Figure 200n

A. The S4 occurs in presystole and is frequently called an atrial or presystolic gallop.
B. The S3 occurs during the rapid phase of ventricular filling. It is a nornal finding and is commonly heard in children and young adults, disappearing with increasing age. When it is heard in the patient with cardiac disease, it is called a pathologic S3 or ventricular gallop and usually indicates ventricular dysfunction or AV valvular incompetence.
C. In constrictive pericarditis, a sound in early diastole, the pericardial knock (K) is heard earlier and is louder and higher pitched than the usual pathologic S3.
D. A quadruple rhythm results if both S4 and S3 are present.
E. At faster heart rates, the S3 and S4 occur in rapid succession and may give the illusion of a middiastolic rumble.
F. When the heart rate is sufficiently fast, the two rapid phases of ventricular filling reinforce each other, and a loud summation gallop (SG) may appear; this sound may be louder than either the S3 or S4 alone.

(FromJ4 Shaver, et it Examination of the Heart, Part IV,Auscultation, Dallas,American Heart Association, 1990,p27.