The Inverness-born fly-half has spent the past three years playing for Aviva Premiership side Bath, during which time he earned three caps for Scotland.
His return north has caused him to delay his ambition of adding to that haul despite an intention to join up with the national team in time for the start of the North American leg of their tour. That will begin with a match against the United States on Saturday but Heathcote is now not expected to report for international duty until later matches with Argentina in Cordoba and South Africa in Port Elizabeth.
The 22-year-old will miss the games and the US and also Canada a week later in Toronto. His absence from the first two matches has precipitated that Ruaridh Jackson - who is in the process of leaving Glasgow Warriors to sign for London Wasps - will feature in the first half of the trip.
"I'm really excited about the change and to have the chance to play in the PRO12 and European Challenge Cup," said Heathcote of his decision to sign for Edinburgh. "[Head coach] Alan Solomons has a really strong vision for the future. There are lots of good young players who are expected to develop under him, which I think will take the club from strength to strength over the next few years.
"From my point of view, I've had about three years of Premiership experience, but am still quite young. I'm sure I'll keep developing as a player in a team that will continue to improve in the coming seasons, especially as that core of young players gets more game time and experience."
Solomons has acknowledged that Heathcote is still a young player but expects him to make an immediate impact on the squad. "I expect him to make a valuable contribution straight away," said the coach.
"His arrival will certainly intensify the competition for places at pivot. At just 22, he also fits well with our increasingly promising group of young Scots at the club."