Effects of Intensive Radiation on the Human Heart

Abstract

Recent awareness of the effect of radiation on the heart reflects the revived interest in the radiobiologic reaction of normal tissue. As early as the first two decades following the discoveries of Roentgen and the Curies, the radiation effect on normal tissue was under study. The astuteness and prophetic vision of the early investigators are well reflected in such reports as Lacassagne and Gricouroff's Action des radiations sur les tissus. Later, as knowledge of the biologic effect of radiation increased, emphasis in the literature shifted to the therapeutic effects of ionizing radiation on neoplasms. Now, with improved apparatus and technics permitting larger doses of radiation not dependent solely on skin tolerance, the previously accepted dogma on normal tissue reaction requires reappraisal. An excellent general review of the radiologic literature on the effect of radiation on the heart has recently been made by Jones and Wedgwood (2). As early as 1897, Sabrazès and Rivière (4) reported the effects of roentgen rays on the frog's heart. In the same year, Seguy and Quénisset (5) published their observations of a patient whose precordial region was exposed to roentgen rays. Gloriozov (1), in 1949, reported the clinical and electrocardiographic effects of radiation on the heart in 10 patients treated for esophageal or lung neoplasm. He concluded that large doses of radiation produced sinus tachycardia, extrasystoles, and degenerative changes in the myocardium. Until that time, the heart had been considered relatively immune to doses of radiation administered in amounts consistent with the technic of those earlier years. In 1957, Whitfield and Kunkler (6) described 4 patients in whom electrocardiographic changes developed during or following radiotherapy to the thorax including the cardiac area. A series of 25 female patients who had received roentgen treatment for carcinoma of the breast was studied by Jones and Wedgwood for nonspecific electrocardiographic changes. This was the first carefully observed series consisting of a relatively large number of patients. The investigators pointed out that most of the cardiac disturbances previously reported as resulting from irradiation fit into two groups: (a) arrhythmias and (b) “extra-cardiac mediastinal disturbances.” They found no evidence that arrhythmias are attributable to radiation; mediastinopericardial reactions, which they consider the more important, are rare. Jones and Wedgwood also noted nonspecific ST-T wave changes several weeks following roentgen therapy. Although the nonspecific changes observed may have been due to mediastinal disturbances, other factors such as electrolyte disturbances, positional changes, and myocardial damage remain as possible causes. In treating intrathoracic neoplasms and postoperative breast carcinomas, particularly with supervoltage roentgen rays, large doses of radiation are delivered to the heart.