Anomalous subaortic left brachiocephalic vein: Prevalence and associated anomalies

CS Ramesh Babu; Arjun Kumar; Om Prakash Gupta

doi:10.4103/JASI.JASI_111_20

ORIGINAL ARTICLE

Year : 2020 | Volume : 69 | Issue : 3 | Page : 137-143

Anomalous subaortic left brachiocephalic vein: Prevalence and associated anomalies

CS Ramesh Babu¹, Arjun Kumar², Om Prakash Gupta²
¹ Department of Anatomy, Muzaffarnagar Medical College, Muzaffarnagar, India
² Dr. O.P. Gupta Imaging Centre, Meerut, Uttar Pradesh, India

Date of Submission	17-Jun-2020
Date of Acceptance	01-Sep-2020
Date of Web Publication	30-Sep-2020

Correspondence Address:
Dr. C S Ramesh Babu
Department of Anatomy, Muzaffarnagar Medical College, N.H. 58, Opp. Begrajpur Industrial Area, Muzaffarnagar - 251 203, Uttar Pradesh
India

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/JASI.JASI_111_20

Abstract

Introduction: Thoracic venous anomalies are very rare with an estimated prevalence of 0.7% in the general population. One of the rarest such anomaly is a subaortic course of the left brachiocephalic vein (LBV) commonly associated with congenital cardiac or aortic arch anomalies. Material and Methods: We retrospectively analyzed chest computed tomography scans of 710 participants and found incidentally two cases of anomalous subaortic course of the LBV in two females. Results: The observed prevalence of subaortic LBV is 0.28% (2/710 cases). Isolated subaortic LBV without any associated cardiac or aortic arch anomaly was observed in a female patient. Rare bilateral ectopic origin of bronchial arteries from corresponding subclavian arteries was also noted in this patient. In another female patient, right aortic arch anomaly was associated with subaortic LBV. The right-sided aortic arch had an aberrant retroesophageal left subclavian artery arising from a Kommerell's diverticulum as the last branch. Discussion and Conclusion: Extensive literature search has yielded only 15 cases of isolated anomalous subaortic LBV in subjects without any cardiac and aortic arch anomaly. Although this condition is asymptomatic, its presence, when detected, should alert the clinician to the possible presence of associated congenital cardiac and aortic arch anomalies. Accurate knowledge of these rare anomalies will enhance the diagnostic accuracy and proper interpretation of radiological images. Such thorough knowledge will avoid interpreting the anomalous vein as an enlarged lymph node, enlarged left superior intercostal vein, and reduce the chances of surgical complications.

Keywords: Aberrant left subclavian artery, Kommerell's diverticulum, left innominate vein, right aortic arch, thoracic venous anomalies

How to cite this article:
Ramesh Babu C S, Kumar A, Gupta OP. Anomalous subaortic left brachiocephalic vein: Prevalence and associated anomalies. J Anat Soc India 2020;69:137-43

How to cite this URL:
Ramesh Babu C S, Kumar A, Gupta OP. Anomalous subaortic left brachiocephalic vein: Prevalence and associated anomalies. J Anat Soc India [serial online] 2020 [cited 2023 Mar 24];69:137-43. Available from: https://www.jasi.org.in/text.asp?2020/69/3/137/296905

Introduction

The left brachiocephalic (left innominate) vein (LBV) is formed by the union of the left internal jugular and subclavian veins at the level of the left sternoclavicular joint. Normally it passes through the prevascular space, from left to right, just above the arch of aorta and anterior to supra-aortic branches to join the right brachiocephalic vein (RBV) to form the superior vena cava (SVC). It is the most anteriorly placed vessel in the superior mediastinum. Anomalous subaortic or retroaortic LBV (ASLBV) is an extremely rare venous anomaly in which the LBV passes below the arch, above the pulmonary artery and behind the ascending aorta to join RBV at or below the level of joining of arch of azygos vein. In such cases, the SVC is short and azygos vein drains into RBV. When present this anomaly is usually associated with congenital heart disease (CHD) or aortic arch anomalies like right aortic arch (RAA). Anomalous subaortic LBV is seen in about 0.5%–1.7% of all children with CHD.^[1] It is estimated that about 80% of cases with anomalous subaortic LBV have associated right ventricular outflow tract obstruction.^[2],[3] Another common association is the presence of right sided aortic arch.^[4] Isolated subaortic LBV is tremendously rare (0.02% prevalence) with only a handful of reports available in the literature.^[5] Since this anomaly is asymptomatic, its presence is detected incidentally at autopsy, surgery or radiological investigations. Incidental detection of anomalous LBV should alert the clinician of possible associated CHD or aortic arch anomalies. We report here incidental observation of two cases of anomalous subaortic LBV while retrospectively analysing contrast enhanced computed tomographic (CECT) chest scans.

