Echocardiographic Changes Related to Pulmonary Hypertension in Preweaned Dairy Calves With Bronchopneumonia: A Case–Control Study in Commercial Dairy Farms

Background: Bronchopneumonia (BP) can cause pulmonary hypertension (PH) and secondary cardiovascular changes. Objectives: The aim of this study was to describe PH–related transthoracic Doppler echocardiography (TTE) changes in pre- weaned dairy calves with BP diagnosed by thoracic ultrasonography (TUS). Animals: One hundred and sixty-four calves were selected from 11 commercial dairy farms. Methods: This is a case–control study. The enrolled calves were grouped according to TUS results into either the control group (with normally aerated lungs) or the BP group (calves with lobar BP). Both groups were then subjected to TTE. Results: Three echocardiographic variables were statistically different between the two groups, which included 104 healthy calves and 60 diagnosed with BP. The internal end-systolic (LVIDs) and end-diastolic diameters of the left ventricle (LVIDd) were significantly (p = 0.033, 0.034, respectively) lower in BP-affected calves (mean ± standard deviation [SD]: LVIDs, 29.65 ± 3.94 mm in healthy calves vs. 28.21 ± 4.44 mm in BP-affected calves; LVIDd, 49.83 ± 4.7 mm in healthy calves vs. 48.11 ± 5.4 in BP-affected calves). The pulmonary artery internal diameter in end-diastole (PAdia) was significantly larger (p = 0.017) in BP-affected calves (16.81 ± 2.68 mm) than in healthy calves (15.75 ± 2.67 mm). Conclusions and Clinical Importance: The observed differences in the affected calves were within the normal reference ranges and exhibited clinical relevance. The lack of evident cardiac disturbances indicates that the BP diagnosis in our study sample was made without relevant cardiac alterations, highlighting the potential of TUS's early diagnostic capabilities during BP episodes.