We wish to thank Dr. Madias for his interest in our report. With regard to electrocardiographic data, the types of bundle branch block were specified in the footnote of Table 1 (of 32 patients with bundle branch block, 28 had left bundle branch block and 4 had right bundle branch block). Table 3 lists major adverse cardiovascular events, which includes sustained ventricular arrhythmias.

A previous study by our group demonstrated that electrocardiographic voltage criteria for left ventricular hypertrophy did not correlate with posterior or septal wall thickening but rather with left ventricular dilatation. Left ventricular dilatation was found to be a predictor of adverse outcomes in univariate analysis in our study.

Our study was not designed to answer the interesting question raised by Dr. Madias, whether intraventricular conduction delay in patients with left ventricular noncompaction is caused by alterations in the extent, distribution, or functional characteristics of the Purkinje network or rather is caused by the absolute thickness of the compacted and noncompacted layers. The 2 mechanisms may play a role, but this needs further elucidation in future studies.