Shone's syndrome consists of a set of four cardiac defects: a supravalve mitral membrane (SVMM), parachute mitral valve, subaortic stenosis (membranous or muscular) and coarctation of the aorta. Essentially, it is both a left ventricular inflow and outflow obstruction. The prognosis is inversely related to the degree of obstruction caused by the SVMM. The SVMM is also first to develop and likely causes the development of the other three defects.