L3.1 Conduction of the heart system

Question 1

Arterial supply of the heart

Answer 1

From coronary A (1st branch of ascending aorta)

Question 2

R. coronary A

Answer 2

• Runs along R. AV groove → branch:
  
  • to SA node
  • R. marginal
  • ~ back of the heart → to midline POS → POS IV branch & AV node branch

Question 3

L. coronary A

Answer 3

• Behind pul trunk → L. AV groove → branch:
  
  • Towards mid-POS heart (anastomose)
  • Circumflex (continuation)
  • ANT IV branch (anastomose POSteriorly)

Question 4

What does the RCA supply

Answer 4

• RV (most) & diaphragmatic surface of LV
• SA node (55%) & AV node (90%)
• If R dominant circulation to heart → crosses over IV septum → gives POS IV branch

Question 5

What does the LCA supply

Answer 5

• LA, LV (most)
• SA, AV nodes
• IV septum & AV bundle

Question 6

Anastomoses of the coronary A

Answer 6

• ‘functional’ end arteries
  
  • Effective in slow occlusions
  • But not effective in sudden occlusions → still result in myocardial infarctions

Question 7

What are coronary heart diseases?

Answer 7

• Blockages → prevents O2 reaching heart muscles → pain & ineffective pumping of blood

Question 8

What is angiography

Answer 8

• Technique to visual the inside of BV/organs

Question 9

What is angioplasty

Answer 9

• Balloon tipped tube inserted in coronary A
• Inflate balloon & squash against wall to re-open vessel

Question 10

Coronary bypass surgery

Answer 10

• When blockage too severe
• Using BV from saphenous V
• From ascending A to distal of blockages

Question 11

Triple bypass

Answer 11

• Saphenous V + Using radial A as well

Question 12

Venous drainage of the heart

Answer 12

• Opens directly to R.A
• Great cardiac V: along ANT IV groove ~ L side of heart → CS
• Middle cardiac V: along POS IV groove → CS (near opening)
• Small cardiac V: drains right side
• L marginal V: drains L side

Question 13

Conduction system of the heart

Answer 13

• Intrinsic pacemaker cells → impulse
  
  • SA node (~70bpm) → AV node in interatrial septum
  • Specialised channels transit signals through ventricles → allows simultaneous contraction
    
    • AV bundle (bundle of His)
    • Purkinje fibres
    • Moderator band → shortcut to ANT pap muscles → allows coordination of contractions
      
      • Prevents tricuspid from everting
• AV node may generate own pace if SA node damaged

Question 14

What is a heart block

Answer 14

• Blocks branch supplying SA/AV node
• Specialised cells die → cardiac cycle out of sync

Question 15

What is the use of an artificial pacemaker

Answer 15

• Through subclavian V → SVC → into heart
• Able to adjust pulse generation