Isomerism means different arrangement. In most of us our heart is on the left of our chest, our spleen and stomach are on the left of our abdomen and our liver is on the right. In addition to this our heart has a left side (strong side) and a right side (flexible side) which are built and connected differently. In some people this process of putting some things on the left and others on the right was confused during development in the womb. This may result in unusual combinations such as having the heart in the wrong place or having two right sides of the heart (two flexible sides and no strong side). Sounds confusing, and it is but think of it like trying to build a car, if the garage send you two right sided headlights you might be able to put it together but it wont look or function quite right. Some parts are duplicated and others are missing completely. There are lots of possible combinations and your cardiologist will explain the meaning and implications of this for you.