If they are close to 4♠ then you don't want to force them to try it by calling 4♥ what you want to do is muddy up the waters enough so they are unsure that 4♠ is the right contract. So just bid 2♥ you have to hope this is sufficient noise for their 2 and 3 ♠ calls to have wide enough variance that they chicken out. At the same time you can't strap partner with a call where he can go wrong; the K♣ and 2 xtra ♥ make up for the insufficient HCP strength.