The temperature dependence of cardioplegic distribution in the canine heart.
BACKGROUND
Cold cardioplegic arrest can produce cooling contracture and suboptimal myocardial protection. This study examines whether cooling contracture is associated with maldistribution of cardioplegic solution, particularly subendocardial hypoperfusion, which may impair recovery.


METHODS
Canine hearts were arrested by antegrade cold and warm blood cardioplegia in random order. Cardioplegic distribution was measured using radiolabeled microspheres before and just after induction of each period of arrest.


RESULTS
With cold cardioplegia, perfusion of left ventricular subepicardial and midwall regions decreased. Subendocardial to subepicardial perfusion ratios increased significantly in the left ventricle as a whole, the anterior and posterior regions of the left ventricular free wall, and the interventricular septum. With warm arrest, transmural flow distribution was not significantly altered from preceding prearrest values. At constant coronary flow, coronary perfusion pressure was initially similar after induction of arrest at both temperatures, but it rose subsequently during warm cardioplegia.


CONCLUSIONS
The data suggest that during normothermic arrest, vasomotor tone regulates cardioplegic distribution, and hyperkalemic vasoconstriction is of slow onset. In the absence of beating and with vasomotion inhibited by hypothermia, cardioplegic distribution during cold arrest appears to be primarily dependent on vascular anatomy. There was no evidence of subendocardial underperfusion during cooling contracture.
Torchiana
D F
DF
Department of Surgery, Massachusetts General Hospital and Harvard Medical School, Boston 02114, USA. torchiana.david@mgh.harvard.edu
Vine
A J
AJ
Titus
J S
JS
Hahn
C
C
Shebani
K O
KO
Geffin
G A
GA
Daggett
W M
WM
D000818:Animals; D002314:Cardioplegic Solutions / Q000493:pharmacokinetics*; D003331:Coronary Vessels / Q000502:physiology; D004285:Dogs; D005069:Evaluation Studies as Topic; D005260:Female; D006321:Heart / Q000502:physiology*; D006324:Heart Arrest, Induced; D008297:Male; D008863:Microspheres; D011897:Random Allocation; D012039:Regional Blood Flow; D013696:Temperature; D014655:Vascular Resistance
D002314:Cardioplegic Solutions