Fourth Heart Sound (S4)
With Left Ventricular Hypertrophy (LVH):
- Aortic Stenosis: Valvar, Sub & Supravalvar
- Hypertrophic Cardiomyopathy
With Right Ventricular Hypertrophy (RVH):
- Pulmonic Stenosis: Valvar, Sub & Supravalvar
- Pulmonary Arterial Hypertension
Extra sounds near S1
Compared with an S3, the S4 is somewhat shorter in duration, sounding snappier rather than dull and thudding. The bell of your stethoscope is necessary to hear an S4, lightly applied to the patient's skin. As with an S3, you will not hear an S4 with the diaphragm, and you may not hear it at all with a bad stethoscope.
To improve your chances of hearing an S4, roll the patient on his or her left side (the left lateral decubitus position) to swing the cardiac apex against the chest wall, bringing it closer to your stethoscope chest piece. An irreverent mnemonic: to remember the cadence of S4-S1 S2, think of a percussion sting played on the drums after a bad joke: "ba-DUM bump."
An S4 implies a forceful atrial contraction. Patients with LV hypertrophy become dependent upon this atrial kick to fill their stiff and incompliant ventricles, and can experience dyspnea or chest pain when they lose it with the onset of atrial fibrillation.