The titular spinning heart is introduced in Chapter 1:

There’s a red metal heart in the centre of the low front gate, skewered on a rotating hinge. It’s flaking now; the red is nearly gone. It needs to be scraped and sanded and painted and oiled. It still spins in the wind, though. I can hear it creak, creak, creak as I walk away. A flaking, creaking, spinning heart (9).

The other mention is in Chapter 3 when Lily says, “I hear the spinning heart on their gate, creaking slowly around. […] It puts me in mind of my own dry joints; my burning hip, my creaking knees” (31).

Presumably, the spinning heart was once a beautiful gate decoration, with shiny red paint and an effortless spin. However, after years of sitting unattended in the weather, it has succumbed to the effects of time. In the same way, the village was once vibrant—the economy was booming, the people had jobs and money, and there was a sense of hope. However, after the economic crash and the widespread loss of jobs, people have grown weary. The spinning heart reflects the forgotten, small rural village—it’s falling apart at the seams because people are leaving to find work, and the ones who are staying are too impoverished to help themselves.