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Figure 1 Identifying Tachycardia P or F Waves From Underlying ECG T Waves
The top panel shows sinus rhythm, and the lower panel tachycardia in the same patient. The RR and QT intervals are identified in each. Linear scaling from the sinus beat (top) was used to generate an "expected" T-wave at the tachycardia RR. This was compared to the actual tachycardia T-wave with superimposed P waves. The first derivative (dV/dt), shown for the X-lead, helped identify P (or F)-wave onset and offset (vertical arrows). Here, P-wave duration (3-axis mean) = 129 ± 17 ms. AT = atrial tachycardia; CL = cycle length; ECG = electrocardiogram.
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