S1

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

S2

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

S3

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.

S4

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.

Systolic Murmurs

May be “crescendo-decrescendo” ejection type, pansystolic, or late systolic; right-sided murmurs (e.g., tricuspid regurgitation) typically increase with inspiration.

Diastolic Murmurs

• Early diastolic murmurs: Begin immediately after S₂, are high-pitched, and are usually caused by aortic or pulmonary regurgitation.
• Mid-to-late diastolic murmurs: Low-pitched, heard best with bell of stethoscope; observed in MS or TS; less commonly due to atrial myxoma.
• Continuous murmurs: Present in systole and diastole (envelops S₂); found in patent ductus arteriosus and sometimes in coarctation of aorta; less common causes are systemic or coronary AV fistula, aortopulmonary septal defect, ruptured aneurysm of sinus of Valsalva.