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Our understanding of the pathophysiology of obstruction in hypertrophic cardiomyopathy has evolved since initial descriptions in the late 1950s. This review addresses the cause of obstruction, from early ideas that a muscular outflow tract sphincter was the cause, through the discovery of systolic anterior motion (SAM) of the mitral valve, to current understanding that flow drag, the pushing force of flow, is the dominant hydrodynamic mechanism for SAM. The continuing redesign and modification of surgical procedures to relieve outflow obstruction have corresponded to ideas about the cause of this condition. In this review we discuss the evolution of surgical procedures to relieve obstruction and review modern surgical approaches. Medical and nonsurgical methods for reducing obstruction are reviewed, as well as efforts to prevent sudden arrhythmic cardiac death. Echocardiography has become central to understanding this complex phenomenon, and for clinical diagnosis, operative planning and intraoperative management.