It’s hard to say exactly what would happen if you had three hearts and one of them stopped. Humans, like cats, have just one heart, so we have no experience with this. Octopuses, on the other hand, do have three hearts.
When I called my friend Kirt Onthank, an alumnus in biology from Washington State University who studies how octopus bodies work, he told me all about the three hearts. Before becoming a professor at Walla Walla University, he also studied biology here at WSU.
Onthank says the answer to your question depends on which of an octopus’s three hearts stops working. Octopuses have two types of hearts. Two of them are called branchial hearts and one is called a systemic heart.
Each branchial heart sits right next to each of the octopus’s gills. The branchial heart pumps blood through the gills and after the blood leaves the gills, the single systemic heart pumps it to the rest of the body.
“The branchial hearts kind of work like the right side of your heart, pumping blood to the lungs, and the systemic heart works like the left side of your heart, pumping blood to the rest of the body,” Onthank says.