"if sustained" is a correct and usable phrase in written English.
You can use it in the same context as "if continued". For example, "If sustained, our efforts in this project will bring us great success."
"Little and often, if sustained, is the best way forward.
Higher yields, if sustained, will mean costlier home mortgage rates.
If sustained, this will be a huge change.
A sub-$40 price, if sustained over many years, could have worked.
If sustained job growth has indeed arrived, why did it take so long?
Such a rate, if sustained, is considered strong enough to spur hiring.
The sharp rise in energy prices, if sustained, is worrisome in this regard.
The family challenge highlights that simple swaps could lead to big changes if sustained over time".
If sustained, that equates to 250,000 fewer British visits this year.
The collective fiscal tightening, if sustained, could push the economy into recession.
The recent fall, if sustained, lowers its import bill by $60 billion, or 3%.
