Introduction The electrocardiogram (ECG) records the flow of electrical impulses throughout the heart Electrical currents flow from negatively charged areas to positively charged areas login to view 5 more bullets C1: Snapshot: Y C2: Content/grammar: Y C3: Images/Videos: N C4: Questions: Y C5: References: N ECG Lead Reference There are 6 limb leads and 6 chest lead, which comprise the 12-lead ECG login to view 7 more bullets Conduction Pathway Depolarization normally begins at the sinoatrial (SA) node login to view 1 more bullet Depolarization from the SA node spreads to the right and left atria After the right and left atria, the wave of depolarization reaches the atrioventricular (AV) node login to view 1 more bullet The impulse then goes to the bundle of His and then the right and left Purkinje fibers Pacemaker rates login to view 1 more bullet Speed of transmission login to view 1 more bullet ECG And Conduction Pathway ECG Basics ECG Finding Information P wave Represents atrial depolarization PR interval Represents the time from the start of atrial depolarization to the start of ventricular depolarization Normally < 200 msec QRS complex Represents ventricular depolarization Normally < 120 msec ST segment Represents an isoelectric point in ventricular depolarization Correlates with phase 2 (plateau) of ventricular action potential T wave Represents ventricular repolarization Becomes peaked in hyperkalemia and flattened in hypokalemia U wave Believed to represent ventricular repolarization but during the late phaseBecomes prominent in hypokalemia J point The point between the end of the QRS complex and the beginning of the ST segment