(Fig. 112-2)

FIGURE 112-2
Heart sounds. A. Normal. S1, first heart sound; S2, second heart sound; A2, aortic component of the second heart sound; P2, pulmonic component of the second heart sound. B. Atrial septal defect with fixed splitting of S2. C. Physiologic but wide splitting of S2 with right bundle branch block. D. Reversed or paradoxical splitting of S2 with left bundle branch block. E. Narrow splitting of S2 with pulmonary hypertension. (From Fowler NO: Diagnosis of Heart Disease. New York, Springer-Verlag, 1991, p 31. Reproduced with permission from Springer.)


Loud: MS, short PR interval, hyperkinetic heart, thin chest wall. Soft: Long PR interval, heart failure, mitral regurgitation, thick chest wall, pulmonary emphysema.


Normally A2 precedes P2 and splitting increases with inspiration; abnormalities include:

  • Widened splitting: Right bundle branch block, PS, mitral regurgitation
  • Fixed splitting (no respiratory change in splitting): Atrial septal defect
  • Narrow splitting: Pulmonary hypertension
  • Paradoxical splitting (splitting narrows with inspiration): Left bundle branch block, heart failure, AS
  • Loud A2: Systemic hypertension
  • Soft A2: Aortic stenosis
  • Loud P2: Pulmonary arterial hypertension
  • Soft P2: Pulmonic stenosis


Low-pitched, heard best with bell of stethoscope at apex, following S2; normal in children; after age 30–35, indicates LV failure or volume overload.


Low-pitched, heard best with bell at apex, preceding S1; reflects atrial contraction into a noncompliant ventricle; found in AS, hypertension, hypertrophic cardiomyopathy, and coronary artery disease (CAD).

Opening Snap (OS)

High-pitched; follows S2 (by 0.06–0.12 s), heard at lower left sternal border and apex in MS; the more severe the MS, the shorter the S2–OS interval.

Ejection Clicks

High-pitched sounds following S1 typically loudest at left sternal border; observed in dilation of aortic root or pulmonary artery, congenital AS or PS; when due to the latter, click decreases with inspiration.

Midsystolic Clicks

At lower left sternal border and apex, often followed by late systolic murmur in mitral valve prolapse.

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