What is a Cardiac Gallop?
A cardiac gallop is an abnormal heart sound consisting of three or four sounds per cardiac cycle, created when either a third heart sound (S3) or fourth heart sound (S4)—or both—are audible in addition to the normal first (S1) and second (S2) heart sounds, producing a rhythm that resembles the cadence of a galloping horse.
Pathophysiology and Clinical Significance
S3 Gallop (Ventricular Gallop)
The S3 gallop occurs in early diastole immediately after S2, during the rapid ventricular filling phase, and is caused by abrupt deceleration of blood flow into a ventricle with decreased compliance or elevated filling pressures 1, 2.
The sound results from abnormally rapid deceleration of early diastolic left ventricular inflow, with deceleration rates typically exceeding 700 cm/sec² in patients with pathologic S3 2.
In adults, an S3 gallop is a critical marker of left ventricular dysfunction and heart failure, indicating elevated filling pressures and reduced ventricular compliance 3.
Patients with evidence of LV dysfunction on examination, including rales and S3 gallop, have a higher likelihood of severe underlying coronary artery disease and are at high risk of poor outcomes 3.
The S3 does not denote heart failure in all contexts—it can be physiologic in young healthy individuals, children, and pregnant women where increased cardiac output and blood volume create enhanced early diastolic filling 4, 2.
S4 Gallop (Atrial Gallop)
The S4 gallop occurs in late diastole just before S1, during atrial contraction, and indicates decreased ventricular compliance requiring forceful atrial contraction to achieve adequate ventricular filling 5.
The atrial sound (S4) is most frequently found in patients with coronary heart disease and is a constant finding in patients with hypertension 5.
Unlike the S3, the S4 does not denote heart failure but rather reflects ventricular stiffness from conditions such as left ventricular hypertrophy, ischemia, or hypertensive heart disease 5.
An S4 can be eliminated with firm pressure on the stethoscope, which helps distinguish it from a split first heart sound or ejection sound 5.
A pathologic S4 is defined by a magnitude of at least half that of the first heart sound or a vibrational frequency of 30 Hz or greater, though both criteria together provide the highest specificity 6.
Summation Gallop
When both S3 and S4 are present and occur in close proximity or simultaneously, they create a summation gallop—a single loud sound that may be louder than either S1 or S2 5.
This occurs commonly in patients with cardiac decompensation associated with coronary heart disease, hypertensive heart disease, and dilated cardiomyopathy 5.
When S3 and S4 occur in close proximity but not simultaneously, a short rumbling murmur may be heard, which can be confused with valvular or congenital lesions 5.
Auscultation Technique and Clinical Pearls
Optimal Detection Methods
Gallop sounds are often faint and best heard with the bell of the stethoscope placed lightly over the cardiac apex with the patient in the left lateral decubitus position 5.
In patients with emphysematous chest or increased anteroposterior diameter, a faint gallop might be overlooked if listening over the usual precordial areas but can be detected easily by listening over the xiphoid or epigastric area 5.
The "inching" technique—keeping S2 in mind as a reference while moving the stethoscope from the aortic area to the apex—provides the most accurate timing of heart sounds 5.
Distinguishing Gallops from Other Sounds
If an extra sound occurs after S2, it is an S3 (ventricular gallop); if it occurs before S1, it is an S4 (atrial gallop) 5.
Pressure applied with the stethoscope eliminates the S4 but does not eliminate ejection sounds or splitting of S1, providing a simple bedside differentiation 5.
Clinical Context and Prognostic Implications
High-Risk Scenarios
The presence of an S3 gallop in the setting of acute coronary syndrome, unstable angina, or non-ST-elevation myocardial infarction identifies patients at substantially higher risk for adverse outcomes and severe underlying coronary disease 3.
In Kawasaki disease, a gallop rhythm suggesting decreased ventricular compliance from myocardial inflammation and edema may be present during the acute illness 3.
Approximately 5% of patients with non-ST-elevation myocardial infarction present with cardiogenic shock, which carries mortality rates exceeding 60%, and physical examination findings including gallop sounds are critical for early recognition 3.
Physiologic vs. Pathologic Distinction
In pregnancy, an S3 is a benign physiologic finding reflecting normal circulatory adaptation from the approximately 50% increase in blood volume and cardiac output 4.
In young healthy athletes (triathletes), the physiologic S3 is associated with rapid early filling but normal ventricular function, and the sound diminishes or disappears with maneuvers that reduce venous return such as head-up tilt 2.
Common Pitfalls to Avoid
Do not dismiss a gallop sound as insignificant without considering the clinical context—in adults with cardiac risk factors or symptoms, it mandates further evaluation including echocardiography 3.
Avoid confusing a summation gallop with a murmur from valvular or congenital disease; careful timing with the cardiac cycle and response to stethoscope pressure helps differentiate 5.
Do not overlook gallop sounds in patients with altered chest anatomy or body habitus; alternative auscultation sites (xiphoid, epigastric) may be necessary 5.
Remember that the absence of a gallop does not exclude heart failure, but its presence in the appropriate clinical setting is highly specific for ventricular dysfunction 3.