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Measuring Central Venous Pressure with the Arm. Cardiac Second Heart Sounds The cardiac second sounds can provide a number of valuable clues to what is going on with the heart.
Introduction to Second Heart Sounds. The Basics of Second Heart Sounds. In the normal heart: During expiration: The second sound S2 is usually single During inspiration: The second sound S2 is made of two component sounds: Aortic valve closure A2 which happens first. Pulmonic valve closure P2 which happens second. What causes the split second heart sounds? Exam Technique in Second Heart Sounds.
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.
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.
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 atrial septal defect 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. Page Contents Physiology S2 Heart Sound represents closure of the aortic valve and pulmonic valve The aortic valve typically closes slightly before the pulmonic valve Higher pressures in the systemic circulation force the aortic valve closed sooner During expiration, the S2 Heart Sound is typically heard as one sound not split During inspiration, the S2 Heart Sound is physiologically split Represents a more significant timing difference between the closure of aortic A2 and pulmonic valves P2 Greater right sided than left sided filling with inspiration results in a greater duration between A2 and P2 Inspiration creates negative intrathoracic pressure Negative chest pressure increases right ventricular filling and volume Preload Negative chest pressure decreases left sided filling from lungs.
Causes: S2 Wide Split Right Bundle Branch Block Slower right ventricular contraction delays pulmonic valve closure Pulmonic Stenosis Prolonged right ventricular emptying due to obstructed flow, results in delayed pulmonic valve closure Mitral Regurgitation. Causes: S2 Paradoxical Split S2 splits during expiration Left Bundle Branch Block Slower left ventricular contraction delays aortic valve closure Pulmonic valve P2 closes before aortic valve A2 , most prominent during expiration During inspiration, P2 is delayed, and therefore coincides with A2, resulting in paradoxical split Aortic Stenosis Prolonged left ventricular emptying due to obstructed flow, results in delayed aortic valve closure.
Causes: Loud S2 Pulmonic Stenosis P2 is louder due to forced closure of the pulmonic valve Arterial Hypertension A2 is louder due to forced closure of the aortic valve.
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