The first essential finding we’re going to learn together is normal splitting of the second heart sound. Now, when you examine a patient, you assess all of the findings. Remember those five fingers? And Harvey has those findings, carotid arterial pulses, jugular venous pulse, chest wall movement, a little tap in early systole, breathing that may vary the acoustic events. We are going to focus on auscultation, and in this case, we are going to listen at the upper left sternal edge with the diaphragm of the stethoscope, where you best hear splitting of the second heart sound. Everyone listen together, and we will use the carotid vessel as a timing mechanism and place a cotton swab on it, so we can identify systole. Everyone listen together and watch breathing [sounds].
And what did we hear? As the patient breathed in, we heard [sounds], breathed out [sounds]. You do that, [sounds]. And why did we hear it? Because as the patient breathed in that dropped the pressure in the chest, then a bit more blood went back to the right heart, delaying the pulmonary closure, blood also pooled in the lungs, therefore, a little less went to the left ventricle and the aortic closure was a little bit earlier. So then you get [sounds].
And the behavior of the second heart sound can be a critically important clue to a diagnosis. For example, in a patient with an atrial septal defect, you may hear a flow murmur coming out in the upper left sternal edge area and, most importantly, the second heart sound remains fixed split. [sounds] It never varies; and even sometimes, the second heart sound can split in expiration, that’s called paradoxic splitting, if there is a reason for delay of left side ejection. Remember, normal splitting, mimic it, remember it [sounds].
Second Heart Sound Splitting
Abnormal splitting of the second heart sound occurs in a variety of pathologic conditions. It may be the key to a diagnosis, as in patients with atrial septal defects who have fixed splitting. Normal children and young adults may have persistence of expiratory splitting when supine, but this typically disappears when they sit or stand.
S1+S2
The relative intensity of the second heart sound may reflect underlying pathology. Normally, the aortic sound is louder than the pulmonary, because it closes at a higher pressure. In systemic hypertension, the aortic sound may be further accentuated, and in pulmonary hypertension, the pulmonary sound may be increased. In aortic and pulmomary stenosis, one component may be diminished due to valve immobility.
Normal Splitting of S2 / A2 Louder than P2
This is a graphic example of normal inspiratory, or physiologic, splitting of S2, in which the first component, A2, is normally louder than the second component, P2. Let us listen together.