Pearls of Knowledge: Four Heart Tones

Advanced Heart Sounds: Recognizing the “Four” Which are Possible

Pearls of Knowledge          © BrainyNurses.com

In listening to the heart, a systematic approach is important. And remember, the more you listen, the better your skills will become.

😊 In acute conditions, listening to heart sounds is very important on presentation and then with subsequent assessments. If heart sounds change, it generally signifies a deterioration in condition.

During an assessment, listen to the following components.

• The strength of the heart sounds.
• The heart sounds heard (S1, S2, S3, S4).
• The heart sounds heard (S1, S2, S3, S4).
• If a friction rub is present. 

Listening to the four possible heart sounds

As the valves close, S1 and S2 are produced. 

• S1 indicates closure of the mitral and tricuspid valves, is heard the loudest in those areas of the heart and occurs during systole.
• S2 indicates closure of the aortic and pulmonic valves, is heard the loudest in those areas of the heart and occurs at the end of systole and beginning of diastole.
• If there is stenosis in the valve, a click may be heard as the valve snaps open.

At times, there are more than two sounds heard. So, as you were listening to “Lub, Dub, Lub, Dub”, you hear “other” sounds.

S3 (gallop)

• Caused by turbulence on ventricular filling
• Indicates heart failure and will be heard before crackles develop.
• Heard in systolic dysfunction which is a problem with contraction.
• An S3 may be normal in children and those under the age of 40 years. 

S4 (gallop)

• Produced when the atria contract.
• Heard in several conditions, including myocardial ischemia or infarction.
• Will also be heard in hypertension, ventricular hypertrophy, AV blocks, and severe aortic or pulmonic stenosis.
• Heard in diastolic dysfunction, which is a problem with filling.
• It will not be heard in atrial fibrillation due to the lack of coordinated atrial contraction.

S3 and S4

• Low pitched sounds heard best with the bell of stethoscope.
• Summation gallop is when both S3 and S4 are heard. 

Some medical professionals feel like they want to “listen” to audio recordings of heart sounds. While this may be beneficial, it is difficult to translate what you heard on a demo into clinical practice. 

Instead, try listening for “sounds” in words you can use to describe the heart sounds.

Variations of heart sounds and splits 

Left-sided events are loudest on expiration

• Mitral and aortic valve closure.
• S3 and S4 are heard at the mitral area with left ventricular failure and left ventricular myocardial infarction. 

Right-sided events are loudest on inhalation

• Tricuspid and pulmonic valve closure.
• S3 and S4 are heard at the tricuspid area with right ventricular failure and right ventricular infarction in conjunction with an inferior wall MI. 

Typically, left-sided events occur before right sided

• Mitral (M₁) before tricuspid (T₁).
• Aortic (A₂) before pulmonic (P₂).
• Splits occur when the right-side events occur before the left-side.
• Split S1 (tricuspid before mitral).
  • “La-Lub-Dub”.
  • Always abnormal.
  • Heard in right bundle branch block and PVCs. 

• Split S2 (pulmonic before aortic)
  • “Lub-Da-Dub”.
  • Normal on inspiration.
  • If on exhalation, then a pathology.
  • Heard in atrial septal defect, right or left bundle branch block, and pulmonary hypertension.