Electrical conduction and the ECG

First an electrical signal is generated by the heart’s own pacemaker, the sinoatrial node, which is located in the right atrium (one of the top chambers). This is then conducted down a pathway via the atrioventricular node to the main left and right ventricles (the main bottom chambers).  In a healthy state, this causes the heart to pump and blood is propelled to the lungs and other organs.  Various processes can modify this activity, for example exercise, adrenaline, various drugs, as well as disease states that can affect the conduction system.

The electrical signal can be represented as an ECG  or electrocardiogram.  The ‘P’ wave represents electrical conduction in the atria, the ‘QRS’ complex represents electrical conduction in the ventricles and the ‘T’ wave represents normalization of electrical current in the ventricles.