The carved wooden hearts are decorated with milagros, folk art charms which are used in the Americas and whose use can be traced back through Spanish explorers and missionaries to ancient Iberians. Traditionally offered to a symbol of a saint in gratitude for an answered prayer or a reminder of the petitioner’s particular needs. The symbolism is not universal – a heart charm could represent a heart condition or a romance.
Depending on your beliefs, I suppose the use of the milagros as decorative items may have corrupted their original intent.
Santa Fe, New Mexico