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. 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. So when you hear 'S2' at the mitral area, you are really hearing A2. Normally, P2 is soft and only heard at the pulmonic region left parasternal, intercostal space 2 , however even in this region A2 is louder.
There are believed to be multiple causes for the physiologic splitting of S2. Both A2 and P2 close when the pressure above the respective valves are greater than the pressure in the ventricles below. Given the lower vascular resistance of the pulmonary artery, during inspiration, the pulmonary artery is able to tolerate more volume of blood before the pressure above the valve increases. Additionally, during inspiration, more blood fills the right ventricle leading to a slightly longer ejection time, adding to the delayed pulmonic valve closure.
This video was created by Dr. Click this link to see his collection of medicine educational videos. The 25 The 25 Visit the Abraham Verghese Interviews Dr. Jerome Kassirer on New Book Signs of Scleroderma can-improv-help-doctors conversation-about-bedside-medicine-gains-momentum. Stanford 25 Skills Symposium Announced!
What will bedside manner look like for new data-driven physicians? The venous return to the right ventricle RV increases during inspiration due to negative intrathoracic pressure and P2 is even more delayed, so it is normal for the split of the second heart sound to widen during inspiration and to narrow during expiration.
Clinically, this is more remarkable with slow heart rates. 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.
0コメント