The quantitatively measured local myocardial perfusion rates with microspheres are used as an objective indicator of even distribution of cardioplegic solution, and the efficacy of the retrograde right atrial route of cardioplegia is cardioplegia
is
evaluated in hearts with various levels of coronary arterial obstruction.
After initial antegrade cardioplegia under the median sternotomy and aortic cannulation, 60 hearts from anesthesized New Zealand white rabbits are divided in random order as normal group(ligated left main coronary artery : MA, MR).and diagonal
group(ligated proximal diagonal artery : LA, LR). Half of each group(N=10) are perfused with antegrade cardioplegia(A) under the pressure of 100 cmH2O and the other half with retrograde right atrial route (R) under the pressure of 60 cmH2O (St.
Thomas
cardioplegic solution mixed with measured amount of microspheres). The myocardium is subdivided into segments as A(atria), RV (right ventricle). S(septum), LV(normally perfused left ventricular free wall), ROI(ischemic myocardium of left
ventricular
free wall). LV and ROI are further divided into N( subendocardium) and P(subepicardium). The resulting local myocardial perfusion rates and N/P of each group are compared with Wilcoxon rank sum test.
The weight of the hearts is 5.94±0.66g, and there are no statistically significant differences(p>0.05, ANOVA) between six compared group. The mean flow rate(F : ml/g/min) of MR group is comparable with MA group(p>0.05), but in N and L group,
there
are
significantly depressed F with right atrial route of cardioplegia, which means elevated perfusion resistance with this route. In spite of no significant differences in delivered doses of microsphere(DEL) between compared groups(p>0.05), ANOVA),
there
are significantly depressed REC and NF in hearts with right atrial cardioplegia which suggests increased requirement of cardioplegic solution with this route.
The interventricular septum showed poor perfusion with right atrial route of cardioplegia without obstruction of supplying coronary arteries. But, with obstruction of coronary artery supplying septum as in M group, the flow rate is superior with
right
atrial route of infusion.
The left ventricular free wall perfusion rates of every ROI with R route are superior to that of A route (p<0.05). But, in LV segments, there are unfavorable effects of right atrial cardioplegia in L group, although the subendocardial perfusion
is
well
maintained in N group.
The LV free wall of left main group shows depressed perfusion rates with antegrade route as compared with ROI segment of diagonal group. But, by contraries, there are increased perfusion rates and superior N/P ratio with retrograde right atrial
route.
It implies more effective perfusion with right atrial route of cardioplegia in more proximal coronary arterial obstruction(i.e., M group as ischemia have superior perfusion rates with right atrial cardioplegia as compared with antegrade route,
and
especially excellent results can be obtained in hearts with more proximal obstruction of coronary arteries witch would otherwise result in more severe ischemic damage. But , the depressed perfusion rates of the segments with normal coronary
artery
in
hearts with coronary arterial obstruction may be a problem of concern with right atrial cardioplegia and needs solution.
Key words : myocardial protection, local myocardial perfusion rate, right atrial cardioplegia, microspheres, coronary arterial disease
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