II. Causes
- Hypoplastic Left Heart Syndrome (HLHS)
- Tricuspid Atresia
- Mitral Valve Atresia
- Ebstein Anomaly
- Double Outlet Right Ventricle (DORV)
- Pulmonary Atresia
- Atrioventricular Canal Defect
III. Management: General
- Staged procedures aim to direct the single ventricle for systemic circulation and passive flow to the pulmonary circuit
- In some cases, Heart Transplantation is an option
IV. Management: Surgery Stage 1 (Norwood Procedure, Birth)
- Performed shortly after birth
- Key goal is to allow single ventricle to provide both systemic and pulmonary circulation
- Establishes permanent flow between right ventricle and aorta
- Restricts pulmonary overcirculation
- High mortality in the first 24-48 hours of procedure
- Normal Oxygen Saturation after Norwood is 75 to 85%
- Three Stage Procedure (Very complex repair)
- Shunt replaces Patent Ductus Arteriosus
- Blalock-Taussig Shunt (subclavian artery to pulmonary artery) OR
- Sano Shunt (right ventricle to pulmonary artery)
- Atrial Septoplasty creates an Atrial Septal Defect
- Neo-Aorta created
- Shunt replaces Patent Ductus Arteriosus
V. Management: Post-Operative Stage 1 (Interstage Period, Post-Norwood, age <6 months)
- Newborns discharged after Norwood Procedure, awaiting Stage 2 repair at 4-6 months
- Delay allows for needed growth
- High risk period for decompensation due to tenuous cardiovascular physiology
- Mortality 10% during the inter-stage period between Stage 1 and 2
- Decompensation Causes
- At risk for severe decompensation even with mild Viral Infections
- RSV BronchiolitisHypoxemia
- Gastroenteritis with Dehydration
- Presentations
- Increased Systemic Vascular Resistance (cold, cyanotic digits)
- Metabolic Acidosis
- Cardiac Ischemia due to coronary steal syndrome
- Shunt thrombosis
- High mortality risk and requires immediate management
- Dehydration is a risk for shunt thrombosis
- Patent shunt normally creates a machinery murmur
- Consider shunt thrombosis if no murmur is heard
- Start IV Heparin if shunt thrombosis is suspected
- Evaluation and Management
- Emergent pediatric cardiology or cardiothoracic surgery Consultation
- Admit or observe all children even with mild illness in this stage
- Maintain a low threshold to transfer to tertiary care
- Avoid excessive Supplemental Oxygen to maintain systemic perfusion
- Oxygen results in vasodilation of pulmonary vessels and shunts flow away from systemic circulation
- Excessive oxygen risks serious Hypotension, shock or death
- Keep Oxygen Saturation goal 75-85% (normal O2 Sat following Norwood)
- Ask parents the range of their child's Oxygen Saturation
- Oxygen results in vasodilation of pulmonary vessels and shunts flow away from systemic circulation
- Preload dependent (excessive intrathoracic pressure decreases venous return)
- Consider small fluid Normal Saline bolus trials (5-10 ml/kg)
- Monitor IVC Ultrasound for Volume Status
- Vasopressors (if needed)
- Norepinephrine and Epinephrine are preferred
- Phenylephrine may be used to temporize
- Consider causes of Hypoxemia <75% Oxygen Saturation
- Consider shunting
- Trial low FIO2 by Nasal Cannula
- Evaluate Blood Pressure and other markers of perfusion
- Obtain Chest XRay
- Obtain Point Of Care Cardiac Ultrasound (e.g. Pericardial Effusion, Lung Ultrasound, Cardiac Function)
- Consider Brain Natriuretic Peptide (BNP)
- Pulmonary-Systemic Flow Ratio (Qp/Qs) evaluates persistently decreased perfusion:
- Normal Pulmonary (Qp, estimated at 25) to Systemic (Qs) ratio is 1:1
- Qs = 100 - Oxygen Saturation
- Qs <25 suggests need for either small fluid bolus trial or Vasopressors
VI. Management: Surgery Stage 2 (Glenn Procedure, age 4-6 months)
- Performed at age 4-6 months
- Bidirectional Glenn Procedure
- Partial Caval Anastomosis
- Superior vena cava is connected to pulmonary artery
- Allows for passive circulation to lung
- Shunt removed
- Blalock-Taussig or Sano Shunt placed during Norwood Procedure is removed
- Partial Caval Anastomosis
- Post-operative changes
- Cardiopulmonary physiology improves and hemodynamic status is more stable than Post-Norwood
- Oxygen Saturation improves to 90%
VII. Management: Surgery Stage 3 (Fontan Procedure, ages 18-36 months)
- Performed between ages 18 to 36 months (up to 48 months)
- Fontan Procedure
- Inferior Vena Cava (IVC) connected to pulmonary artery (PA)
- Allows for pulmonary Blood Flow via passive circulation
- Fenestration may be placed between IVC and PA to regulate flow and prevent pulmonary overload
- Post-operative changes
- Cardiopulmonary status stabilizes significantly compared to prior stages
- Dysrhythmia Risk (longterm risk into adulthood)
- Atrial Dysrhythmias are most common (Atrial Fibrillation, Atrial Flutter, PSVT)
- Supraventricular Tachycardia Management is the same as for other patients (e.g. Adenosine, cardioversion)
- Thrombosis Risk
- Aspirin or other antiplatelet agent OR
- Anticoagulation
VIII. Prognosis
- Single ventricle conditions are uniformly fatal without circulation
- Staged procedures for Single Ventricle Defects have resulted in survival to adulthood in 70% of cases
IX. References
- Claudius and Stroebel in Swadron (2021) EM:Rap 21(11): 6-9
- Civitarese and Crane (2016) Crit Dec Emerg Med 30(1): 14-23
- Sloas and Orman in Majoewsky (2013) EM:Rap 13(9): 10-11
- Rao in Berger (2013) Pediatric Hypoplastic Left Heart Syndrome, Emedicine