The Annals of Thoracic Surgery, Vol 41, 535-541, Copyright © 1986 by The Society of Thoracic Surgeons
Calcium entry blockers and cardioplegia: interaction between nifedipine, potassium, and hypothermia
M Chiavarelli, R Chiavarelli, A Macchiarelli, A Carpi and B Marino
The potential additive protective effect provided by nifedipine to the
University of Alabama Hospitals cardioplegia solution (ACS) was assessed
with the use of a guinea pig heart-lung model of cardiopulmonary bypass and
ischemic arrest. The addition of nifedipine consistently enhanced the
protective properties of ACS infused at 37 degrees C; functional recovery
was similar to that observed with cold ACS. Despite the additional
protection under normothermic conditions, nifedipine did not improve
recovery after infusion at 4 degrees C. The abolition by hypothermia of the
protective effects of nifedipine suggests a similarity in action between
nifedipine and hypothermic protection. The interaction between ACS and
nifedipine was studied on bovine coronary arteries in vitro. Nifedipine
caused a marked reduction in the coronary vasoconstricting effect of ACS,
both under normothermic and hypothermic conditions. The use of nifedipine
in cardioplegia may provide additional protection when uneven distribution
of the cardioplegic solution is expected and hypothermic protection is
unreliable.