Warm retrograde blood cardioplegia saves more ischemic myocardium but may cause a functional impairment compared to cold crystalloid.
OBJECTIVE
Ongoing ischemia, or even ischemia in progress, is regularly encountered in today's patients amenable to cardiac surgery. We set out to assess the effect of 'active resuscitation' during cardioplegia with warm continuous retrograde blood cardioplegia (WB) in a protocol simulating a clinical situation.


METHODS
After 60 min with a regional ischemic injury to the left ventricle, 21 pigs were randomized to receive no treatment (control), cold retrograde intermittent crystalloid cardioplegia (CC) or WB. All animals were put on cardiopulmonary bypass. After 1h of cardioplegia and 1 h of reperfusion the perfused left ventricle was colored with methylene blue. After excision of the hearts a standard planimetri technique was used to determine the area at risk and amount of necrosis (triphenyltetrazolium). Heart rate, mean arterial pressure (MAP), cardiac output and myocardial blood flow were recorded as well as myocardial oxygen consumption, plasma levels of free fatty acids, glucose, lactate and Troponin T from the coronary sinus.


RESULTS
The area at risk of the left ventricle was 13.6+/-1.2%. We found 71+/-2, 61+/-3 and 30+/-2% necrosis of the area at risk in the controls, CC and WB, respectively (P<0.001, CC versus control and P<0.0001, WB against CC and control). Troponin T release was highest in the CC group in the reperfusion period. Glucose levels increased significantly after ischemia in the controls and WB. In accordance with the amount of saved myocardium in the WB group which also had a normal coronary sinus lactate level as opposed to the fourfold increase in the CC group after ischemia. After standstill cardiac output and MAP were significantly lower than baseline values in the WB group only (P<0.05).


CONCLUSIONS
CC did reduce the size of the infarction by about 10% compared to control animals, whereas WB reduced the infarction by more than 50% of that seen after CC. Both modalities are, however, associated with a functional reduction during the first 60 min of reperfusion, WB being the worst.
Department of Cardiothoracic and Vascular Surgery, Faculty of Medicine, University of Tromsø, N-9038 Tromso, Norway. odd.petter.elvenes@unn.no
Odd Petter
OP
Elvenes
Christian
C
Korvald
Reidar
R
Myklebust
Dag
D
Sørlie
D000818:Animals; D001769:Blood; D002314:Cardioplegic Solutions; D002315:Cardiopulmonary Bypass; D003326:Coronary Circulation; D006324:Heart Arrest, Induced / Q000379:methods; D006439:Hemodynamics; D017202:Myocardial Ischemia / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D009206:Myocardium / Q000378:metabolism / Q000473:pathology; D009336:Necrosis; D017680:Potassium Compounds; D013552:Swine; D013696:Temperature
D002314:Cardioplegic Solutions; D017680:Potassium Compounds; C018369:potassium cardioplegic solution