A shift of the normal electrical vectors of the heart, seen sometimes as a result of conduction disease, enlargement of the chambers of the heart, obstructive lung disease, or other conditions.
In electrocardiography, the term is used to signify a change in the heart’s electrical axis based on its position. This change is described as either right or left axis deviation or shift, depending on whether the axis is less than 0 degrees or exceeds 90 degrees.