Isolated left ventricular noncompaction is a recently recognized age-independent cardiac genetic disorder caused by heterogeneous defects in endo-myocardial morphogenesis. Transthoracic echocardiography and cardiac magnetic resonance are the most reliable techniques to make a diagnosis of the disease, noninvasively. Arrhythmic atrial and ventricular disorders have been reported in 20-50% of these patients. The morphological and functional findings are described in a young woman in whom the exclusive clinical sign of isolated ventricular noncompaction was an atrial parasystole.