Tetralogy of Fallot (TOF) is the most common and best studied of the various forms of complex congenital heart diseases. It is characterised by a malaligned ventricular septal defect (VSD), aortic over-ride, right ventricular (RV) outflow tract obstruction and resulting hypertrophy of the right ventricle. Since the era of infant surgery for the correction of congenital heart disease, the repair of TOF represents one of the great success stories in the treatment of congenital heart disease. The 30-year survival for patients with repaired TOF (rTOF) approaches 90%.1 Despite this unequivocal success, it was recognised, as early as the 1970s, that a subset of patients with TOF was dying suddenly. To a great extent, the research focus in TOF has since been to identify those few patients at risk of dying suddenly and to figure out what to do about it. Until relatively recently, the primary manner of addressing this issue has been observational clinical studies.2 Despite decades of study in this manner, however, our understanding of the problem and our ability to identify those at risk remain incomplete.

Dr Benoist et al3 show us an important new direction in congenital heart disease research—the movement from observational clinical study towards a basic science approach. In this study, the researchers simulate repaired TOF physiology in a pig model by inducing pulmonary insufficiency (PI) and RV outflow tract obstruction. The pigs (rTOF) were then allowed to mature for almost 6 months, at which time a series of tests were performed to characterise the degree and nature of the cardiac remodelling that had occurred. Compared with sham-operated animals, conventional MRI of rTOF pigs demonstrated an increase in both end-systolic and end-diastolic RV volumes, and moderate RV dysfunction. Detailed characterisation of RV action potential duration by optical mapping …