A diagnostic EKG showing sinus rhythm indicates that this EKG is a normal EKG and that sinus rhythm is a normal heart rhythm. Sinus rhythm refers to the rhythm of the heart that results from impulses emanating from the sinus node. The sinus node is a small node located in the right atrium, the “high command” of the heart, which automatically and rhythmically generates electrical signals, or “command signals”. Once the electrical signal is sent, it travels along the heart’s electrical conduction system to the right and left atria, causing the atria to contract, and then the electrical signal travels through the AV node to the right and left ventricles, causing the right and left ventricles to contract. It is under the orderly command of this system that the heart can work in coordination to accomplish the work of supplying blood to the whole body. If every electrical signal recorded on the ECG is initiated by the sinoatrial node, it is called “sinus rhythm”, and therefore, a normal heartbeat should be sinus rhythm.