Cardiothoracic Surgery Flashcards
1
Q
Primary vessels affected by atherosclerosis
A
- Proximal LAD
- Circumflex
- Right coronary
2
Q
Outline the pathological process of atherosclerosis
A
- Endothelial injury due to risk factors
- LDL accumulation leads to intimal thickening and atheroma formation
- Platelet adhesion causes microthrombi and release of platelet-derived growth factor
- Monocytes/macrophages engulf cholesterol to become foam cells
- Further LDL is taken up by macrophages causing release of IL-1 and TNF which stimulates smooth muscle and fibroblast proliferation
- Fibroblasts lay down collagen/elastin to mature the plaque
- Chronic inflammatory process leads to calcification
3
Q
What is the role of platelet-derived growth factor in atherosclerosis
A
- Released from endothelial cells
- Attracts monocytes to area which engulf cholesterol to become foam cells
4
Q
How are foam cells formed
A
From monocytes and macrophages engulfing cholesterol
5
Q
What happens to the smooth muscle cells in atherosclerosis
A
Migrate from the media to the intima and transform into secretory cells producing collagen, elastin, chemokines
6
Q
Symptoms associated with varying degrees of stenosis
A
- 50% = asymptomatic
- 75% = exertional angina
- 90% = angina at rest
7
Q
Invasive management of stable angina
A
- PCI if symptoms difficult to control with medical therapy
2. CABG if anatomy unsuitable for PCI
8
Q
Invasive management of unstable angina
A
- PCI if anticoagulation and nitrates unsuccessful
2. CABG if PCI unsafe
9
Q
Invasive management of myocardial infarction
A
- PCI 1st line
2. CABG rarely used
10
Q
Advantages of PCI
A
- Minimally invasive
- Low morbidity
- Low immediate complication rate
11
Q
Disadvantages of PCI
A
- Unsuitable for left main stem lesions
- Early re-occlusion and stent thrombosis
- High rate of symptom recurrence
- Poorer ‘freedom’ from medication
- Requires cardiac surgical back up
12
Q
Advantages of CABG
A
- Reliable revascularisation
- Suitable for a wide range of coronary lesions
- Ability to perform simultaneous procedures e.g. valve replacement
13
Q
Disadvantages of CABG
A
- Major procedure
- Morbidity from sternotomy and conduit harvesting sites
- Late graft failure (especially if saphenous vein used)
14
Q
What investigation must be performed prior to cardiac surgery
A
Coronary angiography (for those undergoing CABG and those with risk factors undergoing valve replacement who would benefit from revascularisation at the same time)
15
Q
Characteristics of Fibrolipid plaques (structure and location within the vessel wall)
A
- Lipid-rich core
- Overlying fibrous cap on the luminal surface
- Tends to spare arteries of the upper limb
- Between intima and lamina
16
Q
Outline the 3 microscopic components of atherosclerotic plaques (cells, connective tissues, lipids)
A
- Cells = mainly vascular smooth muscle cells, macrophages, lymphocytes
- Connective tissue fibres = collagen, elastin, proteoglycans
- Lipids = mainly cholesterol and oxidised cholesterol in the form of LDLs
17
Q
List the risk factors for developing atherosclerosis
A
- Increasing age
- Male sex
- Race
- Smoking
- DM
- Obesity
- HTN
- Hyperlipidaemia
- Family history
18
Q
How many units of blood should be cross-matched prior to cardiac surgery
A
4 units
19
Q
Which medications should be stopped 7 days prior to cardiac surgery
A
- Platelet antagonists (clopi 5 days prior)
- ACE-i due to risk of severe perioperative vasodilatation
20
Q
What is the role of TOE in cardiac surgery
A
- Evaluates cardiac wall and valve function
- Checks for air bubbles after closure
21
Q
Patient position for median sternotomy
A
Supine
22
Q
Skin prep prior to cardiac surgery
A
- Prep chest and both groins in case an intra-aortic balloon pump of femoral bypass is required
- Both arms and legs if harvesting planed
23
Q
Median sternotomy provides good access to
A
- Epicardial coronary arteries
- Ascending aorta
- Aortic valve
- Mitral valve
24
Q
What ligament lies at the top of the midline sternotomy incision
A
Interclavicular ligaments
