The Journal of Thoracic and Cardiovascular Surgery, Vol 76, 590-603, Copyright © 1978 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Effect of cross-clamp time, temperature, and cardioplegic agents on myocardial function after induced arrest
HR Kay, FH Levine, JT Fallon, GJ Grotte, EG Butchart, S Rao, MT McEnany, WG Austen and MJ Buckley
To evaluate the importance of time, temperature, and cardioplegia on the
ability of the canine myocardium to maintain functional and ultrastructural
integrity following induced arrest, we studied 220 dogs by varying
myocardial temperature (34 degrees, 24 degrees, and 11 degrees C.), arrest
time (0 to 120 minutes), and cardioplegic agents. Change in left
ventricular function (LVF) was defined as the arithmetic difference in the
center of mass between prearrest and postarrest LVF curves and was
expressed as percent recovery of left ventricular stroke work. Left
ventricular biopsies were obtained for semiquantitative electron
microscopic analysis. After 90 minutes of cross-clamping, only hearts
protected with combined hypothermia (H) and potassium-induced cardioplegia
(K) significantly recovered prearrest function (24 degrees C.--80 percent,
11 degrees C.--99 percent). Hypothermia (H) alone for 90 minutes was less
protective (24 degrees C.--49 percent, 11 degrees C.--59 percent). H
preserved 84 percent of function after 60 minutes and 91 percent after 45
minutes. Normothermic arrest resulted in only 39 percent return of function
at 45 minutes but could be extended with potassium-induced cardioplegia(K)
to 78 percent at 60 minutes and 54 percent at 90 minutes. The addition of
procaine plus HK improved protection over HK alone (95 percent versus 80
percent) but by itself was not effective. Neither hydrocortisone nor
pretreatment with glucose- insulin-potassium, branched chain amino acids,
or propranolol increased the protective effect of HK plus procaine.
Inadequately protected groups (normothermia or H without K) showed more
myocytic and capillary endothelial damage than the HK groups. No technique
of myocardial protection studied completely preserved LVF, but the
combination of HK plus procaine resulted in maximal recovery of LVF
following cross- clamping for up to 120 minutes.