[Dextrocardia and Wolff-Parkinson-White syndrome. Electrocardiographic diagnosis]

A patient affected by dextrocardia and WPW syndrome with atrio-ventricular bypass connecting the left sided atrium to the left ventricle (located to the right) is described. Signs of organic heart disease were not present. Electrocardiogram showed, in addition to typical features of ventricular pre-excitation, a QS pattern in leads V4-V6. During exercise testing the pre-excitation disappeared and the electrocardiogram recorded with inverted peripheral cables and right precordial leads, did not show alterations. The analysis of this case and of another previously published suggests that a QS pattern in left precordial leads is highly suggestive for dextrocardia, even in presence of ventricular pre-excitation.