Table 1 Action potential–induced global cytosolic Ca2+ transient cycle lengths and local Ca2+ release characteristics in human SANCs.

Data were from 20 single SANCs isolated from four hearts (three male, one female). *P < 0.05, compared to baseline by two-tailed paired t test. CaT CL, Ca2+ transient cycle length; NA, not applicable.

nCaT CL (ms)LCR ensemble (μm2/10 ms)LCR period (ms)
Baselineβ-AR
stimulation
Baselineβ-AR
stimulation
Baselineβ-AR
stimulation
Firing SANCs121676 ± 241971 ± 234*15.9 ± 4.228.1 ± 3.7*870 ± 126530 ± 129*
Arrested SANCs
(responder)
4NA3328 ± 111022 ± 339 ± 10*NA1432 ± 528
Arrested SANCs
(nonresponder)
4NANA11 ± 53 ± 3NANA