About 10% of dogs presented to a veterinarian has a heart disease, which is a leading cause of mortality. Dilated cardiomyopathy and mitral valve disease have a prevalence of 60 to 90% in dogs of predisposed breeds and lead to cardiac dilation, heart failure and death. Despite landmark studies demonstrating that treatment in the preclinical stage prolongs life expectancy, early diagnosis remains very challenging in primary veterinary care practice due to a lack of easy accessible and cost-efficient diagnostic tools. Lack of an available and sensitive screening method results in missed or late diagnosis and decreased life expectancy of the dog. Vectorcardiography allows to map the electric activity of the heart in three dimensions and correlates to cardiac size, as evidenced in our pilot study. The novel lead positioning method in this project provides an innovative vectorcardiogram in a dog friendly manner and provides new possibilities to quantify structural cardiac changes. Based on the morphology of the RELF vectorcardiogram, we will establish new, sensitive parameters for early detection of cardiac enlargement in dogs. Firstly, preliminary parameters will be further validated in the dobermann pinscher breed to evaluate their diagnostic performance for detection of dilated cardiomyopathy in this highly predisposed breed. Secondly, new parameters will be explored and validated for cardiac dilation in cavalier king charles spaniels with and without mitral valve disease. Finally, all discovered parameters will be validated in the general dog population, taking into account the difference in chest configuration between breeds.