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Surgery of Abdomen and Thorax Cavitities > Persistent Right Aortic Arch (PRAA) and Patent Ductus Arteriosus (PDA) > Flashcards

Persistent Right Aortic Arch (PRAA) and Patent Ductus Arteriosus (PDA) Flashcards

1
Q

What is a PRAA?

A

Persistent right aortic arch with left ligamentum arteriosum (PRAA) is a vascular anomaly of the thoracic great vessels, resulting in the oesophagus being encircled and constricted.

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2
Q

What is the most common (95%) vascular ring anomaly in dogs?

A

PRAA

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3
Q

Where does a PRAA extend between?

A

Left pulmonary artery and right aortic arch

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4
Q

What is encircled in a PRAA?

A

Oesophagus

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5
Q

What % of patients with a PRAA has a patent ligamentum arteriosum?

A

10%

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6
Q

When are PRAA clinical signs first identified?

A

At weaning as signs consistent with esophageal constriction

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7
Q

What is the treatment of choice for a PRAA? What is the approach made?

A

Ligation and surgical division of the compressive left ligamentum arteriosum via a left fourth intercostal thoracotomy or via a thoracoscopic approach.

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8
Q

How many primordial embryonic arches are there?

A

6

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9
Q

In an adult which primordial embryonic arches remain in original form?

A

3, 4, 6

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10
Q

What is the embryological cause of a PRAA?

A

The RIGHT 4th arch remains as the aorta (not the left)

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11
Q

What would prevent correction of a PRAA via a left lateral thoracotomy?

A

Concurrent presence of a L Cr vena cava

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12
Q

Clinical signs of a PRAA (5)

A
  • Postprandial regurgitation
  • Poor growth
  • Malnourishment despite a good appetite
  • Signs of aspiration pneumonia (e.g. coughing, pyrexia, dyspnoea)
  • German Shepherd dogs and Irish Setters are overrepresented.
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13
Q

What diagnostic tests aid PRAA diagnosis?

A
  • Serum haem and biocehm
  • Plain thorax x rays
  • Barium contrast study
  • Angiogrpahy (MRI/CT)
  • Oesophagoscopy
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14
Q

What is seen on haem/biochem with a PRAA?

A

Usually within normal limits, unless aspiration pneumonia or another comorbidity present.

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15
Q

What is seen on plain thorax x rays with a PRAA? (3)

A

Cranial oesophageal dilation
Identification of right descending aorta (which may also cause left tracheal deviation)
Aspiration pneumonia.

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16
Q

What is seen on barium contrast studies with a PRAA? (2)

A

Cranial oesophageal dilation
Oesophageal constriction at the level of the heart base.

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17
Q

What is seen on angiography (CT/MRI) with a PRAA?

A

Useful in identifying vascular ring anomaly.

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18
Q

What is seen on oesophagostomy with a PRAA? (2)

A

Aortic pulse on the right side of oesophagus
Extraluminal compression of oesophagus at level of heart base.

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19
Q

How successful is medical management of a PRAA?

A

Unrewarding because of progressive oesophageal dilation and regurgitation.

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20
Q

Prior to surgery of PRAA, what should be done? (2)

A
  • Malnourished animals should be fed liquid food from a height (or via a gastrotomy tube)
  • Aspiration pneumonia should be treated.
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21
Q

What needs to be monitored in surgery and in post op period? (think - age of patients)

A

Glucose

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22
Q

What is the surgical treatment including approach of a PRAA?

A

The treatment of choice is ligation and surgical division of the compressive left ligamentum arteriosum via a left fourth intercostal thoracotomy or via a thoracoscopic approach.

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23
Q

What else need to be divided in PRAA surgery which form under the ligamentum arteriosim?

A

Perioesophageal fibrous bands

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24
Q

What needs to be performed following PRAA surgery, but before routine closure of thoracotomy site?

A

Intraoperative oesophagoscopy and oesophageal balloon dilation should be performed to confirm that all the extraluminal oesophageal compression has been removed

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25
Q

Following PRAA surgery, what is critical in the post-op care?

A

Fed liquid diets from a height

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26
Q

What does post op prognosis of PRAA depend on (4)

A
  • Presence of aspiration pneumonia
  • Presence of oesophageal dysmotility, - Degree of oesophageal dilation
  • Concurrent systemic debilitation.
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27
Q

What are complications of PRAA surgery? High light most common

A
  • Persistent regurgitation **
  • Haemorrhage
  • Oesophageal perforation
  • Fibrotic bands remaining and constricting the oesophagus
  • Pain
  • Perforation/penetration of the vascular structures or lungs.
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28
Q

What is the effect of age at time of PRAA surgery on outcome?

A

No effect

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29
Q

What % of PRAA patients have a poor outcome? (still having daily regurg)

A

13%

30
Q

With a PDA what happens if the pressure in the L heart is higher than the R?

A

Blood will flow from systemic to pulmonary circulations (‘left to right’)

31
Q

What has developed with a PDA if the blood flow will reverse and travel from the pulmonary to the systemic circulations (‘right to left’)?

A

Pulmonary hypertension

32
Q

How can a PDA be closed? (3)

A

-O pen approach and surgical ligation, or preferably
- Percutaneous placement of embolisation coils
- Amplatzer ductal occluders.

33
Q

Which sex is more likely to develop a PDA?

A

Female

34
Q

Which dog breeds are predisposed to a PDA? (11)

A

Keeshonds
Poodles
Maltese
Bichon Frises
Yorkshire terriers
Cocker Spaniels
Pekingese
Collies
Shelties
Pomeranians
Welsh Corgis.

35
Q

Which breed has shown heritability for a PDA? (3)

A

Poodle
Welsh Corgi
Dutch Stabyhoun

36
Q

What is the role of ductus arteriosus in the uterus?

