In a canine model of gradual coronary occlusion, vasoactive drugs primarily improved the myocardial oxygen demand-supply balance by reducing demand rather than increasing collateral blood flow.
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Emphasizes demand reduction for ischemic balance in canines; leaves open translation to human collateral physiology.
The effects of coronary vasoactive drugs on coronary collateral were studied in anesthetized open-chest dogs. The circumflex coronary artery was gradually occluded by an aneroid constrictor. Four to eight weeks later, retrograde coronary blood flow from the peripheral coronary artery and other parameters were studied. The results were as follows.1) Propranolol (0.2 mg/kg) decreased myocardial oxygen consumption represented as pressure rate product and increased peripheral coronary vascular resistance slightly. Retrograde coronary blood flow decreased significantly. The effect of propranolol was to improve the imbalance between myocardial oxygen demand and supply.2) Nitroglycerin (20 μg/kg) caused a reduction in preload and myocardial oxygen consumption. Retrograde coronary blood flow did not increase.3) Diltiazem (0.15 mg/kg) decreased myocardial oxygen consumption. Retrograde coronary blood flow was not significantly changed.4) Isoproterenol (0.2 μg/kg) aggravated the myocardial oxygen demand-supply relationship.5) There was a significant reduction in the regional myocardial shortening in the ischemic area compared with the control area. The response of regional myocardial shortening to the drugs in the ischemic area, however, was similar to that in the control area.
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Yasuhiro Ogino (1979) studied this question.
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