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The Journal of Thoracic and Cardiovascular Surgery, Vol 73, 746-757, Copyright © 1977 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
RC Ciardullo, HV Schaff, JT Flaherty and VL Gott
The effect of a critical coronary artery stenosis on myocardial blood flow
and metabolism in the fibrillating heart was assessed by placing 10 dogs on
cardiopulmonary bypass, venting the ventricle, inducing ventricular
fibrillation, and applying critical stenosis to the left anterior
descending coronary artery (LAD). Endocardial and epicardial blood flows
were measured by the radioactive microsphere technique prior to the
application of the stenosis and after one hour and 2 hours of fibrillation.
Intramyocardial oxygen tension (PO2) and carbon dioxide tension (PCO2) were
continuously monitored in the LAD-supplied myocardium by a mass
spectrometer probe inserted at midmyocardial depth. Selective
arterial-coronary venous lactate differences were determined at control,
one hour, and 2 hours. At the end of the 2 hour period, vital dye injection
defined the distribution of the LAD. Endocardial flow to the myocardium of
the stenosed LAD was reduced by 50 per cent after one hour and by 70 per
cent after 2 hours (p less than 0.05). Epicardial flow fell 40 per cent
after one hour and 50 per cent after 2 hours (p less than 0.05).
Endocardial and epicardial flow in the distribution of the unstenosed
circumflex coronary artery remained unchanged. Changes in myocardial PO2
and PCO2 in the LAD- supplied myocardium indicated the development of
severe ischemia in all 10 dogs and suggested myocardial infarction in 5.
There was a conversion from lactate extraction to lactate production during
the 2 hour period of ventricular fibrillation. From this study, it is
concluded that the myocardium distal to a critical stenosis suffers a
progressive reduction in flow during ventricular fibrillation which does
not occur in regions supplied by unstenosed coronary arteries. Thus
prolonged fibrillation in the presence of a flow-limiting coronary stenosis
may play a role in the pathogenesis of myocardial infarction during
coronary bypass surgery.
ARTICLES
Myocardial ischemia during cardiopulmonary bypass. The hazards of ventricular fibrillation in the presence of a critical coronary stenosis
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