The term 'prefix with cardium' refers to two medical terms: pericardium and epicardium. The pericardium is a double-walled sac that encloses the HEART and the roots of the great vessels. It is composed of an outer fibrous layer and an inner serous layer. The epicardium is the innermost layer of the HEART wall, which is composed of cardiac muscle and connective tissue. Both of these terms have the prefix 'cardium, ' which means 'HEART.'