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. Previous Next. Created with SoftChalk Some Rights Reserved. Table showing the common systolic, diastolic and continuous heart murmurs. Usually vascular in origin when a high-pressure vessel communicates with a low-pressure vessel e.
Because the mitral and tricuspid valves normally close almost simultaneously, only a single heart sound is usually heard. This occurs when the mitral valve closes significantly before the tricuspid valve, allowing each valve to make a separate audible sound. Inspiration delays the closure of the tricuspid valve in a normal person, due to increased venous return, thereby enhancing the splitting of the S1 sound. A RBBB causes the electrical impulse to reach the left ventricle before the right ventricle.
Dyssynchrony then occurs, resulting in the left ventricle contracting before the right ventricle, thus the pressures in the LV rise before that of the right ventricle. This delays the closure of the tricuspid valve, resulting in a split S1 sound. A left bundle branch block has the opposite effect on S1. This forces the tricuspid valve closed earlier, resulting in complete overlap of M1 and T1, and thus no audible split S1 sound.
Four factors affect the intensity of the first heart sound. Because the M1 portion of S1 is much louder than T1, it is only important to discuss what affects the intensity of M1. The second heart sound is produced by the closure of the aortic and pulmonic valves. The sound produced by the closure of the aortic valve is termed A2, and the sound produced by the closure of the pulmonic valve is termed P2. The A2 sound is normally much louder than the P2 due to higher pressures in the left side of the heart; thus, A2 radiates to all cardiac listening posts loudest at the right upper sternal border , and P2 is usually only heard at the left upper sternal border.
Therefore, the A2 sound is the main component of S2. Like the S1 heart sound, the S2 sound is described regarding splitting and intensity. The S2 heart sound can exhibit persistent widened splitting, fixed splitting, paradoxical reversed splitting or the absence of splitting.
The S2 heart sound intensity decreases with worsening aortic stenosis due to immobile leaflets. 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. Normally, S1 is louder than S2 at the apex, and softer than S2 at the base of the heart.
Pathologic changes in the intensity of S1 relative to S2 may be seen in certain disease states. When evaluating the intensity of S2 , note the relative intensity of the aortic component A2 and the pulmonic component P2. Normally A2 is louder than P2. The first heart sound is made up of several components, although the most audible components heard at the bedside are the high frequency vibrations related to mitral and tricuspid closure.
Generally, the louder sound of mitral closure drowns out the softer sound of tricuspid closure. Occasionally the two are separated sufficiently such that there is audible splitting of S1 , heard best at the apex or lower left sternal border.
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