Right ventricular function during acute exacerbation of severe equine asthma

Summary Background Pulmonary hypertension has been described in horses with severe equine asthma, but its effect on the right ventricle has not been fully elucidated. Objectives To evaluate right ventricular structure and function after a 1‐week period of pulmonary hypertension secondary to acute exacerbation of severe equine asthma. Study design Prospective study. Methods A clinical episode of severe equine asthma was induced experimentally in six susceptible horses. Examinations in remission and on day 7 of the clinical episode included a physical examination with clinical scoring, echocardiography, arterial blood gas measurements, venous blood sampling for cardiac biomarkers, intracardiac pressure measurements, right ventricular and right atrial myocardial biopsies, airway endoscopy and bronchoalveolar lavage. After 1 month of recovery, physical examination, echocardiography and cardiac biomarker analysis were repeated. Echocardiographic and pressure measurements were compared with those in 10 healthy control horses. Results All horses developed clinical signs of acute pulmonary obstruction. Right heart pressures increased significantly. Altered right ventricular function could be detected by tissue Doppler and speckle tracking echocardiography. Cardiac troponin concentrations did not increase significantly, but were highly elevated in one horse which exercised in the paddock prior to sampling. Focal neutrophil infiltration was present in two myocardial samples. Even in remission, asthmatic horses showed a thicker right ventricular wall, an increased left ventricular end‐systolic eccentricity index at chordal level and decreased right ventricular longitudinal strain compared with controls. Main limitations The induced clinical episode was rather mild and the number of horses was limited because of the invasive nature of the study. Conclusions Pulmonary obstruction in asthmatic horses induces pulmonary hypertension with right ventricular structural and functional changes.