Interrupted aortic arch

Definition: obstructive anomaly of the aortic arch.

Classification by Celoria et al:

Type A (20%): IAA distal to left subclavian artery.

Type B (78%): between left subclavian and left carotid artery.

Type C (2%): proximal to left carotid artery.

Most of them are associated with a VSD or other defects.

Prevalence 1% of all CHD. Incidence 4:10.000 of all life births. Genetic association to Di-George-Syndrome.

Physiology:

With PDA closure there is an acute increase in LV afterload, a decreased CO, increased LVEDP.  This leads to CCF (in extreme: myocardial ischemia) and shunt reversal along the PFO (and VSD if present).  This in turn causes increased PBF and severe CCF with systemic hypotension.

Diagnosis:

Hypertension of upper limbs is usually not present before Day 5, but usually after PDA closure with signs of CCF of various degree.

ECG: signs of RVH.

CXR: cardiomegaly and pulmonary congestion.

ECHO

Cardiac catheterisation (diagnostic and interventional)

MRI

Preoperative management:

• Commence Prostaglandin E1 (20ng/kg/min) to maintain systemic perfusion. Intubate and sedate to lower the oxygen consumption. Hypoventilation to higher the PVR and to lower the SVR.
• Balanced circulation with PDA open and/or VSD present (aim SpO2 75-85%)
• Dopamine (5-10 mcg/kg/min), dobutamine (5-10 mcg/kg/min) or adrenaline (0.02-0.1 mcg/kg/min) may be required to stabilise for a low CO
  
• Careful fluid resuscitation – this is an obstructive lesion, not hypovolaemic!
• Calcium infusion if there is Di-George Syndrome (see inotropes)

Preoperative preparation:

ECG, CXR, CUS, FBE, xlotting, UECs, FISH, PRBC(4), FFP (2), platelets (2), cryoprecipitate (2).

Methylprednisolone 10mg/kg 12hrs and 6hrs pre surgery in neonates.

Surgery:

Preferred single stage repair with end-to-end or end-to-side anastomosis, patch augmentation, subclavian-flap aortoplasty or extended resection with primary anastomosis and also VSD closure.

Postoperative management:

• Keep intubated, ventilated, sedated and paralysed for 24 hours for patients with preceding high PBF; elective cases can be extubated earlier
• Inotropes: milrinone plus dopamine
• Haemodynamics: age adjusted, in neonates: SBP >60 mmHg but <80 mmHg; MAP >40 mmHg; prevent hypertension (SNP or Esmolol infusion)
• Respiratory: normoxaemia, normocapnea
• Fluid restriction: 1ml/kg/hr, careful trophic feeds
• Haemostasis: Hb 100-140
• Maintain normothermia

Specific problems:

• Acute hypertension (increase of noradrenaline release due to sympathetic stimulation during repair): SNP or Esmolol infusion
• Postcoarctectomy syndrome: hypertension, abdominal pain, ileus (2-3 days post repair)
• PHT if high PBF was preceding (VSD or ASD)
  
• Thoracic duct injury with chylothorax
  
• Laryngeal nerve injury
• Spinal cord injury (spinalis anterior injury): 0.4-1.5%
• Neurological injury due to deep hypothermic circulatory arrest

Outcome:

Perioperative mortality: 5-7%

Recoarctation: 5-50%

Long term antihypertensive treatment required in 30%.

Long term survival after 10 yrs: 94% (IAA and VSD); 72% (IAA and TGA). 5 yrs: 47% (IAA and other defects)

References:

[1] Critical Heart Disease in Infants and Children; 2nd ed, Nichols et al: Interrupted Aortic Arch

[2] Eur J Cardiothorac Surg. 2009 Apr;35(4):565-8: Kobayashi et al: Outcomes following surgical repair of aortic arch obstructions with associated cardiac anomalies

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