Contractile function, energy metabolism and myocardial structure at graded restriction of coronary blood flow

In closed-chest dogs, 30, 50 and 70% restriction of coronary blood flow was carried out by catheterization and autoperfusion of the circumflex branch of the left coronary artery. At 70% restriction, a mild decrease in most contractility indices was observed, without simultaneous impairment of the indices of systemic haemodynamics. Changes in energy metabolism appeared already in the initial stage of coronary insufficiency. A characteristic features at suppression of aerobic oxidation was an increase of the cAMP level of glycolytic activity of the pentoso-phosphate cycle, which ensured a sufficiently high ATP level in the myocardium. A limiting factor were disturbances in the system of energy transport (creatine phosphate, creatine phosphokinase) and of the calcium pump (Ca++-ATPase of the sarcoplasmic reticulum, SPR), which evidently led to a decrease of the inotropic properties of the myocardium at 70% restriction of coronary blood flow. Signs were found of structural lesions of the myofibrils and the SPR.