, even coronary arteriography will not alter therapy in the former patients because angioplasty or bypass surgery are not recommended for mild stenosis. The role of anti-platelet therapy remains to be determined, but theoretically, it is worth the effort.