Cardiac Circulation and Conduction system

Question 1

What are the coronary arteries?

Answer 1

• Supply myocardium and epicardium
• Arise from the ascending aorta. Arise from the base of the aorta; is hidden under auricles

-Main coronary forms the left coronary artery and the right coronary artery:

-Left coronary artery:
Anterior interventricular branch/LAD
Circumflex branch

-Right coronary artery:
Posterior interventricular branch
Right marginal branch

Sometimes, the posterior interventricular branch can arise from the left coronary artery

Clogging is most common in LAD, circumflex and origin of right coronary artery

Question 2

What are the coronary veins?

Answer 2

• Most drain into the coronary sinus.
• The great cardiac vein runs in the anterior interventricular sulcus with LAD.
• The coronary sinus drains directly into the right atrium

Small, middle, and great cardiac veins.

Question 3

What surgical graft is used for coronary artery bypass?

Answer 3

Internal thoracic artery or great saphenous vein

Question 4

What is referred pain?

Answer 4

The pericardium is innervated by the phrenic nerve (somatic afferent innervation: pain, temperature)

The Heart itself is insensitive to touch, cutting, cold, and heat. However, ischemia can stimulate pain endings in the myocardium

Visceral referred pain: transmitted visceral afferent fibers accompanying sympathetic fibers and felt in somatic structures having afferent fibers with cell bodies in the same spinal ganglion

Anginal pain felt in the substernal and left pectoral regions to the left shoulder

Dermatomes of medial cutaneous nerve of the arm, 2nd and 3rd intercostal nerves (T1-T3)

Same spinal cord segments are shared visceral afferents supplying coronary arteries

Question 5

What is the cardiac conduction system?

Answer 5

SAN and AVN (smaller collection of nodal tissue than SAN)

Question 6

What are the steps in the conduction?

Answer 6

Right Bundle:

• Muscle of the IVS
• the anterior papillary muscle (through the moderator band)
• wall of the right ventricle.

Left Bundle:

• Muscle of the IVS
• the anterior and posterior papillary muscles
• wall of the left ventricle.

Question 7

What is the moderator band/septomarginal trabeculae: ?

Answer 7

bridge of tissue that stretches from the interventricular septum to the wall of the right ventricle. It is important in transmitting impulses to the right ventricle

Question 8

What is artificial pacemaker?

Answer 8

• Initiate ventricular contractions at a predetermined rate
• Used to treat slow or irregular heart rate
• Electrode is passed through the (left) subclavian vein to the SVC to the right atrium and through the tricuspid valve into the right ventricle
• Electrodes placed in contact with the endocardium

Question 9

What is the cardiac plexus?

Answer 9

• Supplies the innervation to the heart
• There is superficial and deep cardiac plexus (T1-T4).
• Superficial = between arch of aorta and pulmonary trunk.
• Deep = between arch of aorta and carina

Consists of sympathetic and parasympathetic fibres

• Sympathetics: postsynaptic fibers from superior thoracic paravertebral ganglia of the sympathetic trunks.
• Parasympathetics: vagus nerves

Sympathetic stimulation speeds up conduction, and parasympathetic stimulation slows it down.

Question 10

Angiogram

Answer 10

For an angiogram, you inject radiopaque liquid into veins – this allows you to see the patterns of the vessels.

When there is occlusion, the branches are faint as blood can’t really flow through them