Summary
The protective properties of St. Thomas' Hospital cardioplegic solution (ST-CP) and
Bretschneider's histidine buffer cardioplegic solution (B-CP) were compared in an
isoiated paracorporeal dog heart model. Two groups of 6 hearts each were subjected
to 120 min of cardioplegic arrest at 20 °C, induced by 1000 ml of ST-CP and 3000 ml
of B-CP.
Postischemic left ventricular function was significantly different in the 2 groups.
After 20 min reperfusion and at 20 mmHg enddiastolic pressure, developed left ventricular
pressure recovered 98.8% of preischemic control values in the B-CP group as compared
to 66.4 % in the ST-CP group and peak left ventricular dp/dt recovered 95.5% and 68.6%
of control, respectively. Diastolic left ventricular wall stiffness showed a more
pronounced postischemic rise in the ST-CP group, measured as an 18% increase in diastolic
pressure/volume ratio at 20 mmHg diastolic pressure, this increase being 6 % in the
B-CP group.
Neither lactate metabolism nor myocardial enzyme release differed significantly between
the groups.
The critical importance of cardioplegic washout was illustrated in a third group of
6 hearts, subjected to transaortic perfusion with cold (20 °C) arterial blood at a
rate of 0.4 ml/100 g min over a 100 min period during 2 hours of cardioplegic arrest
by St. Thomas' solution. Left ventricular function was preserved significantly better
in this group than in the ST-CP hearts without washout. Left ventricular developed
pressure and peak dp/dt recovered 84.8% and 87.8%, respectively, of preischemic control
values.
It is concluded, that myocardial protection by B-CP is superior to that by ST-CP in
dog hearts under standardized experimental conditions. Noncoronary collateral blood
flow producing cardioplegic washout in studies with the heart in situ may conceal
different protective properties of cardioplegic methods.
Key words
Cardioplegic arrest - Postischemic left ventricular funetion - Extracoronary collateral
myocardial blood flow
