Everyone knows what the symbol of the heart means , it means love.
God loves us with a human heart. Isn't that marvellous.
Jesus is fully human, he loves and desires our love as well.
The heart of Christ was wounded by the lance. His heart was broken physically as well as emotionally by his suffering. Remember as well as the physical pain Christ was betrayed by a kiss.
There is significance there.
The heart of Christ is symbolised to be on fire with love. The intensity of Christ's love turns to a white heat in the Holy Eucharist.
This feast day is to remind us as St Paul eloquently told us in the letter to the Romans- nothing can separate us from the Love of God