Your heart is responsible for your emotions and empathy. So, feeling with your heart apparently turned to be quite literal.
This is a nice poster describing the work.
Couto B, Salles A, Sedeño L, Peradejordi M, Barttfeld P, Canales-Johnson A, Dos Santos YV, Huepe D, Bekinschtein T, Sigman M, Favaloro R, Manes F, Ibanez A.
The man who feels two hearts: the different pathways of interoception.
Soc Cogn Affect Neurosci. 2013