25
Describe the median sternotomy incision
2cm below the sternal notch to the xiphoid, deepen through the fat with diathermy
26
What drains may be used at closure of the thorax
Under-water drains:
- Pericardium
- Left and right pleurae
27
Immediate complications of midline sternotomy
Vessel (e.g. brachiocephalic) or chamber (e.g. right ventricle) injury
28
Late complications of midline sternotomy
- Sternal dehiscence
- Sternal osteomyelitis
- Wire sinuses
29
How is cardioplegia achieved in CPB
Delivers cold blood with high potassium content to arrest the heart
30
Indications for CABG
- Left main stem stenosis or equivalent (proximal LAD, circumflex)
- Triple vessel disease
- Diffuse disease unsuitable fo PCI
31
What are the physiological conditions created by CPB
- Non-pulsatile flow with mean perfusion pressure of 60mmHg
| - Systemic cooling at 30-32 degrees
32
Why is de-airing performed and where is it usually done
- To prevent air entering the circulation and causing CVA
| - Aortic root or LV apex
33
List the complications of CPB
- Coagulopathy from platelet dysfunction
- Inflammatory activation and vasodilation
- CVA
- Bleeding
- Cardiogenic shock
- Cognitive performance impairment
34
What are the indications for an intra-aortic balloon pump
- Pre-op for poor cardiac output or critical coronary stenosis
- Post-op when more haemodynamic compromise is seen or anticipated
35
How is an intra-aortic balloon pump inserted
Via the femoral artery in the groin and placed in the descending aorta
36
Function of intra-aortic balloon pump
- Reduces afterload and therefore myocardial work
| - Inflates during diastole to augment maximal diastolic pressure to improve coronary perfusion
37
What is involved in a standard triple bypass CABG
1. Left internal mammary to the LAD
2. Portion of long saphenous to the circumflex
3. Portion of long saphenous to the distal right coronary
38
Surface anatomy of the long saphenous vein
1. Ankle - vein immediately anterior to medial malleolus
2. Knee - one hand breadth posterior to medial patellar border
3. Groin - 1cm medial to midinguinal point
39
What nerve must you be wary of when harvesting the LIMA
Phrenic nerve as it crosses IMA at 1st rib
40
Why are radial artery grafts becoming more popular as opposed to saphenous grafts
Due to the risk of late occlusion with saphenous grafts
41
What test must be performed prior to radial artery harvesting
Allen's test to ensure adequate ulnar blood flow
42
What group of people are excluded from radial grafting
Those with high functional requirements of the hands
43
List the immediate complications of CABG
- Bleeding
- Low cardiac output syndrome
- MI
- Neurological complications
44
List the early complications of CABG
- Pneumonia
- Sternal infections
- Leg infections
- Renal failure
- Atrial dysrhythmias
- UGIB and perforation
45
Late complications of CABG
Recurrent stenosis
46
How is low cardiac output syndrome managed
- Maintenance of sinus rhythm (medically or paced)
- Optimise preload/afterload (e.g. use Swan-Ganz)
- Maintain HCT >30%
- Inotropes
- Vasodilators to reduce afterload
- Intra-aortic balloon pump
47
What nerves must you be wary of when harvesting the radial artery
- Superficial radial nerve
| - Lateral antebrachial cutaneous nerve
48
What nerve must you be wary of when harvesting the long saphenous vein
Saphenous nerve (will cause sensory loss over front and medial leg)
49
Signs and symptoms of sternal infection
- Sternal click on moving
- Pain
- Sternal instability
- Discharge/wound breakdown
- Movement of wires on CXR
50
Long term complications of cardiac angioplasty
Restenosis
51
Long term complications of cardiac stenting
Stent thrombosis
52
Criteria for severe aortic stenosis
- Aortic area <1cm^2
- Jet velocity >4ms
- Transvalvular pressure >40mmHg
53
Risk factors for calcific aortic stenosis
- Age
- Bicuspid valve
- Rheumatic fever
- Hypercalcaemia
- Congenital bicuspid valve
54
What type of bacteria causes rheumatic fever
Group A beta-heamolytic streptococcus
55
