Studies on Chronic Effects of Ligation of the Canine Right Coronary Artery

Abstract

Ligation of the right coronary artery in 21 dogs was attended by a mortality rate of 24%. The cause of death was invariably ventricular fibrillation, which developed either immediately after the ligation or within the succeeding 48 hrs. A constant delayed rise and fall of ectopic activity followed the ligation in each case. A peak was reached between 9 and 24 hrs. after ligation, at which time the ecg. was frequently composed entirely of ectopic complexes. Ligation of the right coronary artery was attended by the loss of, or marked reduction in, the Q waves of leads I, II, III, and aVF, and of the R wave of aVp. Leads aVR and aVL exhibited elevation of the ST segment accompanied by depression of the ST segment in leads II, III, and aVF. Neither the evidence obtained by cardiac catheterization nor the tests of tolerance to exercise revealed any incompetence of cardiac function to have resulted from infarction in 33-77% of the total right ventricular muscle. With 1 exception, extensive development of collateral vessels followed ligation of the right coronary artery. These interarterial communications were larger than capillaries 30 days after ligation. Immediate retrograde flow occurred into the ligated artery from adjacent coronary vessels and this immediate flow seems essential to preservation of large areas of cardiac muscle within the boundaries of the area originally rendered ischemic and noncontractile.