Double-inlet left ventricle with rudimentary right ventricle and ventriculoarterial concordance

Seven hearts were studied that had in common the segmental combination of double-inlet left ventricle, rudimetary right ventricle and ventriculoarterial concordance. The prototype of these hearts has been described as the "Holmes heart" or "single ventricle type A1." Five of the hearts had 2 atrio-ventricular valves; in 1 of these the right valve was minimally straddling. The other 2 had a common valve. In 6 of the hearts the rudimentary right ventricle was obliquely situated on the anterior surface of the dominant left ventricle. The trabecular component was anterior and right-sided with the outlet components and pulmonary trunk in left-sided position. In the final case, both trabecular and outlet components of the rudimentary right ventricle were left-sided. Conduction tissue studies were performed in 2 hearts. In 1, the connecting atrioventricular node and bundle were in anomalous anterolateral position, as expected in double-inlet left ventricle. In the other, a ring-like, posterior, nonbranching bundle connected the regular node in the atrial septum to the branching bundle positioned on the anterior interventricular septum. The anatomic findings are related to the likely modes of presentation and differential diagnosis while the conduction tissue findings are discussed in the light of options for surgical repair. Thus, the term "single ventricle" is best avoided when describing hearts that unequivocally possess 2 ventricular chambers.