Cor pulmonale (CP)Cor pulmonale (CP) in a Latin, literally means, ‘pulmonary heart’. Although there has been little consensus about its exact definition, cor pulmonale is usually defined as an alteration in the structure (e.g. hypertrophy or dilatation) and/or function of the right ventricle on account of pulmonary hypertension that occurs as a consequence of respiratory disease. This chapter begins with a description of the pulmonary vascular circuit and a deconstruction of the components of pulmonary hypertension (PH). It enumerates the conditions necessary for the diagnosis of CP, and discusses the importance of ventricular interdependence in the pathophysiology of the disease. It presents a systematic diagnostic approach to CP, focusing on the various lung disease to look for, the early clinical pointers to the development of CP in a patient known to have lung disease and the different tests that may be used to look for right ventricle hypertrophy or dilation given the context of the clinical situation. This chapter may be profitably read in conjunction with the chapter on pulmonary hypertension (Chap. 61 ).