Listera cordata var. nephrophylla is the common variety of this species in our area, larger than the other variety, Listera cordata var. cordata. It is known as the Western Heart-leaved Twayblade and does indeed have heart-shaped leaves. This is the ordinary form with green-colored flowers, but there is another form also with reddish-purple flowers. The plant is from three to six inches (8-15 cm) tall and the tiny flowers are only a few centimeters in size. They have an unusual lip that is deeply cleft and the flowers are almost always found with the ovary already swelling and developing which may indicate that they are self-pollinating (cleistogamous).
Note: there is a reddish form of this species, in our experience about as common as the green-stemmed and green-flowered form. I've included those pictures in a separate post, published quite a bit earlier: http://nativeorchidsofthepacificnorthwest.blogspot.com/2014/05/listera-cordata-var-nephrophylla-fma.html