CASE 6330 Published on 14.01.2008

Ironic perseveration

Section

Cardiovascular

Case Type

Clinical Cases

Authors

F. Fiocchi, G. Ligabue, C. Constantinescu, P. Torricelli

Patient

40 years, male

Clinical History
The patient referred untreated slight hypertension. No other prior relevant clinical history. A routine Echocardiography was performed showing dilatation of the aortic root (major diameter cm 5 at Valsalva sinus) and suspected bicuspid aortic valve with severe valve insufficiency. The echocardiographist suggested performing a cardiac Magnetic Resonance Imaging (MRI).
Imaging Findings
The patient came, asymptomatic, to our attention 2 weeks before its scheduled appointment since he had to leave for summer holidays and he called every day the department secretary to anticipate MRI if another patient could not come. Cardiac MR was performed with respiratory and electrocardiographic trigger and with Gadolinium contrast administration. The examination confirmed the presence of severe aortic insufficiency, aortic ectasia and surprisingly showed a Stanford type A dissection starting from the aortic valve, involving all the three epiaortic vessels (figure 1). The aortic root was extremely expanded due to the aneurismatic evolution of the false lumen (maximum diameters 8,4x7 cm) (figure 2). No MRI sings of penetrating atherosclerotic ulcers and/or intramural haematomas were appreciable on Spin-Echo images (figure 3). The intimal flap was clearly visible on balanced-FFE sequences, performed on all planes (figure 4). Aortic valve was found tricuspid, with high peak velocity seen as aliasing on phase contrast images and moderate regurgitation (figure 5). Contrast-Enhanced MRI showed almost simultaneous opacification of the two lumens (figure 6). No significant pericardial effusion was present (figure 7). The patient was immediately transported to the Hearth-Surgery Department and he was successfully operated during the same night. Of course, luckily, he had to postpone his summer holidays!
Discussion
Aortic dissection is a medical emergency and often patients came with some kind of symptoms, even if sometimes they can be, as in this case, asymptomatic. Hypertension is the most important risk factor for aortic dissection (60-90%). Imaging investigations depend on the clinical situation. MRI is increasingly becoming a first line investigation for evaluating disease of the thoracic aorta, thanks to the advances in gradient hardware, the increasing of the acquisition speed and the possibilities to assess vessel morphology combined with contrast-enhanced MR Angiography. Aortic dissection results from the passage of blood out of the true lumen through a defect in the vessel wall into the tunica media, separating media from intima; this results in the creation of a true and false lumen separated by an intimal flap (1). The side effects result from either proximal or distal migration of the dissection to involve and occlude branch vessels of the aorta. When the dissection migrates proximally to involve the coronary arteries and aortic valve, the consequences are catastrophic. In this case the intimal flap was appreciable until the aortic valve, maybe we arrived just in time! Aortic dissections are classified as Stanford Type A (involving the ascending thoracic aorta) or Stanford Type B (no involvement of ascending thoracic aorta). Type A dissections are surgical emergencies, due to the risk of the rupture into the pericardium causing cardiac tamponade and dissection into the coronary or the brachiocephalic arteries. In Spin-Echo images blood flowing reasonably fast (> 10 cm/see) appears black due to the “flow void” effect of the transit of flowing spins out of the section. Spin-Echo sequences should be performed T1 and T2 weighted in order to detect pathologies of the vessel wall and classify its grade (for example acute, subacute and chronic haematomas/thrombi have different signal intensity). Cine MR imaging adds a valuable adjunct to Spin-Echo imaging, acquiring image data throughout the cardiac cycle. Visualization of blood flow during both systole and diastole allows dynamic or functional assessment of aortic blood flow. On Gradient-Echo images, blood flow is bright: the high signal intensity (bright signal) of vessels is achieved by the entry of unsaturated protons into the image, a phenomenon called time of flight or flow-related enhancement (2). Moreover due to the inherent high signal to noise ratio from blood, true and false lumen and dissection flap are clearly visible. Furthermore, Contrast-Enhanced MRI has excellent spatial and contrast resolution and allows studies to be performed in multiple vascular phases, making it valuable for the diagnosis and classification of aortic dissection and in providing information that is helpful for treatment planning. It can also provide high-quality imaging data suitable for 3D reconstructions. Moreover sub-second Contrast-Enhanced MRI can demonstrate sequential filling of the true and false lumen and may help identify the entry and exit points of the dissection (3).
Differential Diagnosis List
Aortic Dissection, Stanford type A.
Final Diagnosis
Aortic Dissection, Stanford type A.
Case information
URL: https://www.eurorad.org/case/6330
DOI: 10.1594/EURORAD/CASE.6330
ISSN: 1563-4086