An automatic device for freeze-clamping of cardiac tissue within a fraction of the contraction cycle.

An automatic quick-freeze clamping device has been developed. Opposed pneumatic pistons filled with aluminium caps previously cooled in liquid nitrogen are used to compress a portion (100 to 200 mg) of the myocardium to a 0.15 to 0.20 mm thick wafer, colling the tissue from 37 degrees C to -15 degrees C within 10 ms. The clamp is triggered electronically from the R-wave of the ECG. This tissue fixation by freezing within 10 ms is sufficiently rapid to study oscillations of myocardial metabolite levels during the contraction cycle of isolated perfused hearts of small mammals such as the rat and guinea pig whose rate is 4 to 5 beats per second.