Abstract: A myocardium wall thickness measuring transducer comprises a circular beam of high compliance and an elongated spike which extends in the plane in which the beam is disposed. The spike is connected at one point to the beam while a working end of the spike to which a barb is attached, extends through an opening in the beam at a substantially diametrically opposite point. The beam portion, surrounding the opening, is free to move or be displaced relative to the spike. A sensitive strain gauge is bonded to the beam to sense changes in the tension thereof. The working end of the spike is inserted through the epicardium into the myocardium so that the spike and the beam are in a plane substantially perpendicular to the epicardium at the point of insertion. The spike is inserted, to a depth at which a minimal beam deforming force is applied by the myocardium to the beam portion surrounding the opening.