AuscultifyS3 vs S4 Heart Sounds: Gallops Explained
S3 and S4 are the "extra" heart sounds — the gallops. Both are low-pitched, both are best heard with the bell at the apex, and both trip up students because they sit close to the normal S1 and S2. The trick is timing: one comes right after S2, the other right before S1.
The mnemonics that fix the timing
| S3 | S4 | |
|---|---|---|
| When | Early diastole, just after S2 | Late diastole, just before S1 |
| Cadence | S1–S2–S3 = "Ken-TUCK-y" | S4–S1–S2 = "TEN-nes-see" |
| Mechanism | Rapid ventricular filling into a floppy, volume-loaded ventricle | Atrium contracting against a stiff, non-compliant ventricle |
| Typical cause | Heart failure, volume overload; normal in kids & young adults | Hypertension, LVH, aortic stenosis, ischemia; almost always pathologic in older adults |
How to hear them
Use the bell lightly over the apex with the patient in the left lateral decubitus position — this brings the apex to the chest wall and amplifies these low-frequency sounds. Press too hard and the bell becomes a diaphragm, filtering the gallop out entirely. If you hear both S3 and S4 with a fast heart rate, they can merge into a summation gallop.
Why students miss them
S3 and S4 are near the lower limit of hearing, so they're felt as much as heard — a subtle "extra bump" in the rhythm. You will not learn them from a description; you have to hear the Kentucky and Tennessee cadences enough times that your brain flags the deviation from a plain "lub-dub."
Drill the gallops in Auscultify
Auscultify's library has real S3 and S4 recordings captured at the apex, and the Heart Sounds quiz mode plays them without labels so you have to commit — then shows you which gallop it was and why. Alternate them back to back until "Ken-TUCK-y" and "TEN-nes-see" are instantly obvious. The Spectrogram view (Pro) even shows you where the extra sound falls in the cycle.
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