Meeting Abstract

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 afpac1@uaa.alaska.edu

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 s1) 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.