My aunt has a simple heart.

我姑妈有一颗单纯的心。

youdao

"We estimate in WHO that over thirty million lives can be saved in the next ten years by simple measures -- reducing the level of salt by fifteen to twenty percent, reducing the amount of tobacco, and increasing the number of people who are at risk of a heart attack and stroke to be on simple preventive treatment."

VOA: special.2011.05.11

Lillehei solved that problem with cross-circulation, in which a donor, linked to the patient by plastic hose and a simple pump, acted as a living heart-lung machine.

FORBES: Brave heart

What he saw amounted to a bunch of awkward glances, so he came up with a simple gesture, involving a hand over the heart, which allows people to simply acknowledge those in uniform.

CNN: The power of gratitude, a year-round gift

In 1996, Acorn founder Cliff Alferness got the idea that something as simple as putting a sleeve over the heart could stop the heart's deterioration.

FORBES: Heart Failing? Put A Sock On It