The Coronary Circulation

Question 1

What is the blood supply of the heart?

Answer 1

Right and left coronary arteries (RCA) and (LCA), these are the only branches of the ascending aorta but the endocardium receives blood from the chambers of heart

Question 2

When do the coronary arteries fill up?

Answer 2

They fill up when the aortic sinuses fill up in diastole. In systole the aortic valve cusps close the opening of the arteries

Question 3

Name the branches of the right coronary artery

Answer 3

SA node branch, Atrial branches which supply the right atrium, the right (acute) marginal branch and usually the posterior interventricular branch.

Question 4

What two arteries form the anastamosis at the apex

Answer 4

The posterior interventricular branch (posterior descending artery) and the left coronary artery.

Question 5

What are the terminal branches of the left coronary artery?

Answer 5

Circumflex branches and anterior interventricular artery (left anterior descending artery LAD).

Question 6

What does the anterior interventricular branch supply?

Answer 6

The sternocostal surface

Question 7

What artery does the anterior interventricular branch form anastamosis with?

Answer 7

The right coronary artery at the apex.

Question 8

Name the branch of the circumflex artery and what artery it forms an anastamosis with.

Answer 8

Left (obtuse) marginal branch. Anastamosis with RCA

Question 9

What does the right coronary artery and its branches supply?

Answer 9

Walls of the right atrium and right ventricle, SA and AV nodes, posterior part of IV septum and small areas of walls of left ventricle and left atrium

Question 10

What does the left coronary artery and its branches supply?

Answer 10

The walls of the left atrium and left ventricle and most of the IV septum including the AV bundle.

Question 11

What is coronary dominance?

Answer 11

This is the artery that gives off the posterior interventricular (posterior descending) artery. In 80% of people the RCA is dominant.

Question 12

What is coronary co-domincance?

Answer 12

Where both RCA and LCA supply the posterior interventricular artery.

Question 13

What is the order of frequency of occlusion of arteries that cause MIs

Answer 13

Left anterior descending artery(40-50%), right coronary artery (30-40%), and finally the circumflex artery (15-20%)

Question 14

What part of the conducting system is damaged by the left anterior descending artery and the RCA?

Answer 14

LAD - AV bundles and RCA - SA and AV nodes

Question 15

What can you do if the artery becomes narrowed or blocked?

Answer 15

Coronary Artery Bypass Grafting (CABG) or Percutaneous Transluminal Coronary Angioplasty

Question 16

What is a CABG?

Answer 16

This is where you can use another artery (often the internal thoracic artery) to bypass the portion of occluded vessel

Question 17

What is Percutaneous transluminal coronary angioplasty?

Answer 17

A catherter is passed through the femoral artery till it reaches the blocked artery, it is then opened by a ballon. A stent may be left and teh stent may be drug eluting.

Question 18

Name the four coronary veins and where they drain too

Answer 18

Great cardiac, Small cardiac (accompanic right margin branch) and Middle cardiac vein all drain into coronary sinus. The anterior cardiac veins drain independently to RA.

Question 19

Where is the position of the coronary sinus?

Answer 19

It lies between the left atrium and the left ventricle and is surrounded by the muscle fibres of the left atrium.

Question 20

Name the 2 networks the cardiac muscle forms and what separates them

Answer 20

The atrial and ventricular networks which are separated by the fibrous skeleton.

Question 21

What is the role of the ANS

Answer 21

Shortens or prolings the duration of a cardiac cycle, it however, does not start the heart as it acts independently.

Question 22

What are the compounents of the cardiac conduction system?

Answer 22

Sino-atrial node, Atrioventricular node, Atrioventricular bundle (Bundle of His) which splits into a left bundle branch and a right bundle branch) and finally purkinjie fibres.

Question 23

Where is the location of the SA node

Answer 23

Anterior to the opening of the SVC at the upper end of crista terminalis.

Question 24

Where is the rough location of the AV node

Answer 24

At the posto-inferior part of the IA septum close to opening of coronary sinus.

Question 25

Where is the rough location of the AV bundle?

Answer 25

It runs along the membranous part of the IV septum.

Question 26

Where is the rough location of the AV bundle branches?

Answer 26

Along the IV septum with the right bundle branch in the septomarginal trabecula. Both bundles split into purkinjie fibres

Question 27

Describe the nerve supply of the heart

Answer 27

-Supplied by cardioaccelartory and cardioinhibitory centres found in the medulla and the cardiac plexus.

Question 28

What is the effect of the presynaptic sympathetic fibres? and what spinal nerves do they travel in?

Answer 28

They travel in T1-5 spinal nerves and they increase the heart beat, force of contraction and dilate the coronary arteries.

Question 29

What is the parasympathetic effect and what nerves do they travel in?

Answer 29

Travel in vagus nerve (10th cranial nerve) and it decreases the heart beat and constricts coronary arteries

Question 30

Where is the referred pain caused by ischaemia and damage to cardiac muscle felt?

Answer 30

Areas of the skin supplied by T1-5 (anterior chest and medial aspect of left arm)