14.6 Jan. 4 A Novel Assessment of Hemodynamics in the Intact Trout Heart COTTER, P/A; EVERSON, J/J; RODNICK, K/J*; Univ. of Alaska Anchorage; Diagnostic Imaging of Idaho; Idaho State University email@example.com
For the first time, we used simultaneous electrocardiography and echocardiography to characterize hemodynamics of the salmonid heart in vivo. We determined timing patterns of the cardiac cycle; characterized systolic function; and measured flow dynamics through all cardiac valves in tricaine-anesthetized, sexually immature and mature, male and female rainbow trout in freshwater. At 14°C and 32-91 bpm, atrial filling, ventricle filling, and ventricular ejection time (ET) accounted for 43-87%, 14-27%, and 23-44% of the cardiac cycle, respectively. Ventricular ejection occurred entirely during atrial filling and ended prior to the T-wave. At similar heart rates, trout QT intervals were 57% longer than normal human QT intervals, and longer than electromechanical systole (QS2), a finding not observed in mammals. QS2, ET, S1S2(mechanical systole), and PEP (pre-ejection period) were positively related to MV and cardiac cycle length. PEP/ET was independent of MV and cardiac cycle length, suggesting that enlarged ventricles of sexually mature male trout maintain functional capabilities. Sinoatrial flow was of longer duration (0.54 ± 0.03 s) and lower velocity (30.7 ± 2.2 cm s-1) than atrioventricular (AV, 0.19 ± 0.01 s; 83.7 ± 8.2 cm s-1) and ventriculobulbar (VB, 0.30 ± 0.01 s; 64.5 ± 4.5 cm s–1) values. Within each heart, AV and VB valve dimensions were the same (~ 5.5 mm2); velocity and flow duration differences accounted for equal flow volume. In summary, we 1) provide evidence that trout compensate for maturation-associated hypertension and hypervolemia, 2) highlight functional differences between salmonid and mammalian hearts and 3) establish new reference data for cardiac electromechanical coupling in teleosts.