Background
Prominent azygos veins (PAVs) have been described with interrupted inferior venae cavae (IVCs) with heterotaxy. At the authors’ institution, cases of PAVs with uninterrupted IVCs have been noted. The aim of this study was to determine the occurrence rate of PAVs and associated lesions by echocardiography.
Methods
All patients with PAVs were collected; those with interrupted and uninterrupted IVCs were assigned to groups 1 and 2. Normal controls were assigned to group 3.
Results
Among 15,849 patients from January 1, 2001, to March 31, 2008, 55 (0.3%) had PAVs, 42 (76%) in group 1 and 13 (24%) in group 2. Heterotaxy was prominent in group 1, whereas patients in group 2 had no heterotaxy. Patients in group 2 had more structurally normal hearts than those in group 1 (46% vs 14%, P < .01), partial anomalous pulmonary venous return, and one single ventricle. IVC measurements were the same in groups 2 and 3 ( P = .65).
Conclusions
This study demonstrates that a PAV without IVC interruption is not associated with heterotaxy. Patients with PAVs should be carefully examined for partial anomalous pulmonary venous return.
The azygos and hemiazygos veins are remnants of the cardinal veins and drain directly into the superior vena cava. The appearance of a prominent azygos vein (PAV) has mainly been noted in the presence of an interrupted inferior vena cava (IVC). However, this condition does not necessarily represent a congenital heart defect, given that membranes or tumors may lead to IVC interruption. For the most part, PAVs have been present in conditions with heterotaxy, in which the hepatic portion of the IVC is not continuous with the right atrium. Heterotaxy is defined by anomalous positioning of the visceral organs. Typically, patients with heterotaxy can have abnormal positioning of the liver and possibly the spleen, with atrial situs ambiguous. Often, the descending aorta is positioned at the midline just anterior to the spine. Cardiac lesions fall along a spectrum of either left or right atrial isomerism with anomalous systemic and pulmonary venous connections, atrioventricular canal defects, and single-ventricle physiology. There have been case reports, however, of PAVs and uninterrupted IVCs. At our institution, we have also noted cases of PAVs with uninterrupted IVCs on echocardiography. To our knowledge, there have been no studies investigating this lesion carefully. The aim of this study was to determine the occurrence rate of this condition and to establish if there are associated lesions that accompany it.
Methods
All patients were retrospectively collected from the Siemens KinetDx database workstation (Siemens Medical Solutions USA, Inc, Mountain View, CA; KinetDx Solutions, Ann Arbor, MI) from January 1, 2001, to March 31, 2008. Offline measurements were also made using this workstation. All patients’ protected health information was carefully guarded, and our institution’s board approved this retrospective study (institutional review board #15195). The ultrasound equipment used for this study included the Siemens Acuson C512, revision 12.0 (Siemens Medical Solutions USA, Inc), the Phillips iE33 (Philips Medical Systems, Bothell, WA), and Hewlett-Packard 5500 systems (Hewlett-Packard, Andover, MA). At our institution, as part of a complete echocardiographic study, we image the course of the IVC and the superior vena cava to evaluate for anomalies. Additionally, we use many techniques to detect the presence of azygos veins. From the subcostal coronal view, the azygos vein will be on the right side of the spine, while the hemiazygos vein will be to the left side of the spine ( Figure 1 A). Sagittal-plane imaging is useful for imaging the long axis of the azygos vein and the descending aorta with Doppler flow in opposite directions ( Figure 1 B). In patients with poor subcostal imaging, parasternal long-axis views can be used to image the azygos vein entering the superior vena cava just above the right pulmonary artery ( Figure 1 C).
