How is haemodynamics managed in Tetralogy of Fallot (TOF)?

Haemodynamic Management in Tetralogy of Fallot

Haemodynamic management in Tetralogy of Fallot (TOF) should focus on evaluating and treating residual anatomic abnormalities, particularly right ventricular outflow tract obstruction and pulmonary regurgitation, as these directly impact morbidity and mortality.

Pathophysiology and Haemodynamic Considerations

Tetralogy of Fallot is characterized by four components:

• Ventricular septal defect (VSD)
• Right ventricular outflow tract obstruction (RVOTO)
• Overriding aorta
• Right ventricular hypertrophy

The haemodynamic consequences depend on:

• Severity of pulmonary stenosis
• Degree of right-to-left shunting across the VSD
• RV function and adaptation

Assessment of Haemodynamics

Initial Evaluation

• Echocardiography: First-line assessment for RVOTO, pulmonary regurgitation, RV function, and residual VSD 1
• Cardiac MRI: Gold standard for RV volume quantification and pulmonary regurgitant fraction measurement 1
• Cardiac catheterization: Direct pressure measurements of RVOT gradients and dynamic assessment of regurgitant flow 1

Key Parameters to Monitor

• RV systolic pressure (normal vs. elevated)
• RV/LV pressure ratio (>0.7 indicates significant RVOTO) 2
• Pulmonary regurgitation severity
• RV size and function
• QRS duration (>180 ms indicates risk for ventricular arrhythmias) 2

Management of Specific Haemodynamic Issues

1. Right Ventricular Outflow Tract Obstruction

Indications for intervention:

• Peak instantaneous echocardiography gradient >50 mm Hg 2
• RV/LV pressure ratio >0.7 2
• Progressive/severe RV dilatation with dysfunction 2

Management options:

• Surgical relief of RVOTO
• Percutaneous balloon valvuloplasty in selected cases

2. Pulmonary Regurgitation

Indications for pulmonary valve replacement:

• Symptomatic patients with severe PR 2
• Asymptomatic patients with severe PR and any of:
  • Decreased exercise capacity
  • Progressive RV dilatation
  • Progressive RV systolic dysfunction
  • Progressive tricuspid regurgitation
  • RVOTO with RV systolic pressure >80 mmHg
  • Sustained arrhythmias 2

3. Residual VSD

Indications for closure:

• Left-to-right shunt >1.5:1 2
• Combination with other residual lesions leading to RV enlargement 2

4. Arrhythmia Management

Risk stratification:

• QRS duration >180 ms (especially if progressive) 2
• RV dilation and dysfunction
• History of syncope

Management approach:

• Annual surveillance with history, ECG, assessment of RV function 2
• Periodic Holter monitoring 2
• Electrophysiology study for suspected arrhythmias 2
• ICD implantation for documented sustained VT or cardiac arrest 2
• Avoid class Ic antiarrhythmic medications (flecainide, propafenone) and amiodarone in asymptomatic patients with VA 2

Optimal Haemodynamic Profile After TOF Repair

The ideal post-repair haemodynamic profile includes:

• Mild residual PS (PRV/LV < 0.8) to limit the degree of PR 1
• Minimal residual VSD
• Preserved RV function
• No significant arrhythmias

Follow-up Protocol

1. Annual cardiac evaluation at specialized GUCH/ACHD center 2

2. Regular assessment of:

   • RV function and size
   • Pulmonary valve function
   • RVOT gradient
   • QRS duration
   • Exercise capacity

3. Imaging schedule:

   • Echocardiography at each visit
   • CMR every 2-3 years or when clinical status changes
   • Cardiac catheterization when non-invasive tests are inconclusive

Important Pitfalls to Avoid

1. Underestimating pulmonary regurgitation by echocardiography - use multiple imaging modalities 1

2. Missing branch pulmonary artery stenosis due to limited echocardiographic windows - supplement with MRI or catheterization 1

3. Overlooking coronary artery anomalies that may affect RVOT interventions - thorough pre-operative evaluation is essential 1

4. Misinterpreting RV dilation as primarily volume overload when residual RVOTO may be contributing - comprehensive diagnostic approach is needed 1

5. Delaying intervention until irreversible RV dysfunction occurs - timing of pulmonary valve replacement is critical before RV function deteriorates

By systematically addressing these haemodynamic issues in TOF patients, clinicians can optimize outcomes and reduce long-term morbidity and mortality.