In this study, to determine whether preconditioning enhances the process of recovery from post-ischemic dysfunction, ultrasonic crystals were placed in 8 open-chest dogs to measure regional myocardial wall thickening in the ischemic area. A carotid-circumflex coronary artery bypass was created with an electromagnetic flow probe and a fixed stenosis was produced. Ventricular pacing was performed for 15 minutes at a rate of 190-220 bpm. After a 15 minutes rest period, a second pacing was performed in a similar manner. After cessation of the first pacing, circumflex wall thickening remained reduced significantly. Three minutes after cessation of the second pacing, circumflex thickening decreased further. After 15 minutes, wall thickening improved to the value recorded before the second pacing. The degree of improvement from 3 minutes to 15 minutes after the second pacing was greater than that after the first pacing. Thus, preceding demand ischemia modifies the rate of functional recovery from the next post-ischemic dysfunction, indicating that preconditioning of the ischemic myocardium enhances recovery from stunning.
(Internal Medicine 33: 402-406, 1994)