CONICET | Buscador de Institutos y Recursos Humanos

INTRODUCTION The vertebral heart score (VHS) is a method for measuring heart size relative to vertebral length in thoracic radiographs in the dog (Buchanan and Bücheler, 1995). The measurement is based on the sum of the long and short axes of the heart. Each measured is performed caudally from the cranial edge of the 4th thoracic vertebra and has been described as a more objective method for evaluating the cardiomegaly in thoracic radiographs (Jepsen-Grant et al., 2012). For the other hand, is known that endurance exercise causes cardiac enlargement due to eccentric left ventricular hypertrophy (Stepien et al., 1998). At the moment, there are not available studies VHS and its relation to aerobic training. The aim of the present study was to evaluate the cardiomegaly produced by the canine treadmill training through VHS. MATERIALS AND METHODS Nine, 2 to 5 years old, 28.35 + 6.17 Kg healthy dogs were included in this study during 3 month period. Four of the dogs were females and five males and consisted of the following breeds: Presa canario, Greyhound and crossbreed. The animals coming from private property owners were kept under a controlled environment during the experiment. Before treatment, each animal underwent an orthopaedic examination to exclude possible orthopedic diseases. Information on daily exercise was obtained from every dog?s owner, who also signed written consent. The dogs were fed a commercial balanced food Vitalcan® super premium and given water ad libitum. The amount of food was determined for each dog from weight and body condition. Four weeks prior to the experiment, two times for week, the dogs were submitted an adaptation period of minimal exercise (consists of 8 min at 2kph) in motorized treadmill (DobleXX, Argentina). Finished this period, began training on a motorized treadmill for 3 month, twice week. Each exercise session included 2 min at 5 kph and 8 min at 10 kph. The VHS was determined for all dogs. Measurements were performed at weeks 1, 4, 8 and 12. Thoracic radiographs were evaluated by two observers. The long axis of the heart was measured from the ventral border of the carina to the heart apex using a right lateral radiographic view. The short axis of the heart was calculated perpendicular to the long axis at the level of the caudal vena cava. Measurements of both axes were positioned over the thoracic vertebra, starting at T4 according to the description by Jepsen-Grant et al., 2012. The study was design as a complete randomize block design, the block criteria were sex, size and previous physical activity. The data was analyzed as repeated measurements. All statistical analyses were performed using program SAS (Version 9.0, SAS Institute Inc., Cary, NC, USA). RESULTS Throughout the study was observed by VHS a significant increase in heart size (p<0.05) with lineal contrast (p<0,01). DISCUSSION The original report of VHS measurements made by Buchanan and Bücheler established a reference range of 9.7±0.5 vertebral bodies. In this study the range was 10.1±0.1 vertebral bodies to the first week of training, whereas to the last week was 10.6±0.1, which could be caused by aerobic training. At the moment, the most of studies involve dogs with specific cardiac pathologies. However, the VHS showed be a tool useful to determined cardiac enlargement in aerobic training. CONCLUSION To our knowledge, this is the ﬁrst investigation to describe the effect of treadmill training over the cardiomegaly assessing by VHS. Findings from our study indicate that VHS could be useful in determining the cardiac enlargement in sport/training. However, assessments echocardiographic to specify the origin from cardiac enlargement are recommended result of dilatation or heart hypertrophy