Myocardial distribution of antegrade cold crystalloid and tepid blood cardioplegia.
BACKGROUND
Tepid blood (TB) cardioplegia combines the improved rheologic characteristics and the augmented oxygen and substrate delivery of blood cardioplegia with the advantages of moderate hypothermia. In addition, the intramyocardial distribution of continuous TB cardioplegia may also be better than intermittent cold crystalloid (CC) cardioplegia. We sought to compare the distribution of TB and CC cardioplegia at varying infusion pressures.


METHODS
In situ, isolated canine hearts were randomized to antegrade, continuous TB (28 degrees C, n = 8) or intermittent CC (n = 8) cardioplegia infused at 50, 75, and 100 mm Hg. The regional distribution of cardioplegia at each pressure was measured by 15-microm colored microspheres. Cardioplegia distribution was measured from three areas each of the right ventricle (inflow, outflow, and apex) and the left ventricle (anterior, lateral, and posterior). Left ventricular samples were subdivided into subepicardial, midmyocardial, and subendocardial.


RESULTS
Delivery of cardioplegia to all areas of the right and left ventricles showed a linear pressure-flow relationship over the range of pressures tested. Right ventricular distribution was two-thirds of that to the left ventricle, and left ventricular subepicardial distribution was approximately one half of subendocardial flow in both groups at all delivery pressures. However, the subendocardial to subepicardial ratio was significantly greater with TB cardioplegia than with CC cardioplegia. Transmural right ventricular cardioplegia flow was comparable in both groups. In contrast, left ventricular distribution of CC cardioplegia was greater than TB cardioplegia at all three pressures tested.


CONCLUSIONS
The pressure-flow relationship in both CC and TB cardioplegia is linear in both the right and left ventricular myocardium over clinically applicable delivery pressures. The distribution of cardioplegia to the right ventricle is not altered by increased pressure.
Duarte
I G
IG
Cardiothoracic Research Laboratory, Carlyle Fraser Heart Center, Emory University School of Medicine, Atlanta, Georgia 30365-2225, USA.
Shearer
S T
ST
MacDonald
M J
MJ
Gott
J P
JP
Brown
W M
WM
Vinten-Johansen
J
J
Guyton
R A
RA
D000818:Animals; D001769:Blood; D002314:Cardioplegic Solutions / Q000378:metabolism / Q000627:therapeutic use*; D003080:Cold Temperature; D003326:Coronary Circulation; D004285:Dogs; D004699:Endocardium / Q000378:metabolism; D006324:Heart Arrest, Induced / Q000379:methods*; D006346:Heart Septum / Q000378:metabolism; D006352:Heart Ventricles / Q000378:metabolism; D006358:Hot Temperature; D006982:Hypertonic Solutions / Q000378:metabolism / Q000627:therapeutic use; D007036:Hypothermia, Induced / Q000379:methods; D007262:Infusions, Intravenous; D008863:Microspheres; D009206:Myocardium / Q000378:metabolism*; D010100:Oxygen / Q000008:administration & dosage; D010496:Pericardium / Q000378:metabolism; D017680:Potassium Compounds / Q000378:metabolism / Q000627:therapeutic use*; D011312:Pressure; D011897:Random Allocation; D012212:Rheology
D002314:Cardioplegic Solutions; D006982:Hypertonic Solutions; D017680:Potassium Compounds; C018369:potassium cardioplegic solution; D010100:Oxygen