To accommodate the mouse heart, the chamber's cannulae are 20 - 22 gauge stainless steel press fit mounted in a removable female luer to threaded hub assembly. The cannula vertical position is adjusted by threading or unthreading the hub assembly into the lid. The horizontal position of the atrial cannula can be nominally adjusted in the same manner. Two additional female luer access ports are provided in the lid for insertion of instrumentation such as balloon catheters, electrodes, fiber optic cables, etc.