Anatomic and Flow Characteristics of Left Anterior Descending Coronary Artery Angiographic Stenoses Predisposing to Myocardial Infarction.

The impact of the anatomic characteristics of coronary stenoses on the development of future coronary thrombosis has been controversial. This study aimed at identifying the anatomic and flow characteristics of left anterior descending (LAD) coronary artery stenoses that predispose to myocardial infarction, by examining angiograms obtained before the index event. We identified 90 patients with anterior ST-elevation myocardial infarction (STEMI) for whom coronary angiograms and their reconstruction in the three-dimensional space were available at 6 to 12 months before the STEMI, and at the revascularization procedure. The majority of culprit lesions responsible for STEMI occurred between 20 and 40 mm from the LAD ostium, whereas the majority of stable lesions not associated with STEMI were found in distances >60 mm (p < 0.001). Culprit lesions were significantly more stenosed (diameter stenosis 68.6 ± 14.2% vs 44.0 ± 10.4%, p < 0.001), and significantly longer than stable ones (15.3 ± 5.4 mm vs 9.2 ± 2.5 mm, p < 0.001). Bifurcations at culprit lesions were significantly more frequent (88.8%) compared with stable lesions (34.4%, p < 0.001). Computational fluid dynamics simulations demonstrated that hemodynamic conditions in the vicinity of culprit lesions promote coronary thrombosis due to flow recirculation. A multiple logistic regression model with diameter stenosis, lesion length, distance from the LAD ostium, distance from bifurcation, and lesion symmetry, showed excellent accuracy in predicting the development of a culprit lesion (AUC: 0.993 [95% CI: 0.969 to 1.000], p < 0.0001). In conclusion, specific anatomic and hemodynamic characteristics of LAD stenoses identified on coronary angiograms may assist risk stratification of patients by predicting sites of future myocardial infarction.

Aortic Flow Patterns After Simulated Implantation of Transcatheter Aortic Valves.

INTRODUCTION: The functional behavior and hemodynamic characteristics of percutaneously implanted bioprosthetic valves are not known. METHODS: We created aortic models after the simulated implantation of two of the most widely used bioprosthetic valves: the Edwards SAPIEN, and the Medtronic CoreValve. By using computational fluid dynamics analysis we sought to investigate variations in the aortic flow patterns induced by the two valve designs and their association with detrimental phenomena such as vascular remodeling, vascular wall damage and thrombosis. RESULTS: The simulated implantation of models that resemble the two valves resulted in different aortic flow conditions. Vortex formation in the upper ascending aorta was more persistent in the case of the simulated Medtronic valve. The ranges of average wall shear stress (WSS) values were 2.4-3.5 Pa for Edwards and 3.0-5.3 Pa for Medtronic; the calculated WSS values induced endothelial quiescence and an atheroprotective setting in both valves. The average shear stress on the simulated valve leaflets was low; however, hotspots were present in both valves (155.0 Pa for Edwards and 250.0 Pa for Medtronic) which would in theory be able to cause platelet activation and thus promote thrombosis. The pressure drops along the aorta were slightly lower for the Edwards compared to the Medtronic valve (198.0 Pa versus 218.0 Pa). CONCLUSIONS: The presented method allows the assessment of aortic flow conditions following the implantation of bioprosthetic valves. It may be useful in predicting detrimental flow phenomena, thus facilitating the selection of appropriate valve designs.