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MRCS Part B > Thorax > Flashcards

Thorax Flashcards

1
Q

What are the main muscles of the thorax?

A

External intercostals, internal intercostals, innermost intercostals, transversus thosacis

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2
Q

Describe the layout of the intercostal muscles.

A

External intercostals: run infero-laterally from the rib above to the rib below. It is continuous with the external oblique.
Acts to elevate the ribs and increase the thoracic volume.
Innervates by intercostal nerves T1-T11.

Internal intercostals: run infero-posteriorly, continuous with the internal oblique.
Acts to reduce the thoracic volume.

Innermost intercostals: they are separated from the internal intercostals by the neuro vascular bundles.

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3
Q

What are the attachments and the action of the transversus thoracis?

A

Attach from the posterior surface of the inferior sternum to the internal surface of costal cartilages 2-6.
Acts to weakly depress the ribs

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4
Q

What are the 3 attachments of the diaphragm?

A
  • Lumbar vertebra via the arcuate ligament.
  • costal cartilage 7-10 & ribs 11-12
  • xiphoid process of the sternum
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5
Q

Describe the origin of the right and left crura.

A

R crus arises from L1-L3. The fibres surround the oesophageal opening acting as a physiological sphincter.

The L crus arises from L1-2.

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6
Q

What are the openings in the diaphragm and what passes through them?

A

Cabal Hiatus (T8)
- IVC
- Phrenic nerve

Oesophageal Hiatus (T10)
- oesophagus
- vagus nerve
- L gastric branches to oesophagus

Aortic hiatus (T12):
- aorta
- thoracic duct
- azygous vein

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7
Q

What is the innervation to the diaphragm?

A

The phrenic nerve (C3-5)

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8
Q

What is the arterial supply to the diaphragm?

A
  • Inferior phrenic arteries (from aorta)
  • superior phrenic
  • pericardiacophrenic
  • musculophrenic
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9
Q

What are the signs of diaphragm paralysis and what are the causes?

A

It causes paradoxical movement where the affected side moves up on inspiration and down on expiration.

Causes:
- mechanical trauma to nerve or diaphragm itself
- compression to nerve (tumour)
- myopathy such as myasthenia
- neuropathy such as diabetes

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10
Q

How can the mediastinum be divided?

A

Into superior and inferior. The inferior is then further divided into anterior, middle and posterior.

The superior and inferior are divided by an imaginary like passing between the sternal angle and T4 vertebra.

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11
Q

What are the borders of the superior mediastinum?

A

Superior: thoracic inlet
Inferior: line from sternal angle to T4
Anterior: manubrium of sternum
Posterior: T1-T4
Lateral: pleura of lungs

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12
Q

What are the contents of the superior mediastinum?

A

Aortic arch (and branches)
SVC (and tributaries including brachiocephalic, azygous, L superior intercostal)
Phrenic nerve
Vagus nerve
Cardiac plexus
Sympathetic trunk
Trachea
Oesophagus
Thoracic duct
Thymus
Infrahyoid muscles

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13
Q

What are the borders and the contents of the anterior mediastinum?

A

Superior: line from sternal angle - T4
Anterior: body of sternum/ transversus thoracis
Posterior: pericardium
Lateral: parietal pleura

Contents: no major structures in adults, contains loose connective tissue. In children the thymus extends inferiorly.

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14
Q

What are the parts and the branches of the subclavian artery?

A

Divided into 3 parts: proximal, deep and distal to the scalenus anterior.

Branches:

Vertebral
Internal thoracic
Thyrocervical trunk

Costocervical trunk

Dorsal scapula

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15
Q

What are the boundaries and the contents of the middle mediastinum?

A

Boundaries:
Anterior and Posterior: pericardium
Lateral: pleura
Inferior: diaphragm
Superior: line from sternal angle to T4

Contents:
- heart
- tracheal bifurcation
- ascending aorta
- pulmonary trunk
- SVC
- cardiac plexus
- phrenic nerve
- lymph nodes

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16
Q

Describe the path of the phrenic nerve.

A

Travels down the neck on the anterior aspect of the scalenus anterior. Enters the thoracic inlet between the subclavian artery and vein. Runs along the surface of the pericardium anterior to the lung hilum.

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17
Q

What are the contents of the posterior mediastinum?

