Late arrhythmia in patients with repaired tetralogy of Fallot: who is at risk?

Tetralogy of Fallot (TOF) is the most common cause of cyanotic congenital heart defect. Over the last century, the life expectancy of TOF patients has significantly improved. This, however, has brought new challenges both to patients and their health-care providers, the main of them being late arrhythmia. Ironically, late arrhythmia is predominantly generated due to the fibrotic scars caused by the life-saving surgical repair. Once the first two mainly arrhythmia-free decades after the repair pass, the risk of developing late arrhythmia and, therefore, SCD becomes substantial. Consequently, young adults with repaired Tetralogy of Fallot (rTOF) require careful outpatient monitoring.

There have been many attempts to predict the risk of life-threatening arrhythmia in rTOF patients. This has led to the defining of various risk factors, ranging from the widely used QRS prolongation to novel predictors, derived from cardiac magnetic resonance (CMR) based anatomical findings (left ventricular dyssynchrony indexes, right ventricular output tract akinetic length, right ventricular mass-to-volume ratio). The latter predictors have recently established CMR as a tool of high significance in evaluation of rTOF patients.

Although the role of Holter monitoring findings in rTOF patient-assessment remains unclear, it may be useful in those who are 25 years and older. Implantable cardioverter–defibrillator (ICD) implantation is the first-line treatment for secondary prevention of sudden cardiac death (SCD). rTOF patients suffer from the highest rate of inappropriate and the lowest rate of appropriate ICD shocks, when compared to other congenital heart diseases. As a consequence, ICD implantation for primary SCD prevention should be carefully weighed. Catheter-based ablation therapy leads to high rate of initial success when abolishing monomorphic ventricular tachycardia and intra-atrial reentrant tachycardia, however recurrence rates remain high.