Electrocardiographic and genetic evaluation of giant jungle fowl, broilers, and their reciprocal crosses following unilateral bronchus occlusion

Electrocardiography is useful as a noninvasive technique for detecting righ t ventricular hypertrophy in birds developing pulmonary hypertension (PH) a nd pulmonary hypertension syndrome (PHS, ascites). The objective of this st udy was to identify every aspect of the Lead Il ECG wave form (amplitude or duration) that can be correlated with right ventricular hypertrophy [incre ased right:total ventricular weight ratios (RV:TV)] indicative of PH across a broad genetic background. Sham operations were conducted, or PH was indu ced by occluding one extrapulmonary primary bronchus in 14-d-old chicks pro duced from matings of broilers (B x B), Giant Jungle Fowl (J x J), and thei r reciprocal crosses (B x J and J x B). Standard three-lead electrocardiogr ams (ECG) were recorded on Days 28 and 42, and final necropsies were conduc ted to evaluate the incidence of ascites, confirm sex, and obtain ventricul ar weights for calculating RV:TV. Ascites did not develop in the J x J, and one each of the B x J and J x B chicks developed ascites; consequently, on ly data from birds that did not develop ascites were compared. Heart rate w as recorded, and the following amplitudes and durations were measured or ca lculated for three consecutive wave cycles of the Lead II EGG: base of R to the peak of R (RbR), peak of R to base of S (RS), base of S to peak of R' (SR'), S, peak of R' to base of R' (R'R'(b)), and base of S to peak of T (S T). Differences between the ECG of sham and bronchus clamp groups were more prominent in B x B and B x J than in J x B, and bronchus occlusion did not affect the EGG, growth, or RV:TV ratios of J x J. In contrast, sex influen ces were more prominent in J x J and J x B than in B x J and B x B. These o bservations suggest a paternal pattern of inheritance for Lead II ECG wave forms, with crosses sired by broilers (B x B, B x J) exhibiting susceptibil ity to PH and few ECG differences related to sex, whereas crosses sired by Giant Jungle Fowl (J x J, J x B) exhibited resistance to PH and numerous EC G differences related to sex.