The Journal of Thoracic and Cardiovascular Surgery, Vol 90, 912-920, Copyright © 1985 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Quantitative evaluation of the myocardial preservative characteristics of nifedipine during hypothermic myocardial ischemia
WY Moores, JW Mack, WP Dembitsky, WH Heydorn and PO Daily
Nifedipine, a slow calcium-channel blocker, has been used to preserve
myocardial function in the ischemic heart. To quantitatively evaluate the
effectiveness of nifedipine as a cardioplegic agent during moderate
hypothermia (28 degrees C), 15 pigs were evaluated on total and right heart
bypass with measurement at normothermia and after 1 hour of hypothermic
ischemia of stroke volume, coronary blood flow, myocardial oxygen
consumption, and lactate extraction. Myocardial tissue gases (oxygen and
carbon dioxide) were continuously monitored. Animals were divided into
three groups: hypothermic ischemia, hypothermic ischemia with infusion of
nifedipine carrier without nifedipine, and hypothermic ischemia with
nifedipine and its carrier. A significant decrease in stroke volume was
seen in all three groups; however, the depression was significantly greater
following hypothermic ischemia than following cardioplegia with either
nifedipine or its carrier. The mean recovery value of stroke volume was
highest in the nifedipine group, but this difference between nifedipine and
its carrier alone did not reach statistical significance. Coronary blood
flow, myocardial oxygen consumption, lactate extraction, and tissue gases
failed to substantiate a significant benefit when nifedipine was compared
with its carrier alone. We conclude that under these hypothermic
conditions, no proven statistically significant advantage was noted in the
nifedipine group when compared with the nifedipine carrier group in swine.
However, both nifedipine and the carrier were superior as a myocardial
preservative when compared with hypothermic ischemic arrest alone.
