Electrocardiographic Effects of Changing the Nature of the Contact Between the Exposed Heart and the Body

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Abstract
In dog studies designed to improve the accuracy of direct extracellular heart-body leads, the electrocardiographic representation of the heart when maximally insulated (connected to the body only by its vascular pedicdc) was compared with common open-chest experimental situations in which portions of the normally behaving ventricular surface are allowed to remain in contact with the body. The addition of any ventricular surface to the heart-body contact area (by removal of insulation) lowered the R-wave amplitude in all. direct heart-body leads from the ventricular surface or wall. The effects of locally altering the physiological behavior of portions of the left ventricle were also studied. Any portion of the ventricular surfaces of maximally insulated hearts could be altered by locally applied agents to show heart-body lead changes entirely confined to the area of demonstrably local physiological disturbance. Small- or medium-sized areas of transmural regional is chemia likewise produced electrocardiographic changes only in the vicinity of the ischeniic muscle. In the case of less completely in Sn lated hearts, direct heart-body lead changes consequent to localized physiological change