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Jan 12, 2012

Heart murmur, sounds and cardiac cycle


Heart has four chambers and four set of valves. chambers left atrium and left ventricle have valve between  is called  mitral valve, chambers right atrium and right ventricle have valve between them is called  tricuspid valve. Left ventricle ejects blood into aorta (main vessel of systemic circulation) valve between left ventricle and aorta is called aortic valve. Right ventricle ejects blood into pulmonary trunk (vessel that carries blood to lung for oxygen loading of blood) valve between right ventricle and pulmonary trunk is called pulmonary valve

Read this post for knowing more on heart anatomy and circulation click here

Sound originating from heart i.e.  First and second heart sound arises from closer of valves.
  
First heart sound: - closer of mitral and tricuspid valve
Second heart sound: - closer of aortic and pulmonary valve

Ventricles of heart expand to receive blood and contracts and eject blood. Contraction phase of ventricles of heart is called systole, and expansion phase of ventricles is called diastole

Systole and diastole of heart are classified for both right and left ventricular contraction and expansion, not for atrial contraction and expansion

Systole starts with first heart sound and end with second heart sound
Diastole starts with second heart sound and ends with first heart sound.

Both left and right atrial contraction occurs in last part diastole of heart (which fill the ventricle force fully, which contributes just  10% of ventricular filling)
Heart systole i.e. ventricular systole and ventricular diastole are divided into following phases
Heart or ventricular systole
1.      Isovolumteric Contraction: here only pressure builds, due contraction but size of ventricle is not altered, in this phase mitral and tricuspid valve close, followed by opening of aortic and pulmonary valve.
2.       Rapid ejection: - Blood is ejected in to aorta and pulmonary artery
3.       Slow ejection: - blood continues to eject, but in slow phase.
Heart or ventricular diastole
1.       Isovolumteric relaxation: - In this phase.  Aortic and pulmonary valves close due to fall in ventricular pressure, but there is no expansion in size of ventricles.  
2.       Early rapid filling: Most of ventricular filling occurs in this phase and ventricles expand in this phase.
3.       Slow rapid filling :  Ventricular filling slows down
4.       Protodiastole :  No filling of ventricles, both atria and ventricle act as single column, mitral and tricuspid valves fully open
5.       Atrial contraction: Atria contracts and empties, blood into ventricle.
Murmurs:
Murmurs are produced sec to increase flow through normal or secondary to normal flow through abnormal valve
Murmurs due to increased flow (functional murmur)
·         Increase amount of flow is seen leaky valves i.e. regurgitant valves. Previous chamber is added with extra amount blood so in next cycle increased amount blood passes though leaky valve which produces murmurs.
·         Increase flow is also seen in increased circulatory states i.e. anemia, hyperthyroidism, and some in normal person with thin chest wall.
·         Shunt between left and right heart produce increase flow in valve distal to receiving chamber example atrial septal defect, ventricular septal defect, and patent ductus arteriosus.
·         Murmurs of increased flow are also called functional murmurs
·         Sometimes they are innocent, example thin individual
Murmurs due to abnormal valve
·         Abnormal valves produce murmurs by two mechanisms, leaky valve and stenotic valve.
·         Leaky valve also produce murmur  in same cycle apart from increase flow as discussed above