PMC5412638_01
Programmed atrial stimulation was performed on the fifth day after implantation. The basic stimuli (S1) cycle length was 600 milliseconds, and one atrial extrastimulus (S2) was delivered 1714 milliseconds to 250 milliseconds after S1. When the S1-S2 interval was 1714 milliseconds (35 bpm), S2 was captured with reproducibility. When the S1-S2 interval ranged from 1500 milliseconds (40 bpm) to 750 milliseconds (80 bpm), S2 did not capture the atrium. When the S1-S2 interval ranged from 706 milliseconds (85 bpm) to 260 milliseconds, S2 captured the atrium. When the S1-S2 interval was <= 250 milliseconds, S2 did not capture the atrium (atrial effective refractory period = 260 milliseconds). The "noncapture range" lay between 1500 milliseconds and 750 milliseconds.
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Programmed atrial stimulation was performed 1 month after implantation. The S2 stimulus failed to capture the atrium only when the S1-S2 interval was 1000 milliseconds. The "noncapture range" was clearly reduced.
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The S2 stimulus did not capture the atrium only when the S1-S2 interval was 1000 milliseconds (60 bpm) (Figure 2).
PMC5412638_02
PMC5412638_03