In this VETgirl online veterinary continuing education podcast, we review echocardiographic predictors of first onset of atrial fibrillation in dogs with chronic valvular heart disease (CVHD) AKA myxomatous mitral valve disease (MMVD) using speckle tracking. The onset of atrial fibrillation (AF) is a negative prognostic indicator in dogs with underlying structural heart disease, and the likelihood of onset of atrial fibrillation is higher with increases in left atrial size and body weight. Furthermore, the greater the patient's ventricular response rate, or ultimately heart rate, in atrial fibrillation, the worse the prognosis is known to be. As a result, pharmacologic heart rate control is a major goal of treatment in dogs with atrial fibrillation secondary to structural heart disease. Early detection of onset of atrial fibrillation, if possible, would reduce the amount of time during which a dog may be experiencing as-yet undetected rapid atrial fibrillation. Data in humans have determined that certain markers on surface electrocardiogram (ECG) and echocardiogram (ECHO) can be useful in predicting the onset of atrial fibrillation. So, Toaldo et al wanted to evaluate this in a study entitled "Echocardiographic predictors of first onset of atrial fibrillation in dogs with myxomatous mitral valve disease." The goal of this study was to evaluate the utility of several echocardiographically-derived indicators of left atrial and ventricular size and function in predicting onset of atrial fibrillation in dogs with MMVD.