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Figure 1 (A) Short runs of self-limited uniform atrial tachycardia recorded at rest in an asymptomatic 60-year-old man. Note that the atrial ectopic salvos are separated by sinus node pauses of 1010 ms. (B) Relationship between atrial ectopic activity and sinus node cycle length. After a mild exercise, with sinus node cycle lengths between 630 and 670 ms, no ectopic atrial beats are recorded. A slight increase of the sinus node cycle length to 680 ms causes the appearance of a single premature atrial beat. Post-extrasystolic sinus node pauses of 750 and 810 ms are also followed by single atrial extrasystoles (arrows), while a slightly longer pause (830 ms) triggers repetitive atrial discharges.
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