Which semilunar valve closes first

Clinically, this is more remarkable with slow heart rates. The third heart sound S3 represents a transition from rapid to slow ventricular filling in early diastole. S3 may be heard in normal children.

The fourth heart sound S4 is an abnormal late diastolic sound caused by forcible atrial contraction in the presence of decreased ventricular compliance. In these cases, the split is usually wide and "fixed" with no difference between inspiration and expiration due to fixed RV volume see ASD section. In both conditions, the aortic valve A2 closes after the pulmonary valve P2.

Since the respiration only affects P2, its effect in paradoxical splitting is the opposite of normal, i. Murmurs are additional sounds generated by turbulent blood flow in the heart and blood vessels. Murmurs may be systolic, diastolic or continuous. Systolic murmurs are the most common types of murmurs in children and based on their timing within systole, they are classified into:.

The murmur is heard shortly after S1 pulse. The intensity of the murmur increases as more blood flows across an obstruction and then decreases crescendo-decrescendo or diamond shaped.

Innocent murmurs are the most common cause of SEM see below. Other causes include stenotic lesions aortic and pulmonary stenosis, coarctation of the aorta, Tetralogy of Fallot TOF or relative pulmonary stenosis due to increased flow from an ASD. Crescendo decrescendo murmur. Examples: ventricular septal defect VSD , mitral and tricuspid valve regurgitation. Holosystolic murmur. In the latter part of systole, the small VSD may close or become so small to not allow discernible flow through and the murmur is no longer audible.

Decrescendo murmur. Diastolic murmurs are usually abnormal, and may be early, mid or late diastolic. Continuous murmurs are heard during both systole and diastole.

They occur when there is a constant shunt between a high and low pressure blood vessel. Examples: patent ductus arteriosus PDA and systemic arterio-venous fistulas. This may also occur in surgically placed shunts such as a Blalock-Tauussig BT shunt between the aorta and the pulmonary artery. Cardiology Part 2 - EKG. The time between A2 and P2 is variable depending on the respiratory rate, but the split is generally only prominent in children during inspiration.

In adults and during expiration, the split is usually not long enough to suggest two sounds. Abnormal heart sounds may indicate problems with the health of the valves. Murmurs may also be caused by valve stenosis improper opening and cardiac shunts, a severe condition in which a defect in the septum allows blood to flow between both sides of the heart.

Third and fourth heart sounds, S3 and S4, differ from S1 and S2 because they are caused by abnormal contraction and relaxation of the heart instead of the closure of valves and are more often indicative of more severe problems than are heart murmurs.

S3 represents a flabby or weak ventricle that fills with more blood than it is able to pump, while S4 represents a stiff ventricle, such as those found in cardiac hypertrophy.

Learning Objectives Describe the sounds the heart makes. The splitting of the second heart tone, S2, into two distinct components, A2 and P2, can sometimes be heard in younger people during inspiration. During expiration, the interval between the two components shortens and the tones become merged.