Mitral valve disease is the most common cardiac disease affecting dogs. The disease is more common in older dogs and has a high prevalence in some breeds. Affected patients commonly have a left-sided systolic heart murmur. Part of the assessment and evaluation of patients includes imaging of the heart - either by echocardiography or thoracic radiography. Evaluation of the size of the left atrium is helpful for guiding therapy and assessing a patient's prognosis. Chest radiographs are commonly performed in the veterinary practice setting, and in this Specialty Update we discuss a new technique for assessing left atrial size called the VLAS (vertebral left atrial size) and its correlation with clinically significant heart disease in dogs with myxomatous mitral valve disease. Running time: 7 mins Member Fee: $8.95; Free registration for Premium VetVine Membership subscribers: http://vetvine.com/article/181/evidence-based-update-subscriptions