The Annals of Thoracic Surgery, Vol 35, 79-86, Copyright © 1983 by The Society of Thoracic Surgeons
Does secondary cardioplegia provide long-term recovery from ischemic injury?
DM Rose, GR Barnhart and M Jones
Short-term experimental studies have indicated that initial reperfusion
with blood cardioplegia may decrease ischemic injury after aortic
occlusion; however, no long-term studies have been performed. We evaluated
cardioplegic reperfusion in fifteen dogs, divided into three groups of five
each. Group I underwent 2 hours of cardiopulmonary bypass at 37 degrees C.
Group II underwent 2 hours of cardiopulmonary bypass, including 1 hour of
ischemic arrest, at 25 degrees C. Group III was identical to Group II, but
the hearts of the animals were initially reperfused with 500 ml of blood
cardioplegia at 25 degrees C (K+ = 30 mEq/L). Stroke work index (SWI), left
ventricular end-diastolic pressure (LVEDP), dp/dt max and maximal
contractile element velocity (Vpm) were measured preoperatively,
immediately after operation, 21 days postoperatively, immediately after
operation, 21 days postoperatively and 120 days postoperatively. Compliance
curves were evaluated using an intraventricular balloon at 120 days. Groups
II and III had significant (p less than 0.05) elevations of LVEDP at all
three postoperative measurements. The hearts of the Group III animals
(cardioplegic reperfusion group) demonstrated significantly (p less than
0.05 to 0.01) better recovery of SWI immediately after operation (62%
versus 39%), at 21 days (85% versus 69%), and at 120 days (81% versus 66%)
than did those in Group II. However, groups II and III had decreased
compliance at 120 days, compared with that of Group I, and also showed both
gross and microscopic evidence of subendocardial necrosis and fibrosis. It
is concluded that while initial reperfusion with blood cardioplegia appears
to provide better preservation of ventricular function early after ischemic
cardiac arrest, this technique does not prevent later deterioration of
ventricular compliance. Moreover, it produces myocardial fibrosis.