Ultraminiature strain gauge transducer for assessing regional intramyocardial pressure

A probe consisting of an ultraminiature strain gauge mounted on a 1.6-mm diam stainless-steel hypodermic needle for the measurement of intramyocardial pressure is described. Measurements were made of regional intramyocardial pressure throughout the cardiac cycle in 18 dogs. Simultaneous measurements were made in the left ventricular free wall at the subendocardial and subepicardial level. Advantages of the probe are: (a) an ability to localize pressure measurements at various depths within the myocardial wall; (b) minimal trauma and distortion of the myocardial tissue at the site of measurement because of the small volume occupied by the sensor; and (c) the high frequency response and insignificant time delay of the transducer. The method allows a simultaneous comparative assessment of intramyocardial pressure with other hemodynamic events.