Second Heart Sounds
This course will teach you about the second heart sound. Before you take this course you should have finished the Normal Heart Sound and First Heart Sound courses. You should feel comfortable with the material presented.
Using this course
Each lesson in this course includes text describing the heart or lung abnormality and a simulated torso indicating the stethoscope chestpiece location. An audio recording of the sound is provided. Phonocardiograms or waveforms are included with each lesson. These waveforms can be a highly useful aid in learning to recognize heart murmurs. In addition, short videos clips illustrate the heart's motion for each abnormality. These animations indicate the origin of each murmur. Blood flow is also animated. For lung sounds, the source (location) of the sound can be revealed.
After completing a lesson, use the lesson table of contents to navigate to another lesson.
When all lessons have been completed, we recommend using the auscultation practice exercises or quiz. In order to gain a certificate of achievement, please complete the course lessons and practice drill during one session. Most users complete the course's lessons and quiz in 30-45 minutes.
Authors and ReviewersAuthors: Jonathan Keroes, MD, Cardiologist (ret.), David Lieberman, Heart Sound Simulation Consultant. Medical review by Dr. Barbara Erickson.
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Lesson #1: Second Heart Sound - Physiologically Split #2
The second heart sound (S2) is created by the closing of the aortic valve followed by the closing of the pulmonic valve. Careful analysis of the splitting and intensity of the second heart sound can indicate the presence of many cardiac abnormalities. This example shows normal physiological splitting of the second heart sound. Splitting varies between zero and eighty milliseconds depending on the phase of the respiratory cycle. The aortic component of S2 (S2A) precedes the pulmonic component (S2P).
Lesson #2: Second Heart Sound with Persistent Splitting
This example shows persistent splitting of the second heart sound. Splitting varies between thirty milliseconds at peak expiration and sixty milliseconds at peak inspiration. With normal physiologic splitting the second heart sound is not split at peak expiration. With persistent splitting, the second heart sound is split in both inspiration and expiration, although the degree of splitting is reduced in expiration. This type of splitting is associated with Right Bundle Branch Block a condition in which the electrical signal which causes contraction of the right ventricle is blocked.
Lesson #3: Second Heart Sound with Fixed Splitting
This example shows fixed splitting of the second heart sound. The second heart sound remains unchanged through inspiration and expiration at sixty milliseconds. Fixed splitting of the second heart sound (along with murmurs) indicates the presence of an Atrial Septal Defect, a congenital heart defect in which the intra-atrial septum is incomplete resulting in a hole between the left and right atria. The murmurs have been eliminated in this lesson so that you can concentrate on the fixed splitting of the second heart sound. In a later lesson you will hear the fixed splitting of S2 along with the murmurs of Atrial Septal Defect.
Lesson #4: Second Heart Sound: Fixed Splitting, Increased Aortic Intensity
This example shows a second heart sound (S2) with fixed splitting and an aortic component with increased intensity. This pattern is seen in the presence of long-standing severe hypertension where the pressure in the aorta is markedly increased. Once again, we are using fixed splitting of S2 to make it easier to concentrate on the relative intensities of the aortic and pulmonic component of S2. This condition is caused by essential hypertension. Note the increased thickness of the left ventricular wall.
Lesson #5: Second Heart Sound: Fixed Splitting, Decreased Aortic Intensity
This example shows a second heart sound (S2) with fixed splitting and an aortic component with decreased intensity. Once again, we are using fixed splitting to help you hear the difference in intensity between the aortic and pulmonic components of S2. This pattern is seen in the presence of long-standing severe pulmonary hypertension where the pressure in the pulmonary artery is markedly increased. Note the increased thickness of the right ventricular free wall.
Lesson #6: Second Heart Sound and Late Systolic Click
Certain heart sound configurations mimic a split second heart sound. One of these conditions is a late systolic click plus a single second heart sound (S2). Since the late systolic click occurs just before the S2, it is easy to confuse the two with a split S2. Listen carefully to the two sounds. If the first of the pair is of higher frequency and shorter duration than the second, it is a late systolic click followed by a single second heart sound. Another way of distinguishing a late systolic click from a split S2 is to move the stethoscope head to the pulmonic area. The late systolic click will disappear, and you will only hear the single S2. A late systolic click is caused by degeneration of the mitral valve leaflets. This degeneration causes the closing of the leaflets to make a "clicking" sound during late systole. On the anatomy video you will see prolapse of the anterior lateral mitral valve leaflet which is the cause of the late systolic click.
Lesson #7: Second Heart Sound and a Tumor Plop
Another heart sound configuration which mimics a split second heart sound is a single second heart sound followed by a tumor plop (a transient which occurs early in diastole). If you move the stethoscope head to the pulmonic area, the tumor plop will disappear. If you continue to hear two distinct sounds at the pulmonic area, the likelihood is that you are hearing a split second heart sound. The timing and frequency of a tumor plop are identical to that of a third heart sound gallop. It is not possible to distinguish one from the other.
Lesson #8: Opening Snap and Second Heart Sound
An opening snap occurring early in diastole along with a single second heart sound can mimic a split second heart sound. An opening snap is caused by thickened valve leaflets. When they open, it produces a snapping sound. The more severe the thickening the earlier in diastole the opening snap occurs. In this example you are hearing an opening snap, which occurs 75 milliseconds after the start of the second heart sound.