Material and Methods

We retrospectively reviewed CT scans of 710 patients referred to the imaging center for CECT of the thorax for suspected pathologies of the lungs and mediastinum during the period September 2015 to March 2018. The imaging data were collected retrospectively from the archives of the imaging center. The study population included 435 males and 275 females (age ranging from 6 months to 86 years, mean age 51.28 ± 17.70 years). The scans of the patients with malignancies likely to distort the anatomy of aortic arch, poorly enhanced scans, and those with thoracic aortic disease were excluded from the study.

All patients underwent contrast-enhanced multidetector computed tomography by a 64 channel scanner (GE Optima 660, 2011, Tokyo, Japan) and received 90–100 mL of nonionic iohexol contrast (Omnipaque 350 mg I/mL; GE Healthcare, Shanghai, China) at the rate of 5 mL/s intravenously. Written informed consent was obtained by the imaging center from each patient before contrast injection. Sections of 0.625 mm thickness were obtained from the lower part of the neck to the upper part of the abdomen and analyzed in a separate work station (GE: AW Volume share 4.5). After analyzing axial, coronal, and sagittal scans, volume rendered and maximum intensity projections were obtained. The data were collected to study the variations in the branching pattern of arch of the aorta and incidentally two cases having anomalous subaortic LBV were detected.

Results

Two cases of anomalous subaortic LBV were detected incidentally, both in females. Isolated subaortic LBV was detected in a female aged 32 years with a normal left-sided aortic arch. No congenital cardiac anomaly was reported. The anomalous vein was crossing the left lateral side of arch and then turning to the right below the arch and above the pulmonary artery [Figure 1]a and [Figure 1]b. The anomalous vein coursed anterior to tracheal bifurcation and posterior to ascending aorta to join the RBV just below the insertion of azygos vein [Figure 1]b and [Figure 2]. An early branch from the right pulmonary artery was also noted [Figure 1]b. Rare ectopic origin of bronchial arteries (BA) bilaterally from the corresponding subclavian arteries was also observed [Figure 1]b Ectopic right BA arose in the root of the neck from the right subclavian (RSA) while ectopic left BA originated from the left subclavian just above the arch [Figure 1]b.

Figure 1: Volume rendered image (a) anterior view. Isolated anomalous subaortic left brachiocephalic vein descending on the left side of arch and then below the arch and behind the ascending aorta to join right brachiocephalic vein to form the superior vena cava. (b) Posterior view. The ASLBV passes through aorto-pulmonary window above the right pulmonary artery which is giving an early branch (arrow). Note also the presence of ectopic origin of both left bronchial and right bronchial arteries from the corresponding subclavian arteries (LSA, RSA). AA: Ascending aorta, DA: Descending aorta, PT: Pulmonary trunk

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Figure 2: (a-d) Serial axial sections depicting the course of anomalous subaortic left brachiocephalic vein (arrow) passing from the left side of the arch of aorta (a) then behind the ascending aorta and anterior to trachea (b and c) to form superior vena cava (d). DA: Descending aorta

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The second case of subaortic LBV was seen in a female aged 30 years and was associated with a high positioned right-sided aortic arch [Figure 3] and [Figure 4]. The subaortic LBV was passing below the right arch through the subaortic space, above the pulmonary artery and behind the ascending aorta to join the RBV at the level of insertion of azygos vein [Figure 5] and [Figure 6]. The anomalous vein was crossing anterior to the trachea [Figure 5]c. Type II RAA with the branching sequence of left common carotid artery, right common carotid artery, RSA, and Aberrant left subclavian artery (ALSA) was identified [Figure 4]. The aberrant left subclavian artery (ALSA) was arising from a retroesophageal Kommerell's diverticulum and was coursing behind the esophagus to reach the left side [Figure 6] and [Figure 7]. Descending thoracic aorta was present on the right side of the vertebral column. No cardiac anomaly was seen.

