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The increasing application of cardiovascular opacifying procedures to the diagnosis of congenital malformations of the heart and great vessels and to the study of acquired cardiovascular disease has promoted an acceleration of effort toward the search for and formulation of more satisfactory radiopaque media. Within recent years, a number of compounds and formulations of newer types have been introduced while, at the same time, there has been progress in the development of additional opacifying procedures and technics for the diagnosis of congenital heart disease and disease states of the cardiac valves, coronary arteries, and pulmonary circulation. None of our present-day methods of cardiovascular opacification is completely devoid of danger to the patient; none is wholly innocuous. In large measure, the inherent hazards relate to the injected radiopaque medium. In the amounts and dosages necessary for effective opacification, any or all of the currently employed radiopacifying agents can, on occasion, produce undesirable reactions and complications. It has therefore seemed pertinent to give further consideration to certain of the physicochemical and toxicological properties of the various cardiovascular contrast materials we have employed in our clinical studies of the heart, intrathoracic vessels, and pulmonary circulation. While we have used all of the media listed in Table I in certain studies of the abdominal aorta and its branches, we have, for purposes of this publication, restricted our comments to those related to opacification of the heart and intrathoracic vessels. When the site of delivery of the opaque medium is the lower thoracic or upper abdominal aorta, considerations arise as to toxic effects upon the kidneys and intestines. Injections made some distance proximal to the origins of the renal and intestinal arterial supply permit a degree of radiopaque dilution, and hence these problems are of less concern. The majority of reactions and deleterious physiological effects produced by intracardiac or intrathoracic vascular opacifications are due to the transport to and effects of the injected media upon the central nervous system. Full deliberation must therefore be given to the neurotoxic properties of the radiopaque substances. There is a considerable literature dealing with the effect of various radiopaque agents upon the central nervous system. Included among the publications are articles relating to cerebral angiography in relation to the blood-brain barrier (1, 5, 6, 37), technics for pharmacodynamic investigation of contrast media (7, 31), the physiological effects of various media (2, 3, 14, 16–21, 25, 28, 35), cardiovascular responses (11, 27), and clinical evaluation studies (4, 12, 13, 23, 29, 36, 39, 40). Important data are contained in these publications.
Lehman et al. (Sat,) studied this question.