Electrocardiogram

Electricity provides a key to understanding heart function

In the 1850s, researchers experimenting with frogs discovered that a heartbeat is associated with an electrical current. However, it was years before this information could be used in human diagnosis.

Permanent recordings: a landmark in diagnosis

Even with the earliest electrocardiograms (ECGs), researchers and medical practitioners saw that patients with heart disease had abnormal tracings. Because the electrocardiograph produced permanent records of the heart's electrical activities, clinicians were able to compare tracings made at different times and with different patients. Knowledge quickly accumulated about heart attacks, arrhythmia, angina, and other conditions.

From two-room giant to practical portable instrument

The first measurements of the electrical activity of the heart came from electrodes directly touching a frog's heart. When physiologists realized that the heart's electric currents could be detected at the surface of the body, they began attempts to develop a device to measure it in people. Willem Einthoven invented such a device in 1901, but it weighed 600 pounds, filled two rooms, and needed five people to run it.

In 1926, the first portable device was manufactured. It weighed 80 pounds and had to be moved on wheels. Still, the device was practical for use in hospitals, and soon physicians began using the electrocardiograph to monitor patients under anesthesia. Recording methods improved greatly over the years. Today, the bright screen showing tracings of the heartbeat is a familiar operating room fixture.

A truly portable electrocardiograph, the 1960 Sanborn Visocardiette Small electrodes placed on the skin pick up electrical impulses with each contraction of the heart.

X-Ray

Taking the first steps toward imaging the heart

The first images of the heart seen through the skin-and clothing-of a living patient were X-ray images. This was big news: within a month after the discovery of X-rays, the story hit newspapers throughout the world.

Physicist Wilhelm Konrad Roentgen accidentally discovered X-rays in 1895. He called them X-rays because he didn't know what they were.

X-rays went beyond the limits of physical diagnosis because they could be used to see inside the body. Although even the earliest medical X-rays revealed enlarged hearts, X-rays were better for visualizing bones than soft tissue. The technique was not universally accepted in cardiology.

"Indeed I am doubtful if an X-ray examination of the heart has ever thrown the slightest light on any cardiac condition," said Sir James Mackenzie in 1920

Compare the image of the normal heart on the top with the image on the bottom. In the bottom image you see a patient with congestive heart failure whose heart has lost its ability to pump blood efficiently. The heart on the bottom is significantly enlarged, a key indicator of heart failure.

Fluoroscopy

The technique of fluoroscopy was introduced only a month after the X-ray machine. Fluoroscopy couples X-rays with a screen coated with a chemical that glows when struck by the X-rays. Shadows are cast by parts of the body that absorb X-rays, creating an image of bones and fleshy organs such as the heart. Doctors often had patients swallow barium sulfate, which, visible in the esophagus in a chest X-ray, would indirectly help outline the borders of heart chambers.