Haemodynamic response to exercise in Standardbred trotters with red cell hypervolaemia.
Authors: Funkquist P, Nyman G, Persson S G
Journal: Equine veterinary journal
Summary
# Editorial Summary: Haemodynamic Response to Exercise in Standardbred Trotters with Red Cell Hypervolaemia Red cell hypervolaemia (RCHV)—an elevated circulating red cell mass—is recognised in some high-performing horses, but whether this physiological adaptation confers genuine performance benefits or creates cardiovascular strain remains unclear. Funkquist and colleagues compared haemodynamic responses during graded treadmill exercise in 12 RCHV and 9 normovolaemic Standardbred trotters, measuring oxygen uptake, arterial pressures, cardiac output and vascular resistance alongside post-exercise endoscopy for pulmonary haemorrhage. Despite identical oxygen delivery and utilisation between groups—both in terms of absolute oxygen uptake and arteriovenous oxygen content difference—horses with RCHV developed significantly elevated pulmonary artery pressures (both diastolic and systolic) that increased progressively with workload intensity, alongside higher systemic arterial pressures and pulmonary vascular resistance. Most strikingly, 11 of the 12 RCHV horses showed endoscopic evidence of exercise-induced pulmonary haemorrhage, compared with none in the control group. These findings suggest that whilst RCHV does not improve oxygen extraction or reduce the cardiac work required to meet metabolic demands during exercise, the increased blood volume and viscosity impose substantial stress on the pulmonary vasculature, substantially elevating haemorrhage risk without conferring measurable aerobic advantage—an important consideration when evaluating blood doping practices or genetic predispositions toward polycythaemia in performance horses.
Read the full abstract on PubMed
Practical Takeaways
- •Standardbred trotters with red cell hypervolaemia are at high risk for exercise-induced pulmonary haemorrhage; consider pre-exercise screening to identify affected animals
- •RCHV horses do not gain oxygen transport advantage during exercise despite higher blood volumes, suggesting this trait offers no performance benefit while increasing bleeding risk
- •Veterinarians should monitor trotters with elevated resting packed cell volume closely during training, as these horses have significantly elevated pulmonary pressures under workload
Key Findings
- •RCHV horses had significantly higher mean diastolic and systolic pulmonary artery pressure compared to normovolaemic horses, with differences increasing at higher workloads
- •11 of 12 RCHV horses developed exercise-induced pulmonary haemorrhage on endoscopy, compared to none in the normovolaemic group
- •RCHV horses showed higher systemic artery pressure, pulmonary vascular resistance, packed cell volume and haemoglobin during exercise despite similar oxygen uptake and cardiac output to normovolaemic horses
- •Increased red cell volume and high total blood volume in RCHV horses contributed to elevated blood pressures in both pulmonary and systemic circulation during exercise