From the Department of Pharmacology, Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz-51664, I.R.lran.
Abstract: (4338 Views)
Repetitive episodes of brief regional ischemia have been shown to reduce the severity
of life-threatening ventricular anhythrnias and infarct size that occur during prolonged
occlusion of the coronary artery. This phenomenon is known as ischemic preconditioning.
During studies in anesthetized, open chest Wistar rats, we accidentally observed that
poorly ventilated animals had a reduced severity of ischemic arrhythmias. Therefore, we
wished to (1) find out whether acute hypoventilation prior to coronary ligation affords
protection to the ischemic rat hearts, and (2) to evaluate the effect of recovery period of
normoventilation between hypoventilation and prolonged ischemia on the degree of
protection. Male Wistar rats were anesthetized and prepared for left coronary artery
ligation. Following a left thoracotomy, artificial respiration was immediately started with
room air of 1.5 mLll00g and 54 strokes/min. Analysis of ventricular anhythrnias during
30 min occlusion was performed. In some experiments 30 min. sustained ischemia
followed by 2 hours reperfusion and then the percentage of infarct size was measured. The
reduction of volume of ventilation to 1.1 and 0.7 mL/l00g only for 10 min immediately
prior to coronary artery occlusion resulted in a marked decrease (p<0.01) in the total
number of ventricular ectopic beats from 1336±100 in control to 485 ±75 and 328±51,
respectively, mainly by reduction of beats occurring as ventricular tachycardia (VT).
Also, the time spent in VT and in reversible ventricular fibrillation was reduced
significantly (p<0.01 and p