Perfusion of the left coronary artery of open chest dogs at fixed control and ischemic flow rates demonstrated that ST alterations in the electrocardiogram were always associated with significant hemodynamic and metabolic changes. Decreased pressure time per minute, atrial hypertension, increased myocardial oxygen extraction, and the presence of excess lactate accompanied ischemia. In three dogs, hemodynamic changes, the presence of "excess lactate," or both, preceded significant electrocardiographic changes. Whenever coronary flow was insufficient to meet myocardial oxygen demands, a series of metabolic shifts occurred. The most significant of these was inadequate aerobic energy production and stimulation of anaerobic glycolysis. This acceleration of anaerobic myocardial metabolism may be present without notably altering the surface electrocardiogram. The absence of ST shifts does not rule out the presence of concomitant and potentially severe myocardial ischemia.

Coronary Insufficiency: Relations Between Hemodynamic, Electrical, and Biochemical Parameters

The synergism of x-irradiation and cholesterol-fat feeding on the development of coronary artery lesions.

Lesions in the chest developing after radiotherapy in 49 patients are described. Of all the thoracic tissues the lungs proved the most vulnerable to radiation damage. The risk is increased when large areas of lung are irradiated, the total dosage is high, and the course of treatment is given quickly. The 49 cases received irradiation of the thorax for breast cancer, malignant lymphomas, lung metastases, and esophageal and bronchial cancer. Seven of the 49 cases, all with severe bilateral damage, died from it. Thoracic irradiation caused in some cases constrictive pericarditis or was followed by transitory T wave changes in the electrocardiogram. The significance of the latter was uncertain. They were usually unassociated with cardiac symptoms or objective cardiac abnormality and disappeared within a year or less. Twelve of 27 patients studied showed such changes, and sudden death occurred in two. The most frequent manifestation of radiation damage to the bony structure of the thorax was fractured ribs. It usually followed postmastectomy radiotherapy. Other less common bony lesions attributable to radiation are described. Thoracic irradiation of females in childhood may result in mammary hypoplasia and absence of lactation. Radiation stricture of the esophagus was suspected in seven patients, but themore » diagnosis was disproved in each instance so this condition must be rare. The interval between the conclusion of x-ray treatment and development of symptoms attributable to radiation pneumonia varied from one to 16 weeks with a peak incidence at one month. Some people may be more sensitive to the harmful effects of radiation than others, but it was impossible to identify such subjects in advance of treatment. Age and arterial degenerative change did not appear to be relevant factors, but thin people seem more liable to radiation lung damage than those of greater body weight. Dominant influences in radiation lung damage were total dosage, rate of administration, and the percentage of the total lung volume irradiated; the risk was reduced if treatment was protracted in time. Six patients, undergoing wide-field thoracic irradiation, were given prophylactic cortisone in a dose of 75 to 100 mg daily during and for three months after radiotherapy. Of these, one died from radiation lung damage while still taking 50 mg cortisone daily and another developed a small area of radiation pneumonia which cleared completely while taking a similar dose. Phenindione was given to eight patients in whom wide-field thoracic irradiation was necessary, but of these three developed radiation pneumonia and one died from radiation damage to the heart, indicating that this anticoagulant may not diminish pulmonary radiation injury. (BBB)« less

https://thorax.bmj.com/content/thoraxjnl/18/4/371.full.pdf

Radiation Damage to Thoracic Tissues

Electrocardiographic and pathologic changes after cardiac x-irradiation in dogs

Ten dogs received a single exposure of 10 MeV X rays to the heart. Five dogs received 1500 rad to the midline and five received 1000 rad. When the dogs expired or were killed 73-85 days after irradiation, their hearts were examined pathologically. The changes most frequently observed were pericardial effusion and in the right atrium, myocardial necrosis, and fibrosis. The data suggest that under the conditions of this experiment, irradiation of the canine heart causes greatest damage to the right atrium.

The Effects of X Radiation on the Canine Heart

Electrocardiograms were obtained on 52 normal dogs before and after cardiac irradiation with 1,300, 2,000, and 2,500 r. No ectopic cardiac arrhythmias were noted on electrocardiograms obtained 7 to 90 days following the completion of the course of irradiation. A mean increase in the ventricular rate was noted 7 days following the completion of the course of irradiation, but was not present 30 to 60 days later. There was no prolongation of PR interval or QRS duration following cardiac irradiation. At the dosage levels employed, irradiation of the normal canine heart produced no electrocardiographic changes indicative of gross myocardial damage. This was noted to be true as long as 90 days following the completion of the course of irradiation. (auth)

H. Peck

Papers

The effect of cardiac irradiation upon the electrocardiogram of the normal canine heart.

Radiotherapy in angina pectoris: a controlled study.