A
  • thoracic descending aorta and branches (posterior intercostals x9, bronchial arteries, oesophageal arteries, superior phrenic)
  • oesophagus
  • oesophageal plexus
  • thoracic duct
  • azygous system (azygous vein, hemi azygous, accessory azygous)
  • sympathetic trunk
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18
Q

Describe the azygous system.

A

Ascends to the right of the vertebral column (causing a groove in the R lung). It drains into the SVC.

It is initially formed by the combination of the ascending lumbar and R sub costal vein.
It receives tributaries from the hemi-azygous vein, accessory azygous veins from the left and the right 2nd-12th intercostal veins, bronchial veins and the pericardial veins.

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19
Q

What are the branches of the thoracic aorta?

A

Ascending:
- L and R coronary arteries

Arch (ends at the level of T4):
- brachiocephalic
- left carotid
- left subclavian

Thoracic Descending: T4-T12
- bronchial arteries
- mediastinal arteries
- oesophageal artieries
- pericardial arteries
- superior phrenic arteries
- intercostal arteries

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20
Q

What is the ductus venosus?

A

Embryological vessel that allows shunting of blood from the umbilical vein to the IVC, bypassing the liver.
Closes to become the ligamentum venosum.

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21
Q

What is the ductus arteriosus?

A

Vessel allowing shunting of blood from the pulmonary artery to the descending aorta (bypassing the lungs).
Closes to form the ligamentum arteriosum.

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22
Q

What are the functions of the umbilical artery and vein?

A

Umbilical artery: takes deoxygenated blood from the umbilical cord to the placenta

Umbilical vein: takes oxygenated blood from the placenta to the liver. This closes to become the ligamentum teres at birth

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23
Q

What are the tributaries of the SVC?

A

Forms from the union of the L and R brachiocephalic veins (at the level of the 1st costal cartilage)
Tributaries include;
Azygous vein
Mediastinal veins
Oesophageal veins
Pericardial veins

It drains into the R atrium at the level of the 3rd costal cartilage

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24
Q

How can you classify thoracic aortic aneurysms?

A
  1. Ascending
  2. Arch
  3. Descending
  4. Thoraco-abdominal
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25
Q

What is the Crawford classification?

A

I: subclavian- renal
II: subclavian - infrarenal
III: distal descending - infrarenal
IV: above diaphragm to bifurcation

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26
Q

What are the indications for management in a thoracic aortic aneurysm?

A
  • > 5.5 in ascending
  • > 6.5 in descending
  • if >1cm/year in growth
  • symptomatic
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27
Q

What is an aortic dissection?

A

Initial tear causing a false lumen which propagates.

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28
Q

What causes traumatic dissection?

A

May be caused by a deceleration injury. The thoracic aorta is anchored by the ligamentum arteriosum, brachiocephalic and vertebral arteries. In deceleration this part stays fixed whilst the rest moves forward and therefore dissection occurs.

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29
Q

What are the atraumatic causes of dissection?

A

HTN
Media degeneration
Aortitis
CT disorders

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30
Q

How can you classify aortic dissection?

A

DeBakey:
1. Ascending- Descending
2. Ascending only
3. Descending only

Stanford:
A: ascending
B: descending

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31
Q

How do you manage aortic dissection?

A

Permissive hypotension
Stanford A and DeBakey 1/2 need surgical repair
Stanford B and DeBakey 3 can be medically managed unless high risk of rupture or evidence of end organ ischaemia

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32
Q

What are the locations and function of the chemoreceptors?

A

Peripheral: carotid body and aortic body
Central: medulla oblongata

The peripheral receptors act in response to partial pressures of O2 and CO2.
The central only react to CO2.

An increased CO2 stimulates an increased resp rate.

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33
Q

Where are the baroreceptors located and what do they do?

A

Located at the carotid Sonys and the aortic arch.

A sudden rise in BP stimulates an impulse to be sent via the tractus solitaries to the vasoconstrictor tract of the midbrain. This leads to inhibition of the sympathetic system (reduced vasoconstriction) and increased vagal tone at the SA node

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34
Q

What are the layers of the pericardium?

A

Fibrous layer (continuous with central tendon of the diaphragm)
Parietal layer of serous
Serous fluid
Serous pericardium (also known as the epicardium)

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35
Q

What is the function of the pericardium?

