The Journal of Thoracic and Cardiovascular Surgery, Vol 77, 496-503, Copyright © 1979 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Constant-pressure aortic root perfusion versus cardioplegia and hypothermia. Comparison of methods of myocardial protection
JN Cunningham Jr, JS Abbas, PX Adams, I Nathan, I Klugman and FC Spencer
Both coronary perfusion and hypothermic cardioplegia are widely used
methods of myocardial protection during aortic valve replacement. A
theoretical objection to coronary perfusion is that it is not synchronized
with cardiac contractions. Accordingly, a special pump was designed to
provide perfusion at a constant range of pressure. Twenty dogs were studied
during 4 hours of bypass. In six dogs no manipulations were carried out and
hearts were allowed to beat in a nonworking state. Seven dogs underwent 2
hours of aortic cross-clamping and constant-pressure aortic root perfusion.
Seven dogs underwent 2 hours of uninterrupted aortic occlusion with
myocardial protection being maintained by cold potassium-induced arrest,
Contractility did not change significantly in any of the three groups. All
animals demonstrated significant hyperemia after bypass but normal
endocardial/epicardial flow ratios. Although compliance deteriorated in all
groups, the most striking changes were seen following 4 hours of bypass
alone or constant-pressure aortic root perfusion. Hypothermic potassium
arrest, in contrast, provided a slightly greater degree of myocardial
protection, perhaps both by limiting the degree of ischemic injury directly
and by excluding the heart from the circulating blood and the pump
oxygenator system.
