The Journal of Thoracic and Cardiovascular Surgery, Vol 82, 38-44, Copyright © 1981 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Influence of contractility on myocardial water distribution during cardiopulmonary bypass
EG Butchart, WG Austen and MT McEnany
Water equilibrium within heart muscle during cardiopulmonary bypass is an
important aspect of ventricular physiology which must be considered in
efforts to optimize myocardial protection. This study focuses on the
influence of the inotropic state of the ventricle in determining the amount
of heart water and its regional distribution within the free wall of the
left ventricle. Experiments involving cardiopulmonary bypass were performed
in 57 dogs. Three spontaneous levels of myocardial contractility were
identified under conditions of standard preload, afterload, and heart rate.
Each increase in level (grade) was associated with a significantly higher
myocardial wet weight/drug weight (W/D) ratio. In addition, higher levels
of contractility were associated with a marked shift in water distribution
within the left ventricular wall; water tended to accumulate in the inner
half of the better contracting left ventricular wall, the reverse of the
distribution seen at lower levels of contractility. These three grades of
contractility and myocardial water content were not associated with any
significant differences in total or regional myocardial blood flow, as
determined by the use off radioactive microspheres. Maintenance of low
levels of contractility during cardiopulmonary bypass may be desirable in
order to prevent the occurrence of subendocardial edema.
