West's pass to 4♠ makes no sense to me. It was obvious East was looking for heart control. The pass was motivated solely by tactical considerations (a small loss would see the pair through - the important was to avoid large swings). With the diamond ace and spade queen onside, West made all 13 tricks.
This lack of killer instinct cost 5 imps, when 8 imps were up for grabs

Help

West East
1♦ 1♥
1♠ 2♣
3♦ 3♠
4♣ 4♠
pass(??)