What are the anaesthetic considerations for patients post Tetralogy of Fallot (ToF) repair?

Anaesthetic Considerations Post Tetralogy of Fallot Repair

Patients with repaired Tetralogy of Fallot require meticulous anaesthetic management focused on preserving right ventricular function, preventing arrhythmias, and maintaining adequate pulmonary blood flow while avoiding increases in pulmonary vascular resistance.

Preoperative Assessment

Mandatory Cardiovascular Evaluation

• Obtain comprehensive echocardiography to assess RV size and function, severity of pulmonary regurgitation, residual RVOT obstruction, tricuspid regurgitation, and aortic root dilation 1
• Review recent cardiac MRI (the reference standard) for RV volume, systolic function, and pulmonary regurgitation severity 1
• Analyze 12-lead ECG for QRS duration >180 ms, which indicates increased risk of ventricular tachycardia and sudden cardiac death 1
• Assess exercise tolerance objectively through formal exercise testing to evaluate functional capacity and detect exertional arrhythmias 1

Key Residual Pathology to Identify

The most common postoperative complications that impact anaesthetic management include 1:

• Pulmonary regurgitation (most common problem) leading to RV dilation and dysfunction
• Residual RVOT obstruction with RV systolic pressure >50 mmHg or RV/LV pressure ratio >0.7
• RV dysfunction from chronic volume overload
• Tricuspid regurgitation secondary to RV dilation
• Arrhythmias (atrial flutter, atrial fibrillation, ventricular tachycardia)
• Aortic regurgitation from progressive aortic root dilation (occurs in 15% of adults)
• Residual VSDs causing LV volume overload
• Branch pulmonary artery stenosis

Arrhythmia Risk Stratification

• Sudden cardiac death occurs in 1-6% of repaired ToF patients, accounting for one-third to one-half of late deaths 1
• Incidence approximates 2.5% per decade of follow-up, with ventricular tachycardia being the primary mechanism 1
• Consider preoperative Holter monitoring based on hemodynamics and clinical suspicion 1
• Patients with unexplained syncope and impaired ventricular function require EP evaluation before elective surgery 1

Intraoperative Anaesthetic Management

Haemodynamic Goals

Maintain RV function by optimizing preload, reducing afterload, and supporting contractility 2:

• Avoid hypovolemia: RV is preload-dependent, especially with chronic volume overload from pulmonary regurgitation
• Minimize increases in pulmonary vascular resistance: Avoid hypoxia, hypercarbia, acidosis, hypothermia, and excessive positive pressure ventilation
• Prevent tachycardia: Reduces diastolic filling time and coronary perfusion; particularly dangerous with residual RVOT obstruction
• Maintain systemic vascular resistance: Prevents right-to-left shunting if residual ASD/VSD present

Monitoring Requirements

Invasive monitoring is essential given the complexity of residual lesions 2, 3:

• Continuous arterial line secured pre-induction for beat-to-beat blood pressure monitoring
• Central venous access for vasoactive infusions and CVP monitoring
• Transesophageal echocardiography to monitor RV function, volume status, and detect new regional wall motion abnormalities 2
• Continuous ECG monitoring for arrhythmia detection

Anaesthetic Technique

Balanced general anaesthesia with careful titration to avoid myocardial depression 2, 4:

• Induction agents: Etomidate preferred for haemodynamic stability; avoid large doses of propofol which may cause significant vasodilation and myocardial depression 4
• Opioid-based technique: High-dose fentanyl (or sufentanil/remifentanil) provides haemodynamic stability 2, 4
• Volatile agents: Sevoflurane in low concentrations acceptable; avoid high concentrations that depress RV contractility 4
• Muscle relaxation: Pancuronium provides vagolytic effect preventing bradycardia; rocuronium acceptable alternative 4

Vasoactive Support

Inotropic vasodilators are frequently required, particularly for RV dysfunction 2:

• Milrinone: First-line agent providing inotropy and pulmonary vasodilation without increasing myocardial oxygen consumption
• Dobutamine or low-dose dopamine: Alternative inotropic support
• Alpha-adrenergic agents (phenylephrine, norepinephrine): Use judiciously to maintain systemic vascular resistance, but may increase RV afterload 2
• Avoid pure vasoconstrictors in patients with severe RV dysfunction

Critical Perioperative Complications

Arrhythmias

Arrhythmias are frequent and potentially life-threatening 2:

• Ventricular tachycardia related to surgical scarring (particularly RVOT between VSD patch and pulmonary annulus) and haemodynamic abnormalities 1
• Atrial arrhythmias (flutter, fibrillation) from atrial dilation
• Have defibrillator immediately available and antiarrhythmic medications prepared
• Treat underlying haemodynamic causes: Correct hypovolemia, hypoxia, acidosis, electrolyte abnormalities

Bleeding Complications

Expect increased bleeding risk during re-sternotomy and from collateral vessels 2:

• Vascular injury during adhesion removal is common in reoperations
• Aortopulmonary collateral vessels may cause unexpected bleeding
• Ensure adequate vascular access for rapid volume resuscitation
• Have blood products immediately available

Right Ventricular Failure

RV failure is the primary cause of perioperative morbidity 2:

• Monitor RV function continuously with TEE
• Optimize preload with fluid administration guided by TEE
• Reduce RV afterload with pulmonary vasodilators (milrinone, inhaled nitric oxide if available)
• Support contractility with inotropes
• Consider mechanical support (ECMO) if refractory RV failure develops

Special Considerations for Non-Cardiac Surgery

For Patients Requiring Non-Cardiac Procedures

Apply the same haemodynamic principles with additional precautions 3:

• Endocarditis prophylaxis for dental and invasive procedures if residual lesions present 3
• Avoid dehydration which reduces preload and may precipitate arrhythmias 3
• Maintain normothermia to prevent increased pulmonary vascular resistance
• Adequate pain control to prevent tachycardia and increased oxygen consumption; multimodal analgesia with opioids and regional techniques when appropriate 3

Postoperative Management

Early extubation is desirable but only when haemodynamically stable 3, 4:

• Extubation criteria: Haemodynamic stability, adequate oxygenation (SpO2 >95% in repaired patients), normothermia, minimal bleeding
• ICU admission for close monitoring of RV function and arrhythmias 4
• Continue inotropic support until haemodynamically stable
• Aggressive pain management to facilitate early mobilization and prevent pulmonary complications 3

Common Pitfalls to Avoid

• Underestimating RV dysfunction: Even asymptomatic patients may have significantly impaired RV function that decompensates under anaesthesia 2
• Inadequate preoperative assessment: Proceeding without recent echocardiography or knowledge of residual lesions increases risk 1
• Excessive positive pressure ventilation: Increases RV afterload and impairs venous return
• Ignoring QRS duration: QRS >180 ms significantly increases arrhythmia risk and should prompt enhanced monitoring 1
• Failure to anticipate bleeding: Re-sternotomy and collateral vessels make major haemorrhage likely 2