Systemic and Coronary Energetics in the Resting Unanesthetized Dog

Abstract

Phasic coronary inflow and its determinants have been studied by means of differential pressure, 1 a constant pressure flowmeter, 2 an orifice meter, 8 a cannulating type of electromagnetic flowmeter, 4 and a differential transformer. 15 All are cumbersome and require the use of anesthetics, surgical trauma, anticoagulants, and insertion of the device into the coronary artery of the open and/or closed chest anesthetized animal. To obviate these difficulties, a miniature electromagnetic flowmeter has been developed and adapted in this laboratory to permit its implantation for weeks on the coronary arteries of the dog. 6 The present communication is concerned with the use of this device in registering the moment-to-moment rate of inflow into the left coronary artery and its major branches, together with myocardial oxygen usage in the resting unanesthetized dog under essentially normal conditions. MethodsThe experiments reported here were done on more than 75 carefully selected healthy mongrel dogs (18 to 27 kg). These dogs underwent two to three months of a rigorous conditioning and training program preparatory to operation and postoperative studies. Each dog was trained to stand or to lie quietly on a pad.The operations were performed under clean conditions. The instruments and drapes were sterilized and the operative field was prepared as in aseptic surgery but no cap, face mask or gloves were worn. With pentobarbital anesthesia

Effects of Adrenaline and Noradrenaline on Coronary Blood Flow Before and After Beta‐adrenergic Blockade

“…These values are similar to those reported by Gregg & Fisher (1963) in anaesthetized open-chest dogs. The instantaneous flow patterns of the left coronary vessels closely resembled those published by Gregg, Khouri & Rayford (1965). Systolic flow in the branches of the left coronary artery was often appreciable and sometimes amounted to as much as 45% of diastolic flow.…”

Control of myocardial oxygen consumption: relative influence of contractile state and tension development

“…The activation 02 of cardiac muscle might be considered to be made up of three components: electrical activation, contractile site activation and deactivation, and the maintenance of the active state. The 02 cost of electrical activation has been measured in the nonbeating, dog heart and was found to be quite small (38), probably less than 1%o of the total MVo2 of the resting unanesthetized dog (44). Since no mechanical activity took place in the nonbeating heart (38), this electrical activation presumably did not result in the activation of contractile sites on the myofilaments.…”

Direct and reflex effects of nitroglycerin on coronary and left ventricular dynamics in conscious dogs

“…Furthermore, the hypotensive effects of nitroglycerin elicit reflex increases in heart rate and myocardial contractility which would affect the coronary vessels secondarily and might obscure direct coronary vascular effects. Since anesthesia affects the coronary circulation (27)(28)(29), depresses myocardial contractility (30), and alters the normal coronary and myocardial responses to pharmacologic agents, such as cardiac glycosides (29)(30), it is essential to describe the normal coronary and myocardial actions of cardiovascular therapeutic agents such as nitroglycerin in the conscious animal in which the complicating influences of anesthesia are absent. This is of particular importance since nitroglycerin reduces arterial pressure and thereby stimulates the baroreceptors, which exert differing effects in the presence and absence of general anesthesia (28,31).…”