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Semester 1 Year 2 > Coronary Circulation and Conduction > Flashcards

Coronary Circulation and Conduction Flashcards

1
Q

Learning outcomes

A
  1. Describe the origin, course and distribution of the coronary arteries
  2. Explain the importance of the anastomoses between the coronary arteries
  3. Describe the venous drainage of the heart
  4. Describe the anatomical position of the conducting system of the heart and how it controls heart rate
  5. List the arteries that supply the conduction system of the heart
  6. Describe the autonomic innervation of the heart
  7. Discuss the effects of ischaemia of the myocardium and how it may affect the conducting system
  8. Explain where pain originating from the heart is referred to and why
  9. Identify major branches of coronary arteries on angiograms
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2
Q

Spit some facts about the heart

A 
It never sleeps (hopefully!). 
• How is it innervated?
It changes gear.
• Who/what controls this? How?
It cannot use the oxygenated blood in its chambers
• Why?
• Is it “all truth and nothing but
the truth”?
Has its own very reliable blood supply
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3
Q

Describe cardiac muscle

A

striated but involuntary
Fibres branch and join with each other with intercalated discs
work as a single functional organ or syncytium
synchronized contraction
does not tetanize

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4
Q

What are the 5 different effects that can be had on the heart?

A 
Chronotropy
Dromotropy (conduction)
Bathmotropy (excitability)
Inotropy (contractility)
Lusitropy (relaxation)
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5
Q

Describe the course of the blood supply to the heart

A

Supplied by coronary arteries and their branches
Right coronary artery (RCA)
Left coronary artery (LCA)
The endocardium receives oxygen and nutrients directly from the chambers of the heart

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6
Q

Describe the source of the coronary arteries

A

Are the only branches of the ascending aorta

Emerge in aortic sinuses

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7
Q

Describe the right coronary artery

A

Arises from the right aortic sinus

SA nodal branch
Supplies the SA node of the conduction system

Atrial branches supply the right atrium

Right (acute) marginal branch

Usually gives off the posterior
interventricular branch
(aka posterior descending artery)

Anastomoses with branches of Left coronary artery at the apex

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8
Q

Describe the left coronary artery

A

LEFT MAIN STEM
Arises from the left aortic sinus between left auricle and the pulmonary trunk
Shorter but thicker than right coronary artery
Enters the coronary sulcus
Divides into circumflex and anterior interventricular branches

Anterior interventricular branch (left anterior descending, LAD)
− Supplies the sternocostal surface
− Anastomoses with posterior interventricular branch of RCA at the apex
− “Artery of sudden death”

Circumflex branch
Left (obtuse) marginal branch
Anastomoses with the branches of RCA

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9
Q

Summarise coronary blood supply in regards to the RCA and its branches

A

Walls of RA and RV
Sino-atrial and Atrioventricular nodes
Posterior part of interventricular septum (proximal portion of atrioventricular bundle of His)
Small areas of the walls of LA and LV

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10
Q

Summarise coronary blood supply in regards to the LCA and its branches

A

Walls of LA, LV

Most of the interventricular septum including part of the atrioventricular (AV) bundle

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11
Q

What is coronary dominance?

A

The artery that gives off the posterior interventricular/posterior descending artery determines the coronary dominance
In ~80% of the people RCA is dominant

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12
Q

Where are the most likely places for a myocardial infarction to occur?

A
  • LAD 40-50%
  • RCA30-40%
  • Circumflex 15-20%
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13
Q

How may a MI damage the conduction system of the heart?

A 
• LAD (septal branches)
supplies AV bundles
• RCA supplies both SA and
AV nodes
• Heart block (bradycardia)
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14
Q

What are potential sources of vessels for CABG?

A

Internal thoracic artery
(Internal Mammary Artery (LIMA))
Great Saphenous Vein***

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15
Q

What is CABG?

A

Coronary Artery Bypass Grafting

- Bypass of the occluded portion of the vessel in a myocardial infarction

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16
Q

What is coronary angioplasty?