Figure 3: Sagittal section. Higher position of right arch in the superior mediastinum with anomalous subaortic left brachiocephalic vein (blue circle) passing through a larger subaortic space above the pulmonary trunk. AA: Ascending aorta, DA: Descending aorta

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Figure 4: VR image of the right sided arch of aorta with 4 branches – left common carotid artery, right common carotid artery, right subclavian and left subclavian in that order. The left subclavian artery has an aberrant retroesophageal course and exhibits a Kommerell's Diverticulum at its origin

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Figure 5: (a-d) Serial axial sections showing the course of anomalous subaortic left brachiocephalic vein (arrow) which is sandwiched between ascending aorta and trachea. Note the position of descending aorta on the right side of the vertebra

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Figure 6: Serial coronal sections showing the course of anomalous subaortic left brachiocephalic vein (arrow). Note the anomalous retroesophageal left subclavian artery is crossing the midline. PT: Pulmonary trunk

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Figure 7: Axial section showing the right aortic arch and the retroesophageal left subclavian artery arising from Kommerell's diverticulum

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Discussion

Thoracic venous anomalies are very rare with an estimated prevalence of 0.7% in the general population.^[6] ASLBV is one such uncommon systemic venous anomaly and when present, is usually associated with CHD, RAA, and other anomalies. It is present in about 0.5%–1.7% of all children with CHD.^[1] The incidence of this venous anomaly associated with CHD was variously reported as 0.2% at necropsy,^[7] 0.5%–0.98% by echocardiography,^[2],[8],[9] 1.7% by CT,^[4] and 0.57% of surgical cases.^[10] It is estimated that the incidence in the general population is 0.06%–0.37%.^[11] In a review of 1500 angiographic studies of the brachiocephalic veins, Roberts et al. reported only one case of subaortic LBV accounting for an incidence of 0.07%.^[12] In a retrospective analysis of CT scans of 81,425 adult patients without CHD, Yamamuro et al. estimated an incidence of 0.03%–0.062% for anomalous LBV.^[13] For evaluating the incidence of aberrant LBV and persistent left SVC without bridging vein, Kobayashi et al. recently reviewed CT scans of 49,494 patients and found an incidence of 0.055% and 0.15%, respectively, for these two venous anomalies in Japanese patients.^[14] Out of 27 cases of ALBVs detected in their study, only one case had associated CHD, 14 patients had high aortic arches, and in 26 cases, the ALBVs had retroaortic course. Reported prevalence rates were largely derived by the retrospective analysis of the surgical, radiological, and autopsy records [Table 1]. Isolated ASLBV without any associated cardiac and aortic arch anomalies is still rarer,^[5] and some of the adult cases reported since 1980 are summarised in [Table 2].

Table 1: Reported prevalence of aberrant sub-aortic left brachiocephalic vein in cases with and without associated congenital heart disease

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Table 2: Reports of isolated sub-aortic left brachiocephalic Vein in cases of situs solitus (with out any cardiac/aortic arch anomaly)

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Most commonly, the ASLBV was associated with conotruncal anomalies, aortic arch anomalies and deletion of chromosome 22q11.2. Most common associated finding is tetralogy of Fallot (TOF) reported to be present in 40%–93% cases of ASLBV.^[8],[9],[10] Another associated anomaly with high frequency is the presence of right-sided aortic arch (RAA) in 46%–86% of cases.^[2],[10] Anomalous subaortic LBV was more common in those with RAA than those with the left aortic arch (P < 0.0001).^[4] The presence of ASLBV in patients with deletion of chromosome 22q11.2 was also reported.^[10],[27] Ventricular septal defect (VSD) with pulmonary atresia, persistent truncus arteriosus, atrial septal defect (ASD), coarctation of aorta, and persistent ductus arteriosus are rare associations observed.^{[1],[3],[10],[28],[29]}

Nakamura et al. reported the case of ASLBV in a 62-year-old male with lung cancer and no cardiac anomaly. They emphasized the importance of recognition of this vein in lung cancer patients because misinterpretation as an enlarged superior mediastinal lymph node may cause serious complications.^[30] Botha and Odell reported the case of a 19-day-old male neonate with ASLBV associated with persistence of truncus arteriosus, VSD, secundum type ASD, absence of arterial duct, and normal left-sided aortic arch.^[28] They noted that Adachi classified ASLBV into two types-type-I anterior to ductus, type II posterior to ductus. Gerlis and Ho added a third type passing below the left pulmonary artery ^[7] and Botha's case is Type IV-with the absence of arterial ligament and ASLBV cephalad to the pulmonary artery.^[28] Level of entry of ASLBV into SVC was higher than the insertion of azygos vein in seven cases, at the same level in four cases and lower in three cases out of 14 cases studied.^[31] Hoshino et al. described a case of 22q11.2 deletion syndrome with hypoparathyroidism, levocardia, high RAA with aberrant left subclavian artery (ALSA) arising from Kommerell's diverticulum in a 54 year old male.^[27] Hara et al. discussed the difficulties encountered while resecting the enlarged lymph nodes in a lung cancer patient having ASLBV and RAA with ALSA.^[32] Ohkubo et al. reported an anomalous retroaortic LBV with RAA and ALSA in a 49-year-old man.^[33]

