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Gallop rhythm

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A gallop rhythm refers to a (usually abnormal) rhythm of the heart on auscultation. The normal heart rhythm contains two audible sounds, called S1 and S2, giving the well-know "lub-dub" rhythm. They are caused by the closing of valves in the heart. A gallop rhythm contains another sound, called S3 or S4, dependant upon where in the cycle this added sound comes; it can also contain both of these sounds.

Contents

S3

S3 (or third heart sound) is the name of the added sound which occurs shortly after the second heart sound, S2, giving a rhythm much like the cadence in the word 'Kentucky'. It can be a normal finding in people under 30 years of age, but over this age is usually a sign of heart failure. It is usually low-pitched, and is best heard with the bell of the stethoscope. An S3 rhythm is also known as ventricular gallop.

Causes

It is caused by blood rushing in from the atria and striking the wall of the ventricle as it is relaxing.

Associations

It is associated with heart failure, caused by conditions which have:

Rapid ventricular filling

  • Mitral regurgitation - this is when one of the heart valves the usually stops blood going from the left ventricle to the left atria fails, allowing blood into the atria during systole. This means they will be overfilled when they come to contract, leading to the rapid ventricular filling.
  • Ventricular septal defect - this is a hole in the wall between the two ventricles, which allows rapid filling from the other ventricle.

Poor Left Ventricular Function

  • Post-MI - the death of tissue in the ventricular wall due to loss of bloody supply causes areas which do not move as well, if at all (hypokinetic and akinetic), meaning they do not relax quickly enough so the ventricular filling is relatively too quick.
  • Dilated cardiomyopathy - the ventricular walls are abnormal for a variety of reasons, and become thin and floppy so again do not relax well.
In conditions affecting the pericardium or diseases that primarily affect the heart muscle (restrictive cardiomyopathies) a similar sound can be heard, but is usually more high-pitched and is called a 'pericardial knock'.

Treatment

The gallop rhythm itself does not need to be treated; the underlying cause requires correction; depending on the aetiology the gallop rhythm may resolve.

S4

S4 (or fourth heart sound) occurs just before S1 (thus right at the end of one whole cycle), giving a cadence like the word 'Tennessee'. It is never normal. If the problem lies with the left ventricle, the gallop rhythm will be heard best at the cardiac apex (the point of the two ventricles). It will become more apparent with exercise, with the patient lying on their left-hand side, or with the patient holding expiration. If the culprit is the right ventricle, the abnormal rhythm will be most evident on the lower left hand side of the sternum, and will get louder with exercise and quick, deep inspiration Tavel ME. The appearance of gallop rhythm after exercise stress testing. 'Clin Cardiol'. 1996 Nov;19(11):887-91. .

Causes

It is caused by the atria contracting forcefully in an effort to overcome an abnormally-stiff ventricle.

Associations

The S4 rhythm is associated with anything with increases the stiffness of the ventricle, including:

Treatment

Again, they rhythm itself does not require treatment; rather plans should be laid to stop the progression of whatever cause of ventricular dysfunction there is.

Summation Gallop

If a fast heart rate (tachycardia) is present along and S3 and S4 both occur, the rate may become high enough so that the distinction between the two sounds is lost, and they summate into a single sound.

References

External Links

[chfpatients.com] - suitable for non-medical people, but requires some knowledge of medical terms

[familypractice.com] - requires knowledge of medical terms

[Pubmed.com] - journal article on diastolic gallop sounds

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