Ventricular conduction defect in isolated noncompaction of the ventricular myocardium

A 9-month-old boy and 4-month-old girl presented with severe heart failure. The electrocardiogram showed complete and ''incomplete'' left bundle branch block, respectively. In both infants noncompaction of the ventricular myocardium was diagnosed with two-dimensional echocardiography. These cases are thought to be the first descriptions of the occurrence of left bundle branch block with noncompaction of the ventricular myocardium. Noncompaction of the ventricular myocardium should be added to the list of the causes for left bundle branch block in children.