Continuous recording of local myocardial function in normal and ischemic myocardium.

Experiments in anaesthetized open chest dogs are described in which intramyocardial pressure was determined by two methods, both suitable for long time experiments. By means of a Fogarty catheter in connection with a normal transducer the intramyocardial pressure can be measured. With this method the pressure gradient from epicardial to endocardial muscle layers is demonstrated. Insertion of catheter tip manometers leads only to small trauma of the myocardium. This method allows the determination of systolic and enddiastolic tissue pressure together with the dp/dtmax and dp/dtmin. Measurements were performed in normal and in ischemic areas of the myocardium. In the ischemic parts of the myocardium all parameters descline, while in the normal, non ischemic areas the parameters increase, thus demonstrating overactivity, which compensates for the loss of myocardial function in the ischemic parts. The overall function of the heart as a pump remains nearly unaffected. On release of the coronary ligature the negative changes in the ischemic myocardium are rapidly restored. During the phase of reactive hyperemia the parameters measured in the ischemic area even increase above the control values.