Cardiac Physiology

Question 1

How is the heart rate generated when the SA node is damaged?

Why does physiological splitting occur?

Answer 1

AV node will set the pace of the heart (rate 40-60bpm in adults)

Inspiration creates negative pressure in the chest, which increases blood flow to the right heart, so the right ventricle is fuller and therefore empties slower, causing the pulmonary valve to close later than the aortic valve

Question 2

What causes splitting of the FIRST heart sound?

What causes wide fixed splitting of S2?

In which conditions does this occur?

Answer 2

Ebstein’s anomaly, right bundle branch block

Right sided volume or pressure overload, conduction delay, shortened LV ejection

ASD, PAPVD, PS, RBBB, MR

Question 3

Which conditions might you hear a narrowly split S2?

What causes a single S2?

In which conditions does this occur?

Answer 3

Aortic stenosis, pulmonary hypertension

If there is only one AV valve present or if the P2 is not audible

Aortic or pulmonary atresia, TGA, Tetralogy, severe pulmonary stenosis

Question 4

What causes a third heart sound?

What causes an abnormally loud S3?

Why does a fourth heart sound occur?

Answer 4

S3 is related to rapid filling of the ventricle

Dilated ventricles and decreased ventricular compliance eg VSD or CHF

Decreased ventricular compliance due to CHF

Question 5

Where can you best hear an ejection click?

What causes an ejection click?

Answer 5

URSE/ULSE

PS/AS, dilated great arteries eg in pulmonary hypertension or TOF

Question 6

What are the differential diagnoses for an ejection systolic murmur at the ULSE?

Answer 6

Pulmonary flow murmur Pulmonary stenosis
ASD
Coarctation
TAPVD
Pulmonary artery stenosis

Question 7

What are the differential diagnoses for a systolic murmur at the LLSE?

Answer 7

Still’s murmur
VSD
AVSD
Tricuspid regurgitation
TOF
HOCM

Question 8

What are the cause of a mid-diastolic murmur?

Answer 8

Relative stenosis of the mitral valve eg Large VSD&raquo_space; increased PBF
Relative stenosis of the tricuspid valve eg ASD&raquo_space; right atrial overload
Mitral regurgitation - apex (rumble/hum)
Tricuspid Regurgitation - LLSE

Question 9

What are the causes of an early diastolic murmur?

Answer 9

Aortic regurgitation - high pitched ULSE&raquo_space; apex

Pulmonary regurgitation - medium pitched ULSE&raquo_space; LLSE