Biomedical [Basics] what is HEART SOUND?

Heart Sounds

Auscultation of the heart means to listen to and study the various sounds arising from the heart as it pumps blood. These sounds are the result of vibrations produced when the heart valves close and blood rebounds against the ventricular walls or blood vessels. The heart sounds may be heard by placing the ear against the chest or by using a stethoscope. The vibrations producing the sounds can be visually displayed through the use of a heart sound microphone and physiological recorder to produce a phonocardiogram. There are four major heart sounds, but only the first two can be heard without use of special amplification.

• First heart sound. Produced at the beginning of systole when the atrioventricular (AV) valves close and the semilunar (SL; the aortic and pulmonary) valves open. This sound has a low-pitched tone commonly termed the lub sound of the heartbeat.
• Second heart sound. Occurs during the end of systole and is produced by the closure of the SL valves, the opening of the AV valves, and the resulting vibrations in the arteries and ventricles. Owing to the higher blood pressures in the arteries, the sound produced is higher pitched than the first heart sound. It is commonly referred to as the dub sound.
• Third heart sound. Occurs during the rapid filling of the ventricles after the AV valves open and is probably produced by vibrations of the ventricular walls.
• Fourth heart sound. Occurs at the time of atrial contraction and is probably due to the accelerated rush of blood into the ventricles.

RELATIONSHIP BETWEEN HEART SOUNDS AND ECG:

• FIRST HEART SOUND Coincide with R wave of ECG
• SECOND HEART SOUND Coincide with the ending part of T wave of ECG

HEART VALVE FAILURE DISEASES

Aortic Stenosis: 

Here the blood is ejected from the left ventricle through a small opening of the aortic
valve. Because of the resistance to ejection, the pressure in the left ventricle rises.
This causes turbulent blood flow. This turbulent blood impinging the aortic valve
causes intense vibration; it produces loud murmur (sounds related to non laminar flow
of blood in the heart).

Aortic Regurgitation: 

No sound is heard during systole, but during diastole blood flows backward from the
aorta into the left ventricles, causing a blowing murmur. This is produced due to the
valves are damaged.

Mitral Regurgitation: 
Here blood flows backward through the Mitral valve during systole. This produces
sound during systole.

Mitral Stenosis: 

Here the blood passes with difficulty from the left atrium into the left ventricle due to
pressure difference. It produces murmur which is very weak.