A current carrying conductor placed (perpendicularly) in a magnetic field will experience a magnetic force. (F=BIL)
Most of the action is taking place at the bottom of the heart near the magnet. The right half of the heart experiences a magnetic force into the screen, whereas the left half of the heart experiences a magnetic force out of the screen. These two forces form a couple which rotates the heart in an anti-clockwise direction (seen from the top).