Milestones in cardiac ultrasound: echoes from the past. History of cardiac ultrasound.

Although the antecedents of cardiac ultrasound can be traced back to the 1870s, it was in 1954 that Edler and Hertz published their milestone paper. M-mode echocardiography reached its peak in the early 1970s, when the fibre-optic recorder made the method clinically viable. It was not long before real-time two-dimensional imaging was developed, however, and the invention of pulsed Doppler laid the foundation of duplex scanning. In 1985, colour flow imaging gave a fresh impetus to echocardiography. In parallel with the main developments, intravascular and transoesophageal scanning have gained clinical popularity within the last decade, together with techniques for the display of three-dimensional images. Other innovations include contrast agents, pressure gradient measurement and promising methods for tissue characterisation. It seems that current techniques are safe, but this needs to be kept continuously under review.