A

Carries blood from the pulmonary artery to the aorta, bypassing the not yet functioning lungs

37
Q

When does the ductus arteriosus close?

A

Within the first week of life

38
Q

What are the major causes of a PDA? (2)

A

-Smooth muscle hypoplasia
-Asymmetry of the ductus tissue

39
Q

If left untreated, most patients with PDA will…

A

Die within a year from progressive heart failure

40
Q

What clinical signs do patients with a L-R PDA show?

A

Asymptomatic at first and then develop clinical signs associated with left-sided heart failure.

41
Q

What is the main clinical sign of a R-L PDA?

A

Cyanosis

42
Q

What is the main way to diagnose a R-L PDA?

A

Echocardiography with Doppler or bubble study.

43
Q

Clinical signs of L-R PDA (5)

A
  • Exercise intolerance
  • Cough
  • Exertional tachypnoea
  • Dyspnoea
  • Stunted growth
44
Q

Clinical signs of R-L PDA (3)

A
  • Exercise intolerance
  • Differential cyanosis
  • Pelvic limb collapse
45
Q

What is seen on clinical exam with L-R PDA:
A. Pulses
B. Murmur

A

A. Hyperkinetic
B. Continuous murmur at L heart based

46
Q

What is seen on clinical exam with L-R PDA:
A. Pulses
B. Murmur
C. MM

A

A. Normal
B. None or a soft systolic at L heart base
C. Brick red (Polycythaemia)

47
Q

What is seen on thorax xrays with L-R PDA:
A. Pulmonary vasculature?
B. What is seen in DV?
C. Which chambers are enlarged?

A

A. Enlarged
B. Dilation of descending aorta
C. L atria and ventricle

48
Q

What is seen on thorax xrays with R-L PDA:
A. Which chamber enlarged?
B. Pulmonary artery?
C. Pulmonary arteries?

A

A. R atria
B. Marked dilation
C. Enlarged/tortuous

49
Q

What is seen on ECG with L-R PDA? (3)

A
  • Tall R waves (>2.5mV) on lead II in some cases
  • Atrial fibrillation
  • Supraventricular and ventricular ectopic beats
50
Q

What is seen on ECG with R-L PDA?

A

Right axis deviation and increased S wave amplitude due to right ventricular hypertrophy

51
Q

Echocardiography of L-R PDA:
A. …. ventricular hypertrophy
B. Can you visualise PDA?
C. Aortic ejection velocity?
D. Doppler of pulmonary artery shows?

A

A. Eccentric left
B. Yes
C. Increased
D. Reverse turbulent flow in pulmonary a.

52
Q

Echocardiography of R-L PDA:
A. Chamber changes?
B. Can you visualize PDA?
C. What interventricular change?
D. Pulmonary artery

A

A. R atrial dilation and R ventricle hypertrophy
B. Yes
C. Septal flattening
D. Dilated

53
Q

Prior to L-R PDA shunt, what should be treated?

A

Clinical signs of CHF

54
Q

What is the treatment for R-L PDA shunt?

A

Pulmonary hypertension (e.g. sildenafil) and polycythaemia (e.g. phlebotomy, hydroxyurea).
DUCTAL OCCLUSION CONTRAINDICATED

55
Q

What is treatment of choice in L-R PDA shunt?

A

Once stable - surgery.

56
Q

What age can surgical ligation of PDA be performed?

A

8 weeks

57
Q

Where is open surgery of PDA approached from?

A

4-5th intercostal thoracotomy

58
Q

What is the anatomical landmark for a PDA? Where does this run in relation to PDA?

A

The vagus nerve travels along the ventral border of the aorta and is a landmark for identification of the PDA- the vagus nerve courses directly over and perpendicular to the PDA.

59
Q

How is the vagal nerve handled in a PDA Sx?

A

Blunt dissect
Retract dorsally (with a stay suture)

60
Q

What should not be opened when isolated PDA with blunt dissection?

A

Pericardium

61
Q

What ligatures are placed around PDA?

A

Non-absorbable ligatures (e.g. silk or polypropylene) are passed around the PDA and slowly tightened.

62
Q

Why is it not advised to use haemostatic clips in PDA surgery? (2)

A
  • Residual ductal flow
  • Recanalisation
63
Q

Tie 2 sutures for PDA, which is tied first?

A

Closest to aorta

64
Q

What effect should resolved straight away when tying off PDA?

A

No palpable thrill associated with PDA

65
Q

When tying ligature for PDA, at least this is done slowly - why?

A

HR and BP

66
Q

What is surgical mortality of PDA?

A

0-7%

67
Q

Possible complication of surgical ligation of a PDA? (5)

A
  • Intraoperative haemorrhage
  • Recanalisation of the ductus
  • Recurrent laryngeal nerve injury
  • Left atrial herniation
  • Ductus aneurysmal rupture.
68
Q

How can complications of PDA repair be reduced?

A

Serious complications (e.g. death) are reduced with percutaneous occlusion (<1%) compared with an open approach.

69
Q

Possible Amplatzer complication

A
  • Device embolisation
    = detah/cardiac perforation
70
Q

How many dogs with coil embolisation has residual ductal flow?

A

<5%

71
Q

Possible complications of coil embolisation (6)

A
  • Accidental pulmonary artery embolisation (not typically associated with adverse effects in dogs);
  • Significant residual ductal flow requiring a second coil embolisation procedure;
  • Severe femoral artery haemorrhage;
  • Late pulmonary artery embolisation requiring second procedure (surgical ligation);
  • Partial aortic deployment;
  • Haemolysis.
72
Q

How many patients have complete PDA occlusion with amplatzer?

A

100%

Surgery of Abdomen and Thorax Cavitities (10 decks)

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