Measurement of porcine heart temperatures

During cardiac surgery local hypothermia of the heart is used to slow down cellular metabolism. It has been shown by computer simulation that heart muscle is not uniformly cooled to the desired temperatures. The aim of our work was to find out a way for measuring the temperatures of the ventricular wall and the septum with +/-0.1 degrees C accuracy. The measurement protocol should be applicable during operations on the human heart, during which disturbing factors should be minimized. We have tested the protocol and the equipment on porcine hearts. Two types of probes were tested, the contact-probe, which can be attached to the heart-wall surface, and the needle-probe, which can be inserted into the heart tissue. Before experiments the probes were calibrated and their heat transfer characteristics determined. We conclude that the probes and the protocol are suitable for studying the effects of cardioplegia, and for checking the results previously obtained by computer simulation.