Fluid- and Biomechanical Analysis of Ascending Thoracic Aorta Aneurysm with Concomitant Aortic Insufficiency.

We present a comprehensive and original framework for the biomechanical analysis of patients affected by ascending thoracic aorta aneurysm and aortic insufficiency. Our aim is to obtain crucial indications about the role played by deranged hemodynamics on the ATAAs risk of rupture. Computational fluid dynamics analysis was performed using patient-specific geometries and boundary conditions derived from 4D MRI. Blood flow helicity and wall shear stress descriptors were assessed. A bulge inflation test was carried out in vitro on the 4 ATAAs after surgical repair. The healthy volunteers showed no eccentric blood flow, a mean TAWSS of 1.5 ± 0.3 Pa and mean OSI of 0.325 ± 0.025. In 3 aneurismal patients, jet flow impingement on the aortic wall resulted in large TAWSS values and low OSI which were amplified by the AI degree. However, the tissue strength did not appear to be significantly reduced. The fourth patient, which showed the lowest TAWSS due to the absence of jet flow, had the smallest strength in vitro. Interestingly this patient presented a bovine arch abnormality. Jet flow impingement with high WSS values is frequent in ATAAs and our methodology seems to be appropriate for determining whether it may increase the risk of rupture or not.

Multidetector computed tomography sizing of bioprosthetic valves: guidelines for measurement and implications for valve-in-valve therapies.

AIM: To describe a technique for bioprosthetic multidetector computed tomography (MDCT) sizing and to compare MDCT-derived values against manufacturer-provided sizing. MATERIALS AND METHODS: Fourteen bioprosthetic stented valves commonly used in the aortic valve position were evaluated using a Philips 256 MDCT system. All valves were scanned using a dedicated cardiac CT protocol with a four-channel electrocardiography (ECG) simulator. Measurements were made of major and minor axes and the area and perimeter of the internal stent using varying reconstruction kernels and window settings. Measurements derived from MDCT (MDCT ID) were compared against the stent internal diameter (Stent ID) as provided by the valve manufacturer and the True ID (Stent ID + insertion of leaflets). All data were collected and analysed using SPSS for Mac (version 21). RESULTS: The mean difference between the MDCT ID and Stent ID was 0.6±1.9 mm (r=0.649, p=0.012) and between MDCT ID and True ID 2.1±2 mm (r=0.71, p=0.005). There was no difference in the major (p=0.90), minor (p=0.87), area (p=0.92), or perimeter (p=0.92) measurements when sharp, standard, and detailed stent kernels were used. Similarly, the measurements remained consistent across differing windowing levels. CONCLUSION: Bioprosthetic stented valves may be reliably sized using MDCT in patients requiring valve-in-valve (VIV) interventions where the valve type and size are unknown. In these cases, clinicians should be aware that MDCT has a tendency to overestimate the True ID size.

Non-invasive hemodynamic analysis in cardiac resynchronization therapy patients wearing quadripolar left ventricular leads: the importance of pacing electrode selection.

AIM: Quadripolar left ventricular (LV) leads offer multiple choices for LV pacing increasing programming flexibility. Aim of this study is to assess the influence of LV pacing vector selection on hemodynamic parameters for patients who underwent cardiac resynchronization therapy (CRT) using quadripolar LV lead chronically evaluated with a non-invasive approach by Nexfin(®) system provided analysis (BMEYE B.V., Amsterdam, The Netherlands). METHODS AND RESULTS: In 16 CRT patients implanted with a quadripolar LV lead (mean follow-up 8,8 ±13,4 months after implantation), we measured Cardiac Output (CO), Mean Blood Pressure (MBP), Total Peripheral Resistance (TPR), LV dP/dt max and Stroke volume (SV) from each one of the ten available bipolar pacing configurations. All the recorded parameters showed marked differences among the ten pacing configurations, but dP/dt max, SV and TPR were those showing the wider range, depending of the selected pacing vector. The average delta for the whole group of subjects between the maximum and minimum hemodynamic values for each pacing configuration were 15.9% for SV, 21.1% for dP/dt max and 20.3% for TPR. Inter-individual analysis of data failed to identify a link between a specific pacing vector and the hemodynamic response. CONCLUSION: Our study demonstrates that different bipolar pacing configurations, even if arising from a single CS branch, substantially modify the hemodynamic effect of LV pacing in CRT patients. Moreover, the non-invasive hemodynamic analysis suggests the better pacing configuration should be established individually and could represent an important issue in optimizing CRT during follow-up.