Jill K. Berry says the heart map project in her Personal Geographies: Explorations in Mixed-Media Mapmaking was inspired by cordiform maps of the 16th Century and later. (See “Covenant and Liturgy” as well as subsequent posts.)
a tiny bit of background —
In most common maps meridians, lines of longitude, are straight. When meridians are curved, instead, the result is a “cordiform,” or heart-shaped, map. (Read more on pseudoconic projections here.)
Geo Lounge notes that such maps were used in the Renaissance era, and that this was “closely tied to the concept of inner emotions affecting the physical world.” (Citation: Jerry Brotton. A history of the world in twelve maps. New York: Viking, 2013)
Here’s a lovely contemporary example, shared with Creative Commons license:

“The world on Werner projection. 15° graticule. Imagery is a derivative of NASA’s Blue Marble summer month composite with oceans lightened to enhance legibility and contrast. Image created with the Geocart map projection software.”
Look for more on heart maps as “type your heart out” month continues.
NaBloPoMo NOTE: “A Song Every Day” signed up for National Blog Posting Month, a commitment to daily posting for the month of November. Circumstances intervened on some dates. This post is hereby declared, by way of catching up, the official post of November 6.