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 this setting, a S4 is often heard. Also, if an individual is actively having myocardial ischemia, adequate adenosine triphosphate cannot be synthesized to allow for the release of myosin from actin; therefore, the myocardium is not able to relax, and a S4 will be present.
It is important to note that if a patient is experiencing atrial fibrillation, the atria are not contracting, and it is impossible to have a S4 heart sound. Like S3, the S4 sound is low pitched and best heard at the apex with the patient in the left lateral decubitus position.
Below is comparative information for S3 and S4. There are a few common extra heart sounds that the clinician may encounter. Systolic ejection click: A systolic ejection click frequently indicates a bicuspid aortic valve. This sound is heard just after the S1 heart sound. Usually, the opening of the aortic valve is not audible; however, with a bicuspid aortic valve, the leaflets dome suddenly prior to opening and create a systolic ejection click.
The click may be difficult to hear in the presence of significant AS. Mitral valve prolapse click: Mitral valve prolapse produces a mid systolic click, usually followed by a uniform, high-pitched murmur.
The murmur is actually due to MR that accompanies the MVP; thus, it is heard best at the cardiac apex. MVP responds to dynamic auscultation. After sudden standing, preload is decreased, and the click moves earlier in systole. With sudden squatting, preload increases, and the click moves later in systole. Opening snap: In the setting of MS, the increased left atrial opening pressures cause an opening snap to occur when the mitral valve leaflets suddenly tense and dome into the LV in early diastole.
This high-frequency sound is best heard at the apex. Tumor plop: A tumor plop is an early diastolic low-pitched sound just after the S2 heart sound. This is in contrast to the opening snap of rheumatic mitral valve stenosis, which is high pitched. A tumor plop may be followed by a low-pitched diastolic murmur.
If the mitral valve inflow obstruction is significant enough, physical exam findings of congestive HF will be present. Pericardial knock: A pericardial knock can be present in patients with constrictive pericarditis, as the early filling of the LV is limited from the constrictive process. The knock occurs earlier than a S3 heart sound. Back to Healio. Topic Reviews A-Z Save.
Read more about auscultation. Related Content. Please refresh your browser and try again. In addition, the more muscular and stiff "less compliant" left ventricle LV empties earlier than the right ventricle.
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. 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. In these cases, the split is usually wide and "fixed" with no 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.
Murmurs are additional sounds generated by turbulent blood flow in the heart and blood vessels. Murmurs may be systolic, diastolic or continuous.
Systolic murmurs are the most common types of murmurs in children and based on their timing within systole, they are classified into:. The murmur is heard shortly after S1 pulse. The intensity of the murmur increases as more blood flows across an obstruction and then decreases crescendo-decrescendo or diamond shaped.
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.
0コメント