CT Demonstration of the Extracardiac Anastomoses of the Coronary Veins in Superior Vena Cava or Left Brachiocephalic Vein Obstruction
A 66 year old male with treated lung carcinoma, underwent a routine CT scan. The scan revealed stable findings, including catheter-related thrombosis of the lower third of the LBCV.\nAll studies were performed on GE Lightspeed 64-detector CT scanners. In cases 1-3, a pulmonary embolism protocol was followed. Patients received a bolus of 55 mL of non-ionic contrast followed by 35 mL of saline flush through the antecubital veins of the left arm at a rate of 4.5 mL/s. The scan delay was predetermined by a test bolus (20 mL) using the pulmonary trunk as the region of interest. In case 4, 90 mL of non-ionic contrast were administered intravenously through the left arm at a rate of 2 mL/s using a scan delay of 65 seconds. Scans were obtained using 1.25 mm collimation at 0.9 mm intervals through the thorax in cases 1-3; in case 4, the study was obtained with 5 mm collimation at 4 mm intervals and reconstructed at 1.25 × 1.25 mm.\nThe CT scans of the first three patients showed an extensive network of venous collaterals in the upper mediastinum, particularly around the aortic arch and pericardium. These collateral vessels included pericardial, esophageal, bronchial and mediastinal branches of the left brachiocephalic, left vertebral, left pericardiacophrenic, left internal thoracic or superior intercostal veins. The collateral vessels also communicated with the azygos-hemiazygos, phrenic and, in two cases, pulmonary veins. In the fourth patient, the scan showed a collateral venous network joining the left and right inferior thyroid veins in the upper mediastinum and lower neck that communicated with the paravertebral venous plexus and gave rise to several small mediastinal and pericardial branches.\nAt the union of the pericardium with the ascending aorta and pulmonary trunk, pericardial branches were noted to be in continuity with small vessels distributed along the walls of the intrapericardial segments of the great arteries in all patients (-). These vessels measured 1.5-2.5 mm in diameter and extended to the root of the ascending aorta and base of the pulmonary trunk where they crossed the coronary arteries. The vessels crossing the right coronary artery drained into the right atrial appendage (all cases), and those crossing the left coronary artery drained into the anterior interventricular and left coronary veins (cases 1 and 3). In the second case, tiny collateral vessels on the left could only be traced to the level of the left coronary artery due to image-degrading pulsation artifacts; we assume that these veins also drained into the great cardiac vein (). The collateral vessels that crossed the right coronary artery joined the anterior aspect of the right atrial appendage. In case 1, focal collections of contrast measuring about 5 × 8 mm were noted in the wall of the appendage where the collateral vessels fended ().\nThe unusual course of a collateral vessel from the anterior wall of the ascending aorta is demonstrated in . After descending along the wall of the aorta to the aortic root, the vessel made a loop posteriorly and connected with the anterosuperior wall of the left atrium.\nFewer than four or five intrapericardial vessels communicated with pericardial veins. The vessels, except for a single channel in case 4, ramified and intercommunicated as they descended towards the base of the great arteries. shows the single vessel in case 4; it coursed along the left lateral wall of the ascending aorta and drained into the right atrial appendage after passing under the right coronary artery. A common finding among all patients was the presence of at least one collateral channel along the wall of the ascending aorta located close to the aortopulmonary groove.