Electrophysiology study (EPS) tracing showing atrial tachycardia onset and termination

From top to bottom, surface ECG leads I, II, III, and VI and intracardiac recordings in the high right atrium (2 leads) and His bundle, obtained during electrophysiologic study performed in a 79-year-old with an incessant atrial tachycardia with a rate of 130 beats per minute. This figure shows that a tachychycardia similar to the spontaneous tachycardia could be induced using programmed electrical stimulation with one stimulus (St) and terminated with one stimulus, which favors a reentrant mechanism. This tachycardia was successfully ablated by detecting the earliest atrial activation in reference to the onset or the P wave on the surface ECG. Note during the tachycardia that the QRS complexes are preceded (lead II) by a P wave with a configuration different of that of the sinus P wave (last beat).