At favorable vulnerability, North might not pass South’s 1
opening.
In strong club systems, North knows that EW have the values for game and that South isn’t strong enough to punish North for responding, so North can respond 1NT or 2 without much to fear, and some enterprising souls might even try a psychic 1
.
In other five-card major systems, North will consider a forcing or semi-forcing 1NT response, planning to show a weak hand with heart support or tolerance. It will be interesting to see how these light responses will affect EW’s ability to reach any game, and the optimum 4 in particular. There are 1 1 tricks in spades with normal play, while 3NT can be held to nine tricks legitimately on a heart lead, and then only if declarer knocks out the 
A and plays diamonds for three tricks without playing on spades.
If North passes 1, East will double, and where South passes West will choose from among 1, 2 and 1NT.
East might devalue his heart holding and downgrade his slow hand enough to pass 1, but more often will raise to 2 and West should drive to game. East will raise 2 to 4 and a 1NT response to 3NT, and it will be expensive to finish in the wrong strain.
Some South players will volunteer 2, hoping to avoid a double and steal some bidding space. While on this layout South is in no trouble, his aggressive action will simplify the auction for EW because West will bid 2 over 2 and East will drive to 4 whether or not North competes to 3.
The only realistic way that NS might come to three tricks in a spade contract is for North to lead club and for declarer to take the spade finesse and run into a club ruff, but with South marked with the K for his opening bid that would require inattentive play by declarer.
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