Abstract
Simple SummaryExercise-induced pulmonary hemorrhage (EIPH) frequently affects racehorses worldwide and has been widely associated with poor performance; however, scientific evidence supporting this observation is low. The present retrospective study aims to evaluate objectively whether the presence and grade of EIPH could affect some fitness parameters, measured during an incremental treadmill test, in poorly performing Standardbred racehorses. For this purpose, the association between EIPH and the results of a treadmill metabolic test (including blood lactate analysis and venous blood gas analysis) were evaluated in 81 Standardbred racehorses. No relationship between EIPH and aerobic/anaerobic capacity was observed, suggesting that EIPH may affect performance in a different manner. However, EIPH-affected horses were shown to reach higher hematocrit values during exercise compared to EIPH-negative horses; therefore, it may be hypothesized that hemoconcentration may take part in the pathogenesis of EIPH by increasing the pulmonary capillary pressure.Exercise-induced pulmonary hemorrhage (EIPH) is a condition affecting up to 95% of racehorses, diagnosed by detecting blood in the trachea after exercise and/or the presence of hemosiderophages in the bronchoalveolar lavage fluid (BALf). Although EIPH is commonly associated with poor performance, scientific evidence is scarce. The athletic capacity of racehorses can be quantified through some parameters obtained during an incremental treadmill test; in particular, the speed at a heart rate of 200 bpm (V200), and the speed (VLa4) and the heart rate (HRLa4) at which the blood lactate concentration reaches 4 mmol/L are considered good fitness indicators. The present retrospective study aims to evaluate whether EIPH could influence fitness parameters in poorly performing Standardbreds. For this purpose, data from 81 patients regarding their V200, VLa4, HRLa4, peak lactate, maximum speed, minimum pH, and maximum hematocrit were reviewed; EIPH scores were assigned based on tracheobronchoscopy and BALf cytology. The association between the fitness parameters and EIPH was evaluated through Spearman’s correlation analysis. No relationship between EIPH and V200, VLa4, and HRLa4 was observed. Interestingly, EIPH-positive horses showed higher hematocrit values (p = 0.0072, r = 0.47), suggesting the possible influence of the hemoconcentration on the increase of pulmonary capillary pressure as a part of the pathogenesis of EIPH.
Highlights
Exercise-induced pulmonary hemorrhage (EIPH), defined as bleeding occurring from the lungs during exercise, is a highly frequent condition among racehorses worldwide [1], affecting from 43% to 75% of racehorses when diagnosed on a single examination, and up to 95% in the case of repeated examinations [2]
Since the influence of EIPH on performance in racehorses has been widely discussed Since the influence of EIPH on performance in racehorses has been widely discussed without reaching univocal results [5,6,7,8,9,10,11,12,13,14,15,16], the present study aimed to objectively define without reaching univocal results [5,6,7,8,9,10,11,12,13,14,15,16], the present study aimed to objectively define whether EIPH affected some fitness parameters in Standardbreds based on an incremental whether EIPH affected some fitness parameters in Standardbreds based on an incremental exercise test on a treadmill
Higher values values of maximum hematocrit reached during exercise were observed in EIPH-affected of maximum hematocrit reached during exercise were observed in EIPH-affected horses, horses, hinting that the hemoconcentration may contribute to the increase in pulmonary hinting that the hemoconcentration may contribute to the increase in pulmonary capillary capillary pressure
Summary
Exercise-induced pulmonary hemorrhage (EIPH), defined as bleeding occurring from the lungs during exercise, is a highly frequent condition among racehorses worldwide [1], affecting from 43% to 75% of racehorses when diagnosed on a single examination, and up to 95% in the case of repeated examinations [2]. EIPH has frequently been associated with poor performance in Thoroughbreds and Standardbreds [5,6,7,8,9]; scientific evidence supports this hypothesis only partially. Different authors reported an association between the presence of EIPH and the likelihood of a lower position in races [7,10,11]. Severe forms of EIPH (grade 4) have been associated with a shorter duration of the racing career [9], and EIPH of grade ≥ 2 has been associated with a lower likelihood to be in the 90th higher percentile for race earnings [7]
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