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Figure 5 Cardiac nerve stimulation (PS) in the SVC. Surface ECG leads I, II and aVF and a recording of the stimuli (stim) delivered to the basket catheter are depicted. Atrial fibrillation was induced and maintained by rapid pacing from the RAA at a cycle length of 100 ms (low frequency, low amplitude electrical artifacts). A vertical arrow in both panels indicates the onset of PS. At a PS intensity of 13 V, the shortest R-R interval during AF prolonged from 352 ms to 384 ms and the longest R-R interval from 408 to 1464 ms (panel A). Increasing the stimulus amplitude to 22 V led to an even greater increase of the R-R intervals (shortest: 272 ms to 1,008 ms; longest: 380 ms to 2,336 ms) as illustrated in panel B. AF = atrial fibrillation; PS = parasympathetic stimulation; RAA = right atrial appendage; R-R = ventricular rate; stim = stimuli; SVC = superior vena cava.