Intravascular ultrasound findings in patients with abnormal coronary flow reserve after stenting

Computational Hemodynamics of an Implanted Coronary Stent Based on Three-Dimensional Cine Angiography Reconstruction

Coronary stents are supportive wire meshes that keep narrow coronary arteries patent, reducing the risk of restenosis. Despite the common use of coronary stents, approximately 20-35% of them fail due to restenosis. Flow phenomena adjacent to the stent may contribute to restenosis. Three-dimensional computational fluid dynamics (CFD) and reconstruction based on biplane cine angiography were used to assess coronary geometry and volumetric blood flows. A patient-specific left anterior descending (LAD) artery was reconstructed from single-plane x-ray imaging. With corresponding electrocardiographic signals, images from the same time phase were selected from the angiograms for dynamic three-dimensional reconstruction. The resultant three-dimensional LAD artery at end-diastole was adopted for detailed analysis. Both the geometries and flow fields, based on a computational model from CAE software (ANSYS and CATIA) and full three-dimensional Navier-Stroke equations in the CFD-ACE+ software, respectively, changed dramatically after stent placement. Flow fields showed a complex three-dimensional spiral motion due to arterial tortuosity. The corresponding wall shear stresses, pressure gradient, and flow field all varied significantly after stent placement. Combined angiography and CFD techniques allow more detailed investigation of flow patterns in various segments. The implanted stent(s) may be quantitatively studied from the proposed hemodynamic modeling approach.

Current concepts in coronary physiology for the interventionalist

Coronary angiography remains the 'gold standard' for the diagnosis of epicardial coronary disease. However, precise quantification of stenosis severity is limited because of the complex three-dimensional geometry of epicardial plaques. To assist the angiographer in lesion assessment, several physiologic measurements have been developed to evaluate stenosis severity, including coronary flow reserve, relative coronary flow reserve and fractional flow reserve. Physiologic lesion assessment can also be an invaluable tool in coronary intervention, evaluating efficacy of angioplasty and stent deployment.