Holter Monitoring is a 24 hour ECG that electrically records each heart beat for a full day.  The data is downloaded and evaluated.  This evaluation can be a diagnostic tool to assess heart disease that is arrhythmic in nature (producing arrhythmias) or can be used to screen breeding animals in susceptible breeds, such as Boxers and Dobermans.  These breeds are commonly affected with a profound form of heart disease characterized by VPC's (ventricular pre-mature contractions) that are detected by holter.  Arrythmegenic right ventricular cardiomyopathy, a disease often seen in Boxers, is often diagnosed with a holter evaluation.  Dogs that have arrythmegenic cardiomyopathy may have episodes of weakness, fainting or sudden death if the VPC's are close together and in long runs (V-Tach).