A
  • fixed heart in the middle mediastinum
  • prevents overfilling
  • lubrication
  • protection from infection
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36
Q

What is cardiac tamponade?

A

Accumulation of fluid under non distensible fibrous pericardium causing compression of the heart and therefore reduced cardiac output

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37
Q

What layers would you go through in a parasternal approach of pericardiocentesis?

A
  1. Skin
  2. Fascia
  3. Pec Major
  4. Intercostals (x3)
  5. Transversus thoracis
  6. Fibrous pericardium
  7. Parietal layer of serous pericardium
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38
Q

What are the layers of the heart wall?

A

Innermost: endocardium
Loose connective tissue and squamous epithelium.

Myocardium: involuntary striated muscle

Epicardium: visceral layer of the serous pericardium

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39
Q

Describe the surface anatomy of the heart.

A

Draw a line from;
1. The lower border of the 3rd costal cartilage on the right edge of the sternum.
2. The lower border of the 6th costal cartilage on the right edge of the sternum
3. 5th intercostal space, mid clavicular line
4. 2nd intercostal space, L border of the sternum

40
Q

Describe the location and contents of the sulci of the heart.

A

Coronary sulcus: atriventricular groove.
Contains the RCA, circumflex branch of LCA, small cardiac vein and coronary sinus.

Anterior interventricular sulcus:
Contains the LAD and the great cardiac vein

Posterior interventricular sulcus:
Contains the posterior interventricular artery and the middle cardiac vein

41
Q

Describe the coronary artery anatomy.

A

The left coronary artery arises from the left posterior articular sinus. It branches into the left anterior descending, the left marginal and the left circumflex.

The right coronary artery (from the anterior aortic sinus) branches to form the right marginal and the posterior interventricular

42
Q

Describe the venous drainage of the heart.

A

All veins drain into the R atrium via the coronary sinus. This sits in the posterior coronary sulcus and enters the RA near to the tricuspid valve and it has its own valve to prevent reflux - the Thebesion valve.
It receives tributaries from:
- great cardiac vein (sits by LAD in the anterior interventricular groove)
- small cardiac vein (in the coronary sulcus)
- middle cardiac vein (posterior interventricular sulcus)
- posterior cardiac vein (on posterior aspect of L ventricle)

43
Q

What are the features of the RA?

A

Receives blood from the IVC, SVC and coronary sinus.
It’s inner surface has two cavities separated by the muscular ridge called the crista terminalis.
The sinus venosum is smooth walled and receives blood from the SVC and IVC
The atrium proper is anterior and has rough walls due to the pectinate muscles.
The interventricular septum has a depression for the fossa ovale.

44
Q

What are the features of the right ventricle?

A

Triangular in shape, forms the anterior heart border.

The inflow portion has trabeculae carnae which form ridges, bridges and pillows.
The papillary muscles are attached to the tricuspid valve by the chorda tendinae

The outflow portion (superior aspect) is smooth walled.

45
Q

What are the features of the interventricular septum?

A

The superior aspect is membranous
The inferior part is muscular

46
Q

What is the typical cardiac output?

A

5-6L / minute

47
Q

What is Laplace Law?

A

Wall tension = circumference x thickness

48
Q

What is Starling’s Law?

A

Larger end diastolic volume = higher stroke volume due to increased stretch in cardiac fibres.

49
Q

Describe the conducting system of the heart?

A
  1. Action potential is created by the SA node
  2. Spreads across the atria causing contraction.
  3. Reaches the AV node which delays the signal
  4. Conducted via the bundle of His down the interventricular septum
  5. Spreads via the Purkinje Fibres causing the ventricles to contract
50
Q

Where does the SA node sit?

A

In the right atrium where the SVC enters

51
Q

Where does the AV node sit?

A

At the atrioventricular septum near the opening of the coronary sinus

52
Q

What are the signs of an atrial septal defect?

A

Parasternal heave
Split S2
Mid systolic murmur

53
Q

What are the indications for repair of an atrial septal defect?

A
  • L > R shunt
  • AF
  • CCF
  • emboli causing CVA
54
Q

What are the signs of a ventricular septal defect?

A

Systolic murmur
Tachypnoea
Hepatomegaly/Cardiomegaly
Poor feeding

55
Q

When would you repair a VSD?

