Isaac Starr, MD
Here’s a weird observation: If you stand on an old bathroom scale—not a digital one, but one with a needle that points to the number for your weight, based on the pressure your body exerts on its interior springs—hold your breath, stand up straight, and don’t move a muscle. While in that perfect stillness, watch the needle. It will oscillate,
thump, thump, thump, in time with your heartbeat. That is because, with each beat, your heart pushes blood upward into the aorta, where it hits the aortic arch before the blood destined for the body’s lower half hits a wall and flows back downward. The action of that subtle force is enough to shift the needle on your body’s downward pressure by a tiny fraction of a pound,
up, down, up, with each beat.
This may sound like a bit of an obscure medical oddity, and not even one that is useful as a party trick if your scale at home is digital, but it connects to an unexpected story in the history of medicine that goes to show that what’s old can be new again. A central figure in this story is Isaac Starr, MD, a onetime dean of the University of Pennsylvania School of Medicine, and his tale weaves through the dramatically changing medical landscape of the last century.
Introducing the Ballistocardiograph
An explanation very much like the one at the start of this post was first published in the Journal of Anatomy and Physiology in 1877. By the April 28, 1961 edition of TIME magazine, a similar description appeared again, but this time the idea had matured into a measurement technology with a name: the ballistocardiograph. The big news precipitating the TIME article was a new demonstration of the latest ballistocardiography instrument, “developed with the aid of militiamen” by the futuristic-sounding Astro-Space Laboratories, Inc. The article also cited the foundational research by Isaac Starr, a leading researcher in the field who, in 1936, developed the first useful ballistocardiography instrument that could be used in a scientifically repeatable manner, and who had upgraded and refined it over decades. Starr’s work made it possible to compare measurements of these heartbeat-propulsion forces. He found that ballistocardiographs offered doctors a unique insight into the heart’s strength—a different type of knowledge than they could learn from looking at blood pressure, electrical signaling, and other sorts of measurements.
The TIME story ran during what turned out to be a heyday for ballistocardiography. Mere days later, in the May 1961 issue of the journal Circulation, Starr and a Penn colleague published results of 20-year longitudinal studies of healthy adults using the ballistocardiogram. They had begun taking noninvasive ballistocardiographic measurements from both hospital patients and healthy volunteers—medical students and staff, likely including themselves—after creating the first ballistocardiograph machine in 1936. The machine produces a readout in the shape of an irregular sine curve, a bump up and a bump down with each beat of the heart, and in people with heart disease the shape of that curve can be irregular. By 1961, several researchers had shown that, among healthy volunteers, the shape of the curve was normal, but the amplitude, or height, of the curve, declined with age. Starr and his colleague confirmed that with their repeated measurements of 211 initially healthy volunteers over time. They further showed that, for participants who developed heart disease during the course of the study, even though their ballistocardiograph had a normal shape, its amplitude was already lower from the first time they were measured. In essence, people who went on to be diagnosed with heart disease years later appeared to have older hearts than the people who remained healthy.
Starr and a Century of Change
Work on ballistocardiography was a major hallmark of Starr’s luminous career in medicine, one that spanned much of the 20th century as the nature of medical practice underwent dramatic changes. In 1918, while Starr was a third-year Penn medical student, he was in the Student Army Training Corps but wasn’t called to serve in the war. Instead, he was on the domestic front lines of patient care during a massive pandemic flu outbreak. In that era, whiskey was the medicine in greatest demand, and countless patients died daily from what modern experts suspect were complications of pneumonia that might have been prevented had antibiotics been available. (Starr’s firsthand account of the 1918 flu pandemic is a major focus of a feature story in the Winter 2018 issue of Penn Medicine magazine.)
Starr graduated from medical school in 1920, then returned to Penn as an instructor in 1922 after completing his residency at Massachusetts General Hospital. He joined the research group of Alfred Newton Richards, a physician who made important discoveries about kidney function, but Starr ultimately chose to pursue studies of the heart instead of the kidneys.
Starr’s first clinical studies of the heart involved a procedure that used ethyl iodide, but Starr disliked being stuck with needles and did not want to subject his patients to that either, according to an account from an interview with Starr in 1983 published in the book Innovation and Tradition at the University of Pennsylvania School of Medicine. With that in mind during a program of the American Physiological Society in the early 1930s, he eagerly took up the challenge of reviving the concept of ballistocardiography. Separately, he also conducted studies of venous pressure and congestion and contributed to the understanding of the mechanisms of congestive heart failure.
