Catheters: A Pipeline to the Heart

Though heart catheters have been used to take measurements in animal physiology studies since 1861, medical researchers used to be afraid that their use in humans might injure the heart.

In 1929, Werner Forssman proved heart catheters were safe by using one on himself. Forssman threaded one of the tubes through a vein in his arm all the way to his heart. He then walked to the X-ray department to record the event on film.

Since Forssman's fearless discovery, catheters have been used to deliver drugs and imaging dyes to the heart, make measurements inside the heart, and even perform surgical procedures. Teamed with the fluoroscope, opaque dyes made blood vessels and heart chambers visible. Physicians were able to see malfunctioning valves and defects in heart tissue, such as holes between chambers.

To use a catheter, a physician makes a small cut at the elbow crease or groin to locate an artery, then threads a sheath or guide catheter through the blood vessel. This "pigtail" catheter would be passed inside the sheath, directly to the heart.

Angiography takes its place in cardiac medicine

When a technique was developed in the late 1950s to deliver dyes directly to the coronary arteries, it changed the course of cardiovascular medicine. With the new technique, called selective coronary angiography, doctors could clearly see the flow of blood through the coronary arteries. They were able to detect blockages in those arteries that caused chest pain and might lead to heart attacks.

Within 10 years, surgical intervention to treat coronary arteries was possible. Today, coronary angiography remains critical for presurgical diagnosis and monitoring.

Making arteries visible and invisible

Compare the normal angiogram on the left with the one on the right. In both, you're seeing dye-filled coronary arteries.

The patient on the right is suffering from angina, or chest pains, and the image reveals the cause. The red circle highlights a partial blockage of an artery, where very little dye passes because plaque has accumulated.

The blue arrows point to evidence that there is a complete blockage in a second artery. In the normal image, you see a descending artery with two branches. In the image on the right, these branches are missing. That's because no dye at all is getting past the blockage.

Perfusion Imaging

Using pseudocolor to visualize heart muscle health

This kind of image, called myocardial perfusion imaging, allows cardiologists to "see" the blood supply to heart muscle. Injured muscle tissue can be detected because it doesn't take up as much blood as healthy tissue.

To create these images, a radioactive compound is injected into the patient's bloodstream. A special camera detects the amount of radioactivity taken up by the heart, and a computer assigns colors based on the levels in each area.

This image shows a normal perfusion image of the heart.

This image shows abnormally thick heart muscle, which may be a sign of cardiomyopathy.

This image shows signs of coronary heart disease. When coronary arteries are blocked, some heart tissue doesn't get enough blood. It also doesn't take up as much of the indicator compound.

Echocardiogram

Seeing the heart with sound

In 1954, two German physicians did the first experiments with cardiac ultrasound by borrowing a sonar device from a nearby shipyard. They were excited about the prospects of a technique that didn't involve dyes or any physical invasion of the body.

An ultrasound machine, like sonar, sends out high-frequency sound waves, which bounce off solid materials. The machine builds an image based on the reflected waves that return.

American cardiologist Harvey Feigenbaum promoted echocardiography in the 1960s and 1970s, inviting many young cardiologists to study the technique at his lab. It spread quickly in the 1970s, when cardiologists learned that they could use it to assess patients with heart murmurs, congestive heart failure, and other common conditions.

Since then, the technology has improved tremendously with greater computer power leading to advances in digital image processing. Echocardiography is now the second most commonly used diagnostic technique after electrocardiography.

Echocardiograms show a thickening of heart muscle

Compare the normal echocardiogram, above, to the one below, which shows hypertrophic cardiomyopathy, or abnormally thickened heart muscle. Notice that the black space within the normal left ventricle is much smaller, which means it holds less blood. That's because the walls of the heart, which appear white, are so expanded. You can see the septum between the right and left ventricle is very thick, as is the outer wall of the ventricle at the bottom of the image.

Color images reveal problems with blood flow

Color flow echocardiography enables physicians to see the movement of blood through the heart. It makes obvious the leakage or backflow of blood, called regurgitation, which indicates poorly functioning valves.

Red and blue in these echocardiograms indicate the direction of flow of blood. Red indicates movement toward the source at the top of the image. Blue indicates movement away.

This view of the heart shows both the aortic and mitral valves. MV-mitral valve AV-aortic valve LA-left atrium

Here the left ventricle is contracting to pump blood through the aortic valve into the aorta. The blue color in the left atrium indicates a problem with the mitral valve. The valve should be preventing blood from entering the atrium.

Here the left ventricle is relaxing. The red color indicates that some blood is flowing, as it should, from the left atrium into the ventricle. However some blood is flowing back into the ventricle from the aorta, indicating a problem with the aortic valve. (The blue color shows normal swirling of blood in the ventricle.)