Congenital heart disease in the ICU

Contents

Overview

Congenital heart disease (CHD) affects approximately 8 per 1000 live births. With advances in paediatric cardiac surgery, over 90% of children with CHD in high-income countries survive to adulthood. The ICU clinician encounters CHD primarily in three contexts: the neonate with a ductal-dependent lesion, the post-operative paediatric cardiac surgical patient, and the adult with palliated or unrepaired CHD presenting with complications.

Classification

Acyanotic lesions (left-to-right shunts, no mixing of deoxygenated blood into systemic circulation at rest):

  • Ventricular septal defect (VSD) — most common CHD
  • Atrial septal defect (ASD)
  • Patent ductus arteriosus (PDA)
  • Atrioventricular septal defect (AVSD) — common in Down's syndrome
  • Coarctation of the aorta

Cyanotic lesions (right-to-left shunting or mixing, causing systemic desaturation):

  • Tetralogy of Fallot (ToF) — VSD, right ventricular outflow tract obstruction, overriding aorta, right ventricular hypertrophy
  • Transposition of the great arteries (TGA) — aorta arises from the morphological right ventricle, pulmonary artery from the morphological left ventricle; the two circulations run in parallel, incompatible with life without mixing
  • Pulmonary atresia
  • Tricuspid atresia
  • Hypoplastic left heart syndrome (HLHS)
  • Total anomalous pulmonary venous drainage (TAPVD)
  • Truncus arteriosus

Physiology

Left-to-Right Shunts

Blood flows from the high-pressure systemic circulation to the low-pressure pulmonary circulation. The pulmonary-to-systemic flow ratio (Qp:Qs) is above 1. Consequences: pulmonary overcirculation → pulmonary vascular remodelling → pulmonary hypertension. If uncorrected, pulmonary vascular resistance eventually exceeds systemic, reversing the shunt direction (Eisenmenger syndrome).

Single Ventricle Physiology

Conditions such as HLHS, tricuspid atresia, and some forms of pulmonary atresia result in a single functional ventricle supplying both circulations. Surgical palliation proceeds through staged operations — Norwood/Sano or Damus-Kaye-Stansel procedure in the neonatal period, then Glenn (bidirectional cavopulmonary anastomosis) at 4–6 months, then Fontan completion at 2–4 years.

In the Fontan circulation, the systemic venous return flows passively through the pulmonary vasculature to the pulmonary veins without a subpulmonary pumping chamber. The Fontan circulation is preload-dependent, sensitive to rises in pulmonary vascular resistance, and intolerant of tachyarrhythmia. Any factor increasing PVR — hypoxia, hypercarbia, acidosis, high PEEP — can precipitate acute circulatory failure.

Ductal-Dependent Lesions

Some cardiac lesions depend on patency of the ductus arteriosus for either pulmonary or systemic blood flow:

Ductal-dependent pulmonary circulation: pulmonary atresia, critical pulmonary stenosis, severe Fallot variants — blood reaches the lungs only via the PDA.

Ductal-dependent systemic circulation: HLHS, critical coarctation, interrupted aortic arch — the descending aorta is perfused via the PDA.

A neonate with a ductal-dependent lesion presents with shock or cyanosis as the duct closes in the first days of life. The diagnosis may not have been made antenatally.

Management: prostaglandin E1 (alprostadil) infusion to maintain ductal patency. Standard dose 5–10 nanograms/kg/min, titrated to effect. Side effects include apnoea (common at higher doses — many neonates require intubation), hyperthermia, and hypotension.

Post-operative ICU Care

Low Cardiac Output Syndrome

Low cardiac output syndrome (LCOS) occurs in approximately 25% of patients in the first 12–24 hours after cardiac bypass. It results from myocardial stunning, ischaemia-reperfusion injury, and residual anatomical lesions. Features include tachycardia, oliguria, poor peripheral perfusion, and metabolic acidosis.

Assessment: near-infrared spectroscopy (NIRS) monitoring of cerebral and somatic oxygenation; pulmonary artery or atrial pressure monitoring; echocardiography to assess function and residual lesions.

Management: optimise preload, ensure adequate heart rate and rhythm, provide inotropic support (dopamine, adrenaline, milrinone), reduce afterload where appropriate. Mechanical circulatory support (ECMO, Berlin Heart) if refractory.

Junctional Ectopic Tachycardia

JET is the most common arrhythmia after repair of lesions near the AV node (VSD repair, AVSD repair, ToF). It is characterised by an automatic tachycardia at a rate of 170–240 bpm with AV dissociation or retrograde P waves.

Management: core cooling to 34°C slows the ectopic focus; amiodarone; ensuring adequate magnesium levels. Avoid atropine and catecholamines. Atrial pacing at a rate slightly above the JET rate restores AV synchrony and improves output.

Other Complications

Pulmonary hypertensive crisis: See below.

Diaphragm palsy: Phrenic nerve injury during surgery produces unilateral diaphragm paralysis, preventing successful extubation. Confirmed on fluoroscopy or ultrasonography. May require diaphragm plication.

Chylothorax: Thoracic duct injury causes chyle accumulation in the pleural space. Characteristic milky pleural fluid; confirmed by pleural fluid triglycerides >1.1 mmol/L and lymphocyte count. Management: low-fat diet (medium-chain triglycerides) or nil by mouth with TPN, octreotide infusion. Surgical ligation if medical management fails after 4–6 weeks.

