The S2 should split into two components when the patient inspires. The aortic valve (A2 or aortic second sound) closes sooner than the pulmonic valve (P2 or pulmonic second sound), and it is the louder component of S2; this occurs because the pressures in the aorta are higher than the pulmonary artery.
Full Answer
What is a split S2?
Split S2. Wiggers diagram of various events of a cardiac cycle, with 2nd heart sound at bottom. A split S2 is a finding upon auscultation of the S2 heart sound. It is caused when the closure of the aortic valve (A2) and the closure of the pulmonary valve (P2) are not synchronized during inspiration.
What is fixed S2 splitting in respiration?
Fixed S2 splitting denotes absence of significant variation of the splitting interval with respiration, such that the separation of A2, and P2, remains unchanged during inspiration and expiration.
What causes S2 to split in heart?
The splitting of S2 occurs because inspiration brings more blood into the right ventricle. Right ventricular ejection is prolonged, and the pulmonary valve (P2) closes later. A loud, single S2 indicates either pulmonary hypertension or congenital heart disease involving one of the semilunar valves.
What is the degree of splitting of the S2 molecule?
The degree of splitting of the S2 varies with respiration, increasing with inspiration and decreasing or becoming single with expiration (see Fig. 2-7).
What does split S2 indicate?
The second heart sound (S2) represents closure of the semilunar (aortic and pulmonary) valves (point d). S2 is normally split because the aortic valve (A2) closes before the pulmonary valve (P2). The closing pressure (the diastolic arterial pressure) on the left is 80 mmHg as compared to only 10 mmHg on the right.
Is splitting of S2 normal?
It is physiologically normal to hear a "splitting" of the second heart tone in younger people, during inspiration and in the "pulmonary area", i.e. the 2nd ICS (intercostal space) at the left edge of the sternum.
What causes wide splitting of S2?
Persistent (Widened) Split S2 Any condition that causes a nonfixed delay in the closure of the pulmonic valve, or early closure of the aortic valve, will result in a wide split S2.
Why is S2 fixed in ASD?
Because the atria are linked via the defect, inspiration produces no net pressure change between them, and has no effect on the splitting of S2. Thus, S2 is split to the same degree during inspiration as expiration, and is said to be “fixed.”
When is split S2 abnormal?
In younger subjects inspiratory splitting averages 0.04 to 0.05 second during quiet respiration. With expiration, A2 and P2 may be superimposed and are rarely split as much as 0.04 second. If the second sound is split by greater than 0.04 second on expiration, it is usually abnormal.
What are the causes of S1 and S2 in a normal heart?
The "lub" is the first heart sound, commonly termed S1, and is caused by turbulence caused by the closure of mitral and tricuspid valves at the start of systole. The second heart sound, "dub" or S2, is caused by the closure of the aortic and pulmonic valves, marking the end of systole.
What are abnormal heart sounds?
Abnormal heart sounds are called heart murmurs. A heart murmur may occur in between regular heartbeats and sound like one of the following: a rasping. a whooshing. a blowing.
When is the S2 heart sound heard?
The second heart sound (S2) represents closure of the semilunar (aortic and pulmonary) valves (point d). S2 is normally split because the aortic valve (A2) closes before the pulmonary valve (P2). The closing pressure (the diastolic arterial pressure) on the left is 80 mmHg as compared to only 10 mmHg on the right.
What causes first heart sound?
The first heart sound (S1) represents closure of the atrioventricular (mitral and tricuspid) valves as the ventricular pressures exceed atrial pressures at the beginning of systole (point a). S1 is normally a single sound because mitral and tricuspid valve closure occurs almost simultaneously.
What is fixed splitting?
Fixed Splitting. A widened interval of A2 and P2 that shows no change during the respiratory cycle is termed fixed splitting. The most common cause of fixed splitting is an atrial septal defect.
What type of murmur is ASD?
However, ASD with moderate-to-large left-to-right shunts result in increased right ventricular stroke volume across the pulmonary outflow tract creating a crescendo-decrescendo systolic ejection murmur. This murmur is heard in the second intercostal space at the upper left sternal border.
What is a narrowly split S2?
A narrowly split S2 is found in conditions in which the pulmonary valve closes early (e.g., pulmonary hypertension) or the aortic valve closure is delayed (e.g., AS). This is occasionally found in a normal child. 3.
What is the S2 sound?
S 2 is best appreciated at the left upper sternal border and varies with the respiratory cycle. During inspiration, the pulmonary valve closes after the aortic valve, creating a split sound; in expiration, the two valves close at the same time. The normal inspiratory split of the components of S2 is approximately 0.05 second.
What is abnormal splitting?
Abnormal splitting may be in the form of wide splitting, narrow splitting, a single S2, or paradoxical splitting of the S2 (rarely). 1. A widely split and fixed S2 is found in conditions that prolong the RV ejection time or that shorten the LV ejection. Therefore, it is found in:
Where is the S2 audible?
In every normal child, with the exception of occasional newborns, two components of the S2 should be audible in the upper left sternal border. The first is the A2; the second is the P2.
Is it normal to split S2 during inspiration?
Splitting of the S2 during inspiration is a normal finding and should be sought in all patients. The aortic and pulmonary pressure in diastole closes the semilunar valves. Many forms of congenital or acquired heart disease have an impact on the pulmonary circulation and, consequently, often affect the S2.
Is S2 single or split?
S 2 is single in patients with severe pulmonary hypertension, because of earlier closure of the pulmonic component, and in patients with atresia of one of the semilunar valves (pulmonary atresia or hypoplastic left heart associated with aortic atresia). S2 is narrowly split in patients with mild or moderate pulmonary hypertension.
What is split S2?
A split S2 is a finding upon auscultation of the S2 heart sound. It is caused when the closure of the aortic valve (A 2) and the closure of the pulmonary valve (P 2) are not synchronized during inspiration.
Is it normal to hear a split heart tone?
It is physiologically normal to hear a "splitting" of the second heart tone in younger people, during inspiration and in the "pulmonary area", i.e. the 2nd ICS (intercostal space) at the left edge of the sternum.
What is the split of the second heart called?
When the split closes in inspiration and becomes audible in expiration, it is called paradoxical splitting of second heart sound. Please note that a wide split of second heart sound as in right bundle branch block ...
Why does the second heart sound split?
Paradoxical splitting of second heart sound. Normal split of second heart sound is due to the delay in pulmonary valve closure compared to a ortic valve. This is mostly contributed to by the pulmonary hang out interval. Hang out interval is the time taken for the actual valve closure after the pulmonary artery and right ventricular pressure tracings ...
Why is there a paradoxical splitting in the second heart?
Most common cause of paradoxical splitting of second heart sound is left bundle branch block, in which aortic closure is delayed due to the delay in left ventricular activation. Paradoxical splitting in aortic stenosis indicates severe aortic stenosis causing delay in A2.
Is an audible expiratory split a paradoxical split?
An audible expiratory split may also be heard in young individuals in supine position. This physiological expiratory split closes in sitting and standing positions [1]. Paradoxical splitting of second heard sound can also be called reversed splitting.
