Heart sounds for beginners S1, S2, S3 & S4

Introduction to Heart Sounds

[00:00] Hello and welcome back. My name is Dr. Coleman and in this tutorial we're covering heart sounds. So let's get straight down to business. Heart sounds are usually presented in medical notes in an abbreviated form and they're presented as S1, S2.

Understanding S1 and S2 in the Cardiac Cycle

[00:20] and S1 again. The gap between S1 and S2 is known as systole, and this represents the period of time when the heart contracts. The space between S2 and S1 is known as diastole, and this represents the period of time when the heart relaxes. This diagram is really useful because it depicts one movement through the cardiac

The Mechanism Behind S1 and S2 Heart Sounds

[00:40] cycle and frames heart sounds temporally in relation to whether they occur during, before or after heart contraction or relaxation. Let's take a closer look at the S1 and S2 heart sound. The S1 heart sound is usually described as sounding like the word lub and the S2 heart sound

[01:00] dub. Let's put the heart sounds in so you can appreciate this better. Let's now take a closer look at what causes the S1 and S2 heart sounds. The S1 heart sound occurs when the tricuspid and mitral

How Heart Valves Contribute to Heart Sounds

[01:20] valves close simultaneously. This is followed by ventricular contraction, otherwise known as systole, and this forces blood through the pulmonary and aortic valves. And the S2 heart sound occurs when the pulmonary and aortic valves close. A period of heart muscle

[01:40] relaxation then occurs and this is known as diastole, after which the cardiac cycle starts all over again. Let's now add in the heart sounds with this animation.

Anatomical Locations for Auscultation of Heart Sounds

[02:00] The four heart valves and their respective heart sounds can be auscultated in the following anatomical areas. Let's now move on to S3, otherwise known as the third heart sound. This heart sound occurs

[02:20] during early diastole just after s2. The word Kentucky is often used to illustrate the timing of the third heart sound in relation to s1 and s2. Let's add in the heart sound so you can appreciate this better.

The Third Heart Sound (S3) – Causes and Clinical Significance

[02:40] To better understand how the S3 heart sound occurs, we have to add in some blood flow to our animation. The first heart sound is caused by the closure of the tricuspid and mitral valves. And the second heart sound is caused by the closure of the pulmonary and aortic valves.

[03:00] The S3 heart sound is produced by the rapid filling of the ventricles during diastole. This produces audible vibrations which are heard as the S3 heart sound. Let's now add the heart sounds to the animation. We're going to start in slow motion but then we'll speed it up to real time.

[03:20] The S3 heart sound is a low frequency sound heard best with the bell of the stethoscope at the apex of the heart. It is heard in early diastole.

[03:40] and is often referred to as a ventricular gallop. It is caused by rapid ventricular filling, which distends the ventricle and tautons papillary muscles. The S3 heart sound is a physiological occurrence and can normally be heard in children and in young healthy adults below the age of 30. But

The Fourth Heart Sound (S4) – Mechanism and Auscultation

[04:00] But the S3 heart sound can also be an abnormal finding and typically can be found in pathology such as cardiomyopathies, aortic and mitral regurgitation, and constrictive pericarditis. Let's now take a look at the fourth heart sound, otherwise known as S4.

[04:20] The S4 heart sound occurs just before S1 in late diastole. The word Tennessee is often used to help describe the rhythm produced by the added fourth heart sound. Let's add in the heart sound so you can better understand it.

[04:40] Let's now take a closer look at why the fourth heart sound occurs. Now because the S4 heart sound occurs momentarily before S1, I have changed our graphical representation so that it now starts with diastole and ends with systole.

[05:00] Blood flows into the atria and ventricles during diastole. And the fourth heart sound occurs when atrial contraction forces blood into abnormal, non-compliant ventricles. This produces audible vibrations which are heard as the S4 heart sound. The S1 heart sound is produced by closure of the tricuspid and mitral

[05:20] valves and the S2 heart sound is produced by the closure of the pulmonary and aortic valves. Let's add in the heart sounds now so that you can see this work. We'll start this one in slow motion and then speed it up to real time.

Differentiating S3 and S4 Heart Sounds

[05:40] The S4 heart sound is heard best at the cardiac apex with the bell of the stethoscope. It is heard in

[06:00] late diastole and is often described as an atrial gallop rhythm. It occurs due to blood being forced into non-compliant ventricles, which means this heart sound only occurs in conditions where the ventricles are particularly stiff and do not relax normally. The term diastolic dysfunction describes this phenomenon.

Pathological Conditions Associated with S3 and S4

[06:20] So as a result, a fourth heart sound is never physiological. It can be heard abnormally in conditions such as hypertrophic cardiomyopathy and systemic hypertension. Now this brings us to the end of the tutorial. If you found this video helpful, make sure you smash that subscribe button.

Conclusion and Next Steps for Learning

[06:40] and share this video with your friends. As always, thanks for stopping by, I really appreciate it. I will see you for the next tutorial.