1. Applied anatomy of the heart

Question 1

Briefly describe an overview of the innervation of the heart and where these nerves lie

Answer 1

Innervated by the autonomic system
Supplied by cardiac plexus of nerves - lies anterior to the bifurcation of the trachea (carina) and posterior to the arch of the aorta
Contains parasympathetic from vagus, sympathetic from sympathetic trunk and visceral general afferents
These fibres extend from the plexus to the coronary vasculature and to the conducting system of the heart i.e. the SAN

Question 2

Describe the parasympathetic innervation of the heart and give the pathway of innervation

Answer 2

Acts to slow the heart rate and reduce the force of contraction
Cardioinhibitory centre in the medulla
Release of Ach
Extends to primary neurone from cell bodies in the reticular formation of the medulla
These synapse with the vagus nerve
Post ganglionic neurones then extend to the SAN and the AVN

Question 3

Describe the sympathetic innervation of the heart and give pathway of innervation

Answer 3

Acts to increase the heart rate and to increase the force of contraction
Via the cardioacceleratory centre in the medullary reticular formation
Descend down through white matter tracts in the lateral horn of the grey matter (the autonomic region)
Preganglionic sympathetic neurones then emerge from the thoracic spinal cord - from T1 to T4
Extend to SAN and AVN `

Question 4

SO briefly compare the pathway of sympathetic and parasympathetic innervation of the heart

Answer 4

Parasympathetic synapses with and reaches the heart via the vagus nerve
Sympathetic is via the spinal cord - lateral horns of T1 to T4 and involves pre and post ganglionic neurones

Question 5

Describe the medulla as the site of control for cardiac innervation

Answer 5

Medulla is the primary site in the brain to regulate sympathetic and parasympathetic outflow to the heart and blood vessels
Medullary centre is modified by the hypothalamus and higher centres

Question 6

Describe the nuclei of the vagus nerve and where the parasympathetic outflow arises

Answer 6

Has three nuclei - dorsal motor nucleus, nucleus ambiguus, solitary nucleus
Parasympathetic outflow comes mainly from neurones in nucleus ambiguus and some from dorsal motor nucleus

Question 7

Briefly describe cardiac pain (angina) and how it is felt

Answer 7

This is pain caused by ischaemia
Stimulate sensory nerve endings in the myocardium - nociceptors on the ends of visceral afferent nerve fibres can recognise a build up of lactate
These travel through teh sympathetic trunk and enter the spinal cord through T1 to T4
This means that the angina is not felt in the heart and is referred (T1 to T4)

Question 8

Where can cardiac pain be referred?

Answer 8

Generally referred to the skin supplied by T1 to T4 i.e. the medial upper arm and the neck/jaw
Also to the epigastrium T5 to T9

Question 9

What are the branches of the right coronary artery?

Answer 9

Right marginal

Posterior descending

Question 10

What are the branches of the left coronary artery?

Answer 10

Left anterior descending (LAD)
Left marginal
Left circumflex

Question 11

What region of the heart does the right coronary artery supply?

Answer 11

Right ventricle

Right atrium - SAN and AVN

Question 12

What region of the heart does the left coronary artery supply?

Answer 12

Left ventricle
Left atrium
Interventricular septum

Question 13

What is the interventricular septum and what is it’s structure?

Answer 13

The curved slanting wall that separates the right and left ventricles of the heart - composed of a muscular lower part and a thinner more membranous part

Question 14

What is the blood supply to the interventricular septum?

Answer 14

Supplied by both the right and left coronary arteries - left anterior descending and the posterior descending

Question 15

What is the most common variation of the coronary arteries?

Answer 15

The origin of the posterior descending artery - whether it originates from the right or left coronary artery (circumflex)
70-85% right dominance
8-15% left dominance

Question 16

Give the location of chest leads for an ECG

Answer 16

V1 - right sternal edge, 4th intercostal space
V2 - left sternal edge, 4th intercostal space
V3 - halfway between V1 and V2, at the level of the left 5th rib
V4 - left 5th intercostal space midclavicular line
V5 - left intercostal space, mid-axillary line
V6 - left 5th intercostal space, mid axillary line

Question 17

Which regions of the heart do the following leads correspond to?

1. II, III, aVF
2. I, aVL
3. V1, V2,
4. V3, V4
5. V5, V6

Answer 17

1. Inferior
2. Lateral
3. Septal
4. Anterior
5. Lateral

Question 18

Which heart valves are open during diastole/systole?

Answer 18

Aortic and pulmonary and open during systole

Mitral and tricuspid are open during diastole

Question 19

What is valvular disease and how can it be caused?

