The heart in a dream often stands in directly for emotion and love -- how open, guarded, or full your feelings currently are. A racing or aching heart can point to intense emotion you haven't fully processed, while a calm, strong heartbeat often reflects genuine vitality and emotional steadiness.
Mercury in the sixth house of a nativity, the native shall change from one religion to another, & will have his felicity in part impedited by reason of his inconstancy. - William Lilly (1602.-1681.)