The Stanford 25

An Initiative to Revive the Culture of Bedside Medicine

Cardiac Second Sounds 

Introduction: The cardiac second sound is a source of some confusion.

GOALS:

  • You should be able to diagnose pulmonary hypertension.
  • Suspect left or right bundle branch block.
  • Be able to comment on each component (for example, A2 is absent or soft in aortic stenosis, or P2 loud in pulmonary hypertension).

It is worth understanding and fully mastering.

The second sound S2 is  made of  two component sounds:

  1. Aortic valve closure (A2) which happens first.
  2. And Pulmonic valve closure (P2) which happens next.
  3. REMEMBER, A2 is heard widely all over the chest. So when you hear ‘S2’ at the mitral area, you are really hearing A2.
  4. Identification of variations in these sounds provides important diagnostic information.
  5. REMEMBER P2 is confined to pulmonary area. That means if you HEAR SPLITTING OR P2 DISCRETE from A2 OUTSIDE THE PULMONARY AREA, THINK PULMONARY HYPERTENSION!

Technique:

[Stanford 25 video forthcoming, see videos below for 2nd sounds and auscultation technique.]

  • Splitting best heard in the 2nd left interspace. Use diaphragm.
  • Best heard on your patients when they are recumbent and in quiet inspiration.
  • Note width of split, timing in respiratory cycle (e.g. late inspiration in normal splitting).

Findings:

Pathological sounds:

  • “Wide splitting” normal A2, delayed and equally loud P2, disappears on inspiration.
    • Ddx: most commonly RBBB, rarely other things such as aortic regurg, and pulmonic stenosis.
  • “Fixed splitting” normal A2, delayed and equally loud P2, does NOT vary with respiration.
    • Ddx: ASD and rarely right ventricular failure.
  • “Paradoxical Splitting” P2 before and as loud as A2. May appear on expiration, disappears on inspiration.
    • Think LBBB.
  • PRACTICE HEARING NORMAL SPLITTING ON  YOUR PATIENTS SO THAT YOU CAN THEN PICK UP ABNORMAL SPLITTING.

Embedded Videos & Links (Not produced by Stanford, click through for credit and source).

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Written by stanford25admin

June 7, 2010 at 3:43 pm

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