If you google the phrase “kidney transplant romance,” you'll find an entire page of books on Amazon.com devoted solely to kidney transplant romance novels. I am not even making this up. Similarly, if you google the phrase “heart transplant romance” you'll find the Amazon page for heart transplant romance novels, such as “A Valentine Heart” by M. Latron:
"George Valentine thought he could live forever on love alone. The day he died he gave his heart to another man who was in desperate need. Little did George know that he would be giving Ernest Harper more than just his heart, and that his wife Amy would finally find a way to heal."