Pulmonary valve replacement in patients with tetralogy of Fallot and pulmonary regurgitation: early surgery similar to optimal timing of surgery?

Tetralogy of Fallot is the most common form of cyanotic congenital heart disease, with a prevalence of 0.26–0.8 per 1000 live births. Total repair for tetralogy of Fallot has been available for 50 years with a favourable outcome in most patients. Today, one is faced with an increasing number of patients with residual pulmonary regurgitation. It was previously thought that pulmonary regurgitation in Fallot patients was rather harmless. However, accurate measurements of right ventricular volumes using cardiovascular magnetic resonance (CMR) imaging have visualized important enlargement of the right ventricle in patients with severe pulmonary regurgitation. Moreover, it has been recently demonstrated that pulmonary regurgitation leads to progressive right ventricular dilatation and, with time, to right ventricular dysfunction, exercise intolerance, ventricular arrhythmias, and sudden death. Pulmonary valve replacement can be performed electively with little risk and may improve symptoms of right ventricular failure and provides excellent mid-term survival. The surgical procedure has a peri-operative mortality of 1–4% and a 10-year survival of 86–95%. Previous echocardiographic evaluation of right ventricular dimensions in children and adolescents showed a decrease in end-diastolic volume and end-systolic volume after pulmonary valve replacement. However, in adults, radionuclide angiography measurements showed no effects of pulmonary valve replacement on right ventricular volumes and ejection fraction. To date, CMR is the gold standard for evaluation of right ventricular volumes and quantification of the degree of pulmonary and tricuspid regurgitation. There are distinct advantages of CMR over other imaging modalities in that CMR is independent of geometrical assumptions for evaluation of right ventricular volumes,mass, and function.Moreover, the unlimited field of view of CMR permits extensive evaluation of other right ventricular abnormalities such as aneurysms of the right ventricular outflow tract and regional right ventricular wall motion abnormalities. In a previous study by Vliegen et al., CMR was used in 26 adult Fallot patients (mean age 29 years) with pulmonary regurgitation and right ventricular dilatation to assess right ventricular functional parameters. Patients underwent CMR imaging with a median of 5 months before and 7 months after pulmonary valve replacement, and the authors observed a remarkable haemodynamic improvement in right ventricular function; right ventricular end-systolic and end-diastolic volumes decreased and right ventricular ejection fraction increased from 25 to 43%. For the first time, improvement of right ventricular function after pulmonary valve replacement was observed using CMR data. On the basis of these findings, accurate assessment of right ventricular volumes assisted in better timing of pulmonary valve replacement. The authors recommended a more liberal policy in pulmonary valve replacement in Fallot patients with pulmonary regurgitation and right ventricular dilatation. Valsangiacomo Büchel et al. studied 20 children (mean age 14 years) with tetralogy of Fallot and severe pulmonary regurgitation with right ventricular dilatation using CMR, 6 months before and 6 months after pulmonary valve replacement. The authors clearly showed that early pulmonary valve replacement resulted in beneficial remodelling of the right ventricle. Following pulmonary valve replacement, right ventricular volumes decreased and right ventricular mass showed a reduction from a mean of 49 to 36 g/m. Careful analysis showed that normalization of right ventricular function and mass by pulmonary valve replacement was largely dependent on the pre-existing right ventricular end-diastolic volume. Prompt remodelling of the right ventricle occurred when the right ventricular end-diastolic volume exceeded 150 mL/m, and the authors concluded that a cut-off level of 150 mL/m should be used as a practical guide to advocate valve surgery. In line with the findings by Vliegen et al., CMR may therefore usefully assist in better timing of pulmonary valve replacement in Fallot