What occurs to the aortic valve in rheumatic fever
Fibrosis of the valve with fusion of the commisures
56
How is the risk of endocarditis reduced pre-operatively
- Dental examination
- Chest examination
- Urinalysis
- Temperature check
57
Mechanical Vs Bioprosthesis - who receives which
- Young active people without major comorbidity should receive a mechanical valve
- Elderly patients should receive bioprosthesis
58
What are the two approaches to TAVI
1. Retrograde transfemoral or subclavian approach
| 2. Antegrade transapical approach (via left anterolateral mini-thoracotomy)
59
How does aortic regurgitation typically present
Pulmonary venous HTN
60
Causes of aortic regurgitation
- Rheumatic disease
- Annuloaortic ectasia (associated with Marfans)
- Endocarditis
- Large-vessel vasculitis
- Acute 'Type A' dissection
61
Indications for treatment in aortic regurgitation
- Chronic = symptomatic patients or those developing LV dilatation
- Acute = type A aortic dissection is an emergency
62
Which leaflet tends to be affected in mitral regurgitation
Larger crescent-shaped posterior leaflet
63
Causes of mitral regurgitation
- Stretched baggy leaflet
- Chordal rupture
- Papillary muscle dysfunction
- Papillary muscle rupture secondary to MI
- Ventricular dilatation
64
Symptoms of mitral regurgitation
- Atrial dilatation causes AF
| - Pulmonary oedema from rising pressure in pulmonary circulation
65
How is mitral regurgitation treated
Repair is superior to replacement but this is seldom possible
66
Why is mitral valve repair preferable to replacement
- Patient may avoid warfarin
- Less prosthetic material to become infected
- Superior haemodynamics
67
How is the mitral valve accessed on A) first attempt, and B) re-do
- First attempt = median sternotomy
| - Re-do = right thoracotomy due to adhesions
68
What coronary artery is at risk during mitral valve surgery
Circumflex
69
Most common cause of mitral stenosis
Rheumatic fever
70
Consequences of severe mitral stenosis
- Left atrial hypertrophy
- Pulmonary oedema
- Eventually right ventricular hypertrophy and secondary tricuspid regurgitation
71
Preferred management of severe mitral stenosis
Percutaneous valvotomy
72
List the causes of ejection systolic murmur
- Aortic stenosis
- Pulmonary stenosis
- HOCM
- ASD
- Fallot's
73
List the causes of pan-systolic murmur
- Mitral regurgitation
- Tricuspid regurgitation
- VSD
74
List the cause of late systolic murmur
- Mitral valve prolapse
| - Coarctation of aorta
75
List the causes of early diastolic murmur
- Aortic regurgitation
| - Pulmonary regurgitation (Graham-Steel Murmur)
76
List the causes of mid-diastolic murmur
- Mitral stenosis
| - Austin-Flint murmur (severe aortic regurgitation)
77
Features of dilated cardiomyopathy
Loss of ventricular function and increased ventricular volume
78
Typical cause of restrictive cardiomyopathy
Amyloid deposition within the myocardium
79
HOCM inheritance pattern
Autosomal dominant
80
Definition of sudden cardiac death
Unexpected death from a cardiac cause within an hour of onset of acute symptoms
81
Treatment of HOCM
- Beta blockers and calcium antagonists
| - Septal myomectomy to relieve subaortic obstruction
82
CXR features of restrictive pericarditis
Calcified cardiac shadow
83
Symptoms of restrictive pericarditis
- Fluid retention due to RHF
| - Exerttional dyspnoea
84
Surgical management of restrictive pericarditis
Pericardectomy by either median sternotomy or left anterior thoracotomy (must be wary of phrenic nerve)
85
What part of the atrial septa do ASDs develop from
Primum and secondum portions
86
Clinical signs of ASD
- Parasternal heave
- Fixed splitting of the second heart sound
- Mid-systolic (ejection systolic) flow murmur
87
Symptoms of ASD that indicate need for intervention
- Left-to-right shunt causing pulmonary HTN and exertional dyspnoea
- AF or HF
- Paradoxical embolus causing CVA
88
Treatment of ASD
- Percutaneous closure (cardiology)
| - Pericardial patch repair
89
What determines the degree of left-to-right shunt in VSD
Size of the defect
90
