Functional assessment of cardiac performance in the developing zebrafish heart.(a) Representative velocimetry and acceleration profiles from Danio rerio embryos and larvae during development. (b-h) Cardiovascular parameters measured at 1, 2, 4 and 5 days post-fertilization from a single zebrafish (dotted line with triangles) and a population average (solid line with squares). (b) Peak velocity, (c) minimum velocity, (d) peak acceleration, (e) peak deceleration, (f) heart rate (no error bars are present for the single fish measurement because beat-to-beat variability is not calculated), (g) stroke volume, and (h) cardiac output. Single-fish data presented are the average obtained by analyzing four to six individual heart beats. Error bars are the SEM and represent intrafish variability. For population average data n = 5 for days 1, 2, and 4; n = 4 for day 5. Error bars are the SEM and represent interfish variability. Laser-Scanning Velocimetry Data Analyzer smoothing parameters used for trace, velocity, and acceleration smoothing were 5, 10, and 20, respectively.