The Annals of Thoracic Surgery, Vol 28, 166-175, Copyright © 1979 by The Society of Thoracic Surgeons
Effect of therapeutic-dose irradiation on left ventricular function in conscious dogs
KV Arom, VS Bishop, FL Grover and JK Trinkle
Every week, 8 conscious, chronically instrumented dogs underwent left
ventricular (LV) function studies before, during, and after cardiac
irradiation with cobalt 60 (myocardial dose of 5,000 rads at 200 rads per
day through a 5 X 5 cm port). During the weekly LV function studies, left
atrial pressures were raised by rapid infusion of balanced saline solution.
Heart rate, aortic pressures, left and right atrial pressures, LV pressure,
left ventricular end-diastolic pressure (LVEDP), and maximum rate of rise
of LV pressure were recorded. Electrocardiograms were made. Cardiac outputs
were obtained by thermodilution. Stroke volume, LV stroke work, and LV
minute work were calculated. LV function curves were constructed each week.
All dogs lost weight and became irritable after approximately 800 rads. The
electrocardiograms showed signs of myocardial injury after 1,200 rads. All
variables were slightly depressed during the first 8 weeks following
irradiation. At the eleventh week, both left atrial pressure and LVEDP
increased significantly and LV function declined. There was also clinical
evidence of LV failure at rest and after volume loading. This study
documents that external cardiac irradiation, in a therapeutic dose and
schedule range, causes depression of LV function. These functional changes
were partially reversed when the follow-up study was continued to six
months after irradiation.