HOME

TheInfoList



OR:

The fourth heart sound or S4 is an extra
heart sound Heart sounds are the noises generated by the beating heart and the resultant flow of blood through it. Specifically, the sounds reflect the turbulence created when the heart valves snap shut. In cardiac auscultation, an examiner may use a stet ...
that occurs during late diastole, immediately before the normal two "lub-dub" heart sounds (S1 and S2). It occurs just after atrial contraction and immediately before the systolic S1 and is caused by the atria contracting forcefully in an effort to overcome an abnormally stiff or hypertrophic ventricle. This produces a rhythm classically compared to the cadence of the word " Tennessee." One can also use the phrase "A-stiff-wall" to help with the cadence (a S4, stiff S1, wall S2), as well as the pathology of the S4 sound.


Physiology

The normal heart sounds, S1 and S2, are produced during the closing of the
atrioventricular valves A heart valve is a one-way valve that allows blood to flow in one direction through the chambers of the heart. Four valves are usually present in a mammalian heart and together they determine the pathway of blood flow through the heart. A heart v ...
and
semilunar valves A heart valve is a one-way valve that allows blood to flow in one direction through the chambers of the heart. Four valves are usually present in a mammalian heart and together they determine the pathway of blood flow through the heart. A heart v ...
, respectively. The closing of these valves produces a brief period of turbulent flow, which produces sound. The S4 sound occurs, by definition, immediately before S1, while the atria of the heart are vigorously contracting. It is manifest as a vibration of 20 to 30 Hz within the ventricle. While the mechanism is not absolutely certain, it is generally accepted that S4 is caused by stiffening of the walls of the ventricles (usually the left), which produces abnormally turbulent flow as the atria contract to force blood into the ventricle. S4 is sometimes audible in the elderly due to a more rigid ventricle. When loud, it is a sign of a pathologic state, usually a failing left ventricle. If the problem lies with the left ventricle, the gallop rhythm will be heard best at the cardiac apex. It will become more apparent with exercise, with the patient lying on the left-hand side, or with the patient holding expiration. If the problem is in the right ventricle, the abnormal sound will be most evident on the lower left hand side of the sternum and will get louder with exercise and quick, deep
inspiration Inspiration, inspire, or inspired often refers to: * Artistic inspiration, sudden creativity in artistic production * Biblical inspiration, the doctrine in Judeo-Christian theology concerned with the divine origin of the Bible * Creative inspirat ...
. S4 has also been termed an atrial gallop or a presystolic gallop because of its occurrence late in the heart cycle. It is a type of
gallop rhythm A gallop rhythm refers to a (usually abnormal) rhythm of the heart on auscultation. It includes three or four sounds, thus resembling the sounds of a gallop. The normal heart rhythm contains two audible heart sounds called S1 and S2 that give th ...
by virtue of having an extra sound; the other gallop rhythm is called S3. The two are quite different, but they may sometimes occur together forming a quadruple gallop. If the heart rate is also very fast ( tachycardia), it can become difficult to distinguish between S3 and S4 thus producing a single sound called a summation gallop.


Treatment

The S4 heart sound itself does not require treatment; rather plans should be laid to stop the progression of whatever causes the underlying ventricular dysfunction. The S4 heart sound is a secondary manifestation of a primary disease process and treatment should be focused on treating the underlying, primary disease.


References


External links

* {{DEFAULTSORT:Fourth Heart Sound Cardiology