A, Summary of electrocardiographic (ECG) data from 59 wild-type (WT) and 16 Tg(SCN5A-D1275N) fish at 1 year old. Different cut-offs of PP intervals were used to determine an episode of SA. B, Two wild-type (WT) fish and 3 Tg(SCN5A-D1275N) fish that were considered to have SA when 1.2 seconds was used as cut-off, but not if 1.6 seconds was used as cut-off, were further analyzed by reviewing the raw ECG. We considered WT fish 1 and 2 and Tg fish 2 as SA-positive, and others were not because of low frequency of long PP interval. An PP interval more than 1.5 seconds was recommended as a criterion to define SA in zebrafish. C, Representative SA episodes in a WT fish and a Tg(SCN5A-D1275N) fish. epm indicates episodes per minute.