There was much to hear on auscultation at the apex. First, we heard a fourth sound, then a first sound and the murmur began with that first sound. It was holosystolic and high frequency. It went even through the second heart sound, and then a third sound. [Sounds] A lot to hear at the apex. Let's listen together, using the carotid once again to time systole. [Cut-away]
And what is the significance of the acoustic events we heard at the apex? Well, let's start with the filling sounds, the S4 in presystole and the S3 in early diastole. These are due to reduced compliance of the left ventricle. The S4 is the atrium contracts sending blood into the ventricle, and the S3 in early diastole, when a major amount of blood fills that ventricle. And then we heard a murmur, a murmur quite different than the murmur we heard at the lower left sternal edge. The murmur we heard at the apex is holosystolic, high in frequency. It is most consistent with the type of murmur you hear with mitral regurgitation.
Oscilloscope
By viewing an oscilloscopic imaging and simultaneously listening, we can further appreciate these auscultatory events.
Murmur descriptors
Murmurs may be characterized by descriptors that include location, timing, contour and frequency.
Pressure curves
These simultaneous left atrial, left ventricular and aortic pressure curves illustrate the relationship of the hemodynamic events to the timing, contour and frequency of the systolic murmur. The murmur is holosystolic, as it begins with mitral closure, obscuring the first heart sound and continues up to the second heart sound, as left ventricular pressure exceeds left atrial pressure throughout this period. In our patient, the holosystolic murmur is decrescendo, as left atrial pressure increases in late systole. The murmur is high frequency, primarily, because blood is flowing from the high pressure left ventricle to the low pressure left atrium.
S3 and S4
Third and fourth heart sounds were also heard at the apex. There was no respiratory variation as may occur when right sided in origin. These findings reflect reduced left ventricular compliance. The third heart sound is due to rapid deceleration of blood into the left ventricle in early diastole, while the fourth heart sound results from left atrial contraction of blood into the left ventricle in late diastole.