Peter Guest

Prediction of thoracic aortic aneurysm expansion: validation of formulae describing growth

BACKGROUND The expansion rate of thoracic aortic aneurysms may be an important and clinically relevant index of the risk of rupture. The aims of this study were to assess the validity of three published exponential equations that predict expansion rate in a separate sample population, and to calculate an expansion rate formula for this cohort of patients. METHODS We studied 88 consecutive patients undergoing serial computed tomographic or magnetic resonance imaging scanning to monitor thoracic aortic aneurysm progression. In interval scans of at least 6 months, we measured minimum coronal aortic diameter at seven set levels and maximal diameter, yielding 780 segment-intervals. RESULTS The linear expansion rate (mean 2.6 mm/year) increased with incremental aortic diameter (aortic diameter < 40 mm: 2.0; 40-49 mm: 2.3; 50-59 mm: 3.6; > or = 60 mm: 5.6 mm/year; p < 0.01). Regression analysis showed close correlation between predicted and sample data, but there were significant differences between observed and expected measurements. The Yale formula underestimated growth by 0.8 mm, while Mt. Sinai and Osaka formulae overestimated actual change by 1.5 and 0.2 mm, respectively. The expansion rate derived from our population was: last diameter = initial diameter x e(0.00367 x time) (r = 0.617). CONCLUSIONS Although formulae derived from one thoracic aortic aneurysm sample population may not extrapolate exactly to others, there is close concordance of results for patient populations in three different continents.

Reproducibility of thoracic aortic diameter measurement using computed tomographic scans.

OBJECTIVES Decisions to recommend elective surgical repair of thoracic aortic aneurysms (TAA) may be based on size or expansion rate, which are used as indices of the risk of rupture. Measurement error may thus affect clinical decision-making. In order to evaluate the reproducibility of aortic diameter measurements of TAA, we assessed departmental inter- and intra-observer variability of measurement of pre-selected computed tomographic scan images of aneurysmal segments of the thoracic aorta. METHODS We compared measurements of minimum aortic diameter made by four observers in 50 pre-selected scans and at different times by two observers using a calliper method and a measurement tool within the scan. Differences in measured dimension were analysed using Wilcoxons signed ranks test and the repeatability assessed using the method of Bland and Altman. RESULTS There were no significant inter-observer differences among three observers but there were significant differences between another observer and two other observers (P < 0.05). No significant intra-observer differences existed. The best intra-observer repeatability was 2.25 while the worst inter-observer repeatability was 4.37. The mean and maximum difference in measurement were +/-0.88 mm and +/-8.0 mm, respectively. Variability of measurement increased with aortic diameter. CONCLUSIONS Calliper measurement of TAA is an acceptable measurement method for surveillance of TAA but appears most accurate with a single observer. Increasing error is seen with increasing diameter which may compound error in estimation of expansion rate. Standardisation of technique is advisable for multiple observers and aortic units should adopt quality assurance protocols to minimise error.

Near-infrared spectroscopy: an important monitoring tool during hybrid aortic arch replacement.

Near-infrared spectroscopy can be helpful for monitoring the adequacy of cerebral perfusion during cardiovascular surgery. We report changes seen in regional oxygen saturation due to intraoperative thrombosis of the left common carotid artery graft during hybrid aortic arch replacement for traumatic aortic injury.

Multiplanar reformatting and three-dimensional reconstruction : for pre-operative assessment of the thoracic aorta by computed tomography

INTRODUCTION Conventional CT demonstrates pathology of the thoracic aorta. This study aimed to evaluate the additional contributions to surgical planning of multiplanar reformatting, maximum intensity projections and three-dimensional (3-D) reconstruction. DESIGN Retrospective. SUBJECT AND METHODOLOGY: Fifty-three patients with newly diagnosed pathology of the thoracic aorta were scanned over a 15-month period; 25 scans were spiral acquisitions. Scans were acquired during and following rapid injection of 100 ml of intravenous iopromide. The reconstructed data was displayed as axial images, oblique or other multiplanar reformats and shaded surface display 3-D reconstructions. Two radiologists and two surgeons reviewed the images. The axial images were assessed initially, subsequently the reformats and 3-D reconstructed views were examined looking particularly for additional information that might add to the surgical management. RESULTS Pathologies encountered were aortic dissection (21 patients, including two with Marfans syndrome), saccular aneurysms (eight), fusiform aneurysms (16), aortic root and ascending aortic dilatation (seven) and coarctation (one). The relationship of aneurysms and dissections to major vessels are better shown with 3-D reconstruction or oblique reformats. Morphology of saccular aneurysms, particularly the neck, is well shown with 3-D reconstruction. Coarctation was best demonstrated by oblique reformats. There was little additional information from 3-D reconstruction or reformats in assessment of type A dissection. Improved spatial orientation by visualization in varying projections was helpful for surgical planning in certain cases of type B dissection, fusiform aneurysms and aortic root and ascending aortic root dilatation. Spiral acquisitions have the advantage of speed and hence a greater anatomical coverage for a single breath-hold. CONCLUSION Oblique reformats and 3-D reconstruction, although using identical data as the axial images, in specific cases were felt to aid surgical assessment of aneurysms and dissections, thus assisting pre-operative planning.

Homograft replacement of thoraco-abdominal aorta for a leaking mycotic aneurysm

We report the case of a 67-year-old, diabetic patient who underwent antibiotic-preserved homograft replacement of a thoraco-abdominal segment of the aorta for leaking mycotic aneurysm. This was successful in eradicating the sepsis and no graft complication had occurred at (18 months). Follow-up with computed tomography (CT) scanning.

Transposition of Arch Vessels and Endovascular Stenting of Saccular Aneurysm of Distal Arch—A Case Report

Abstract  Endovascular repair of thoracic aneurysms has emerged as an attractive alternative especially in high‐risk patients. However, the aortic curvature and potential coverage of the epiaortic vessels limit the use of stent‐grafts in aneurysms located in the aortic arch. We report a case with a saccular aneurysm in the distal arch and proximal descending aorta, where we have transposed the epiaortic vessels to gain a longer proximal neck in the aortic arch to safely deploy an endovascular stent.