Ventricular activation pattern in ectothermic vertebrates investigated by optical mapping(OP), ECG(ECG), electrodes(E) or markers (M).

In the formed hearts of mammals and birds, epicardial ventricular activation is from apex to base.1Left-to-right activation is only reported in broad-hearted turtles.2Arbel et al (1977) using ventrally placed electrodes find that as the apex becomes activated the current spreads towards the base. As they could not evaluate if the base was activated earlier, and since the zebrafish outflow region is indeed activated later than the apex their results may be in agreement with the present study.*Species where first point of activation definitely was neither base nor apex. From [33], [59]–[81].