(Reuters) - Troubled UAE hospital operation NMC Health said on Tuesday it had debt of $6.6 billion (5.6 billion pounds), much higher than earlier estimates, and it appointed a former PwC partner as chief restructuring officer to tackle the problem.The company, which has been in crisis since U.S. firm Muddy Waters' short attack, revised its debt position from $5 billion earlier in March, and named Matthew J. Wilde as chief restructuring officer. (https://reut.rs/2WLiQQF)