Left ventricular noncompaction is a condition characterized by prominent ventricular trabeculations, often accompanied by systolic dysfunction. The present case involves an adult with a small ventricular septal defect, initially exhibiting mild systolic dysfunction and slightly prominent left ventricular trabeculations progressing over 13 years to severe dilated cardiomyopathy and overt noncompaction. The present case strongly suggests a correlation between the extent of noncompaction and the degree of systolic dysfunction. The initial presence of a small ventricular septal defect and mild trabeculations highlights the genetic determinants of non-compaction and the importance of closely following patients with mild noncompaction due to the possibility of progression. More sensitive diagnostic criteria are needed to avoid overlooking mild cases, which may show prominent trabeculations without reaching a requisite ratio of compacted to noncompacted tissue.