HEART AND HEART SOUNDS

 Normal heart sounds and cardiac mumurs

Hello everyone, welcome to my blogpost yet again. Today, I will discuss a very important topic from the clinical point of view. Yes, I am talking about the the cardiac mumurs which are the pathological heart sounds indicative of some underlying cardiac pathologies.

In order to understand cardiac murmurs, we need to understand the normal heart sound.

Normal heart sounds

          The normal heart sound, grossly called the LUB-DUB, is produced as a result of closure of the mitral(bicuspid) and tricuspid valve. This first heart sound is called S1.

          The second heart sound is produced by the closure of semilunar valves. i.e. aortic and pulmonary components. The second heart sound is called S2.

          The closure of these valve occur as a result of the pressure difference between atrium and ventricles, which I will brief on next.

          Normally, the process begins when the blood filled in the atrium, is pushed to the ventricles. During the contraction phase of the atrium, which is known as atrial systole, the ventricles remain in a relaxed state to allow free entry of blood from the atrium to ventricles. During the atrial contraction the mitral and tricuspid valve open towards the ventricles and project in the ventricular area.(This unidirectional opening of valve is assisted by a band of fibrous tissues called chordae tendinae). This allows the blood to flow into the relaxed ventrical. At this point of time, the mitral and bicuspid valve remain open, while the aortic and pulmonary valves remain closed to prevent the early ejection of blood. Once the ventricle is filled up with blood, now the ventricle starts its contraction. Due to increase in ventricular pressure during ventricular systole, the mitral and bicuspid valves are pushed back in position producing the first heart sound. Now, at this point of time, following the closure of mitral and tricuspid valves, the aortic and pulmonary valve open and the blood is ejected in the aorta and lungs. After the total ventricular systole the semilunar valves are closed and after this the blood again returns to the atrium and the same process repeats again. The closure of semilunar valves produces S2 or the second heart sound.

          Turbulence in this pathway causes abnormal heart sound. i.e. a damage in the structure or function of any of the cardiac valves produces abnormal heart sound.

CARDIAC MURMURS OR ABNORMAL HEART SOUNDS

          As said, any changes in the structure or function of the cardiac valves produces cardiac murmurs.

          These murmurs are classified on the basis of the event of the cardiac cycle during which the sound occurs .i.e whether it occurs during systole or diastole.

          Hence, there are majorly two types of murmurs.

1.        Systolic murmur

2.      Diastolic murmur.

They are studies in reference to the two heart sounds S1 and S2.

They can also be understood on the basis of the shape of the sound produced.

 SYSTOLIC MURMURS

As the name suggest, these type of murmurs occur during the systolic phase of the cardiac cycle. Typically heard between S1 and S2, these murmurs are heard when the ventricles undergo contraction or systole, leading to closure of mitral and tricuspid valve and opening of semilunar valves during which blood is ejected at a rapid pace in the aorta and the lungs. Thus, the abnormal heart sound may be caused of there is improper closing of mitral and tricuspid valve(regurgitating valves) or if there is problem in ejection of the blood from the semilunar valves(narrowing or stenosis). The involvement of the respective valve can be known by auscultating the respective area on the chest like if the murmur is heard on tricuspid area on the chest, it is indicative of tricuspid regurgitation.

These are further classified on the basis of time during systolic contraction. i.e whether they occur toward the end of the systole(late systoli) or during the entire systolic phase(holosystolic or pan systolic) or in between the systole for a short period of time(mid systolic).

1.       Late systolic murmur: As the name suggests, these are heard towards the end of the systole.

      The reason for being a late sound is that the either leaflets of the valve become weak causing them to prolapse totally and then not closing properly (prolapse or mitral or tricuspid valve) during systole, or if the chordae tendinae are not working properly which normally prevent the valve from moving in the opposite directions. Thereby not able to hold the valves in place which commonly occurs fllowing to injury to the heart muscle as in heart attack as a result of lack of blood flow.

