Jugular vein is a natural non invasive right heart catheter inserted permanently in the right atrium . It faithfully reflects the right heart hemo-dynamics  during  every heart beat.

The information you gather is dependent upon the time you spend and mind you you apply on this biological catheter.Wenke back did so nicely he was able to identify progressive a and c interval and a drop of c wave  before even the ECG machine was invented.

The following table  illustrates  the difference