Discussion
Diagnosis With Brief Discussion
- Diagnosis
- Anomalous Left Brachiocephalic Vein
- Radiologic Findings
- Chest PA shows somewhat high-positioned aortic arch.
Contrast enhanced CT scans show an anomalous vein that courses downward along the left lateral aspect of the aortic arch, curves into AP window, and crosses the midline between the trachea and the ascending aorta. It enters the superior vena cava at the level of azygos arch. The normal left brachiocephalic vein is not seen in its normal position, and the prevascular space is occupied by the aortic arch and great arteries. The right main pulmonary artery is noted inferior to the above-mentioned vessel.
- Brief Review
- The incidence among patients with congenital heart disease is from 0.015-0.2% by autopsy to 0.98% by ultrasonography. In previous reports ALBCV has been said to be commonly associated with congenital heart disease. This is because radiological evaluation has been usually given only to patients with cardiovascular disease. In recent reports, ALBCV frequently exists by itself, without other congenital heart diseases.
In the 8th week of fetal development, the precardinal anastomosis appears between both precardinal veins, after which the left cardinal vein disappears. Therefore, the blood flow from the left head and neck regions is carried mainly via precardinal anastomosis into the proximal right precardinal vein. This anastomosis develops into the left brachiocephalic vein. Anomalous left brachiocephalic vein (ALBCV) is thought to be the precardinal anastomosis situated posterior to trunk arteriosus (ventral aorta).
The exact pathogenesis of this anomaly is unknown. There are several hypotheses. One speculated that, in addition to a left brachiocephalic vein, some minor interconnections might exist in the mediastinum between the paired precardinal veins during fetal development. Others suggested that ALBCV is secondarily formed when the aortic arch remains high in the mediastinum in the 8th embryonic week and obstructs the normal pathway of the ventral anastomotic vein. In addition to high aortic arch, abnormal elongation of the aorta, which results in narrowing of the prevascular space and widening of the subaortic space, increase the chance for the development of precardinal anastomosis posterior to the aortic sac.
ALBCV must be distinguished from other major vessels especially in a preoperative examination. An atrophic right pulmonary artery and a high positioned pulmonary artery may be similar to the crossing part of the ALBCV, and the descending portion of the ALBCV must be differentiated from the persistent left SVC. One should confirm each vascular courses and junctions by CT or MR. Recognition of this venous anomaly before cardiac catheterization or cardiovascular surgery is important because the ALBCV passes adjacent to the pulmonary artery and ductus arteriosus.
- References
- 1. Takada Y, Narimatsu A, Kohno A, et al. Anomalous left brachiocephalic vein: CT findings. JCAT 1992;16(6):893-896.
2. Kim HJ, Kim HS, Lee G. Anomalous left brachiocephalic vein: spiral CT and angiographic findings. JCAT 1994;18(6):872-875.
3. Fujimoto K, Abe T, Kumabe T, et al. Anomalous left brachiocephalic (innominate) vein: MR demonstration. AJR 1992;159:479-180.
4. Kim SH, Chung JW, Im G, et al. Subaortic left innominate vein: radiologic findings and consideration of embryogenesis. J Thorac Imag 1999;14:142-146.
- Keywords
- Vascular, Congenital,