The authors present a new improvement of the cardiac catheter, by means of a set by modulation frequency, mounted on the blood-pressure and intercardiac murmurs and sounds. They insist on the inoffensiveness and facility of operation of this micromanometer catheter since it does not imply any new risk to ordinary cathererization. The authors explain some of the results obtained with this new method in the investigation of normal and abnormal murmurs and sounds of the heart, and demonstrate its fundamental importance in the diagnosis of some cardiopathological cases from such research.