Pulmonary vein isolation (PVI) is an established procedure for atrial fibrillation (AF) patients. Pre-procedural screening is necessary prior to PVI in order to reduce the likelihood of AF recurrence and improve overall success rate of the procedure. However, current reliable methods to determine AF triggers are invasive. In this paper, we present an approach to relate the regional characteristics of left atrial (LA) shape to existence of low-voltage areas (LVA) which indicate the presence of scar in invasive exams. A cohort of 29 AF patient-specific clinical images were each segmented into 3D surface bodies representing the LA. Iterative closest point based similarity transformation was used to find the best fit sphere to each patient-specific LA and the mean deviation of LA wall to this sphere of best fit was determined using a signed point-to-surface regional distance metric. Regional departure from the best-fit sphere was reduced into a metric of global LA sphericity. Next, the LA was divided into six regions to perform an analysis of regional sphericity. Regional sphericity analysis revealed that sphericity of the inferior-posterior LA region was found to be related to several clinical variables, including a direct correlation with body mass index (BMI) and an inverse correlation with left ventricular ejection fraction (EF), which presents a diseased heart that has been asymmetrically inflated. Our observations therefore demonstrate promise in being leveraged as a non-invasive patient selection tool to increase the success rate of PVI procedures.
Left atrial appendage (LAA) is the source of 91% of the thrombi in patients with atrial arrhythmias (~2.3 million US adults), turning this region into a potential threat for stroke. LAA geometries have been clinically categorized into four appearance groups viz. Cauliflower, Cactus, Chicken-Wing and WindSock, based on visual appearance in 3D volume visualizations of contrast-enhanced computed tomography (CT) imaging, and have further been correlated with stroke risk by considering clinical mortality statistics. However, such classification from visual appearance is limited by human subjectivity and is not sophisticated enough to address all the characteristics of the geometries. Quantification of LAA geometry metrics can reveal a more repeatable and reliable estimate on the characteristics of the LAA which correspond with stasis risk, and in-turn cardioembolic risk. We present an approach to quantify the appearance of the LAA in patients in atrial fibrillation (AF) using a weighted set of baseline eigen-modes of LAA appearance variation, as a means to objectify classification of patient-specific LAAs into the four accepted clinical appearance groups. Clinical images of 16 patients (4 per LAA appearance category) with atrial fibrillation (AF) were identified and visualized as volume images. All the volume images were rigidly reoriented in order to be spatially co-registered, normalized in terms of intensity, resampled and finally reshaped appropriately to carry out principal component analysis (PCA), in order to parametrize the LAA region’s appearance based on principal components (PCs/eigen mode) of greyscale appearance, generating 16 eigen-modes of appearance variation. Our pilot studies show that the most dominant LAA appearance (i.e. reconstructable using the fewest eigen-modes) resembles the Chicken-Wing class, which is known to have the lowest stroke risk per clinical mortality statistics. Our findings indicate the possibility that LAA geometries with high risk of stroke are higher-order statistical variants of underlying lower risk shapes.
Endovascular aneurysm repair (EVAR) of juxtarenal aortic aneurysms (JAA) is particularly challenging owing to the
requirement of suprarenal EVAR graft fixation, which has been associated with significant declines in long term renal
function. Therefore, the ability to design fenestrated EVAR grafts on a personalized basis in order to ensure visceral and
renal perfusion, is highly desirable. The objectives of this study are: a) To demonstrate novel 3D geometric methods to
virtually design and deploy EVAR grafts into a virtually designed JAA, by applying a custom surface mesh deformation
tool to a patient-specific descending aortic model reconstructed from computed tomographic (CT) images; and b) To
virtually evaluate patient-specific renal flow and wall stresses in these patient-specific virtually EVAR geometries, using
computational fluid dynamics (CFD). The presented framework may provide the modern cardiovascular surgeon the ability
to leverage non-invasive, pre-operative imaging equipment to personalize and guide EVAR therapeutic strategy. Our CFD
studies revealed that virtual EVAR grafting of a patient-specific JAA, with optimal fenestration sites and renal stenting,
led to a 179.67±15.95% and 1051.43±18.34% improvement in right and left renal flow rates, respectively, when compared
with the baseline patient-specific aortic geometry with renal stenoses, whereas a right and left renal flow improved by
36.44±2.24% and 885.93±12.41%, respectively, relative to the equivalently modeled JAA with renal stenoses, considering
averages across the three simulated inflow rate cases. The proposed framework have utility to iteratively optimize
suprarenal EVAR fixation length and achieve normal renal wall shear stresses and streamlined juxtarenal hemodynamics.
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