The Journal of Thoracic and Cardiovascular Surgery, Vol 77, 608-618, Copyright © 1979 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Myocardial depression after elective ischemic arrest. Subcellular biochemistry and prevention
PC Gillette, WW Pinsky, RM Lewis, EP Bornet, JM Wood, ML Entman and A Schwartz
The hemodynamic and cardiac biochemical effects of global ischemic arrest
during cardiopulmonary bypass (CPB) were studied in 54 animals and compared
to seven animals without ischemic arrest. Ischemic arrest alone reduced the
first derivative of left ventricular force of contraction (LV dF/dt) to 52
percent of control 10 minutes after resuming function and to 64 percent
after 1 hour of reperfusion. Cardiac output was depressed to 52 percent of
control after 10 minutes of reperfusion, and to 74 percent of control after
60 minutes of reperfusion. In six animals, moderate hypothermia (26 degrees
C.) resulted in no protection of cardiac function from ischemic arrest,
whereas profound hypothermia to 18 degrees C. resulted in values of LV
dF/dt and cardiac output nearly equivalent to the CPB control group (no
arrest). A continuous infusion of a hyperkalemic hypothermic solution
slightly improved the degree of protection over hypothermia alone. The
sarcoplasmic reticulum (SR) isolated from hearts which had undergone 60
minutes of ischemic arrest bound significantly less calcium when the
isolation was done after 10 minutes of reperfusion as well as when it was
done after 60 minutes of reperfusion. The time to spontaneous release of
calcium from the SR also was significantly longer. Moderate hypothermia did
not result in improved SR function, whereas deep hypothermia induced by
local cooling or by hypothermic potassium infusion retained SR function at
normal levels. Oxidative phosphorylation of mitochondria isolated after 60
minutes of reperfusion was also depressed. The mitochondrial respiration
rate after normothermic ischemic arrest was 155 natoms of oxygen per
minutes versus 237 natoms for the hypothermic hyperkalemic group.
Respiratory control index was 5.5 for the normothermic group versus 9.4 for
the hypothermic group. It is concluded that hypothermia, whether effected
by surface cooling or by hypothermic potassium infusion, allowed full
recovery of hemodynamic and biochemical functions within 1 hour of
reperfusion.