LATE SYSTOLIC MURMUR (MITRAL VALVE):The damage to the mitral component can be judged by auscultating the apex,

LATE SYSTOLIC MURMUR (TRICUSPID VALVE): The damage to the tricuspid component can be judged by auscultating the lower border of sternum,

MID SYSTOLIC MURMUR: These mumurs commonly occur in between S1 and S2 in midway of the ventricular contraction. Since this stage coincides with gradual opening of semilunar valves, it is most commonly heard in problems of aortic or pulmonary component. They follow a  horizontal diamond shaped sound i.e. gradual rise. Peaking and then falling before second heart sound gets completed.(CRESCENDO-DECRESCENDO). The sound occurs because the ventricle seems to work harder to push the blood into the aorta against strong resistance as in case of  stenosis and thus leading to a simultaneous clicking sound called EJECTION CLICK or even in case of HCM(HYPERTROPHIC CARDIOMYOPATHY) where the ventricle has to exert more pressure to pump blood. Even heard in cases of ATRIAL SEPTAL DEFECTS. It may also be heard during pregnancy, anaemia etc. due to icrease in the transit of blood due to the overload of blood.

Hence, it is common in.

1.        Aortic stenosis

2.      Pulmonary stenosis

3.     Valvular sclerosis.

4.      Increased transit due to fluid overload

5.     ASD

6.     HOCM/HCM.

HOLOCYSTOLIC/PAN SYSTOLIC MURMUR: This type of murmurs can be heard throughout the systole. Hence, the name is attributed to this murmur. Unlike midsystolic murmur, in which there is a rise and fall of the sound, this murmur remains constant in throughout S1 and S2.

          This murmur occurs when the ventricles contract with a force leading to forceful closing and a bulge of the AV valves in to the atria, thereby creating a Jetstream of blood in the atrium from retrograde valve opening and creating a continuous sound of this stream of blood in the reverse direction.

          This murmur is commonly seen in:

1.        Mitral valve regurgitation

2.      Tricuspid valve regurgitation

3.     Ventricular septal defects. (VSD).

DIASTOLIC MURMURS

        These murmurs are produced during the diastolic phase of cardiac cycle where the S2 is produced as a result of CLOSURE OF AORTIC AND PULMONARY VALVES and initiation of OPENING OF ATRIO VENTRICULAR VALVE. Thus, they are called diastolic murmurs. Since they are produced after closure of semilunar valves they are heard after the S2 or before initiation of S1 when AV valves close.

          They are further classified into the following.

1.        Early diastolic murmur

2.      Mid diastolic murmur

3.     Late diastolic murmur/presystolic murmur(as they are heard just before S1/closure of AV valves)

1.        Early diastolic murmur: This type of murmur occurs when the pulmonary or the aortic component slide back in the reverse direction of their natural movement due to backpressure by blood. Thus, it is common in AORTIC AND PULMONARY REGURGITATION. A variant of such murmur called AUSTIN FLINT MURMUR occurs with excessive AORTIC REGURGITATION. Can even occur in aortic insufficiency.

2.      Mid diastolic murmur: This murmur occurs midway between S2 and S1 and is common in mitral and tricuspid stenosis because the atria have to push harder to pump the blood to the ventricle after closure of semilunar valve. The sound may split midway due to the fact that the atrium has to undergo contraction in order to pump the residual blood left over due to stenosis. This can also occur when there is increased flow or preload is more, and the atrium has to work harder to transit the blood to the ventricle causing this murmur.

These may also be seen in atrial myxoma or tumors in the heart, which causes narrowing of the Mitral or tricuspid valve as in cases of stenosis.

3.     Late diastolic/Presystolic murmurs: These occurs just before S1 or

Closure of AV valves and thus called late systolic or presystolic murmur,because it can be heard just before atrial contraction.

Most common condition causing these murmurs are COMPLETE HEART BLOCK, where both atrium and ventricles work independently.

                                                 

 

These were the commonest murmurs and their causes. Stay tuned for more new upcoming medical blogs.