Electrocardiogram

The invention: Device for analyzing the electrical currents of the
human heart.
The people behind the invention:
Willem Einthoven (1860-1927), a Dutch physiologist and
winner of the 1924 Nobel Prize in Physiology or Medicine
Augustus D. Waller (1856-1922), a German physician and
researcher
Sir Thomas Lewis (1881-1945), an English physiologist
Horse Vibrations
In the late 1800’s, there was substantial research interest in the
electrical activity that took place in the human body. Researchers
studied many organs and systems in the body, including the nerves,
eyes, lungs, muscles, and heart. Because of a lack of available technology,
this research was tedious and frequently inaccurate. Therefore,
the development of the appropriate instrumentation was as
important as the research itself.
The initial work on the electrical activity of the heart (detected
from the surface of the body) was conducted by Augustus D.Waller
and published in 1887. Many credit him with the development of
the first electrocardiogram. Waller used a Lippmann’s capillary
electrometer (named for its inventor, the French physicist Gabriel-
Jonas Lippmann) to determine the electrical charges in the heart and
called his recording a “cardiograph.” The recording was made by
placing a series of small tubes on the surface of the body. The tubes
contained mercury and sulfuric acid. As an electrical current passed
through the tubes, the mercury would expand and contract. The resulting
images were projected onto photographic paper to produce
the first cardiograph. Yet Waller had only limited sucess with the
device and eventually abandoned it.
In the early 1890’s,Willem Einthoven, who became a good friend
of Waller, began using the same type of capillary tube to study the
electrical currents of the heart. Einthoven also had a difficult time working with the instrument. His laboratory was located in an old
wooden building near a cobblestone street. Teams of horses pulling
heavy wagons would pass by and cause his laboratory to vibrate.
This vibration affected the capillary tube, causing the cardiograph
to be unclear. In his frustration, Einthoven began to modify his laboratory.
He removed the floorboards and dug a hole some ten to fifteen
feet deep. He lined the walls with large rocks to stabilize his instrument.
When this failed to solve the problem, Einthoven, too,
abandoned the Lippmann’s capillary tube. Yet Einthoven did not
abandon the idea, and he began to experiment with other instruments.
Electrocardiographs over the Phone
In order to continue his research on the electrical currents of the
heart, Einthoven began to work with a new device, the d’Arsonval
galvanometer (named for its inventor, the French biophysicist
Arsène d’Arsonval). This instrument had a heavy coil of wire suspended
between the poles of a horseshoe magnet. Changes in electrical
activity would cause the coil to move; however, Einthoven
found that the coil was too heavy to record the small electrical
changes found in the heart. Therefore, he modified the instrument
by replacing the coil with a silver-coated quartz thread (string).
The movements could be recorded by transmitting the deflections
through a microscope and projecting them on photographic film.
Einthoven called the new instrument the “string galvanometer.”
In developing his string galvanomter, Einthoven was influenced
by the work of one of his teachers, Johannes Bosscha. In the 1850’s,
Bosscha had published a study describing the technical complexities
of measuring very small amounts of electricity. He proposed the
idea that a galvanometer modified with a needle hanging from a
silk thread would be more sensitive in measuring the tiny electric
currents of the heart.
By 1905, Einthoven had improved the string galvanometer to
the point that he could begin using it for clinical studies. In 1906,
he had his laboratory connected to the hospital in Leiden by a telephone
wire.With this arrangement, Einthoven was able to study in
his laboratory electrocardiograms derived from patients in the hospital, which was located a mile away. With this source of subjects,
Einthoven was able to use his galvanometer to study many
heart problems. As a result of these studies, Einthoven identified
the following heart problems: blocks in the electrical conduction
system of the heart; premature beats of the heart, including two
premature beats in a row; and enlargements of the various chambers
of the heart. He was also able to study how the heart behaved
during the administration of cardiac drugs.A major researcher who communicated with Einthoven about
the electrocardiogram was Sir Thomas Lewis, who is credited with
developing the electrocardiogram into a useful clinical tool. One of
Lewis’s important accomplishments was his identification of atrial
fibrillation, the overactive state of the upper chambers of the heart.
During World War I, Lewis was involved with studying soldiers’
hearts. He designed a series of graded exercises, which he used to
test the soldiers’ ability to perform work. From this study, Lewis
was able to use similar tests to diagnose heart disease and to screen
recruits who had heart problems.
Impact
As Einthoven published additional studies on the string galvanometer
in 1903, 1906, and 1908, greater interest in his instrument
was generated around the world. In 1910, the instrument, now
called the “electrocardiograph,” was installed in the United States.
It was the foundation of a new laboratory for the study of heart disease
at Johns Hopkins University.
As time passed, the use of the electrocardiogram—or “EKG,” as
it is familiarly known—increased substantially. The major advantage
of the EKG is that it can be used to diagnose problems in the
heart without incisions or the use of needles. It is relatively painless
for the patient; in comparison with other diagnostic techniques,
moreover, it is relatively inexpensive.
Recent developments in the use of the EKG have been in the area
of stress testing. Since many heart problems are more evident during
exercise, when the heart is working harder, EKGs are often
given to patients as they exercise, generally on a treadmill. The clinician
gradually increases the intensity of work the patient is doing
while monitoring the patient’s heart. The use of stress testing has
helped to make the EKG an even more valuable diagnostic tool.