The Aztec headdress worn by Erik Estrada was originally used in the 1947 movie Captain from Castile (1947), worn by the Aztec ambassador Cacamatzin.
Generally, Aztec and Maya human sacrifices were captured warriors from neighboring cities or losers of the sacred ball game played before religious ceremonies to choose sacrifice victims. Sacrifices were performed to guarantee that the gods would continue to send rain, make the sun rise every day and guarantee fertility and a good harvest.
Whether by coincidence or design, this episode where murder victims had their hearts cut out was first aired on Feb 14, Valentine's Day; a holiday known for "hearts".
This episode was combined with episode Demon in Lace (1975) to make the "movie" Kolchak: Demon and the Mummy (1975).
Erik Estrada would soon star in the TV series CHiPS, also produced by Cy Chermak.