referred to as "TEN-nes-see" (i.e. the bang of atrial systole)
S4 gallop is
caused by atrial contraction against a stiff or noncompliant left ventricle (due to sudden rise in end-diastolic pressure following atrial contraction)
almost always abnormal; heard in
Younger adults & children, Lt. ventricular hypertrophy (aortic stenosis, HOCM, hypertension), Acute MI
(in HOCM a double apical impulse may be felt as a result of a palpable S4)
may consider normal in healthy older adults