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. Index of Core Concept Chapters. A bout Core Concepts. The Cardiac Cycle — Left ventricular pressure — Aortic pressure — Left atrial pressure Cardiac cycle of the left side of the heart.
More information: Examples of innocent murmurs. Stills murmur Pulmonary flow murmur Venous hum. In severe aortic stenosis, the A2 component may not be audible at all. Normally, A2 occurs just before P2, and the combination of these sounds make up S2. A physiologic split S2 occurs when the A2 sound precedes P2 by a great enough distance to allow both sounds to be heard separately. This happens during inspiration when increased venous return to the right side of the heart delays the closure of the pulmonic valve major effect , and decreased return to the left side of the heart hastens the closure of the aortic valve minor effect , thereby further separating A2 and P2.
During expiration, the distance narrows, and the split S2 is no longer audible. A paradoxical split S2 heart sound occurs when the splitting is heard during expiration and disappears during inspiration — opposite of the physiologic split S2.
A paradoxical split S2 occurs in any setting that delays the closure of the aortic valve including severe aortic stenosis and hypertrophic obstructive cardiomyopathy, or in the presence of a left bundle branch block.
Enlarge Persistent Widened Split S2 Persistent widened splitting occurs when both A2 and P2 are audible during the entire respiratory cycle, and the splitting becomes greater with inspiration due to increased venous return and less prominent with expiration. This differs from a fixed split S2, which exhibits the same amount of splitting throughout the entire respiratory cycle and is explained below.
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. In mitral regurgitation, this is due to a large proportion of the left ventricular stroke volume entering the left atrium, causing the left ventricular pressure to decrease faster.
Enlarge Fixed Split S2 A fixed split S2 is a rare finding on cardiac exam; however, when found, it almost always indicates the presence of an atrial septal defect. A fixed split S2 occurs when there is always a delay in the closure of the pulmonic valve, and there is no further delay with inspiration; compare this to a widened split S2, as described above. To explore why an ASD results in a fixed split S2, we must consider the altered cardiac hemodynamics present, which result in a fixed delay in PV closure.
During inspiration, as usual, there is an increase in venous return to the right side of the heart and thus increased flow through the PV — delaying its closure. The alteration in a person with an ASD occurs during expiration. As the person expires, the pressure in the right atrium decreases because there is less venous return. The decreased pressure allows more blood to flow abnormally through the ASD from the high pressured left atrium to the right atrium, ultimately resulting again in increased flow through the pulmonic valve — again, delaying its closure.
The S3 sound is actually produced by the large amount of blood striking a very compliant LV. Enlarge If the LV is not overly compliant, as is in most adults, a S3 will not be loud enough to be auscultated. A S3 can be a normal finding in children, pregnant females and well-trained athletes; however, a S4 heart sound is almost always abnormal.
A S3 can be an important sign of systolic heart failure because, in this setting, the myocardium is usually overly compliant, resulting in a dilated LV; this can be seen in the image below.
Enlarge Normal LV vs. Dilated LV S3 Present. S3 is a low-pitched sound; this is helpful in distinguishing a S3 from a split S2, which is high pitched.
A S3 heart sound should disappear when the diaphragm of the stethoscope is used and should be present while using the bell; the opposite is true for a split S2. Also, the S3 sound is heard best at the cardiac apex, whereas a split S2 is best heard at the pulmonic listening post left upper sternal border. To best hear a S3, the patient should be in the left lateral decubitus position.
If the LV is noncompliant, and atrial contraction forces blood through the atrioventricular valves, a S4 is produced by the blood striking the LV. Therefore, any condition that creates a noncompliant LV will produce a S4, while any condition that creates an overly compliant LV will produce a S3, as described above. A S4 heart sound can be an important sign of diastolic HF or active ischemia and is rarely a normal finding.
Diastolic HF frequently results from severe left ventricular hypertrophy, or LVH , resulting in impaired relaxation compliance of the LV. In that case, the split is usually wide and fixed with no change 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. 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. A figure showing normal and abnormal splitting of the second heart sound.
Some Rights Reserved. Date last modified: July 7,
0コメント