New approach to local thermodilution: use of pig tail catheters to avoid basic difficulties.

The use of pit tail catheters and the placing of the thermistor distal to the lumen for the cold injectate have allowed the development of a new catheter for local thermodilution with many advantages. Apart from its small size and possibility of percutaneous introduction, the spatial orientation of the thermistor to the rest of the catheter and to the port of injection ensures: (a) its absolute thermal insulation; (b) avoidance of contact with vessel walls: and (c) constant spatial relationship between the lumen for injection and the thermistor as regards the dynamics of flow and temperature change.