Study to Evaluate Safety, Tolerability, Pharmacokinetics and Pharmacodynamics of LCZ696 Followed by a 52-week, Double-blind Study of LCZ696 Compared With Enalapril in Pediatric Patients With Heart Failure

This study consists of two parts (Part 1 and Part 2). The purpose of Part 1 is to evaluate the way the body absorbs, distributes, metabolizes and removes the drug LCZ696. This will help determine the proper dose of LCZ696 for Part 2 of the study. The purpose for Part 2 is to compare the effectiveness and safety of LCZ696 with enalapril in a double-blind manner, in pediatric heart failure patients over 52 weeks of treatment.