Topographical distribution of perioperative cerebral infarction associated with transcatheter aortic valve implantation

Transcatheter aortic valve implantation (TAVI) is associated with a high incidence of cerebrovascular injury. As these injuries are thought to be primarily embolic, neuroprotection strategies have focused on embolic protection devices. However, the topographical distribution of cerebral emboli and how this impacts on the effectiveness of these devices have not been thoroughly assessed. Here, we evaluated the anatomical characteristics of magnetic resonance imaging (MRI)-defined cerebral ischemic lesions occurring secondary to TAVI to enhance our understanding of the distribution of cardioembolic phenomena.Forty patients undergoing transfemoral TAVI with an Edwards SAPIEN-XT valve under general anesthesia were enrolled prospectively in this observational study. Participants underwent brain MRI preprocedure, and 3 ± 1 days and 6 ± 1 months postprocedure.Mean ± SD participant age was 82 ± 7 years. Patients had an intermediate to high surgical risk, with a mean Society of Thoracic Surgeons score of 6.3 ± 3.5 and EuroSCORE of 18.1 ± 10.6. Post-TAVI, there were no clinically apparent cerebrovascular events, but MRI assessments identified 83 new lesions across 19 of 31 (61%) participants, with a median ± interquartile range number and volume of 1 ± 2.8 lesions and 20 ± 190 μL per patient. By volume, 80% of the infarcts were cortical, 90% in the posterior circulation and 81% in the right hemisphere.The distribution of lesions that we detected suggests that cortical gray matter, the posterior circulation, and the right hemisphere are all particularly vulnerable to perioperative cerebrovascular injury. This finding has implications for the use of intraoperative cerebral embolic protection devices, particularly those that leave the left subclavian and, therefore, left vertebral artery unprotected

Cardiac MRI is superior to gated blood pool imaging in the assessment of left ventricular function in patients post-cardiac transplantation

Background: Gated Blood Pool Imaging (GBPI) has low inter-test variability compared to echocardiography, and is often used when accurate repeated measurements of left ventricular ejection fraction are required such as in the surveillance of post-transplant patients. The aim of this study was to determine if cardiac MRI (CMR) could replace Gated Blood Pool Imaging for annual assessment of left ventricular (LV) function in the surveillance of patients post-cardiac transplantation

Measuring dimensions of emmetropic and myopic eyes with magnetic resonance imaging

Magnetic resonance imaging (MRI) is a powerful tool to investigate\ud ocular dimensions, as it is unaffected by assumptions regarding\ud the refractive indices of the ocular media. We used MRI\ud to measure the axial (cornea to retina), horizontal (retina to\ud retina) and vertical (retina to retina) dimensions in emmetropic\ud and myopic eyes (up to -7 D) of more than 50 volunteers aged 18\ud to 35 years. Volunteers were positioned supine in a General\ud Electric Twin Speed 1.5 Tesla clinical scanner. Images of the right\ud eye were acquired using a 7.5 cm receive-only radio frequency\ud surface coil. A mirror was mounted above the subject at approximately\ud 45 degrees that directed gaze to a bright LED at a distance\ud of approximately six metres straight ahead of the subject.\ud Axial (horizontal through middle of eye) and sagittal (vertical\ud through visual axis) sections were taken with a T1-weighted fast\ud spin echo sequence (TR = 400 ms, TE = 16.8 ms, slice thickness\ud three millimetres, 156 micron x 156 micron pixels, acquisition\ud time 130 seconds). Most eyes showed considerable asymmetry in\ud the axial sections, with lens tilts of up to 10 degrees relative to\ud the visual axis. While the well-known increase in axial length with\ud increase in myopia was an obvious feature of our data, there was\ud considerable variability in shape of both emmetropic and myopic\ud eyes