Definition: wide morphological spectrum with mild aortic stenosis (AS) to HLHS.
Most common is valvular AS (70 – 80%), followed by subvalvular AS (10 – 20%) and supravalvular AS (rare), which is common in Williams Syndrome (1:20.000 live births: mental retardation, behavioural traits, elfin facies with AS and peripheral PA stenosis).
All LVOTO can be associated with other defects.
Physiology:
LVH due to increase in afterload, subendocardial ischemia leading to coronary ischemia with cardiomyopathy; reduced blood fow through LVOT leading to hypoplasia of mitral valve, LV and aortic arch.
Diagnosis:
ECG (left axis, LVH), ECHO.
In critical AS there is early presentation with cardiogenic shock when PDA closes.
In mild forms: failure to thrive, increased WOB.
Only 15% present under age 1yr.
Management preoperatively with critical AS:
- PGE1 infusion (20ng/kg/min) to maintain PDA patency for systemic perfusion
- Intubation and ventilation as required
- Milrinone (0.25-0.5 mcg/kg/min) and noradrenaline (0.02-0.1 mcg/kg/min) to improve CO, avoid β-adrenergic drugs (worsening diastolic dysfunction, tachycardia)
Preoperative preparation:
ECG, CXR, CUS, FBE, clotting, UEC, PRBC (4), FFP (2), platelets (2), cryoprecipitate (2).
Methylprednisolone 10mg/kg 12hrs and 6hrs pre surgery in neonates.
Surgery:
Dependent on morphological structures, development of LV and LVOT and associated defects (aortic root and mitral valve diameter, LV/RV ratio).
Single ventricle pathway (HLHS) or two-ventricle surgery for AS: surgical valvotomy, percutaneous balloon valvotomy, dilation of LVOTO (Konno procedure) and/or aortic valve replacement with pulmonary autograft and pulmonary homograft (Ross procedure) or combined Ross-Konno procedure.
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)
- Haemodynamics: SBP >60 mmHg, MAP >40 mmHg (increasing over time), LAP 8-12 mmHg, CVP 8-12 mmHg
- Respiratory: normoxaemia, normocapnea
- Fluid restriction: 1ml/kg/hr, trophic feeds
- Haemostasis
Specific problems:
- Low CO: keep paralysed, don’t wean inotropes <24 hrs
- Anatomical coronary artery problems (check ECG, troponin) → early investigation (ECHO, Cathlab)
- Coronary artery spasm: start GTN 5-10 mcg/kg/min
- Arrhythmia: SVT (adenosine, digoxin), JET (slow amiodarone), bradycardia (pacing), AV block (pacing)
- Low urine output: start PD
- Severe AI (15-20%) mainly in balloon valvotomy
- Residual AS
- No anticoagulation required in Ross-Konno procedure (in valved conduits consider anticoagulation)
Outcome:
- Depending on the underlying lesion; average PICU stay: 5-8 days
- Pulmonary homograft needs reoperation with age
- Autograft may develop AI
References:
[1] Critical Heart Disease in Infants and Children; 2nd ed, Nichols et al: Left Ventricular Outflow Obstruction
[2] J Thorac Cardiovasc Surg. 1966 Apr;51(4):484-92: Cornell et al: Supravalvular aortic stenosis
[3] Eur J Cardiothorac Surg. 2007 Jun;31(6):1013-21: Alsoufi et al: Management options in neonates and infants with critical left ventricular outflow tract obstruction
[3] Circulation. 2006 Nov 28;114(22):2412-22: Aboulhosn et al: Left ventricular outflow obstruction: subaortic stenosis, bicuspid aortic valve, supravalvar aortic stenosis, and coarctation of the aorta
[4] Ann Thorac Surg. 2003 Nov;76(5):1398-411: Brown et al: Surgery for aortic stenosis in children: a 40-year experience
[5] J Card Surg. 2012 Jan;27(1):103-11. Anagnostopoulos et al: Surgical management of left ventricular outflow tract obstruction
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