Your doctor will diagnose cardiomyopathy based on your medical and family histories, a physical exam, and the results from one or more tests: blood test, chest x ray, electrocardiogram (EKG), Holter and event monitors, echocardiography, stress testing, and genetic testing. To confirm a diagnosis or prepare for surgery, additional procedures may include cardiac catheterization, coronary angiography, and myocardial biopsy.