Correlation of Intramyocardial Electrocardiograms with Polarographic Oxygen and Contractility in the Nonischemic and Regionally Ischemic Left Ventricle

A new technique for simultaneous amplification and recording of intramyocardial oxygen-reduction currents and electroeardio-graphic voltages from the tips of platinum oxygen electrodes was combined with cinematographic muscle contraction records from exposed dog hearts. The picture of localized ischemia produced by occlusion of medium-sized coronary arterial branches was compared, under stable systemic circulatory conditions, with the changes of myocardial oxygenation, electrical activity, and contractility, separately or together. Myoeardial electro-cardiographic abnormality appeared as early as disturbances of local oxygen and contraction at the centers of ischemic areas; at the borders, only the myocardial electrocardiogram was unequivocally abnormal. The epicardial electrocardiogram could be normal despite severe, acute disturbance of electrical activity in the underlying myocardium, and was not useful for the study of small isehemic areas, the onset of ischemia, or the borders of any isehemic area. No single index of myocardial function was dependable for following the course and estimating the extent of regional ischemic dysfunction, or for distinguishing it from traumatic or nonisehemic myocardial disturbances. The most complete description of the sequence of ischemic events was derived from the analysis of changes in local myocardial electrical activity. For this, however, it was necessary to interpret and compare direct heart-body electrocardiograms from myocardial and epicardial sites inside and outside an ischemic area, with attention to simultaneous records of myocardial oxygen and local contraction. Such a combination of indices is considered essential for adequate description and differentiation of any localized myocardial change in a working, blood-perfused heart.