Right ventricular function during acute exacerbation of severe equine asthma
Decloedt, H. Borowicz, M. Slowikowska, K. Chiers, G. Van Loon and A. Niedzwiedz
This prospective study aimed to identify changes to the structure and function of the right heart associated with an acute exacerbation of equine asthma. Six horses with a history of severe equine asthma were used, which were in remission at the beginning of the study. An acute episode of equine asthma was experimentally induced via exposure to straw and mouldy hay for 7 days. Horses were then returned to a dust-free environment and treated with daily intravenous dexamethasone until resolution of clinical signs.
All horses developed clinical signs within 2 days. Clinical and endoscopy scores were higher in horses following allergen exposure compared to pre-exposure and PaO2 and pH were lower. Cardiac biomarkers did not change. Following exposure, significant increases in right atrial, right ventricular and mean pulmonary artery pressure measurements were demonstrated. The highest pressures were found in horses with the highest clinical and endoscopic scores, likely reflecting increased severity of disease. When echocardiographic measurements in the experimental group were compared to healthy controls, significant differences in several measurements were found including greater right ventricular wall thickness in the disease group suggesting hypertrophy due to right ventricular pressure overload. Neutrophil infiltration and interstitial fibrosis were noted in myocardial biopsies from three of six horses, providing evidence of myocardial inflammation and remodelling in response to pressure overload.
Equine asthma results in pulmonary hypertension and secondary changes to the right side of the heart, related to pressure overload.