People with heart face shape have a pointy chin and wide forehead. Sunglasses which are too big or too wide framed will make your face outline more wide and you chin smaller. So you should avoid sunglasses with cocking frame on the upper. If you try small frames and polygon sunglasses will flatter you. Personally, I think small round frame may also suitable for you. As for the color, red make you feel powerful and confident, blue make you calm down and purple make you grace and elegant. Which kind of feeling are you seeking for?
The feature of heart-shaped face are near T shape, especially the chin raises in front obviously,the width of forehead slightly smaller than the zygoma, but greater than the mandible. To balance the proportions of heart shape face, choose shades that are wider at the bottom. The sunglasses of shapes with round edges look great on heart shaped faces and soften the broad upper part of the face. Colored frames and arms with strong detail will soften the lower portion of your face shape by accentuating the eye area. rimless frames, especially in light colors, are also a smart choice. They highlight your cheekbones and draw the eye away from a wide forehead.
People having a heart-shaped face should choose sunglasses that are of more delicate styles, such as wire or oversize plastic frames that will not draw attention to the forehead. Glasses with bottom-heavy frames that add width to lower face or narrow, round frames that soften the forehead will also flatter you. You are also required to choose styles with low-set temples to draw attention to downward. Do remember to avoid Top-heavy styles that draw attention upward and decorative temples that accentuate the broad upper face. There are some famous stars with heart shaped face like Jennifer Aniston, Halle Barry, David Spade. You may refer to their choice of sunglasses.