Hemodynamic exercise testing and hormonal status in a sheep model of congestive heart failure.

Backgrounds: The aim of the present study was to investigate the hormonal status and hemodynamic performance of a sheep model of congestive heart failure at rest and during maximum exercise.
Methods: The current investigation was a prospective, experimental study and was carried out in an experimental laboratory. Animals were randomly assigned to a congestive heart failure or control group. In the congestive heart failure group, sequential intracoronary embolization with 90-micron polystyrene microspheres was performed until the left ventricle ejection fraction fell below 35%. All animals were chronically instrumented to continuously monitor the pulmonary artery flow, right ventricle pressure, and left ventricle pressure. Blood samples were collected for hormone assays (atrial natriuretic factor, endothelin, renin plasmatic activity, noradrenaline, and adrenaline), and hemodynamic variables, including expired gases, were measured at baseline and during exercise.
Results: Six animals in each group were studied. Compared to the controls, all of the studied plasma hormones were elevated in the model, and the most discriminative measurement was the atrial natriuretic factor (175±57 vs. 52±5 pg/mL, P<0.01). Exercise performance decreased by 30% to 40% in congestive heart failure animals compared to that of the controls (peak exercise VO2, 30±7 vs. 51±5 mL/min, P<0.01; anaerobic threshold, 21±7 vs. 37±2 mL/min, P<0.01; cardiac output, 201±33 vs. 350±45 mL/min.kg, P<0.01.
Conclusion: Intracoronary embolization in sheep produces a stable and reproducible model that acceptably simulates congestive heart failure in humans. This model is suitable for the long-term assessment of therapeutic strategies and was designed to improve exercise capabilities.