FAQ on Heart Sounds and Murmurs

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Heart Sounds Introduction:

Heart sounds are produced by blood turbulence through the closing heart valves. There are four heart sounds: S1, S2, S3 and S4.

What creates the first heart sound called S1?

S1 or a lubb is caused by blood turbulence associated with closure of AV valves.

Where is the first sound heard best?

It is heart best after the AV valves close, namely, right after the Ventricular Systole or Ventricular systole (second step of the cardiac cycle).

What creates the sound of the second heart sound, called S2?

S2 or a dubb is caused by blood turbulence associated with closure of the semilunar valves.

Explain the physiologic splitting of the S2 heard upon inspiration?

The heart is divided into two sections, namely, the right and the left. Sometimes, this causes the lubb-dubb sounds to be divided, a process called the “split S2” caused when the right and the left valves close at different paces. This may be normal, but may also indicate enlarged ventricles.

Where is the second heart sound heard the best?

These sounds are best at the surface of the chest in locations that are slightly different from the locations of the valves.

Additional Reading:

Basic Cardiology

1. Electrical Activity of the Heart
2. Heart Muscle Mechanics
3. Heart Sounds and Murmurs
4. Additional FAQ on Heart Sounds and Murmurs
5. Cardiac Conduction Diagram
6. Blood Pressures in Cardiac Chambers
7. What is Pulsus Paradoxus?
8. FAQ on Heart Murmurs and Mechanisms of Turbulent Flow
9. Notes on Fetal Circulation
10. FAQ on Ischemic Myocardial Infarction
11. FAQ on Electrocardiograms / ECG / EKG
12. FAQ on Cardiac Conduction
13. The Heart as a Pump, the Cardiac cycle and Cardiac Output
14. What are the most common causes of aortic stenosis?
15. What is Pulseless Electrical Activity?
16. Causes and Complications of Arteriovenous Fistulas
17. CHADS2 Score for Atrial Fibrillation Stroke Risk
18. How to Reduce Blood Pressure without Medications?
19. Types of Shock
20. Locations of Heart Murmurs on Chest Wall
21. Types of Heart Blocks

Electrocardiogram (EKG/ECG) Topics

1. EKG Chest Leads
2. EKG Limb Leads
3. Quick 12-Lead ECG/EKG Format

Cardiology Videos

1. Video of Cardiology Examination in a Clinical Setting

Medical Images

Useful Medical Images & Diagrams (link opens in a new window)

Related Topics

1. Thorax Anatomy
2. Vascular Disorders
3. Heart Disorders
4. Histology of the Cardiovascular System
5. Jugular Venous Distention Workup
6. ER Chest Pain Workup
7. Cardiac Examination for Internal Medicine
8. FAQ on Blood Pressure
9. FAQ on principles of fluid and flow dynamics of Blood

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