The ProShares Short Bitcoin Strategy ETF, which allows traders to bet on a fall in bitcoin futures, hit a record low on Tuesday as the cryptocurrency surged on growing optimism that the launch of an exchange-traded fund tracking bitcoin is imminent. Bitcoin, the world's largest cryptocurrency, hit an 18-month high on Tuesday, extending Monday's 10% surge, on speculation over the likely approval of a spot bitcoin ETF that was fueled by BlackRock's iShares ETF listing on the website of clearing house DTCC. The ProShares fund had hit its peak of $45.61 a little over a year ago as crypto assets tumbled following the collapse of FTX, but struggled to hold on to gains this year amid the sharp recovery in bitcoin.