Answer 19

Any disease involving the loss of function of any of the heart valves

Inflammation of the valve e.g. due to infection (most common)
Ageing, ischaemic heart disease
Fibrosis and calcification (most common)
Stenosis
Regurgitation
Rheumatic disease

Question 20

What are the four types of valvular disease?

Answer 20

Mitral regurgitation
Aortic stenosis
Mitral valve stenosis
Aortic regurgitation

Question 21

Describe mitral regurgitation

Answer 21

Most common type
Mitral valve does not close properly during systole
SO rather than all blood going up to the aorta from the ventricle, some goes back into the atrium
Leads to an overload of blood volume in the left atrium
Overall increased end diastolic volume and reduced cardiac output
This can lead to atrial enlargement and also to left ventricle dilation due to an increased preload

Question 22

Describe aortic stenosis

Answer 22

Also occurs during systole
One of the loudest – heard at the right second intercostal space
The aortic valve is stenotic and so the left ventricle must generate an increased pressure to overcome the increased afterload created
Leads to left ventricular concentric hypertrophy due to the overload i.e. the wall of the left ventricle increases the size of the chamber decreases
Hypertrophied myocardium has a reduced compliance and a decreased coronary blood flow reserve – can lead to systolic and diastolic failure

Question 23

Describe aortic regurgitation

Answer 23

During diastole
The aortic valve fails to close properly
So increased build up fluid in the left ventricle and the left ventricle dilates – the volume overload leads to an increased preload
The left ventricle becomes very dilated

Question 24

Describe mitral valve stenosis

Answer 24

Diastolic murmur
Left atrium must generate a higher pressure to overcome the increased afterload
Leads to atrial enlargement and increased atrial pressure – can also cause pulmonary oedema and can lead to AF
The ventricular filling is reduced and this leads to a reduced cardiac output
Enlarged left atrium can lead to strokes and emboli entering the circulation

Question 25

How is pulmonary oedema caused?

Answer 25

Left sided heart failure increases hydrostatic pressure the venous end and so all the blood is not drawn away from the arterial end to the venous end due to a lack of a pressure gradient - this results in pulmonary oedema

Question 26

When might pulmonary vs. systemic oedema occur and how do these present?

Answer 26

Systemic oedema will occur in right sided heart failure and presents as swelling at the ankles
Pulmonary oedema will occur in left sided heart failure and presents as e.g. respiratory crackles and orthopnoea

Question 27

How will congestive heart failure present in terms of oedema?

Answer 27

Patient will present with symptoms of both right and left sided failure i.e. pulmonary and systemic oedema

Question 28

Define ‘chronotropic drug’ and give the different types

Answer 28

Chronotropic drugs alter the heart rate and rhythm by affecting the electrical conduction system of the heart e.g. altering the rhythm produced by the SAN

Positive chronotropes - increase the heart rate

Negative chronotropes - decrease the heart rate

Question 29

Define ‘inotropic drugs’ and give the different types

Answer 29

These are drugs that alter the force of the contraction of the heart muscle

Positive inotropes - increased myocardial contractility

Negative inotropes - decrease myocardial contractility

Question 30

Which region of the brain do parasympathetic neurones to the heart extend?

What do these neurones synapse to?

Answer 30

Medulla - the cardioinhibitory centre

Synapse onto the vagus nerve

Question 31

From which region of the brain do the sympathetic neurones to the heart extend?

Answer 31

Medulla - cardioacceleratory centre in the reticular formation

Question 32

Which part of the spinal cord to sympathetic neurones to the heart travel in?

Answer 32

Travels in the lateral horn of the grey matter - autonomic part

Question 33

Which part of the grey matter in the spinal cord is the autonomic region?

Answer 33

Lateral horn

Question 34

Which vertebral levels do the sympathetic neurones to the heart extend from?

Answer 34

Thoracic region - T1 to T4

Question 35

What structure acts to modify the medulla in the brain?

Answer 35

The hypothalamus

Also other higher centres

Question 36

Parasympathetic outflow to the heart comes from which of the vagus nuclei?

Answer 36

Nucleus ambiguus mainly

Small amount from the dorsal motor nucleus

Question 37

What is the blood supply to the AVN?

Answer 37

From the posterior descending artery - variance of whether this is left or right coronary artery

Question 38

Where is the left anterior descending artery located?

Answer 38

Right apex

Question 39

What is the significance of an atheroma in the LAD?

Answer 39

An atheroma here will be of more dire consequences than anywhere else