Electrocardiographic evaluation of broilers following unilateral occlusionof an extrapulmonary primary bronchus

This study was conducted to provide a comprehensive evaluation of both the amplitudes and durations of the Lead II electrocardiogram (ECG) in nonascit ic and ascitic broilers. At 14 d of age, male and female broiler chicks wer e sham-operated (SHAM, n = 27), or pulmonary hypertension was initiated by occluding one extrapulmonary primary bronchus (BRONCHUS CLAMP, n = 57). Lea d II ECG and BW were recorded on Days 28 (ECG1) and 42 (ECG2), necropsies w ere conducted on all birds dying after Day 28, and final necropsies were co nducted on Day 49. Data collected at necropsy included the presence (ASCITI C) or absence (NONASCITIC) of ascites, sex, and ventricular weights for cal culating the right:total ventricular weight ratio (RV:TV), which serves as a reliable index of pulmonary hypertension. In each bird, three consecutive ECG1 and ECG2 wave cycles were quantified for both amplitude and duration of the following wave segments: R-b-R, R-S, S-R', R'-R-b', and S-T. The S w ave amplitude was calculated by subtracting R-S from R-b-R and heart rate ( HR) was measured from the peak of one T wave to the peak of the next. Ln th e majority of comparisons, ASCITIC and BRONCHUS CLAMP broilers had larger S , R'-R-b', and S-T amplitudes, longer R-S, R'-R-b', and S-T durations, and a slower HR than NONASCITIC and SHAM broilers, regardless of sex. The diffe rences in ECG wave forms and durations between ASCITIC and NONASCITIC broil ers were greater on Day 42 (ECG2) than on Day 28 (ECG1), but when both ECG were used to develop a regression equation to estimate RV:TV, the R-2 was 0 .79. The most important Lead II ECG parameters associated with the developm ent of ascites were an increasingly negative S wave amplitude and greater a mplitudes and durations for R'-R-b' and S-T as well as a decrease in the HR .