Auscultation | Echocardiography | ECG | MRI | Pedigree

Auscultation

Auscultation is the act of listening, with a stethoscope, to sounds made by the heart, lungs, and blood. It is performed as one of the initial and very important steps in cardiac diagnosis.

Aortic phenomena include 'sounds,' which are brief vibrations caused by momentary events, and 'murmurs,' which are the sound of turbulence as blood flows through some narrow orifice or tube. The two sounds heard in everyone are the first sound (S1 or 'lub,' in lub-dub) caused by closing of the mitral and tricuspid valve as the ventricles begin to contract and pump blood into the aorta and pulmonary artery. The second sound (S2 or 'dub') is caused when the ventricles finish ejecting, begin to relax, and allow the aortic and the pulmonary valves to close.

One approach for analyzing heart sounds is to record them using a microphone and to then display the electrical signals graphically. This is called a phonocardiogram, in which the x-axis represents time and the y-axis voltage (which is a measure of the intensity of sound). The picture below shows a simple phonocardiogram of four heartbeats. The first and second sounds of the first heartbeat are labeled. In our laboratory exercises, this type of display is used to help you identify problems associated with abnormal heart sounds.

One of the more common abnormal phenomena that can be detected with a stethoscope is a murmur—a somewhat prolonged 'whoosh' that can be described as blowing, rumbling, soft, harsh, and so on. The phonocardiogram below shows a murmur between the first and second sounds, or during the systolic part of a heartbeat. Because of its timing, the abnormal sound could be related to either a narrowing of one of the aortic or pulmonory valves or to a leak through the mitral or tricuspid valves. Without a thorough check-up by an experienced physician, it is difficult to determine the precise cause of a murmur.

Finally, it should be noted that heart sounds vary tremendously, depending on the patient's posture, on the position of the stethoscope on the chest, and on how deeply or rapidly the patient is breathing. A skilled physician will take all these factors into account when analyzing the result of an auscultation.

Here are some example sounds:

Aortic Regurgitation: There is a strong blowing murmur immediately following the second sound as blood leaks back into the ventricle from the aorta during diastole. Instead of "lub-dub," it sounds like "lub-whoosh."

Mitral Regurgitation: The blowing murmur fills the whole systolic period completely as the blood leaks back into the atrium from the ventricle as it contracts. Instead of "lub-dub," you get "whoooooosh."

Aortic Stenosis: A murmur from stenosis isn't as harsh sounding as one from regurgitation. Here, an obstruction of the passage to the aorta causes a rumbling murmur during systole between the first and the second sound. Instead of "lub-dub," you get "lub-rumble-dub," though it may be difficult to hear the "lub" and the "dub" distinctly.