The Story of The Development of Noninvasive Heart Care
New article traces contributions of an engineer and physician collaborators looking to assess the heart from the outside in
Fifty-one years ago the average American home cost $30,000, Elvis Presley wooed listeners with Hard Headed Woman, and the hula hoop was introduced. That same year, 1958, a team comprised of a groundbreaking engineer — Dean Franklin — in concert with two exceptional physicians — Drs. Robert Rushmer and Robert Van Citters ““ was laying the foundation for what would eventually become a radical new approach to health care: the noninvasive imaging and treatment of the heart. The discoveries of these pioneers would eventually lead to a doctor’s ability to see the heart without cutting open the body; allow patients to have their hearts monitored despite being miles away; and provide reassurance to parents that a fetus’ heart was normal rather than waiting until the offspring was born.
The details of these efforts are chronicled in a new article, “Standing on the Shoulders of Giants: Dean Franklin and His Remarkable Contributions to Physiological Measurements in Animals,” by R. Dustan Sarazan and Karl T.R. Schweitz. The article appears in the September 2009 edition of Advances in Physiological Education (http://advan.physiology.org/cgi/content/full/33/3/144). The American Physiological Society (APS; www.the-aps.org) publishes the quarterly journal. The APS has been an integral part of the scientific discovery process since it was founded in 1887.
Dean Franklin: Ultrasound, Ultrasonic Transit Flow Meter, and Doppler Flow
Dean Franklin was a teenager during World War II, but was drafted in 1950 and selected for training in radar. He subsequently became chief instructor in the U.S. Army’s advanced radar school. In 1952, he was recruited by Boeing to work on the BOMARC missile project and was later hired as an electronics technician in the laboratory of Robert Rushmer at the University of Washington Medical School.
Initially, Franklin’s role was limited to fabricating the Whitney gauge, a relatively crude device that could be attached to a dog’s heart tissue to measure cardiac dimensions. At the time, Rushmer was pioneering the concept of collecting cardiovascular data from conscious animals with implanted instrumentation, instead of the unconscious, open-heart animals that were the standard. While working in Rushmer’s laboratory Franklin melded what he learned about the cardiovascular system with what he had learned about radar during his military service. With the support of Dr. Rushmer, a pediatrician and physiologist with a great interest in the heart, they were able to develop ultrasound instruments to measure blood flow, despite the prevailing view of the late 1950s that ultrasonic measurements of blood flow were impossible. Franklin’s device was successful enough to be among the first breakthroughs to use ultrasound for physiologic measurements. It was used, for the first time, on conscious animals and eventually humans.
By 1962, Franklin and a colleague had invented the first fully functional ultrasonic transit time flow meter, which measures blood flow in intact arteries; the sonocardiometer, which measures the dimensions of the heart; and the ultrasonic Doppler flow meter, which measures the velocity of liquids containing suspended particles such as red blood cells. As a result of these developments, a new generation of scientists launched the first noninvasive ultrasound imaging devices, which are now the industry standard in human medical technology. These devices are descended directly from Franklin’s first flowmeter and sonocardiometer.
Scripps Clinic and the San Diego Zoo
That same year, Franklin joined Robert L. Van Citters at the Scripps Clinic in San Diego and established a relationship with the San Diego Zoo. Through this arrangement, the researchers had their first opportunity to work with animals other than dogs. While at Scripps, Franklin designed and built the first telemetry device for remote monitoring of physiologic signals (other than temperature). It was first tested on an exercising boxer dog at the Zoo hospital and subsequently was used for telemetry experiments in baboons and a variety of other animal species across the globe. The telemetry widely used in hospitals that we know today evolved from these experiments.
Out of Africa, Into Alaska
After three years at Scripps, Franklin and Van Citters conducted telemetered experiments in Kenya for the purpose of understanding the effects of exercise in baboons in their natural habitat and the unusual hemodynamic issues confronted by giraffes with the large hydrostatic pressure gradient between their heads, their hearts and their feet. The pair was successful in developing and implanting tiny devices in the heart that the animals could wear for long periods. The devices, small implantable blood pressure transducers, Doppler flowmeters and a radio telemetry system, were surgically implanted, the animals recovered and the experimenters were able to carry out long distance monitoring of blood pressure in the animals.
Franklin and Van Citters continued to focus more sharply on the physiology of exercise, especially the distribution of blood flow to various organs during extreme exercise. Classic physiology predicted a reduction in renal flow during a fright reaction, though in one of the African experiments, a baboon was threatened by a giraffe but its renal flow did not change. Nor did it change among treadmill-exercising dogs in experiments previously conducted in Rushmer’s laboratory.
Ultimately, Franklin and Van Citters used their telemetery systems to study Alaskan sled dogs, similar to those in the famous Iditarod race. They traveled to Alaska and instrumented several dogs, surgically inserting flowmeters and pressure gauges. After the dogs recovered from surgery and were reconditioned to their previous exercise capacity, their performance was tested. They were able to run 20 consecutive 4-minute miles without showing any sign of exhaustion and no evidence of blood flow deficit to visceral organs, even during extreme exercise.