In experiments previously reported (1) it was found that platinum electrodes for polarographic measurement of oxygen availability have given fairly steady control readings in the left ventricular muscle of the dog. When the animals breathed pure oxygen, electrode readings rose 50-200%o. When a coronary branch was occluded they declined considerably at the borders of the ischemic area, approached zero at its center, and returned to the base line shortly after release of the ligature. If the artery was occluded with the dog breathing room air, pure oxygen breathing did not change values at the center of the ischemic area. However, it did cause a rise in the readings at the "borders" before the occlusion was released. These conclusions were based on studies of 12 anesthetized dogs using two or three electrodes simultaneously in each experiment.We have since developed a more stable dog preparation, using larger numbers of electrodes and obtaining more frequent readings which give a more complete description of the changes in local oxygen availability during short periods of coronary occlusion. Our particular concern has been to learn the size of the "border" areas that may be favorably affected by oxygen inhalation as well as the magnitude and regularity of the oxygen effect. This paper will describe the method we now use, and present a statistical analysis of the results of the first seven experiments in which we have used it. These studies would seem to have a bearing on the 1 This investigation was supported by research grants from the National Heart Institute, of the National Institutes of Health, Public Health Service (USPH-398 and 392) and from the Life Insurance Fund for Medical Research.use of oxygen inhalation for the treatment of acute myocardial infarction in man. METHODApparatus. In our earliest experiments we used the polarographic apparatus described by Montgomery and Horwitz (2) for use in the skin. Since then certain modifications have been made. We now use continuous electrolysis with six to 10 electrodes in the circuit at all times, their individual current variations being recorded when desired on a D'Arsonval galvanometer with a sensitivity of 5 X 10' amps./mm. The circuit modification is shown in Figure 1 and described in its legend. Open tip platinum electrode construction and the principles of polarography as applied to animal tissues have been described by Davies and Brink (3) and Montgomery and Horwitz (4). For the indifferent electrode we have found it necessary to immerse the dog's entire hind foot in a glass dish of saturated NaCl solution from which contact is made to the salt bridge of a calomel half cell. For electrode connections to the switch box No. 30 plain enameled wire was further insulated by placing it inside vinyl tubing. Anesthesia and gas administration. Healthy dogs weighing [15][16][17][18][19][20][21][22] Kgms. were given morphine sulfate intramuscularly (3 mg./Kgm.) followed in 45 minutes by slow intravenous injection of 0.25 cc./Kgm. of a mixture containing equal parts...

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A 45-year-old woman with angina pectoris, beginning at the age of 16 and progressing to produce incapacitation, was found to have an anomalous left coronary artery arising from the pulmonary artery. Because of the severity of symptoms and progression of disability, the anomalous artery was ligated at its origin from the pulmonary artery. Pressure in the left coronary system increased from 35/10 to 105/30 mm Hg. Since operation the patient has been relieved of her symptoms. There was no evidence of increased myocardial ischemia after ligation. This indicates that operative treatment of this anomaly can be carried out successfully in the older age group. It is also suggested that a fourth stage of progression of this anomaly occurs in which there is an exaggeration of the intercoronary communications between the right and left coronary systems. This produces such a large arteriovenous shunt that blood flow to the myocardium is again reduced, resulting in a "coronary steal syndrome."

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