A

Surgical repair of a damaged or blocked vessel in the heart

  • Percutaneous Transluminal Coronary Angioplasty
  • With or without stent (drug-eluting v bare-metal stents)
  • Anticoagulation medication
17
Q

What are cardiac veins

A

Cardiac veins accompany the coronary arteries and their branches
Most of the venous blood drains into RA via coronary sinus

18
Q

What is the source of venous return from the coronary arteries?

A

Cardiac veins

Most of the venous blood drains into RA via coronary sinus

19
Q

Name the cardiac veins

A

Great cardiac (anterior interventricular) vein joins the coronary sinus

Small cardiac vein accompanies right marginal branch

Middle cardiac (posterior interventricular) vein drains into coronary sinus

Anterior cardiac veins drain independently into the RA

20
Q

Describe the coronary sinus

A

Lies between the LA and LV

Surrounded by muscle fibers
from LA

Drains 60% of the venous blood of the heart into the RA

40% is drained by smallest cardiac veins (the besian veins) and anterior cardiac veins

21
Q

Describe the cardiac conduction system

A

Cardiac muscle fibers form 2 networks separated by fibrous skeleton: Atrial and ventricular networks

There is a group of specialized, modified cardiac muscle cells that
− lie immediately beneath the endocardium
− can generate electrical impulses without external stimuli

Cardiac muscle cells distribute electrical impulses through the myocardium,
– causing the heart to contract in the proper sequence

Autonomic nervous system shortens or prolongs the duration of a cardiac cycle

22
Q

What are the components of the cardiac conduction system?

A 
− Sinu-atrial node (SA node)
− Atrioventricular node (AV node)
− Atrioventricular bundle (bundle of His)
• Left bundle branch
• Right bundle branch 
− Purkinje fibers.

None of these are macroscopic

23
Q

Describe the sino-atrial node

A

Keith-Flack node

Pace-maker

The basic depolarization rate of the SA node is 70 to 80 beats per minute

Located anterior to the opening of the SVC, upper end of crista terminalis

Usually supplied by branches of the right coronary artery

24
Q

Describe the atrioventricular node

A

Aschoff-Tawara node

Located at the postero- inferior part of IA septum, close to the opening of the coronary sinus

Usually supplied by AV nodal branch of the right coronary artery

25
Q

Describe the atrioventricular bundle

A

Bundle of His
− Continuation of the AV node
− Runs along the membranous part of the IV septum.
− Splits into right and left bundle branches

26
Q

Describe the right bundle branch of the atrioventricular bundle

A

− Descends on the right side of the
membranous part of the IV septum.
− Enters the septomarginal trabecula to reach the base of the anterior papillary muscle
− Splits into Purkinje fibres which spread out into the ventricular walls

27
Q

Describe the left bundle branch of the atrioventricular bundle

A

− Descends on the left side of the
membranous part of the IV septum.
− Splits into Purkinje fibres

28
Q

How may conduction pass from the atria to the ventricles through the skeleton?

A

The AV bundle of His is (and should be) the only conductive route through the fibrous skeleton

This system ensures synchronous contraction, in the correct sequence, toward the outflow of each chamber

29
Q

Describe nerve supply to the heart

A

Cardioacceleratory and Cardioinhibitory centers in the Medullary reticular formation

Superficial and deep cardiac plexus
− Lie inferior to the aortic arch, adjacent to the bifurcation of both the
pulmonary trunk and the trachea
− Supply conduction system, coronary blood vessels, and myocardium
1. Presynaptic sympathetic fibres travel in T1-5(6) spinal nerves
− Increase the heart beat and force of contraction
− Dilate coronary arteries
2. Parasympathetic fibres reach in vagus
− Decrease the heart beat (and force of contraction * Controversy)
− Constrict coronary arteries
3. General visceral afferents

30
Q

Discuss cardiac pain and how it may be referred

A

Pain caused by ischaemia and damage to cardiac muscle

Visceral sensory nerve endings are activated

GVA (General Visceral afferent) (sympathetic) fibers carrying the sense travel with sympathetics in T1-5 spinal nerves

Pain fibres from organ and skin travel to spinal cord together

Pain not felt in heart but referred to somatic areas (skin) supplied by T1-5 (anterior chest wall and possibly medial aspect of the left arm

Semester 1 Year 2 (69 decks)

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