1♦ -  1♥ is a straightforward opening but then East has a dilemma. I prefer a 1♠ rebid to 3♦ because West has not denied four Spades at this stage although there is slight risk because 1♠ is not forcing.

When West bids 3NT over 1♠ suggesting a Losing Trick Count of 7 then East (with a losing trick count of 5) knows slam may be on. It is notoriously difficult to check for Aces when you have a void so West may as well bid 6♦ .

6♦ is an easy make. East wins whatever is led in hand. Draws trumps. Plays ♥ A and another Heart, overtaking in Dummy and continuing Hearts until the ♥ K appears.