Hypoplastic left heart

Definition: abnormal left heart development resulting in underdevelopment of LV, aortic valve, aorta, mitral valve and aortic arch. Incidence 0.2:1000 of all live births.

Physiology:

PDA dependent systemic perfusion: PDA closure results in acidosis, hypoxaemia and shock.

In patients with restrictive ASD/PFO, cardiogenic shock develops right after birth.

Diagnosis:

Prominent loud single second heart sound

ECHO

Differential diagnosis:

Coarctation, critical AS, IAA (all PDA dependant systemic lesions)

Preoperative management:

• Secure vascular access (two peripheral IVs or UVC)
• Commence prostaglandin E1 (20 ng/kg/min) to maintain systemic perfusion. Watch for apnoeas
• If deteriorating with pulmonary over-circulation (increasing saturations, decreasing perfusion): intubate and sedate to lower oxygen consumption with hypoventilation to increase PVR (aim for a pH 7.30-7.35) and to lower SVR (hypercarbia). SNP (0.5-4 mcg/kg/min to lower SVR – aim MAP >35 mmHg in neonates)
• With restrictive ASD/PFO: immediate intubation and resuscitation, urgent BAS or septectomy (10% of HLHS)
• No enteral feeds until surgical correction, consider gastric protection
  

  ---

Management of low CO preoperative:

•  SpO2 >85 – excessive pulmonary blood flow: intubation, sedation, filling, SNP
• Impaired systemic ventricular function (+/- tricuspid regurgitation): consider intubation, dobutamine, milrinone
• SpO2 <65% and acidosis: confirm diagnosis of restrictive ASD via ECHO;intubation, resuscitation, urgent BAS
• Restrictive PDA (variable SpO2) → increase prostin

Preoperative preparation:

ECG, CXR, CUS, renal US, FISH, FBE, clotting,UECs, PRBC (4), FFP (2), platelets (2), cryoprecipitate (2)

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

Surgery: 

Primary cardiac transplantation – not done in Australia (consider also compassionate care).

Staged repair: Norwood procedure (preferably if stable on Day 3 or 4 of life) or Hybrid procedure (bilateral PA band, PDA stenting) Glenn Shunt (4-8mths), Fontan (18 mths – 4 yrs).

Norwood procedure: reconstruction of aortic root and aortic arch, disconnection of pulmonary trunk and incorporating the RV stump into systemic circulation; lung perfusion by BT Shunt (diastolic runoff) or Sano-Shunt (obstruction).

Postoperative Management:

• Keep intubated, ventilated, sedated and paralysed for 24-48 hrs
• Inotropes: milrinone plus dopamine or adrenaline plus noradrenaline, aim MAP >40 mmHg in neonates, aim for maximal vasodilation to reduce strain on RV
• Haemodynamics: SBP > 60 mmHg, MAP >40 mmHg (increasing over time), CVP 8-12 mmHg
• Respiratory: balance circulation (SpO2 70 – 85%), normocapnea
• Fluid restriction: 1ml/kg/hr
• Haemostasis
• Introduce feeds when haemodynamically stable (not before day 2)
• Introduce captopril gradually when tolerating feeds and haemodynamically stable
• Commence aspirin 5 mg/kg OD once enteral full feeds established
• Consider clopidogrel 0.2 mg/kg OD (all surgical lines and pacing lines must be removed prior)
• Consider long term central venous access for feed intolerance and need for long term parenteral nutrition

Specific problems:

• Low CO: keep paralysed, don’t wean inotropes <24 hrs → adaption of the RV for systemic circulation
• Anatomical coronary artery problems (check ECG, troponin). Early investigations (echo, cathlab)
• Coronary artery spasm (start GTN 5-10 mcg/kg/min)
• Arrhythmia and pacing
• Low urine output: start PD
• ECHO assessment: function of systemic RV, patency of BT shunt/Vmax across Sano shunt, degree of tricuspid regurgitation, adequacy of ASD, evaluation of neoaorta and arch
• Feed intolerance: consider feeding protocol

Outcome:

Mean ICU stay: 5 days

Mortality 30 days: up to 40%

HLHS w/ restrictive ASD and BAS: mortality up to 50%

References:

[1] Lab Invest 1952, 1(1): 61-70: Lev M: Pathologic anatomy and interrelationship of hypoplasia of the aortic tract complexes

[2] Pediatr Clin North Am 1958, 5(4):1029-1056: Noonan et al: The hypoplastic left heart syndrome; an analysis of 101 cases

[3] Cardiol Clin 1989; 7:377-385: Norwood: Hypoplastic left heart syndrome

[4] Ann Thorac Surg 1991; 52:688-695: Norwood: Hypoplastic left heart syndrome

[5] N Engl J Med 1983; 308:23-26: Norwood et al: Physiologic repair of aortic atresia-hypoplastic left heart syndrome

[6] Circulation 2004;109;2326-2330: Vlahos et al: Hypoplastic Left Heart Syndrome With Intact or Highly Restrictive Atrial Septum: Outcome After Neonatal Transcatheter Atrial Septostomy

[7] Am Heart J. 2011 Jan;161(1):138-44: Trivedi et al: Arrhythmias in patients with hypoplastic left heart syndrome

[8] Korean Circ J. 2010 Mar;40(3):103-11: Honjo et al: Hybrid palliation for neonates with hypoplastic left heart syndrome: current strategies and outcomes

[9] Pediatric Anesthesia 2010 20: 38-46: Naguib et al: Anesthetic management of the hybrid stage 1 procedure for hypoplastic left heart syndrome (HLHS)

[10] N Engl J Med 2010;362:1980-92: Ohye et al: Comparison of Shunt Types in the Norwood Procedure for Single-Ventricle Lesions

[11] Eur J Cardiothorac Surg. 2013 Mar 7. Münsterer et al: Treatment of right ventricle to pulmonary artery conduit stenosis in infants with hypoplastic left heart syndrome.

[12] Circulation. 2012 Sep 11;126(11 Suppl 1):S123-31. Baba et al: Hybrid versus Norwood strategies for single-ventricle palliation.

All Marc’s PICU cardiology FOAM can be found on PICU Doctor and can be downloaded as a handy app for free on iPhone or Android. A list of contributors can be seen here.