When listening to heart sounds you can best hear S1 at the?

There are 2 main heart sounds that can be heard during auscultation: S1 and S2, also affectionately known as ‘lub’ and ‘dub’ respectively.

Normal heart sounds. Source: University of Michigan Murmur library

S1 heart sound corresponds to the closing of the mitral and tricuspid valves during systole. During systole, ventricular pressure rises, leading to opening of the aortic and pulmonary valves as well as closure of the mitral and tricuspid valves.

S2 heart sound corresponds to the closing of the aortic and pulmonary valves at the beginning of diastole. S2 may be subdivided into aortic (A2) and pulmonary (P2) sounds as the aortic valve closes slightly before the pulmonary valve. The splitting between A2 and P2 can be exaggerated by inspiration, particularly in young individuals.

The pulse can be felt during systole between S1 and S2. This is particularly important for differentiating between systolic and diastolic murmurs (covered separately here), as well as identifying any pathological heart sounds.

Pathological Extra Heart Sounds – Clicks, Snaps, S3/S4

Ejection systolic click

Causes:

• Aortic stenosis
• Pulmonary stenosis

Ejection systolic click with ejection systolic murmur. Source: University of Michigan Murmur library

Mid-systolic click

Cause of mid-systolic click: Mitral valve prolapse

Midsystolic click. Source: University of Michigan Murmur library

Opening snap

Causes of opening snap:

• Mitral stenosis
• Tricuspid stenosis

Opening snap with mid-diastolic murmur. Source: University of Michigan Murmur library

S3 and S4 heart sounds

S3 and S4 are extra heart sounds arising after S2.

S3 occurs during ventricular filling. It can be a normal finding in people aged 40 or under. Pathological causes are mostly related to heart failure and include:

• Ischaemic heart disease
• Dilated cardiomyopathy
• Hypertrophic cardiomyopathy
• Mitral regurgitation

 S3 heart sound. Source: University of Michigan Murmur library

S4 arises when the atria contract against a stiff ventricle (such as in states of ventricular hypertrophy). Causes include:

• Hypertension
• Pulmonary hypertension
• Aortic stenosis
• Hypertrophic cardiomyopathy

S4 heart sound. Source: University of Michigan Murmur library

Tumour plop

A rare diastolic heart sound classically associated with the movement of the tumour in atrial myxomas. 

Changes in Volume

The loudness of heart sounds can be altered by changes in the force of valve closure.

Loud S1 heart sound

Causes:

• Mitral stenosis
• Atrial fibrillation

Loud A2 heart sound

Cause: Systemic hypertension

Loud P2­ heart sound

Causes:

• Pulmonary hypertension
• Atrial septal defect

Pathological Changes in S2 split

Wide-splitting S2 – splitting increases with inspiration:

Causes:

Fixed splitting S2 – splitting not affected by breathing:

Cause: Atrial septal defect

Reversed splitting S2 ­– splitting decreases with inspiration (so much so that it can lead to P2 arising before A2):

Causes: