Effects of coronary dilators on segmental forces in normal and ischemic regions of the canine left ventricular wall

Changes in segmental forces of contraction (determined by a strain gauge arch) in non-ischemic (normal) and ischemic regions of the same left ventricular wall were studied in dogs anesthetized with morphine and pentobarbital. A branch of the left anterior descending coronary artery was completely occluded, and 10 min after occlusion coronary dilators were injected intravenously. The results can be summarized as follows. 1) Coronary occlusion markedly reduced the segmental force of contraction in the ischemic region, while it did not affect that in the normal region. Heart rate did not change markedly after coronary occlusion. 2) Either nitroglycerin (100 microgram/kg) or sodium nitrite (2.5 mg/kg) increased heart rate, and it also increased segmental force of contraction in the normal region while it decreased that in the ischemic region. 3) Papaverine (1 mg/kg) increased heart rate and segmental forces of contraction in both normal and ischemic regions. 4) Dipyridamole (250 microgram/kg) slightly increased heart rate, and it also increased segmental force of contraction in the normal region but not in the ischemic region.