This document discusses cardiac disorders and diagnostic tests used to evaluate heart function. It describes the layers and electrical activity of the heart and some common cardiac disorders like angina, myocardial infarction, and congestive heart failure. Important diagnostic tests are discussed that can be invasive like cardiac catheterization or non-invasive like electrocardiography, echocardiography, MRI scans, and serum enzyme tests of creatine kinase, lactate dehydrogenase, troponin, and AST. These tests provide information about heart size and shape, electrical activity, blood flow, and detect abnormalities.