2. Universidad Cardenal Herrera-CEU

Equine ventricular repolarisation wave can be influenced by many physiological and pathological factors. T wave abnormalities have been related to a shorter time for ventricular filling, reduced stroke volume, cardiac output and exercise performance in racehorses. The present research performed electrocardiographic recordings in 14 four-year-old male Andalusian horses, when they were untrained and after three months of an aerobic training programme. Leads I, aVF, V10, V1R, V3R, V1L and V3L were used. It was aimed to assess the incidence of abnormal T waves in this breed, according to the criteria of abnormalities established for other equine breeds, to evaluate if the changes induced by training in the T wave are the same that those reported in the athletic heart syndrome in canine and human athletes and, to analyse if the abnormal T waves could have been related to changes in the plasma concentrations of Na, K, and Cl, since these electrolytes are involved in the cardiac electrical processes. It was found out that the incidence of abnormal T waves was quite high in the Andalusian breed, especially in the precordial leads. Moreover, the incidence of abnormal T waves increased in precordial leads and decreased in lead I and aVF after training. The abnormal T waves after training were shorter and had the same voltage, changes which were different to those presented for the athlete’ heart syndrome. The horses with abnormal T waves had higher plasma K concentrations, both before and after training. Plasma Na and Cl concentration at rest decreased after training. Plasma Na concentrations were positively related to T wave duration and negatively to T wave voltage.

Plasma K accumulation during exercise results from the balance between exchange through biological membranes (mainly muscle fibres and erythrocytes), distribution to other tissues and the haemoconcentration. In the present study, the effect of exercise and training on plasma K concentrations and its relationships with other physiological variables have been analysed in two equine breeds. Twenty male Andalusian (AN) and ten Angloarabian (AA) horses, 7 females and 3 males, were subjected to two standardised exercise tests, composed of four workloads, before and after training. Heart rate (HR) was monitored and venous blood was withdrawn at rest, before each exercise level and during recovery. The following parameters were analysed: packed cell volume (PCV), plasma K, lactate (LA) and total protein (TPP). Furthermore, the horses were filmed and three kinematic parameters were studied: stride duration (SD), frequency (SF) and length (SL). Exercise induced an increase in K from 6 and 8 m/sec in AA and AN horses respectively, a steady-state until the end of the exercise and a decrease after 2 min of recuperation. Some interbreed differences existed, with higher K levels in the AN horses, due to the higher relative exercise intensity, stride frequency and haemoconcentration. K was correlated with HR, PCV, TPP, SL, SD and SF. Training caused a decrease in K in AN, but not in AA horses. Plasma K seems to be a good indicator of the physical effort intensity, fitness and training degrees, but it was not related to the magnitude of the glycolytic response to exercise.

El objetivo de este trabajo ha sido describir un sistema de pun-tuación objetivo, a partir de índices de funcionalidad cardiovas-cular y metabólica, que permita la discriminación entre caba-llos según su potencial atlético. Se han estudiado 45 caballosadultos, Pura Raza Española (PRE), machos. Tras un calenta-miento al trote (4 m/s), los animales realizaron un test de ejer-cicio, a velocidades de 5, 6,7y8m/s, cubriendo 1.000 m encada carga de esfuerzo. Se monitoreó la frecuencia cardiaca(FC) y se extrajeron muestras de sangre venosa en reposo,tras el calentamiento, después de cada fase del test y a los 2,4, 6, 8, 10, 15 y 30 minutos de una recuperación activa. Ensangre entera, se determinó la concentración de hemoglobina(HB) y el valor hematócrito (HTO). En plasma, se midieron losniveles de lactato (LA). Los índices de funcionalidad oxidativoshan sido: HBo’ y HTOo’ (HB y HTO a 8 m/s), V150 y VLA2 (ve-locidad a 150 lpm y 2 mmol/L de LA respectivamente), FCLA2(FC a 2 mmol/L de LA) y LA150 (LA a 150 lpm). Como índicesglicolíticos-mixtos, se han considerado: FCmáx (FC máxima),FCo’ (FC a 8 m/s), LAmáx (LA máximo), V200 y VLA4 (veloci-dades a 200 lpm y 4 mmol/L de LA), FCLA4 (FC a 4 mmol/Lde LA) y LA200 (LA a 200 lpm). Los índices que mejor han dis-criminado a los caballos PRE según su nivel de forma físicahan sido VLA2, LA150 y HTOo’ (oxidativos) y FCo’, VLA4 yV200 (glicolíticos-mixtos). VLA2, VLA4 y V200 estuvieron co-rrelacionados positivamente con el potencial físico y FCo’,HTOo’ y LA150, de modo negativo.