A

Always needs surgical management

56
Q

What is a patient ductus arteriosus and what are the features?

A

This is a connection between the pulmonary artery and aortic arch. Normally closes at birth due to the reduction in maternal prostaglandins.

Features include:
Tachycardia
Tachypnoea
Pulmonary oedema
Pansystolic murmur
Hepatomegaly
Failure to thrive

57
Q

How do you manage a patent ductus arteriosum?

A

Medical: indomethacin
Surgical: ligation

58
Q

What is tetralogy of Fallot?

A
  1. VSD
  2. Pulmonary stenosis
  3. Overriding aorta
  4. RV hypertrophy
59
Q

What is coarctation of the aorta?

A

Stenosis of the aorta at the site of the ligamentum arteriosum.
May present with syncope/claudication or BP mismatch

60
Q

How do atherosclerotic plaques form?

A

Endothelial injury.
LDL accumulates.
Platelet adhesion causes the release of plt derived growth factor attracting monocytes.
Monocytes engulf cholesterol causing oxidation of LDL and then forms foam cells.
This stimulates smooth muscle and fibroblast proliferation. The smooth muscles migrate into the intima and fibroblasts lay down collagen and elastin. Plaque forms

61
Q

How do you manage an MI?

A

Morphine, nitrates, aspirin, clopidogrel
PCI

62
Q

Which ECG leads would show changes in an RCA artery infarct?

A

Leads II, III, aVF
(Inferior location)

63
Q

If leads V1-V4 show ecg changes where would the infarct be?

A

Septal - LAD artery

64
Q

If ecg changes were present in leads I, aVL, V5, V6 which vessel is affected?

A

The circumflex (anterolateral)

65
Q

How do you manage VT?

A

If they are unstable then need immediate cardio version.

If stable then:
- amiodarone (via central line)
- lidocaine
- procanamide

NOT verapamil

66
Q

What are the risk factors for aortic stenosis?

A

Age
Rheumatic fever
High calcium
Bicuspid valve

67
Q

What are the eponymous signs for aortic regurgitation?

A

Quinkes: visible pulsation in capillary bed
Mullers: pulsation of the uvula
Traubes: pistol shot femoral auscultation
Corrigons pulse: collapsing pulse
DeMussets: pulsatile head bobbing

68
Q

What are the causes of aortic regurgitation?

A

Rheumatic fever
Marfans
Endocarditis
Vasculitis
Type A dissection

69
Q

What are the features of aortic regurgitation?

A

Dyspnoea
Orthopnoea
Pulmonary oedema
Angina
Wide pulse pressure
Early diastolic murmer
Syncope

70
Q

What are the common organisms causing endocarditis?

A

Staph A and Staph Epidermis are the most common.

Strep Viridans and enterococcus
Then the HÁČEK group: (commensals or the oral cavity).
Haemophilis, cariobacterium, eikenella, kingella

71
Q

What is the patho physiology of infective endocarditis?

A

Causes vegetation containing fibrin, inflammatory cells and microbes on the heart valves which may erode, embolise or produce and abscess

72
Q

What is the diagnostic criteria for infective endocarditis?

A

Dukes criteria.
Need to have 2 major, or 1 major and 3 minor, or 5 minor

Major:
- +ve blood culture
- involvement of the endocardium on echo
- new murmur

Minor:
- fever >38
- +ve blood cultures but atypical
- predisposing factors (IVDU)
- vascular/immune signs
- +ve echo but atypical

73
Q

What are the peripheral signs of infective endocarditis?

A

Splinter haemorrhages
Oslers nodes
Jane way lesions
Roth spits
Vasculitic rash

74
Q

What are the indications for surgery in infective endocarditis?

A
  • haemodynamic compromise
  • CCF
  • Valve obstruction
  • Abscess formation
  • Septic emboli
  • Fungal
  • Failure to respond to medical treatment
75
Q

Describe the path of the vagus nerve from its origin to the diaphragm.

A

The vagus nerve arises from the medulla and exits the cranium via the jugular foramen. It travels within the carotid sheath between the CCA and the IJV.
The L side loops around the ligamentum arteriosum.
The R side loops around the subclavian artery

76
Q

What does the vagus nerve supply in the abdomen?

A

Anterior= stomach, pylorus, liver, hand pancreas, D1/2 of duodenum

77
Q

How do inotropes work?