Starr was respected as a researcher and clinician over the course of many decades at Penn. In December 1945, around the time that penicillin first became available outside the military, he was named dean of the School of Medicine. In that role, he succeeded William Pepper, MD, who had served for 33 years, since before Starr himself enrolled as a student. Starr served as dean only until 1948, stepping back into his faculty position to focus on his research. In 1957, he was awarded the Albert Lasker Award of the American Heart Association for “fundamental contributions to knowledge of the heart and the circulation.”
Starr formally retired in 1961, the year he published his major 20-year ballistocardiography study in Circulation. That same year, a far more famous longitudinal heart study was published; the Framingham Study, which had enrolled healthy participants a decade earlier and observed many aspects of their lives, showed in its first major paper that high cholesterol, high blood pressure, and smoking were all risk factors for heart disease, ushering in a new phase of preventive care. (The Framingham Study cohort is still being used for new health insights today.)
Even as an emeritus professor, Starr continued to receive grant funding from the U.S. Public Health Service to continue his research, and he continued coming to campus, via public transit when he first became too infirm to drive, and later contracting with a taxi service. When the last of his grants was due to expire in 1970, the 75-year-old Starr wrote to the University treasurer and enclosed a check for $1,000 to the Trustees of the University of Pennsylvania. The Ballistocardiographic Research Fund he then established would continue to fund his own research—partly through annual checks he wrote himself, partly through donations from his son, Harold, and partly through a cut (65 percent) of the revenue from the ballistogardiographic tests performed on Penn’s hospital patients. Through this plan, Starr continued working at least part-time through the mid-1980s. (Correspondence among Penn officials in 1971, however, indicates that Harold Starr contributed to his father’s fund primarily “to keep the elderly Dr. Starr occupied.”)
During those self-funded years, the elder Starr published a follow-up to his 20-year study. This one focused on a single healthy volunteer followed over a span of a remarkable 37 years. The subject was not named, but was identified as a man who worked in Starr’s ballistocardiographic laboratory. The subject’s first ballistocardiograph was taken at age 41 (the age Starr was in 1936, when he invented his first reliable ballistogardiograph) and the last at age 78 (the age Starr was in 1973, the year this paper was published). The paper appeared in a far more obscure journal, Bibliographica cardiologica.
Starr might not have known it yet, but ballistocardiography had begun to fall out of fashion.
By the time Starr stopped working, cardiovascular medicine was a radically different enterprise than it had been in the 1960s, let alone the 1930s when he began working on heart disease. Researchers had virtually stopped publishing about ballistocardiography at all. Starr died, at age 94, in 1989.
The Rise, Fall, and Possible Rise of Ballistocardiography
If you look up research on ballistocardiography today, the decline in its popularity toward the end of Starr’s life is unmistakable. For a given keyword search, PubMed displays a small chart of publications in its index that match the term, organized by year of publication. For ballistocardiography, if you download the data and group by decade, it looks like this:
While it’s quite evident that Starr’s work in the middle of the century occurred at a peak of interest in ballistocardiography, there is also a hint that something new might be happening lately. Is ballistocardiography rising again?
It is an unusual pattern for a medical technology, according to Paul Mather, MD, a professor of Clinical Medicine in Cardiovascular Medicine at Penn. He notes that medical tools tend not to wax and wane; technological advances show linear growth most of the time and exponential growth some of the time when a new technology or circumstance opens up a new opportunity. “Most human inventions have occurred in the last 100 years, not in the last 100,000 years,” he says, because technological advances in the 20th and 21st centuries have opened opportunities for exponential growth in many arenas.
It may well be that new technology has set the stage for a new exponential rise for ballistocardiography. Recent publications in PubMed’s index on the topic include studies of wearable devices and sleep monitors, even “smart” bathroom scales—all methods that take advantage of ballistocardiography’s noninvasive ability to measure dynamics of movements happening inside the body from subtle motions on the outside.
Mather speculates that the technique may be integral to recent technological advances in his own specialty, heart failure. Heart failure is about the mechanics of how the heart works—or fails—as a pump. Due to newer computational abilities available today and a greater ability to understand the mathematics behind the flow dynamics of blood going through that pump, newer implanted devices coming into common use, including pulmonary artery catheters and cardiovascular resynchronization pacemakers, might use ballistocardiographic principles as part of their computational method to interpret the fluid dynamics of blood’s movement through the heart and blood vessels (an area of study known as rheology).
“It’s fascinating to think we can go back to this old technology and say, ‘hey, this can tell us things,’” Mather says. With a better three-dimensional measurement of blood flow, “now we’re starting to apply it to the human pump and not just modeling it on a static mechanical pump. This is reinventing ballistocardiography to become a more hemodynamic measurement of pump efficiency.”
What’s old may be new again—with the technologies of a new century. No need to hold your breath.