Imaging of the aortic root on high-pitch non-gated and ECG-gated CT: awareness is the key!

Abstract

The aortic pathologies are well recognized on imaging. However, conventionally cardiac and proximal aortic abnormalities were only seen on dedicated cardiac or aortic studies due to need for ECG gating. Advances in CT technology have allowed motionless imaging of the chest and abdomen, leading to an increased visualization of cardiac and aortic root diseases on non-ECG-gated imaging. The advances are mostly driven by high pitch due to faster gantry rotation and table speed. The high-pitch scans are being increasingly used for variety of clinical indications because the images are free of motion artifact (both breathing and pulsation) as well as decreased radiation dose. Recognition of aortic root pathologies may be challenging due to lack of familiarity of radiologists with disease spectrum and their imaging appearance. It is important to recognize some of these conditions as early diagnosis and intervention is key to improving prognosis. We present a comprehensive review of proximal aortic anatomy, pathologies commonly seen at the aortic root, and their imaging appearances to familiarize radiologists with the diseases of this location.

Keywords: Aneurysm; Aortic root; Aortic valve; CT angiography; High-pitch CT.

Fig. 1

A 67-year-old man with medically managed type B aortic dissection and metastatic colon cancer. Conventional non-ECG-gated CT chest image, high-pitch non-ECG-gated CT image, and ECG-gated CTA image highlighting improved visualization of heart and proximal aortic structures with high-pitch exam even without ECG gating. Abbreviations: LA, left atrium; LV, left ventricle; RV, right ventricle; S, sinus of Valsalva; DA, descending thoracic aorta

Fig. 2

Illustration demonstrating the anatomy of the aortic root

Fig. 3

Reformatted 3-chamber view (a) and axial (b) CTA of the heart and proximal aorta showing the normal relation of the aortic root to the left atrium. No soft tissue should be present between the wall of the left coronary sinus and the left atrium (black arrow). In patients with aortic root infection, this space (black arrow) is increased with soft tissue. Abbreviations: AA, ascending aorta; LA, left atrium; LV, left ventricle; PA, pulmonary artery; An, annulus; S, sinus of Valsalva; STJ, sinotubular junction

Fig. 4

An illustration (a) and a CTA short axis image (b) through the sinuses of Valsalva highlighting the nomenclature and anatomy

Fig. 5

A 43-year-old man with Marfan syndrome and bicuspid aortic valve: sagittal (a) and axial (b) CTA images shows aortic root aneurysm with dilatation centered at the sinuses of Valsalva (white arrow in a) with effacement of the sinotubular junction and normal caliber ascending aorta and bicuspid aortic valve (black arrow in b). A “tulip-shaped” configuration of the aortic root is better appreciated on the volume rendered image (c)

Fig. 6

A 41-year-old-man with incidentally detected sinus of Valsalva aneurysm. Non-contrast chest CT (a) obtained as a work-up for fever showed an incidental dilatation (white arrow) of the aortic root (CT was done with high pitch, enabling the anatomic evaluation of aortic root despite the lack of ECG gating). Follow-up contrast-enhanced-gated CTA images (b and c) showing an incidental aneurysm of the noncoronary sinus of Valsalva (black arrow)

Fig. 7

A 55-year-old female with Staphylococcus aureus sepsis, cardiogenic shock, and pulmonary lesions concerning for septic emboli. Axial (a) non-ECG-gated chest CT showed hyperdense purulent pericardial effusion (black arrow in a) with a contrast filled outpouching at the aortic root (white arrow) and left pleural effusion (star). The contrast outpouching was not recognized by a non-cardiovascular imager. Follow-up axial (b) and coronal (c) high-pitch CT images (venous phase) after 1 month of treatment showed resolution of pericardial effusion but enlarged pseudoaneurysm (white arrow) exerting mass effect on the left anterior descending coronary stent. Surgical repair of the pseudoaneurysm with coronary artery bypass grafting was performed due to continued chest pain