Pulmonary Hypertensive Crisis

Acute pulmonary hypertensive crisis is a sudden rise in pulmonary vascular resistance causing acute right ventricular failure, systemic hypotension, and rapid circulatory collapse.

Triggers in the post-operative period: pain, agitation, suctioning (causing hypoxia and hypercarbia), cold, metabolic acidosis.

Prevention

Maintain alkalosis (pH 7.45–7.55), normoxia, normocapnia or mild hypocapnia. Adequate sedation and analgesia. Avoid unnecessary airway suctioning.

Management of Acute Crisis

  • 100% oxygen
  • Manual hyperventilation to correct hypercarbia and achieve mild alkalosis
  • Deepen sedation
  • Inhaled nitric oxide (iNO) 20 ppm — reduces PVR without systemic vasodilation
  • IV prostacyclin or sildenafil
  • Adrenaline or vasopressin for systemic pressure support
  • If refractory: consider ECMO as a bridge

Adult Congenital Heart Disease

Adults with CHD now outnumber children with the condition in developed countries. Common presentations to adult ICUs include:

Fontan failure: Increasing hepatic congestion, protein-losing enteropathy (hypoalbuminaemia, oedema), arrhythmias, and progressive systemic ventricular dysfunction. Managed with diuresis, antiarrhythmic therapy, and in selected patients, Fontan conversion or cardiac transplantation.

Eisenmenger syndrome: Fixed pulmonary hypertension with reversed shunting. Supplemental oxygen, pulmonary vasodilators (bosentan, sildenafil), avoidance of vasodilators that reduce systemic vascular resistance without also reducing PVR (these worsen the right-to-left shunt). Cardiac and/or lung transplantation is the only definitive option.

Arrhythmias: Atrial flutter and AF are common in adults with repaired CHD, particularly those who have undergone atriotomy. Haemodynamically significant arrhythmias require immediate cardioversion; long-term management with antiarrhythmics or catheter ablation.

Viva Questions

What is the Fontan circulation and what are its potential complications in the ICU?

The Fontan circulation describes the haemodynamic state after surgical completion of single-ventricle palliation, in which systemic venous return flows passively through the lungs — driven by the pressure gradient between the systemic venous system and pulmonary veins — without a subpulmonary ventricle. This works only when pulmonary vascular resistance is low; any increase in PVR (hypoxia, hypercarbia, acidosis, high mean airway pressure) impairs pulmonary blood flow and reduces cardiac output. The circulation is also exquisitely preload-dependent, since passive pulmonary flow requires adequate venous filling pressure. In the ICU, Fontan patients are at risk of a number of complications: arrhythmias (which remove the atrial contribution to cardiac output and are poorly tolerated), hepatic congestion from chronically elevated venous pressure (leading to Fontan-associated liver disease), protein-losing enteropathy from intestinal lymphatic congestion, and progressive failure of the single systemic ventricle. Mechanical ventilation must be managed carefully — avoiding high PEEP, maintaining spontaneous breathing where possible, and accepting mild hypercarbia to minimise mean airway pressure.

How would you manage pulmonary hypertensive crisis in a post-operative paediatric patient?

A pulmonary hypertensive crisis is a medical emergency. The immediate response is to provide 100% oxygen, manually hyperventilate to reduce PaCO2 and achieve mild alkalosis (pH 7.45–7.55), and deepen sedation and analgesia to reduce catecholamine-driven rises in PVR. Inhaled nitric oxide at 20 ppm reduces pulmonary vascular resistance selectively without lowering systemic blood pressure and should be started immediately. Prostacyclin by inhalation or intravenous sildenafil can be added as second-line pulmonary vasodilators. Systemic blood pressure should be supported with vasopressors or vasopressin if there is systemic hypotension — vasopressin is useful as it maintains systemic vascular resistance without increasing PVR. If the patient fails to respond, ECMO should be considered as a bridge to recovery. Prevention is equally important: routine avoidance of known triggers (hypoxia, hypercarbia, acidosis, pain, suctioning) using targeted sedation, multimodal analgesia, and ventilator settings that maintain adequate alveolar oxygen delivery.

A neonate presents cyanosed and hypotensive. What ductal-dependent lesions would you consider and how would you manage them?

In a cyanosed neonate presenting in the first days of life, I would immediately consider ductal-dependent lesions. The two broad categories are those with ductal-dependent pulmonary circulation — pulmonary atresia, critical pulmonary stenosis, and severe Tetralogy of Fallot — and those with ductal-dependent systemic circulation — hypoplastic left heart syndrome, critical aortic stenosis, interrupted aortic arch, and severe coarctation. Cyanosis with a single second heart sound and no murmur in a collapsed neonate suggests HLHS; cyanosis with a systolic murmur and differential saturations between arms and legs suggests coarctation or interrupted arch. Management requires urgent prostaglandin E1 infusion (alprostadil, starting at 5 nanograms/kg/min) to reopen or maintain the ductus, alongside respiratory and haemodynamic stabilisation. Many neonates require intubation because prostaglandin E1 causes apnoea, particularly at higher doses. Early echocardiography confirms the anatomy. Urgent paediatric cardiology and cardiac surgical review is required, as these lesions require staged surgical correction or palliation.