Effect of increasing volume of cardioplegic solution on postischemic myocardial recovery

Multidose cardioplegia has been reported to be superior to single-dose cardioplegia in protecting the heart during ischemia. However, large volumes of cardioplegic solution may be detrimental because of washout of adenine nucleotide degradation products that accumulate during ischemia, which limits recovery of adenosine triphosphate. We designed an experiment to test the effects of increasing the volume of cardioplegic solution on postischemic myocardial recovery. Four groups were studied: Group 1, initial 2 minute single dose of cardioplegic solution; Group 2, infusion of cardioplegic solution every 30 minutes for 1 minute; Group 3, infusion of cardioplegic solution every 20 minutes for 1 minute; and Group 4, infusion of cardioplegic solution every 20 minutes for 2 minutes. All groups were ischemic for 2 hours at 20 degrees C. Although washout of nucleotide degradation products during the ischemic interval increased with higher volumes of cardioplegic infusion, the total washout (infusion plus initial 5 minutes of reperfusion) was not different among all groups. The multidose groups recovered function better and had significantly higher levels of total tissue purines after 30 minutes of reperfusion. There was no difference in adenosine triphosphate levels among all groups after reperfusion. We conclude that increasing the volume of cardioplegic solution, within a clinically relevant range is not associated with increasing loss of adenine nucleotides from the cell or with impaired functional recovery of the heart.