Clinical features of VSD in infants
- Tachypnoea
- Hepatomegaly
- Poor feeding/growth
- Cardiomegaly
- Biventricular hypertrophy on ECG
91
Clinical features of VSD in older patients
- Systolic murmur
| - Non-specific symptoms
92
What is Eisenmenger syndrome
Reversal of the left-to-right shunt in VSD secondary to pulmonary HTN
93
Surgical management of VSD
Pericardial patch repair
94
Describe a PDA
Abnormal presence of a lumen in the ductus arteriosus
95
What is the function of the ductus arteriosus in the fetus
Connects pulmonary artery to the arch of aorta which allows fetal blood to bypass the pulmonary circulation
96
What initiates the closure of the ductus arteriosus and how long does it take
- Loss of maternal prostaglandins after birth
| - 4 weeks
97
Management of PDA
- NSAIDs may induce closure
- Percutaenous blockade of the PDA by IR
- Surgical ligation of the PDA
98
List the anatomical abnormalities that make up Tetralogy of Fallot
1. VSD
2. Pulmonary stenosis
3. Over-riding aorta
4. RV Hypertrophy
99
Describe a Blalock-Taussig shunt
Communication is made between the systemic and pulmonary circulations in order to bypass the pulmonary stenosis
100
Definitive surgical management of Tetralogy of Fallot
1. Closure of the surgical shunts
2. Relief of pulmonary stenosis
3. Patch repair of VSD
101
Describe an atrial myxoma
- Benign cardiac tumour
- Pedunculated
- Most commonly arise from the intra-atrial septum in the left atrium
102
Diagnosis and management of atrial myxoma
- Diagnosed on echo
| - Excision is performed via median sternotomy using CPB
103
Describe the histology of small cell lung cancer
- Poorly differentiated small cells (oat cells)
- High mitotic rate
- Propensity to secrete neohormonal substances
104
Most common lung cancer
Adenocarcinoma
105
Which type of lung cancer is most likely to present in never smokers
Adenocarcinoma
106
Criteria for T1 lung disease
<=3cm surrounded by lung/visceral pleura, not involving main bronchus
107
Criteria for T2 lung disease
>3 - <=5cm or involvement of main bronchus without carina or invasion of visceral pleura or atelectasis
108
Criteria for T3 lung disease
>5 - <=7cm or tumour of any size that involves the chest wall, pericardium, phrenic nerve, or satellite nodules in the same lobe
109
Criteria for T4 lung disease
>7cm in dimension, or any tumour with invasion of mediastinum, diaphragm, heart, great vessels, RLN, carina, trachea, oesophagus, spine or separate tumour in different lobe of ipsilateral lung
110
What percentage of non-small cell lung cancer patients undergo surgery
20%
111
List the contraindications to lung cancer surgery
- Malignant pleural effusion
- Stage 3b or 4 disease
- FEV1 <1.5L
- Tumour near hilum
- Vocal cord paralysis
- SVCO
112
How do you calculate post-op FEV1
(Lung segments left after excision / total number of functioning lung segments preoperatively) x Preoperative FEV1 = Estimated postop FEV1
113
Purpose of mediastinoscopy
Allows examination and biopsy of the paratracheal, tracheobronchial, and subcarinal nodes
114
Outline the mediastinoscopy procedure
1. 1cm incision above sternal notch and deepen through platysma and strap muscles
2. Lift thyroid superiorly and divide pretracheal fascia
3. Ensure visual of right brachiocephalic artery
4. Find plane between trachea and pretracheal fascia
5. Insert scope along fascia
115
List the risks associated with mediastinoscopy
- Brachiocephalic artery injury
- Tracheal injury
- Oesophageal perforation
- Minor bleeding from perforation of bronchial artery
- Major bleeding from biopsy of azygous vein
- Torrential bleeding from biopsy of aortic arch/pulmonary trunk
- Injury to left RLN
116
Indications for mediastinoscopy
Lymph nodes >1cm on CT
117
How may aortopulmonary nodes be sampled
VATS procedure
118
Incision of choice for emergency, resuscitation room procedures for the management of cardiac or thoracic injuries
Anterolateral thoracotomy
119
Outline the anterolateral thoracotomy incision
Incise from lateral edge of sternum along 5th interspace
| be wary of IMA!