Normally, the LBV develops from (a) left anterior cardinal (precardinal) vein and (b) transverse inter-precardinal anastomosis. The exact embryogenesis of the anomalous retro-aortic LBV remains uncertain. Adachi (1933) has suggested the presence of double precardinal anastomoses (ventral superior transverse and dorsal inferior transverse plexuses) around the primitive aorta.^[34] Normally, the ventral superior transverse plexus develops into LBV, but the regression of superior and persistence of the inferior transverse plexus result in the development of anomalous LBV [Figure 8]. Takada et al. thought that this venous anomaly resulted from the precardinal anastomosis being situated posterior to the truncus arteriosus and double (circumaortic) LBV as a consequence of persistence of both cranial ventral and caudal dorsal precardinal anastomosis.^[35] Minami et al. and Kim et al. believed that this anomaly can form secondarily when the elongation of the aortic arch prevents the normal cranial ventral precardinal anastomosis to develop.^[36],[37] Elongation of the aortic arch leads to narrowing of the prevascular space and widening of the subaortic space (aorticopulmonary window). This widening increases the chances for the persistence of caudal dorsal precardinal anastomosis posterior to the aorta and formation of anomalous LBV.

Figure 8: Scheme showing the embryological basis of subaortic left brachiocephalic vein. (a) The developing aorta is surrounded by two venous plexuses connecting right and left anterior cardinal veins. (b) Persistence of ventral superior transverse plexus develops into normal left brachiocephalic vein passing anterior to supraaortic branches. (c) Instead persistence of dorsal inferior transverse plexus and involution of superior plexus gives rise to subaortic left brachiocephalic vein

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Arch of aorta and its supraaortic branches develop from paired pharyngeal arch arteries. Normally, the left fourth aortic arch artery develops into the arch of the aorta and right fourth arch artery and part of right dorsal aorta forms part of RSA artery. Distal portion of the right dorsal aorta disappears. RAA is formed due to the involution of left fourth arch artery and persistence of right fourth arch artery and right dorsal aorta. Along with this anomaly if the dorsal inferior transverse venous plexus persists, anomalous subaortic LBV is formed [Figure 9].

Figure 9: Scheme showing the development of arch of aorta and its branches. (a) Normal development of arch of aorta from left fourth arch artery and left dorsal aorta. (b) Development of right aortic arch due to persistence of entire right dorsal aorta and involution of left dorsal aorta. Persistence of distal part of left dorsal aorta along with left seventh intersegmental artery develops into aberrant left subclavian artery. Anomalous subaortic left brachiocephalic vein develops due to persistence of dorsal inferior transverse plexus

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In one female patient, we observed anomalous LBV with RAA having aberrant retroesophageal LSA (ALSA) arising from Kommerell's diverticulum (Type II RAA). Right sided aortic arch is present in 0.05%–0.1% of radiology series and 0.04%–0.1% of autopsy series.^[38] Edwards classified the RAA into three types. Type I is RAA with mirror image branching (left brachiocephalic trunk, right common carotid, and RSA), Type II is RAA with ALSA (left common carotid, right common carotid, RSA, and ALSA) and Type III is RAA with isolation of LSA. Type I and Type III are usually associated with some form of cyanotic CHD like TOF (conotruncal anomalies) but not Type II. Arazińska et al. reported that Type II RAA is the most common type of RAA observed in their retrospective analysis (11/20 patients).^[38] Anomalous subaortic LBV combined with RAA and retroesophageal ALSA represented <0.005% in the prevalence of the adult population.

BA originate ectopically from the arch of aorta, subclavian arteries, thyrocervical trunk, and vertebral arteries. Ectopic origin of BA from subclavian arteries bilaterally is very rare.^[39] We have observed bilateral ectopic origin of BA from corresponding subclavian arteries in a female patient.

Conclusion

Although this venous anomaly is asymptomatic having no pathophysiologic repercussions, it should alert the clinician to the possibility of associated CHD and aortic arch anomalies. This variant may mimic an enlarged lymph node resulting in the misinterpretation in imaging studies. This anomaly can cause difficulty during insertion of central venous catheter through a left-sided approach. It can cause difficulties by obstructing the surgical field during corrective surgeries for congenital cardiac anomalies. It can also be mistaken for a persistent left SVC, enlarged left superior intercostal vein or a vertical vein in cases of partial anomalous pulmonary venous return.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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