Methods

Standard definitions of ventricular morphology were used to identify the right ventricle and the left ventricle. DI-DORV was defined as congenital heart disease in which 2 distinct AV valves commit exclusively to the right ventricle and/or the infundibulum, and the aorta and main pulmonary artery are also aligned with the right ventricle and/or the infundibulum. The presence of a left ventricular (LV) cavity was allowed, provided no AV valve was attached to it and no great artery arose from it. Also, atresia of the aortic or pulmonary outflow tract was allowed, as long as the corresponding vessel was spatially aligned with the right ventricle or with the infundibulum. Straddling or common AV valve was considered an exclusion criterion.

Cases were ascertained by a query of the cardiac registry in the Department of Pathology and the electronic database of the Cardiovascular Program at Children’s Hospital Boston from 1950 through June 2007. Cardiac specimens, fetal and postnatal echocardiograms, cardiac magnetic resonance (CMR), cardiac angiography, and medical record data were reviewed. The Children’s Hospital Committee on Clinical Investigations approved the review of specimens, imaging studies, and medical records.

Specimens were systematically reviewed for segmental anatomy, cardiac position (classified as levocardia, dextrocardia, or mesocardia), systemic and pulmonary venous connections, AV valve morphology, RV myocardial architecture, the presence of an LV cavity, the type of conus (classified as subpulmonary, subaortic, bilateral, or bilaterally absent), aortic and pulmonary outflow tract obstructions, great vessel anomalies, and associated anomalies.

All available fetal and postnatal echocardiograms, CMR, and cardiac catheterization angiograms were analyzed for the same anatomic details as in the specimen review. In addition, ventricular function, AV valve stenosis and/or regurgitation, and semilunar valve function were assessed on all preoperative studies.

The following clinical data were abstracted from patients’ medical record: date of birth, gender, associated noncardiac anomalies, surgical and catheter-based procedures, arrhythmias, and clinical outcomes.

To compare morphologic and outcome characteristics of DI-DORV with those of DILV, patients with the latter diagnosis were randomly selected from the electronic database of the Cardiovascular Program. For each patient with DI-DORV, 2 patients with DILV matched by age at latest follow-up were selected.

Categorical data were compared using Fisher’s exact test and are expressed as number (percentage). Continuous data are expressed as median (range), and comparisons between groups were made using the Mann-Whitney U test. Statistical analyses were performed using Stata version 10.1 (StataCorp LP, College Station, Texas). A p value <0.05 was considered statistically significant.

Results

Among the 22 patients with DI-DORV, 19 had clinical and imaging data, and the remaining 3 only had heart specimens available for review. Of the 19 patients with clinical records, 5 subsequently died and had autopsies, bringing the number of heart specimens included in the study to 8. The incidence of DI-DORV in our autopsy material was 8 in 3,849 (0.2%) and in our clinical experience 19 in 205,786 patients (0.009%, or 1 in nearly 11,000). The demographic characteristics, diagnostic methods, and pertinent clinical and outcomes data of the study patients are listed in Table 1 . The median age at diagnosis was 1 day (range 0 to 180) and the median length of follow-up of the 19 patients with clinical records was 3.2 years (range 0 to 33). The male/female ratio was 1.3.

Several initial palliative procedures were performed in the 19 patients with clinical records, including systemic artery–to–pulmonary artery shunting in 7, pulmonary artery banding in 4, stage I Norwood procedures in 3, bidirectional Glenn shunting in 3, and ventricular septation in 2 ( Table 1 ). At latest follow-up, 13 patients had FSV palliation with modified Fontan procedures (n = 10) or bidirectional Glenn shunting (n = 3). Additional surgical procedures were performed in 5 patients. Overall mortality (n = 4) in the 19 clinically followed patients was 21%. An additional patient underwent heart transplantation. Among all patients with DI-DORV in this series, 15 (68%) were alive at latest follow-up.

Ventricular septation was attempted in 2 patients. Patient 1 was initially diagnosed with DORV and multiple large ventricular septal defects and underwent transcatheter device closure of the supposed muscular defects at age 4 months in anticipation of subsequent biventricular surgical repair. The patient developed complete heart block, low cardiac output, and multiple organ failure and died 3 days after the procedure. Patient 19 was initially diagnosed with a markedly deficient ventricular septum, excessive LV trabeculations, and aortic coarctation. Surgery consisted of closure of the supposed ventricular septal defects and aortic coarctation repair and was complicated by severe ventricular dysfunction and mitral regurgitation requiring mitral valve repair at age 3 months, followed by mitral valve replacement at age 4 months. The patient underwent 2 subsequent operations to relieve recurrent aortic outflow obstruction and was alive with ventricular dysfunction at age 1 year.

Table 2 lists the anatomic characteristics of the study patients. Abdominal and atrial situs were normal in all. Levocardia was present in 20 (91%) and dextrocardia in patients 3 and 4 (9%). Of the 22 patients, the type of ventricular loop could not be determined in 17 (77%) because the location of the ventricular septum could not be ascertained in the absence of an LV cavity. In those cases, the ventricular loop was designated “X,” indicating unknown ventricular loop ( Table 2 ). In the remaining 5 patients, the presence of a small, posteriorly located LV cavity allowed the determination of ventricular looping: right-handed in 4 and left-handed in 1.

The AV valves in all patients exhibited structural abnormalities varying from mild myxomatous thickening to severe hypoplasia and/or marked redundancy with accessory leaflet tissue and chordae tendineae ( Figure 1 ). Moreover, the attachments of the AV valves of all patients were abnormal, most commonly with attachments of both valves to a muscle band of varying thickness located between the valves ( Figure 2 ). In most patients (n = 15 [68%]), neither AV valve resembled a tricuspid or a mitral valve. In the remaining 7 patients, 1 or both AV valves resembled a tricuspid or a mitral valve ( Figure 2 , Table 2 ). Functional assessment of the AV valves by preoperative echocardiography found mild regurgitation of 1 or both AV valves in 10 of 15 patients (67%) and moderate regurgitation of the right AV valve in 1 of 15 (7%).

Heart specimen showing DI-DORV with few trabeculations. The right AV valve (RAVV) and left AV valve (LAVV) enter exclusively into a right ventricle (double-inlet right ventricle). The yellow probe shows the right atrium–to–right ventricle axis, and the red probe shows the left atrium–to–right ventricle axis. Note the smaller RAVV compared to the LAVV. The morphology of neither valve is typical for a tricuspid or mitral valve. The aorta (Ao) and main pulmonary artery arise from the right ventricle (double outlet). The white arrow indicates the unobstructed aortic outflow tract, and the arrowhead shows the narrowed pulmonary outflow tract.

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