Hello,

" Scientists have modified human embryos to remove genetic mutations that cause heart failure in otherwise healthy young people in a landmark demonstration of the controversial procedure."

Source: from the Guardian


It’s a long sentence and I’d try to break it into two parts.
1) Scientists have modified human embryos to remove genetic mutations in a landmark demonstration of the controversial procedure.
2) The genetic mutations cause heart failure in otherwise healthy young people

So what does “otherwise” mean here?