In 1987 idiopathic dilated cardiomyopathy was a disorder of unknown cause that directly affected one or both cardiac ventricles in a diffuse or multifactorial fashion, and that produced heart failure, at least in some patients. Although a viral etiology had been proposed, dilated cardiomyopathy could be associated with numerous genetic and non-genetic diseases. However in 1987, the role of genetic factors was not known in humans. Although the condition was usually dismissed as sporadic, numerous families with multiple affected members have been observed.