Appropriate shapes of an Electromagnet
A circular coil shape is the optimum use of wire to obtain the largest magnetic flux. Any deviation from a circle will use more wire for a given coil area and the extra coil resistance can reduce the peak current into the coil or, necessitate more power having to be delivered to the coil to obtain the same current.

There is a more subtle effect too. The magnetic field around the areas that form the V section in the heart will be significantly weaker because the wire will have to nip in and out sharply and the magnetic fields will tend to cancel at this point.

Having said all of that if you wind a circular coil and reshape the magnetic field into a heart shape by reshaping the iron this won't be such a problem.