Mechanisms of mortality in embryos with persistent truncus arteriosus

Purpose: Early incubation neural crest ablated (EXP)chick embryos to develop persistent truncus arteriosus (PTA), and have high in ovo mortality. We assessed hemodynamics in mid incubation embryos with PTA, using echocardiography. Methods: We evaluated 10 to 18 day EXP (n=84)and CON (n=76) embryos. The intra and inter observer variabilities of left ventricular dimensions, cardiac output, stroke volume, andheart rate averaged 10 and 12 %. Embryos of these ages were compared using 2-way ANOV. Results: In both CON and EXP hearts, there was approximately a 65% increase in ascendingaortic (AAo) blood flow and stroke volume from 10 to 18 days of incubation (p<0.001). Heart rate, cardiac output, stroke volume and LV end diastolic volume were equal in CON and EXP embryos. Left ventricular (LV) diastolic and area in the four chamber view (0.12 ± 0.08 cm², CON; 0.11 ± 0.06 EXP) were equal in the two groups. LV systolic length and area (0.042 ± 0.011 cm², CON; 0.062±0.012, EXP) were significantly higher in EXP embryos (p≤0.05). LV area ejection fraction (68.3 ± 11%, CON; 45.0 ± 14 %, EXP, p≤0.0001) and Stepson's rule volume ejection fraction (LWEF) (81.9 ± 8 %, CON; 58.0 ± 12 %, EXP, p≤0.0001) were both significantly decreased in EXP embryos. LWEF was the same for CON and EXP embryos without PTA. The incidence of pericardialeffusion and significant tricuspid regurgitation increased from 15 % at 12 daysto 80% at 18 days. Conclusion: Left ventricular function is markedly depressed in neural crest ablated chick embryos, in the absence of significant left ventricular volume overload. As incubational ageincreases, signs of hemodynamic compromise and congestive heart failure become more frequent and more prominent.