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Tetralogy of Fallot (TOF) is one of the most common congenital heart disorders. The mortality rate reaches up to 50 % of untreated patients by the age of 6 years.. Although short-term outcomes of total repair with current procedures are excellent, the potential for late complications is an important concern for the growing number of post-repair survivors.
Long term sequelae following TOF repair include pulmonary regurgitation leading to progressive right ventricular dilatation and eventually right side heart failure, arrhythmia, residual RVOT obstruction, tricuspid regurgitation, and ventricular septal patch leak. These conditions may necessitate surgical intervention for management.
Indications for intervention after TOF repair, according to European Society of Cardiology (ESC) guidelines, can be summarized as follows:
Table (2): Indications for intervention after TOF repair, according to European Society of Cardiology (ESC)
Pulmonary valve replacement following TOF repair is indicated in the following conditions:
1. RV end-diastolic volume index ≥160 mL/m2
2. RV end-systolic volume index ≥70 mL/m2
3. LV end-diastolic volume index ≤65 mL/m2
4. RV ejection fraction ≤45%
5. RVOT aneurysm
6. Clinical criteria: exercise intolerance, symptoms and signs of heart failure, cardiac medications, syncope, sustained ventricular tachycardia.
There is strong evidence that elimination or significant reduction of pulmonary regurgitation is associated with symptomatic improvement, decrease in RV end-diastolic and end-systolic volumes. In addition, there is some evidence that indices of exercise tolerance improve.
Arrhythmia is potentially the most serious late complication following TOF repair. Nearly all types of arrhythmia can occur following TOF repair, namely, bradyarrhythmia, supraventricular arrhythmia, or ventricular arrhythmia. ICD implantation can be a useful option to prevent life threatening arrhythmias in patients with severe right ventricular dysfunction who have been resuscitated after ventricular fibrillation or who have had episodes of rapid sustained ventricular tachycardia in spite of chronic use of amiodarone. Also treatment of ventricular tachycardia, by means of cryoablation, following endocardial mapping, is being used with good results.
Although patients with combined RVOTO and PR had significantly smaller RV end-systolic and end diastolic volumes and higher RV mass compared with patients with isolated PR, combined RVOTO and PR is associated with reduced exercise capacity. Furthermore, PPG across the RVOT was the only independent predictor of exercise capacity. Re-intervention is indicated when PPG across RVOT is ≥64 mmHg regardless of symptoms.
During surgery for TOF repair, intra operative TEE should be done to assess residual RVOTO. IOE can differentiate dynamic from fixed RVOTO & can measure PG across RVOT. This is essential in decision making regarding to revise TOF repair intraoperatively or not. Revision is indicated only in case of fixed RVOTO and PPG ≥ 40 mm Hg.
Residual ventricular septal defect (VSD) requiring re-intervention is rare after tetralogy of Fallot total repair. Closure of these VSDs is indicated if associated with significant left to right shunt, or clinical symptoms. Significant VSD is described as being more than 2 mm or causing left to right shunt ≥ 30%. transcatheter closure has emerged as a safe and effective alternative to surgery in patients with native or post-operative residual VSD.
The outlook for patients with TOF has dramatically improved in the past decades, reflecting the evolution in treatment of all forms of congenital heart disease. Enthusiasm regarding the decreased operative mortality and the near-normal life expectancy for postrepair survivors, however, is tempered by remaining late morbidity and rare sudden death in the long term. Meticulous follow up and management is likely to change the future outcomes for post-repair survivors.