What causes the first heart sound?

closure of mitral and tricuspid valves

What causes a quiet first heart sound?

long PR or mitral regurgitation

What causes a loud first heart sound?

mitral stenosis

What causes the second heart sound?

closure of aortic and pulmonary valves

What causes a quiet second heart sound?

aortic stenosis

What causes a third heart sound?

caused by diastolic filling of the ventricle

When is a third heart sound considered normal?

If < 30 years old

What conditions is a third heart sound heard in?

• left ventricular failure (e.g. dilated cardiomyopathy)
• constrictive pericarditis (called a pericardial knock)
• mitral regurgitation

What causes a fourth heart sound?

caused by atrial contraction against a stiff ventricle

What conditions might you hear a fourth heart sound?

• aortic stenosis
• HOCM
• hypertension

What is the normal order you hear the valve closures in second heart sound?

aortic valve (A2) closely followed by that of the pulmonary valve (P2)

What are the causes of a widely split second heart sound?

• deep inspiration
• RBBB
• pulmonary stenosis
• severe mitral regurgitation

What are the causes of a reversed (paradoxical) split second heart sound?

• LBBB
• severe aortic stenosis
• right ventricular pacing
• WPW type B (causes early P2)
• patent ductus arteriosus

When is the fourth heart sound heard?

just before S1 when the atria contract to force blood into the left ventricle.

When is the third heart sound heard?

just after S2 when the mitral valve opens, allowing passive filling of the left ventricle.