Left ventricular size and systolic function in Thoroughbred racehorses and their relationships to race performance

Abstract

Cardiac morphology in human athletes is known to differ, depending on the sports-specific endurance component of their events, whereas anecdotes abound about superlative athletes with large hearts. As the heart determines stroke volume and maximum O2 uptake in mammals, we undertook a study to test the hypothesis that the morphology of the equine heart would differ between trained horses, depending on race type, and that left ventricular size would be greatest in elite performers. Echocardiography was performed in 482 race-fit Thoroughbreds engaged in either flat (1,000 -2,500 m) or jump racing (3,200 -6,400 m). Body weight and sex-adjusted measures of left ventricular size were largest in horses engaged in jump racing over fixed fences, compared with horses running shorter distances on the flat (range 8 -16%). The observed differences in cardiac morphologies suggest that subtle differences in training and competition result in cardiac adaptations that are appropriate to the endurance component of the horses' event. Derived left ventricular mass was strongly associated with published rating (quality) in horses racing over longer distances in jump races (P Յ 0.001), but less so for horses in flat races. Rather, left ventricular ejection fraction and left ventricular mass combined were positively associated with race rating in older flat racehorses running over sprint (Ͻ1,408 m) and longer distances (Ͼ1,408 m), explaining 25-35% of overall variation in performance, as well as being closely associated with performance in longer races over jumps (23%). These data provide the first direct evidence that cardiac size influences athletic performance in a group of mammalian running athletes. Thoroughbred horses; athletic performance; heart size RESULTS FROM EXTENSIVE RESEARCH into the effects of athletic training and competition on the human heart have demonstrated differing effects of various types of exercise and training (22). Prolonged periods of high cardiac output with minimal change in arterial blood pressure, typical of long-duration endurance training (dynamic exercise), produce increased diastolic load and stimulate compensatory increases in cardiac chamber size (10). In contrast, short-duration "power" training (static exercise), associated with increased cardiac afterload and arterial blood pressure, produces increased left ventricular (LV) wall thickness due to compensatory concentric myocardial remodeling (15). Although sport-specific cardiac adaptations have been studied for many human athletic disciplines with differing static and dynamic exercise components (9, 19), most studies have compared elite human athletes competing in sports at extremes of the power/endurance spectrum. The differences in cardiac adaptation between athletes performing dynamic exercise over different distances, with subtle differences in the power/endurance components of their competitive events, have not yet been fully explored.The role of the heart in defining athletic performance has been the subject of speculation and interest ...

Two-Dimensional- and M-Mode Echocardiographic Measurements and Indices of Cardiac Function in Spanish Colts and Fillies of Different Age

“…Comparison of echocardiographic measurements in Spanish foals to previously reported values for other equine breeds: LVID, LVFWT, IVST and MV measurements were smaller in the Spanish foals than the values presented for Thoroughbreds [20,31,32] and Standardbreds [1,5,33] older than 20-24 months. In addition to the different age, most of the papers listed above showed data for animals in training.…”

“…It is tempting to speculate if these (6.295-9.678) data are the result of the genetic selection of Thoroughbred horses for speed racing, whereas the Spanish horses are mainly used for dressage or as saddle horses and genetic selection has followed mainly morphological characteristics. In fact, it has been demonstrated that an eccentric cardiac hypertrophy occurs in response to race training attributable to an increased diastolic stress and thus, higher heart chambers are expected in the trained Thoroughbreds and Standardbreds horses [31][32][33]. Another reason to explain the differences between breeds in the echocardiographic measurements is the effect of HR, which was almost 2-fold higher in the Spanish foals than in Thoroughbreds and Standardbreds [1,5,32].…”

“…In fact, it has been demonstrated that an eccentric cardiac hypertrophy occurs in response to race training attributable to an increased diastolic stress and thus, higher heart chambers are expected in the trained Thoroughbreds and Standardbreds horses [31][32][33]. Another reason to explain the differences between breeds in the echocardiographic measurements is the effect of HR, which was almost 2-fold higher in the Spanish foals than in Thoroughbreds and Standardbreds [1,5,32]. Patteson et al [21] demonstrated that bradycardia is associated with increased LVIDs and decreased LVFWTs and IVSTs.…”

Doppler sonographic examination of the common carotid artery in horses with heart disease

“…Die Verkürzung der PEP bei Aortenklappeninsuffizienz ist auf die erhöhte Kontraktilität (Ishikawa et al 1975, Lewis et al 1977, Atkins und Snyder 1992 , Stadler et al 1994, Patteson et al 1995, Stadler et al 1995, Young et al 2005, Gehlen et al 2005 Bei den Pferden mit Aortenklappeninsuffizienz (AVI) wurde eine signifikante Erhöhung der systolischen Geschwindigkeiten und der diastolischen Rückflussgeschwindigkeit sowie der Widerstandsindizes und eine verminderte enddiastolische Geschwindigkeit gefunden. Bei AVI ist auch eine erhöhte Vmax an der Aortenklappe zu finden.…”

Influence of 3 month of training on heart size and myocardial function in trotters

“…Körperliches Training hat eine Auswirkung auf die Herzgröße und die Herzfunktion (Young 1999, Buhl et al 2005, Young et al 2005, Sleeper et al 2014. Pferde zeigen dabei ähnli-che trainingsinduzierte Anpassungen des Herzens wie der Mensch, wobei diese Anpassungen beim Pferd jedoch meistens etwas geringer ausgeprägt sind (Harmeyer 2005).…”