Modern echocardiography owes a salute to the Navy

Staten Island Advance By Staten Island Advance Staten Island Advance
on May 17, 2010 at 5:25 AM, updated May 17, 2010 at 5:27 AM

STATEN ISLAND, N.Y. — Medicine has not been slow or shy about adapting for its own use the innovations of other disciplines. The space program for example, developed the home digital blood pressure device, originally designed for astronauts. A recent adaption of aviation’s checklist to improve the safety of surgical procedures made the talk-shows and the bestseller list. This week, I highlight the intellectual gifts from the Navy to the practice of echocardiography.

In actual fact, nature pre-empted the Navy by a few million years, as dolphins and bats have always used sound for communication and detection. Man appeared to get into the act around 1912 after the Titanic disaster, when underwater echo-ranging equipment was patented in both England and the United States. During World War I, under great secrecy, the Antisubmarine Division of the Royal Navy developed and deployed submarine detecting equipment, called ASDIC, which used active sound generation and detection of the echoes reflected off underwater structures.

Knowing the speed of sound traveling in water, the time from generation to reception of the reflected sound, determined the distance to the reflecting object, hopefully an enemy submarine. By the time of the outbreak of World War II, the Royal Navy had developed a number of different types of ASDIC equipment and shared the technology with the U.S., where it was called SONAR (Sound Navigation and Ranging), the sound equivalent of RADAR (Radio Detection and Ranging).

The adaption of this technology to the development of echocardiography is a lesson in networking.

In 1953 Dr. Inge Edler, head of cardiology at the University Hospital, Lund, Sweden, was searching for a better way to evaluate the function of the mitral valve (located between the heart’s upper left holding chamber and lower pumping one). Surgery was available to open a closed valve but not to close a leaking valve, and the diagnostic difference was a matter of life or death.

Fortuitously, Dr. Hellmuth Hertz was working as a graduate student at the University. He was exceedingly well connected, being the son of the Nobel prize winner and director of the Siemens research laboratory. Dr. Edler, enlisted his help, and with a borrowed naval SONAR device from the local shipyard, they began to record the movements of the heart wall and the mitral valve.

Publication of their work set off a multitude of further research and in the ensuing decade, development of the clinical and technical aspects of echocardiography expanded exponentially.

The same principles applied. The ultrahigh frequency sound generated by a probe placed on the chest was reflected off deeper structures in the chest. The longer the time it took for the echo to return (and we are talking in millionths of a second) the deeper the reflecting structure would be.

This allowed a two dimensional picture of the beating heart to be visualized in real-time on a computer screen. Now the motion of the heart walls and the valves could be studied, but the movement of the blood was still invisible. The submarine could be seen, but whether it was moving and how fast remained a mystery.

The answer came in an unexpected way!

In 1803, in Mozart’s Salzburg, Austria, on a cold November night, Christian Andreas was born into the Doppler family which, for generations, had prospered in the stone masonry business. However, he was frail and sickly and as he grew it was apparent that he could not join in the physically exacting family trade, so he became a professor of mathematics.

At the age of 38, he published his most brilliant mathematical concept which has become universally known as the Doppler Principle. You can tell, however, from the title of the paper, “On the colored light of the double stars of the heaven,” that he really did not have the echocardiogram in mind.

Doppler considered both light and sound to be propagated in the form of waves or frequencies. He postulated that if the source of the energy and its observer were getting closer, then the frequency would appear to be bunched up and compressed and it would be appreciated at a higher pitch (if it were sound) or a shorter wave length (if it were light). Conversely, if the source were getting further away, the observer would appreciate the sound to be at a lower pitch than the actual emitted sound or, if light, at a longer wave length and redder than the actual emitted light.

The most common example of the principle is the sudden drop in pitch of a train whistle as the train passes the observer. When the Navy incorporated this principle into their SONAR, they could spot the submarine and determine whether it was coming or going and how fast!

Again medicine adapted the Navy’s technology and when the echocardiographic probe was modified to measure the frequency of the sound in addition to the timing of the echo it could then utilize the Doppler Principle to tell whether blood was flowing backward or forwardthrough a valve and, if so, how fast. Blood flow and the amount of leakage were now measurable.

By moving the probe to other sites it became possible to quantitate the degree of blockage in the arteries of the neck and the veins of the leg, using the fact that blood flows faster

In the war against disease, it is good to have the Navy on our side.