Cardiac Sympathetic and Parasympathetic Nerves

(From Meek S, Morris F. Introduction. I—leads, rate, rhythm, and cardiac axis. BMJ. 2002;324[7334]:415-418.)

In the normal heart, the electrical axis is approximately 59 degrees (A). Left axis deviation shifts the electrical axis to less than 0 degrees (B); right axis deviation is associated with an electrical axis of greater than 100 degrees.