Rationale and Design of an International Multicenter Registry of Patients With Repaired Tetralogy of Fallot to Define Risk Factors for Late Adverse Outcomes: The INDICATOR Cohort

Although early survival after tetralogy of Fallot (TOF) repair in the modern era is excellent, studies on late outcomes have shown increasing rates of mortality and morbidity. Despite multiple publications on factors associated with late complications, risk factors for major outcomes (death and sustained ventricular tachycardia [VT]) remain poorly defined. Consequently, the International Multicenter TOF Registry (INDICATOR) was established. This article describes the development, structure, and goals of this registry and characterizes the initial cohort derived from four large congenital heart centers in the United States, Canada, and Europe. A data coordinating center with a core cardiac magnetic resonance (CMR) laboratory and statistical core was established. Subjects with repaired TOF who had CMR imaging performed between 1997 and 2010 and ≥1 year follow-up were included. Clinical end points were death and sustained VT. Demographic, electrophysiologic, exercise, and outcome data were collected. A total of 873 subjects fulfilled inclusion criteria (median age at repair 2.9 years and at CMR imaging 22.8 years). Of these, 9 % had QRS duration >180 ms on electrocardiogram (ECG). On CMR imaging, 38 % had severe right-ventricular (RV) dilatation (≥160 mL/m²), and 6 % had severe RV dysfunction (ejection fraction < 35 %). Of the 551 subjects with exercise testing available, 28 % had severely decreased exercise capacity with <50 % predicted peak oxygen consumption. The INDICATOR cohort allows robust statistical analysis to evaluate major clinical outcomes in patients with repaired TOF. Continued follow-up and further expansion of the registry may provide new insights into innovative therapeutic strategies to improve late outcomes.