The Role of Heart Sounds Recording and Analysis in the Dyspneic Ed Patient

Extra diastolic heart sounds are produced as a result of increased stiffness and decreased compliance of the left ventricle. The third heart sound (S3) occurs 0.12 to 0.16 seconds after the second heart sound in early diastole (Figure 1). Of the many proposed theories, the most likely explanation is that excessive rapid fi lling of a stiff ventricle is suddenly halted, causing vibrations that are audible as the third heart sound. The fourth heart sound (S4) occurs after P wave onset and before the fi rst heart sound in the cardiac cycle. It is produced in late diastole as a result of atrial contraction causing vibrations of the left ventricular muscle, mitral valve apparatus, and left ventricular blood mass. Atrial and ventricular “gallops” have been described in the literature dating back to the late 1800’s. The ventricular gallop is recognized as a third heart sound. The atrial gallop is synonymous with a fourth heart sound. Auscultation of the S3 and S4 Both an S3 and S4 are auscultated in similar fashion. Harvey has suggested the “inching” technique as a way to distinguish the often times pathologic S3 and S4 from the physiologic S1 and S2. In both situations it is best to examine the patient in the left lateral position using the bell of the stethoscope. Starting at the aortic area (where the S2 is the loudest) the examiner “inches” down to the cardiac apex, using the S2 as a reference point. If one encounters an extra sound in diastole, just after the S2, this is an S3 or diastolic gallop. The S3 is generally absent at the base, so that as the examiner moves toward the apex the S3 is encountered. The opposite maneuver results in detection of an S4. In this instance the examiner inches from the apex upward Figure 1.