gallop rhythm
A gallop rhythm is a three- or four-beat cadence of the heart sounds that resembles the rhythm of a galloping horse. The two normal heart sounds, lub-dub, become lub-dub-dub or da-lub-dub when an extra, low-pitched sound is added in diastole, the filling phase. Said aloud the cluster of beats has the rolling, three-syllable feel of hoofbeats, which is how the sign got its name.
The added sound is a third heart sound (S3) or a fourth heart sound (S4). An S3 occurs in early diastole as blood rushes into a ventricle and is abruptly checked, and in adults it often signals a volume-overloaded, poorly functioning ventricle, as in heart failure. An S4 occurs in late diastole when the atrium contracts against a stiff ventricle and suggests reduced compliance, as in a thickened or hypertrophied heart.
A gallop is heard best with the bell of the stethoscope, with the patient turned onto the left side, because these low-frequency sounds are easy to miss. In the right clinical setting an S3 gallop is a meaningful sign of heart failure, though an S3 can be a normal finding in children and young, healthy adults.
Listening over the apex with the patient on her left side, a doctor hears a soft, low extra sound after the second heart sound — an S3 gallop in a woman with decompensated heart failure.
A low-pitched extra sound after S2, best heard with the bell at the apex, is the S3 of a gallop.
An S3 gallop in an older adult with breathlessness strongly supports heart failure, but the very same sound can be entirely normal in a healthy young person — context is everything.