The Heart is the Self
Ramana Maharshi taught that the Heart is not the physical heart, but the spiritual Heart, which is the Self. It is the source of the 'I' thought and the abode of the Self.
When Ramana Maharshi spoke of the Heart, he was not referring to the physical heart, but to the spiritual Heart, which is the Self. The Heart is the source of the "I" thought and the abode of the Self. It is located on the right side of the chest, not the left where the physical heart is.
The practice of self-inquiry leads one to the Heart. As one traces the "I" thought back to its source, one is led to the Heart, where the "I" thought merges into the Self. This is not a physical location, but a spiritual center of consciousness.
Abiding in the Heart is abiding in the Self. When one is established in the Heart, one is established in the Self. This is the goal of all spiritual practice - to abide in the Heart, which is the Self.