This mantra comes from the Yoga Sutras, Book 2, verse 35

Hridaye means on the heart

Citta is consciousness

Samvritta means knowledge, awareness

By focusing and holding concentration on the region of the heart, the yogi acquires a thorough knowledge of the contents and tendencies of consciousness.

“The citadel of purusha (consciousness) is the heart.  It is the anahata chakra (heart chakra) the seat of pure knowledge as well as consciousness.  By focusing and holding concentration there a yogi can become aware of consciousness and of true, pure knowledge.  He learns to unfold and tap the source of his being, and identify himself with the Supreme.”  - from Light on the Yoga Sutras of Patanjali by B.K.S. Iyengar.

I hope you enjoy watching this video.  It comes from the Iyengar yoga conference of 2016 in Boca Raton, Florida.  It features 3 of the top Iyengar yoga teachers in the US.  Their devotion in performing a series of back bends is very inspirational!  Near the end of the video, at 15:25, they do this chant.