Subclavian Steal Syndrome: Diagnosis with Perfusion Metrics from Contrast-enhanced MR Angiographic Bolus-timing Examination—Initial Experience

Diagnostic Performance of Combined Contrast-Enhanced Magnetic Resonance Angiography and Phase-Contrast Magnetic Resonance Imaging in Suspected Subclavian Steal Syndrome

PURPOSE

The study sought to evaluate the efficacy of magnetic resonance imaging (MRI) in patients with suspected subclavian steal syndrome (SSS) using both contrast-enhanced (CE) MR angiography and phase-contrast (PC) MRI.

METHODS

Fifteen suspected SSSs from 13 patients were evaluated using CE-MR angiography and PC-MRI. Ten patients also received dynamic CE-MR angiography.

RESULTS

All MRI examinations were technically successful. By combining CE-MR angiography with PC-MRI, 10 SSSs were diagnosed in 9 patients. The delay enhancement dynamic technique predicted SSS with a sensitivity, specificity, and accuracy of 57.1%, 100%, and 72.7%, respectively. Without the dynamic technique, affected delay-enhanced arteries were poorly visualized and could be mistaken for occluded vessels. Retrograde vertebral flow by PC-MRI was used to predict ipsilateral SSS with a sensitivity, specificity, and accuracy of 100%, 60%, and 86.7%, respectively. There were 2 false positives including 1 patient with a proximal total occlusion of the affected vertebral artery and another with brachiocephalic steal syndrome rather than SSS. This suggested that retrograde vertebral flow does not always indicate SSS.

CONCLUSIONS

CE-MR angiography combined with PC-MRI is efficacious when evaluating SSS in clinical practice.

Neurosonology and noninvasive imaging of the carotid arteries

In this chapter, we review imaging of the extracranial carotid arteries and the indications for noninvasive carotid artery evaluation, measuring the degree of arterial stenosis and plaque morphology. We also analyze the types of noninvasive imaging, including carotid duplex ultrasound, transcranial Doppler, magnetic resonance angiography, and computer tomography angiography. We look at each of these modalities, briefly discussing techniques, benefits, limitations, and sources of error. Furthermore, we discuss the apparent accuracy and the need for multimodality imaging. Finally, an imaging algorithm for the evaluation of the extracranial carotid arteries is proposed, which is in routine use at our hospital.

Dynamic MR angiography of upper extremity vascular disease: pictorial review

Unlike peripheral lower extremity vascular disease, upper extremity vascular disease is relatively uncommon. While atherosclerosis and embolic disease are the most common causes of upper extremity ischemia, a wide variety of systemic diseases and anatomic abnormalities can affect the upper extremity. Upper extremity ischemia poses a significant diagnostic and therapeutic challenge for both clinicians and radiologists. Although history and physical examination remain the mainstays of diagnosis, imaging can be vital in confirming suspected disease and guiding treatment planning. Digital subtraction angiography is often the preferred method for detection of upper extremity vascular disease, particularly for characterization of complex arteriovenous anatomy such as in vascular malformations and for evaluation of dialysis fistulas and grafts. However, this modality is invasive, requires iodinated contrast agents and radiation, and may fail to demonstrate significant extraluminal disease. More recently, magnetic resonance (MR) angiography techniques have made important advances, permitting higher temporal and spatial resolution that is preferable for diagnosing upper extremity vascular disorders. In this review, the authors present an overview of upper extremity MR angiography techniques and protocols, revisit the often variable vascular anatomy of the arm and hand, and offer examples of various pathologic entities diagnosed with MR angiography. Finally, several imaging pitfalls that one must be aware of for accurate diagnosis are illustrated and reviewed.

Incidence of neurological complications following overstenting of the left subclavian artery

OBJECTIVE

Aortic endovascular stent-graft implantation is associated with low morbidity and mortality rates. Overstenting of the left subclavian artery may be necessary to create a satisfactory proximal 'landing zone' for the stent-graft. Few cases have been published reporting adverse neurological events after overstenting of the left subclavian artery. We thus evaluated whether this procedure is associated with a higher rate of neurological complications by focusing on the management of the supra-aortic vessels.

METHODS

Twenty patients suffering from aortic arch aneurysms (n=3), descending aortic aneurysms (n=7), acute (n=6) and chronic (n=4) type-B aortic dissections underwent stent-graft repair with complete (n=14) or partial (n=6) overstenting of the left subclavian artery. Three patients underwent overstenting of the entire aortic arch with ascending aortic-bi-carotid bypass grafting. One patient with right carotid and vertebral artery occlusion underwent initial carotid-to-subclavian bypass. All patients subsequently underwent neurological examination and Doppler ultrasound for detection of neurological and peripheral vascular complications.

RESULTS

Aortic stent-graft repair was successful in all patients without acute neurologic complications. Two patients developed late central adverse neurological events: right-sided vertebral artery occlusion with brainstem infarction (n=1) and impaired binocular vision combined with dizziness (n=1), necessitating secondary subclavian transposition in one patient. Peripheral symptoms related to occlusion of the left subclavian artery were observed in five patients as sensory and motoric deficits of the left hand and arm.

CONCLUSIONS

Overstenting of the left subclavian artery as treatment of aortic pathologies in high-risk patients is feasible but associated with the risk of neurological complications and peripheral symptoms. Side effects were mild or transient in most of our patients. Detailed preoperative exploration of vascular anatomy and pathology via Doppler ultrasound, CT- or MRI scan is mandatory to avoid adverse neurological events. Prior surgical revascularization of the left subclavian artery is essential in patients with high-grade stenoses, occlusions, or anatomic variants of the supra-aortic branches. Delayed surgical revascularization is necessary only in patients with relevant subclavian steal syndrome or severe peripheral vascular symptoms.