Commentary

Abstract

In the article by Alva and associates, the authors report their institutional experience with double-chambered right ventricle over an 8-year period. This report serves to expand our knowledge on the morphologic nature of this entity. Their objective was to study the muscular division of the right ventricle by correlating morphologic, echocardiographic, and angiographic findings. Double-chambered right ventricle, the partitioning of the right ventricle into 2 chambers, has been recognized since at least 18671Peacock T. Malformation of the human heart.in: Churchill and Sons, London1967: 75-79Google Scholar and is produced by prominent anomalous muscle bundles within the right ventricular cavity. Although frequently associated with membranous ventricular septal defects,2Simpson W Sade R Crawford F Taylor A Fyfe D. Double-chambered right ventricle.Ann Thorac Surg. 1987; 44: 7-10Abstract Full Text PDF PubMed Scopus (26) Google Scholar other anatomic forms have also been reported.3Baumstark A Fellows K Rosenthal A. Combined double chambered right ventricle and discrete subaortic stenosis.Circulation. 1978; 57: 299-303Crossref PubMed Scopus (41) Google Scholar, 4Gallucci V Scalia D Thiene G Mazzuco A Valfre C. Double-chambered right ventricle: surgical experience and anatomical considerations.Thorac Cardiovasc Surg. 1980; 28: 13-17Crossref PubMed Scopus (17) Google Scholar, 5Rowland T Rosenthal A Castaneda A. Double chamber right ventricle: Experience with 17 cases.Am Heart J. 1985; 89: 455-462Abstract Full Text PDF Scopus (67) Google Scholar Most recently, my colleagues and I6Moran AM Hornberger LK Jonas RA Keane JF. Development of a double-chambered right ventricle after repair of tetralogy of Fallot.J Am Coll Cardiol. 1998; 31: 1127-1133Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar reported our own institutional experience of the development of double-chambered right ventricle in postoperative patients with tetralogy of Fallot, with a minimal occurrence rate of 3.1%. An underlying anatomic substrate was recently suggested by Wong and colleagues.7Wong PC Sanders SP Jonas RA Colan SD Parness IA Geva T et al.Pulmonary valve–moderator band distance and association with development of double-chambered right ventricle.Am J Cardiol. 1991; 68: 1681-1686Abstract Full Text PDF PubMed Scopus (64) Google Scholar They described the presence of a displaced insertion of moderator band into the septal band. This pattern of insertion was recognized both in pathologic specimens and in clinical cases. The evaluation in human beings used 2-dimensional echocardiographic methods. This displacement of the moderator band was further quantified as the distance of the insertion point from the pulmonary valve indexed to the tricuspid valve. The report by Alva and colleagues furthers our understanding of this pathologic entity. They confirm the frequent association with membranous ventricular septal defects and even include a single patient after repair of tetralogy of Fallot. By evaluating several normal anatomic specimens, they highlight the variability in the presence of the moderator band (noting prominent septoparietal trabeculations without the presence of a discrete moderator band in 2). More important, they provide quantitative evidence of 2 distinct anatomic subtypes of double-chambered right ventricle, suggesting that these represent either displaced septoparietal trabeculations or moderator bands that undergo marked hypertrophy. Finally, they provide a quantitative method for assessing the position of such muscle bars relative to the long axis of the right ventricle using angiographic imaging. It is unfortunate that they were unable to attempt a similar analysis using echocardiography, since this is the initial imaging modality of choice in the current era. This inability is sure to reflect the retrospective nature of their study. Although this report increases our knowledge of this intriguing anatomic entity, several questions are left unanswered. The prospective application of previously described ratios (listed above) to identify at-risk patients is awaited. If successfully validated, this could lead to “prophylactic interventions” at the time of other cardiac operations. Clinically, the long-term follow-up of surgically treated patients warrants evaluation, because we6Moran AM Hornberger LK Jonas RA Keane JF. Development of a double-chambered right ventricle after repair of tetralogy of Fallot.J Am Coll Cardiol. 1998; 31: 1127-1133Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar have previously reported recurrence of such obstructions. Finally, the stimulus to hypertrophy in such patients is as yet unknown and may, in part, reflect altered flow dynamics. Further work is required.