Surface ECG
The surface ECG gives the outside view of cardiac activation. In EP, it becomes even more useful when paired with intracardiac timing.
A systematic first pass
1. Rate & regularity
Establish atrial and ventricular rates and whether each is regular.
2. Atrial activity
Look for P waves or other atrial activity and ask how it relates to the QRS.
3. Ventricular activation
Assess QRS width and morphology, then relate it to atrial timing and rhythm mechanism.
Core components
The P wave represents atrial depolarization, the QRS complex represents ventricular depolarization, and the T wave reflects ventricular repolarization. Intervals provide timing information, but interpretation always depends on the clinical and rhythm context.
EP connection
A surface tracing can suggest a mechanism; intracardiac electrograms and pacing maneuvers help test that hypothesis.
Learning objectives
ECG pattern practice
Question 1
Before deciding whether a narrow-complex tachycardia is AVNRT, AVRT or atrial tachycardia, which first step is most useful?
Question 2
Which surface ECG component represents ventricular depolarization?
Trusted resources
Laboratory processes, protocols, equipment, personnel, safety and quality.
Open HRS resource →
Recommended reading and competency topics for invasive electrophysiology.
Open ESC resource →
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