When the Stethoscope working as a Echocardiography!!!How to diagnosis the myocardial Hypokinesia Vs.Akinesia by Sthetscope ??? The Third heart sound ( s3)

Written by : Dr.Nabil paktin,MD.FACC.

The third heart sound or S3 is a rare extra heart sound that occurs soon after the normal two “lub-dub” heart sounds (S1 and S2). One can use the phrase “SLOSH’-ing-in” to help with the cadence (SLOSH S1, -ing S2, -in S3), as well as the pathology of the S3 sound.

 

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S3 may be normal in people under 40 years of age and some trained athletes but should disappear before middle age. Re-emergence of this sound late in life is abnormaland may indicate serious problems like heart failure. Third  heart sound when present in a child or young adult implies the presence of a supple ventricle that can undergo rapid filling. Conversely, when heard in a middle-aged or older adult, an S3 is often a sign of disease, indicating increased ventricular filling due to congestive heart failure or severe mitral or tricuspid regurgitation.The sound of S3 is lower in pitch than the normal sounds.

It has also been termed a ventricular gallop or a protodiastolic gallop because of its place in early diastole. It is a type of gallop rhythm by virtue of having an extra sound; the other gallop rhythm is called S4. 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  The fourth heart sound (S4) occurs just before the first heart sound in  the cardiac cycle. It is produced in late diastole as a result of atrial contraction causing vibrations  of the LV muscle, mitral valve apparatus, and LV blood mass.

S3 is thought to be caused by the oscillation of blood back and forth between the walls of the ventricles initiated by the inflow of blood from the atria. The reason the third heart sound does not occur until the middle third of diastole is probably because during the early part of diastole, the ventricles are not filled sufficiently to create enough tension for reverberation. It may also be a result of tensing of the chordae tendineae during rapid filling and expansion of the ventricle. )  Among several proposed theories, the most likely explanation is that excessive rapid  filling of a stiff ventricle is suddenly halted, causing vibrations that are audible as the third heart  sound.

 

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

Rapid ventricular filling

Mitral regurgitation – this is when one of the mitral valve leaflets that usually stop blood flowing from the left ventricle to the left atria fails, allowing blood into the atria during systole. This means that the left atria will be overfilled, leading to rapid ventricular filling when the mitral valve opens.

Elevated left atrial and left ventricular filling pressures, usually a result of a stiffened and dilated left ventricle

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 blood supply causes wall areas which do not move as well as normal (hypokinesia), or not at all (akinesia), meaning they relax more slowly, so the ventricular filling is relatively too rapid. During this period of time diagnosis of 3^rd heart sound by sthetscope is working instead of echocardiography in bedside and emergency status .

Dilated cardiomyopathy – the ventricular walls are abnormal for a variety of reasons, and become thin and stiff so do not relax well.

S3 can also be due to tricuspid regurgitation, and could indicate hypertensive heart disease.

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’.

Any cause of ventricular dysfunction, including ischemic heart disease, dilated or hypertrophic cardiomyopathy, myocarditis, cor pulmonale, or acute valvular regurgitation, may qualify. Myocardial ischemia without ventricular dysfunction or volume overload is not a cause of an S3. The presence of an S3 is the most sensitive indicator of ventricular dysfunction.

Any cause of a significant increase in the volume load on the ventricle(s) can cause an S3. Examples include valvular regurgitation, high-output states (anemia, pregnancy, arteriovenous fistula, or thyrotoxicosis), left-to-right intracardiac shunts, complete A-V block, renal failure, and volume overload from excessive fluids or blood transfusion. In some patients, for reasons that are not clear or because of chest size, obesity, or lung disease, an S3 may never be heard despite severe hemodynamic impairment. Therefore, the absence of a third heart sound cannot be used to exclude ventricular dysfunction or volume overload. In addition, the intensity of the third heart sound is influenced by several factors and correlates only roughly with the clinical status of the patient.

The third heart sound must be differentiated from other diastolic sounds. Competing possibilities include: splitting of the second heart sound, an opening snap of the mitral or tricuspid valve, a diastolic click related to mitral valve prolapse, a tumor “plop” from a left atrial myxoma, a pericardial knock, a summation gallop, and an atrial gallop. The distinguishing features of each of these sounds are listed in With experience, the third heart sound should not be confused with other diastolic sounds because of its very low pitch and late timing relative to the aortic closure sound

The third heart sound tests the ausculatory skills of the examiner because it is often the most difficult heart sound to hear. This is caused by several factors:

1-      The sound is usually of very low intensity and is easily obscured by extraneous room sounds, lung or abdominal noise, or tightening of the chest wall muscles.

2-      The sound does not radiate widely and is audible only over a small area of the chest wall.

3- The usual frequency (pitch) of the sound is near the lowest level that the human ear can detect. The inexperienced ear is unaccustomed to listening for a sound of this low frequency.