Angina pectoris, the most common clinical manifestation of coronary artery disease (CAD), results from an imbalance between myocardial O2 supply and demand, most often due to atherosclerotic coronary artery obstruction. Other major conditions that upset this balance and result in angina include aortic valve disease (Chap. 114. Valvular Heart Disease), hypertrophic cardiomyopathy (Chap. 115. Cardiomyopathies and Myocarditis), and coronary artery spasm (see below).