Fig. 8

A 75-year-old man with shortness of breath and chest pain that underwent high-pitch CTA pulmonary artery (a) that was negative for pulmonary embolism but a concern for aortic dissection was raised by the cardiovascular radiologist. Aortic protocol CTA confirmed a type A dissection with entry point adjacent to coronary bypass graft (arrow in b and c) that was very subtle on the CTA pulmonary artery (a)

Fig. 9

A 72-year-old male with chest pain after conventional angiography done as a part of valve-in-valve surgical clearance. Non-contrast (a) and contrast-enhanced (b) CTA images showing hyperdense aortic wall thickening at the sinotubular suggesting focal intramural hematoma, related to intimal injury from difficult right coronary artery cannulation

Fig. 10

A 33-year-old male with a history of intravenous drug abuse with infectious endocarditis status post aortic valve replacement, presenting with fever. Axial (a and b) and volume-rendered (c) CTA images showing soft tissue (star) between the aortic root and the left atrium consistent with a paraaortic abscess. A pseudoaneurysm (white arrow) is also seen, and there is a mass effect on the left main coronary artery (black arrow) with moderate narrowing

Fig. 11

A 47-year-old male with atypical chest pain. Axial CTA image (a) shows circumferential wall thickening (arrow) of the ascending aorta. Axial fused and coronal maximum intensity projection (MIP) F-18 FDG PET-CT images (b and c) shows increased FDG uptake in aortic wall (arrow) consistent with active vasculitis (temporal artery biopsy showed giant cell arteritis)

Fig. 12

A 57-year-old male with chest pain. Axial (a) CTA image shows hypervascular mass between the ascending aorta and the main pulmonary artery (arrow). Further characterization with MRI (b–d) was performed, the mass had bright T2 signal with increased perfusion and wash out on delayed images. Pathology confirmed paraganglioma

Fig. 13

A 64-year-old male status post aortic valve replacement using Hall tilting disc valve (Medtronic, Inc., Minneapolis, Minn) and shortness of breath with increasing prosthetic aortic valve gradient on echocardiogram. Coronal oblique CTA reconstructed images reveal ovoid hypoattenuating lesion (Hounsfield unit, 172) at the inferior surface of the valve ring causing restricted valve opening, consistent with pannus formation

Fig. 14

A 67-year-old female status transcatheter aortic valve replacement (TAVR) using Sapiens valve (Edwards Lifesciences) with suspected aortic valve lesion on echocardiogram. Axial (a) and coronal oblique (b) reconstructed CTA images reveal biconvex hypoattenuating (Hounsfield unit, 74) leaflet and left cusp thickening causing restricted motion (seen on cine), consistent with thrombus

Fig. 15

A 65-year-old male with acute chest pain. Contrast enhanced axial CTA (a) image shows asymmetrical hypodensity adjacent to right lateral wall of ascending aorta (arrow). Non-contrast CT (b) confirmed hypodense fluid attenuation consistent with superior pericardial recess; potential mimic of intramural hematoma

Fig. 16

A 89-year-old female patient with acute chest pain. Contrast enhanced axial CT (a) image was suspicious of a small pseudoaneurysm (arrow); however, non-contrast CT (b) image identified the outpouching as surgical pledget (arrow)

Fig. 17

A 58-year-old female post-op day 10 status post supracoronary ascending aorta replacement with graft repair and concern of pseudoaneurysm on a pulmonary embolism rule-out CT (not shown). Axial (a) and sagittal (b) high-pitch CTA images show a smooth contrast filled outpouching from proximal graft (white arrow) near to the anastomosis (black arrow in a). This smooth outpouching is a normal post-operative appearance, related to over sewn reperfusion catheter stump from cardiopulmonary bypass during surgery

Fig. 18

A 69-year-old male, 6-week status post open ascending aortic aneurysm repair with chest pain, presented with acute chest pain. Axial (a), coronal (b), and sagittal (c) CTA images show a smooth outpouching (black arrow) near graft repair consistent with perfusion catheter stump (expected post-surgical finding). Additionally, there is another irregular outpouching (white arrow), and irregularity and associated anterior pericardial hematoma (star) is concerning for a pseudoaneurysm. The patient had an emergent repeat surgical graft repair