Would growing a big heart make the Grinch strong?

In the classic Dr. Seuss tale, How the Grinch Stole Christmas, the Grinch starts out with a heart “two sizes too small.” This grump lives alone on a mountain with only his dog, Max. Annoyed by his neighbors’ Christmas celebrations, the Grinch disguises himself as Santa Claus and steals all the Whos’ toys, food and decorations.

Poised to throw it all off a mountain, he stops when he hears joyful singing from Whoville. His heart fills, and “they say that the Grinch’s small heart grew three sizes that day.” That gave the Grinch “the strength of 10 Grinches plus two,” says the 1966 movie of the same name. He pulls the stolen goods back from the brink and returns everything.

Would a too-small heart make you grumpy like the Grinch? And what would happen if your heart went from too small to really big in an instant? The answer depends on what causes the heart to shrink or swell, experts say. And whether or not you are a snake.