Heart Sounds and ECGs

Question 1

Describe the first normal heart sound.

Answer 1

• S1
• Occurs due to the closure of AV valves at the start of ventricular systole.
• Described as ‘‘lub”

Question 2

Describe the second normal heart sound.

Answer 2

• S2 caused by the closure of semilunar valves
• Marks the beginning of ventricular diastole
• Described as ‘‘dub’’

Question 3

Describe the third heart sound.

Answer 3

• S3 occurs during the early phase of ventricular filling when blood flows rapidly from the atria into the ventricles. This creates vibrations in the ventricular walls.
• Normally not audible in dogs but may be heard in certain conditions.
• Indicates the passive filling of ventricles during diastole.

Question 4

When might S3 be heard in dogs?

Answer 4

• Young athletic dogs
• Dilated cardiomyopathy

Question 5

What is the fourth heart sound?

Answer 5

• S4 produced during atrial contraction (late diastole)
• Rarely audible in dogs under normal conditions
• Reflects active filling of ventricles

Question 6

When might S4 be heard?

Answer 6

• Ventricular compliance is reduced e.g. hypertrophic cardiomyopathy

Question 7

Which heart sounds are typically audible in healthy canines?

Answer 7

S1 (lub) and S2 (dub)

Question 8

Describe abnormal heart sounds and their causes.

Answer 8

• s3 or s4
• Murmurs: abnormal whooshing or swishing sounds caused by turbulent blood flow.
• Gallop rhythm: occurs when S3 or S4 become prominent.

Question 9

Common causes of heart murmurs:

Answer 9

• Mitral valve disease
• Congenital defects
• Dilated cardiomyopathy
• Anemia
• Heart worm disease