Our database was queried for the term “azygos vein,” and any patient with a qualitatively ascertained PAV was included in the study. Each patient’s echocardiogram was carefully reviewed for an IVC that connected to the right atrium ( Figure 2 A). In the setting of an uninterrupted IVC, the term “prominent” specifically refers to an azygos or hemiazygos vein that is similar to the diameter of the IVC ( Figure 2 B). Careful measurements of the IVC and azygos vein were obtained to establish whether the azygos veins were prominent in these patients. Patients with interrupted IVCs were assigned to group 1, and group 2 included patients with uninterrupted IVCs. The associated lesions for each group were noted, as well as demographic data such as height, weight, body surface area, and age. A χ 2 test was used to compare the proportions of patients with structurally normal hearts between groups 1 and 2. Patients in group 2 had measurements of the IVC before and after hepatic vein drainage as well as the diameter of the azygos vein ( Figures 2 A and 2 B); all venous measurements were made at the largest diameter during the cardiac cycle. A separate cohort, group 3, consisted of normal patients with the same body surface area as those in group 2, for which the same IVC measurements were made. Normal patients were defined as those without any identifiable congenital heart disease by echocardiography. Groups 2 and 3 were compared using Student’s t test to see if there was any difference in measurements between the two groups. Any patients with anomalous drainage of the pulmonary veins into the systemic veins were excluded from this statistical comparison to avoid tainting the comparison.
Results
A total of 15,849 patients were studied during the study period, of whom 55 (0.3%) had PAVs. Group 1 consisted of 42 patients, while group 2 consisted of 13 patients. In other words, 24% of patients with PAVs had uninterrupted IVCs. The vast majority of patients in group 1 had heterotaxy, whereas group 2 included no patients with heterotaxy ( Table 1 ). Three patients in group 2 had anomalous drainage of the right pulmonary veins. One of these patients had direct drainage into the azygos vein, presumably leading to its prominence. Table 2 demonstrates the size of the prehepatic and posthepatic IVCs along with the azygos venous measurements in all patients in group 2 without anomalous pulmonary venous return. The χ 2 analysis presented in Table 3 reveals that patients in group 2 had a higher incidence of structurally normal hearts than those in group 1 (46% vs 14%, P < .01). There was no difference in IVC measurements indexed to body surface area between groups 2 and 3 ( Table 4 ).
| Lesion | Group 1 | Group 2 |
|---|---|---|
| Heterotaxy ∗ | 25 | 0 |
| No associated cardiac lesions | 6 | 6 |
| Sinus venosus ASD, anomalous right pulmonary veins † | 1 | 1 |
| Anomalous right pulmonary veins to SVC or azygos vein | 0 | 2 |
| Coarctation of the aorta | 3 | 0 |
| Critical pulmonary stenosis | 2 | 0 |
| Truncus arteriosus | 0 | 1 |
| Isolated VSD | 2 | 0 |
| DORV with isolated VSD | 1 | 0 |
| Tricuspid atresia | 0 | 1 |
| Patent ductus arteriosus | 0 | 1 |
| Situs inversus totalis | 0 | 1 |
| Hypoplastic left-heart syndrome | 1 | 0 |
| Tetralogy of Fallot | 1 | 0 |
| Total | 42 | 13 |
∗ Noted to have left atrial isomerism, complete atrioventricular canal, and DORV.
† The patient in group 1 was also noted to have scimitar syndrome.
| Patient | Body surface area (m 2 ) | Prehepatic IVC (mm) | Posthepatic IVC-RA (mm) | Azygos vein (mm) |
|---|---|---|---|---|
| 1 | 0.1 | 1.5 | 1.7 | 2.5 |
| 2 | 0.2 | 4.6 | 7.5 | 4.7 |
| 3 | 0.21 | 1.0 | 2.0 | 4.0 |
| 4 | 0.22 | 3.2 | 8.6 | 2.5 |
| 5 | 0.22 | 3.4 | 4.4 | 4.1 |
| 6 | 0.28 | 4.9 | 2.6 | 3.5 |
| 7 | 0.42 | 2.1 | 8.6 | 5.3 |
| 8 | 0.48 | 3.3 | 4.8 | 7.0 |
| 9 | 0.69 | 7.0 | 5.3 | 6.5 |
| 10 | 1.42 | 3.3 | 9.8 | 5.6 |
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