120
Incision of choice for elective thoracic procedures
Posterolateral thoracotomy
121
What type of ventilation is required for thoracic procedures
Single lung ventilation using dual lumen ET tube
122
Indications for pneumonectomy
Centrally located tumours or those that impinge the central bronchial tree
123
What is the fate of the space created by pneumonectomy
Fills with fluid over 3 months
124
What is a bronchopleural fistula
Breakdown of the bronchial stump allows respiratory organisms to enter the space - indicated when the air-fluid level exists beyond its expected time
125
Drain used for pneumonectomy
Single basal drain
126
Drain used for lobectomy
Basal and apical drain
127
List the causes of cyanotic congenital heart disease
- Tetralogy of Fallot
- Transposition of the great arteries
- Tricuspid atresia
- Pulmonary valve stenosis
128
Outline the management of mesothelioma
- Mostly palliative
- A select few undergo pleuropneumonectomy
- Palliative pleurodesis to alleviate SOB and accumulation of fluid
129
What causes SOB in mesothelioma
Pleural effusion
130
List the indications for lung transplantation
- COPD in young patients with A1AD
- CF
- Fibrosing lung disease
- Congenital heart disease
131
Donor criteria for lung transplantation
- Age <=55
- ABO-compatible
- Clear CXR
- PaO2>39.9
- <20 pack year smoking hx
- Absence of chest trauma
- No aspiration/sepsis
- No cardiopulmonary surgery
- Negative sputum gram stain
- No purulent secretions on bronchoscopy
132
Who is thoracic aortic aneurysm more likely to occur in
Those with connective tissue diseases such as Marfan's
133
Outline the Crawford classification of thoracic aortic aneurysm
1. Descending aorta from left subclavian to renal
2. Descending aorta from left subclavian to beyond renal
3. Distal half of descending thoracic aorta and substantial part of abdominal aorta
4. Diaphragm to aortic bifurcation
134
Investigations for thoracic aortic aneurysm
- MR angiogram
- CT
- TOE
- Contrast aortography
135
Complications of thoracic aortic aneurysm
- Acute proximal dissection
- Rupture
- Peripheral embolism
- Aortic regurgitation
136
Most likely site of thoracic aortic rupture
1cm distal to left subclavian just prior to ligamentum arteriosum
137
CXR changes associated with thoracic aortic rupture
- Widened mediastinum
- Trachea/oesophagus to right
- Depression of left main stem bronchus
- Widened paratracheal stripe
- Space between aorta and pulmonary artery obliterated
- Rib fracture/left haemothorax
138
Describe aortic dissection
Blood escapes from the aortic lumen via the intimal layer and tracks outside the inner layers of the aortic media to create a false lumen
139
Causes of aortic dissection
- HTN
- Medial degeneration
- Aortitis (from syphilis or large-vessel vasculitis)
- Connective tissue disease
140
Outline the Stanford classification of aortic dissection
- Type A = dissection affecting ascending aorta
| - Type B = dissection affecting descending aorta
141
Symptoms of aortic dissection
- Shock
- Pain
- Symptoms of end-organ ischaemia (cold legs, paraplegia, oliguria)
142
GOLD standard investigation for aortic dissection
Aortography
143
Blood pressure target in aortic dissection
Permissive hypotension with SBP 90-100 using infusible beta blockers
144
Management of Stanford A dissection
Aortic root repair with synthetic tube graft (may include aortic valve repair also with composite graft)
145
Management of Stanford B dissection
- Medical with BP control
| - Surgery reserved for those at risk of rupture or to correct end-organ ischaemia using descending synthetic graft
146
Major complication of Stanford B dissection
Spinal cord ischaemia due to occlusion of the vertebral arteries
147
How does blood enter the heart in those with left sided SVC
Via coronary sinus
148
Most likely lung segment to be affected in the event of aspiration
Superior segment of right inferior lobe
149
Heart rate in those receiving cardiac transplant
Sinus tachy as vagus nerve transected
150
Incision used for repair of Type A dissection
Median sternotomy
151
Preferred method of extraction of inhaled foreign body
Rigid bronchoscopy