A

They act via:
- alpha 1 receptors in the peripheries causing vasoconstriction
- beta 1 receptors in the heart cause +ve chronotropic and +ve inotropic affect
- beta 2 receptors in the coronary vasc causing vasodilation

78
Q

What is cardiac output?

A

Stroke volume x Heart rate

79
Q

What can affect cardiac output?

A

Preload
After load
Heart rate
Contractility

80
Q

What is pulse pressure?

A

Systolic - diastolic

81
Q

What is MAP?

A

1/3x systolic + 2/3x diastolic

82
Q

Give some examples of positive inotropes and how they work.

A

Noradrenaline - acts on alpha receptors causing vasoconstriction

Adrenaline - acts on alpha 1, beta 1 and beta 2

Dobutamine - acts in beta 1 and beta 2 (strong inotrope, weak chronotrope)

Metaraminol - acts on alpha 1 to increase SVR
Need to be aware can cause low flow to kidneys

83
Q

What is a pulmonary artery catheter?

A

This is a multi-lumen catheter with an inflatable balloon at its proximal tip. It inserts into the pulmonary artery via the IJV.

84
Q

What are the functions of the lumens in a pulmonary artery catheter?

A

Balloon inflation
Delivery of IV or pacing wires
Measure pressure in proximal RA and pulmonary artery
Measure the CO via thermodilution

Therefore it can measure the CVP, PCWP, CO, ppO2
And indirectly measure: SVR, stroke volume and ventricular pressure

85
Q

What are the complications of inserting a pulmonary artery catheter?

A

Pneumothorax
Infection
Valve damage
Thrombus
Perforation
Arrhythmia
Incorrect placement leading to incorrect results

86
Q

What is a normal CVP?

A

2-6mmHg or 2-10cmH2O

87
Q

Why is CVP useful?

A

It is a measure of RA pressure and therefore indirectly LA pressure.
It is useful in managing shock as it measures the preload.

The response of the CVP to fluid is diagnostic.
If the CVP rises and stays high then giving more fluid will not change CO.
If it rises then falls it suggests the fluid is being redistributed and if it rises very transiently it suggests the patient is very underfilled.

88
Q

Describe the steps of a median sternotomy.

A
  1. Incision 2cm below sternal notch to xiphoid
  2. Divide the suprastenal ligament
  3. Divide and he xiphoid with scissors and saw the sternum
  4. Retract and apply bone wax
  5. Finger sweep the thymus away
  6. Identify the brachiocephalic vein
  7. Divide the pericardium and apply stay sutures
89
Q

What are the complications of a sternotomy?

A

Vessel injury (brachiocephalic artery and vein and right ventricle)
Sternal dehiscence
Osteomyelitis
Wire sinus

90
Q

What is cardioplegia?

A

This is a K+ rich solution which is given into the aortic root to flow into the coronaries.

91
Q

What are the complications of cardiopulmonary bypass?

A
  • coagulopathy due to hypothermia and heparin
  • CVA due to air/ calcium embolism
  • Cardiogenic shock leading to Low CO
92
Q

What are the complications of a CABG?

A
  • bleeding (due to dehiscence, coagulopathy, cannula site leak)
  • reduced CO (due to cardiogenic shock, incomplete revascularisation)
  • CVA
  • nerve damage
  • infection (sternal infection, endocarditis, leg infection)
  • renal failure
  • AF
93
Q

What are the causes of pneumothorax?

A

Primary:
- Spontaneous
- Marfans
- Bulla/blebs

Secondary:
- Trauma
- Pathological (asthma, COPD, infection, malignancy)
- Iatrogenic (Central line)
- post operative

94
Q

What is the management of pneumothorax?

A

PRIMARY:
If stable then consider simple aspiration, if fails then consider chest drain.

SECONDARY:
If breathless, >2cm, >50 then chest drain.

95
Q

How do you insert chest tube?

A

Informed consent
Gather equipment (blade, underwater seal chest tube, artery forceps)
Clean field
Insert into triangle of safety: 4-5th intercostal space, just anterior to the mid-axillary line.
Inject LA, cut overlying skin, finger thoracotomy, insert chest drain ensuring all holes are inside the chest cavity,
connect to water seal system
secure drain
re-examine and chest XR

MRCS Part B (14 decks)

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