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Figure 4 A single extra stimulus at RSPV 3–4 during AG stimulation initiated a short run of AT. Traces from the top: electrocardiogram leads II and aVR; a His bundle recording (Hb); right atrial electrogram (RA); multi-electrode catheter extending from the AG toward the superior vena cava (SVC D2 7–8); pacing site from the second pair of electrodes on the RSPV (3–4); multi-electrode catheter extending from the AG toward the right atrial appendage (RA D-27–8); arterial blood pressure (BP). (A) AG stimulation at 4 V slowed the heart rate from 126 to 99/min (not shown). The last S1-S1 interval is shown followed by a single atrial premature depolarization (APD) (S1-S2 = 120 ms), which induced a short run of AT. The cycle length of the AT progressively slowed (cycle length 98, 106, 110, and 124 ms) before terminating. (B) Initiation and maintenance of AF during AG stimulation by a single APD at the same S1-S2 coupling, 120 ms, as in A. Autonomic ganglia stimulation at 7 V induced heart rate slowing from 132 to 81/min (not shown). A single APD S1-S2-120 ms now initiated AF, which was associated with complex fractionated electrograms (SVC 5–6; RA 3–4; boxed areas). This type of electrogram was seen in all episodes of induced AF at one or more sites. When AG stimulation stopped, the electrograms invariably showed restoration of discrete potentials with isoelectric intervals before termination. Autonomic ganglia stimuli have been reduced in order to clearly differentiate the electrograms from the AG stimulus artifacts. Other abbreviations as in Figures 1 and 2.
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