The Annals of Thoracic Surgery, Vol 26, 535-547, Copyright © 1978 by The Society of Thoracic Surgeons
The effects of intermittent ischemic arrest on the perfusion of myocardium supplied by collateral coronary arteries
WR Chitwood Jr, RC Hill, LH Kleinman and AS Wechsler
Six weeks after placement of an ameroid constrictor on the circumflex
coronary artery, blood flow in a collateral region was compared with flow
in myocardium supplied by normal arteries during cardiopulmonary bypass (80
mm Hg). Myocardial blood flow was determined using radionuclide-labeled
microspheres (8 to 10 mu) before 10 minutes of ischemic arrest and after 1,
5, and 10 minutes of reperfusion. The retrograde circumflex pressure was
monitored continuously and served as an additional index of perfusion of
the collateral region. During reperfusion, endocardial flow in the
collateral region remained unchanged despite a threefold increase in a
similar layer having normal arteries (p less than 0.01). Following ischemic
arrest, mean transmural and subendocardial hyperemic responses both
persisted for longer than 10 minutes in normal regions. Simultaneously,
peripheral circumflex pressures decreased at 1 and 5 minutes of reperfusion
(p less than 0.001) but returned to control within 10 minutes. Persistently
elevated endocardial flow in the normal arteries and the absence of a
hyperemic response in the collateral region during an associated decrement
in retrograde circumflex pressure may indicate incomplete flow repayment
even after 10 minutes of reperfusion. Marked transmural flow imbalances
despite adequate coronary perfusion pressures suggest that intermittent
ischemic arrest may cause cumulative ischemia, and this occurrence may be
detrimental especially in collateral regions of myocardium.
