Straddling tricuspid valve'

Eleven cases of double inlet left ventricle have been presented. Double inlet left ventricle is characterized by the tricuspid valve opening partly (partial type) or completely (complete type) into the morphological left ventricle. The morphological right ventricle is usually hypoplastic but may be normally formed. Even when the right ventricle is hypoplastic, both the sinus and the outflow portions of the right ventricle are recognizable. Double inlet left ventricle has been classified into two groups according to whether the ventricles are normallyplaced (noninverted; concordant with the atria) or inverted (discordant with the atria.) This classification indicates the anatomical relation of the atrioventricular valves and the ventricles. When the ventricles are noninverted, a right-to-left shunt results from the communication of the right atrium with the left ventricle. On the other hand, with inverted ventricles a left-to-right shunt resultsfrom the left atrium communicating with the inverted left ventricle. Further details in circulation depend upon the great vessel-ventricular relations. Clinically, the patients presented with cyanosis when pulmonary stenosis was present and with congestive cardiacfailure when pulmonary stenosis was absent. The electrocardiogram is helpful in suggesting the presence of inverted or noninverted ventricles. Right and left atriograms are essential for the diagnosis of straddling tricuspid valve in noninverted and in inverted ventricles, respectively.