Inflow Expansion Research Articles

LIFETIME MANAGEMENT OF AORTIC STENOSIS IN EXTREME SETTING

Abstract A 51–year–old male patient returned to our attention due to symptomatic severe aortic stenosis. Despite the severity of the aortic valve disease, he had been previously turned down from aortic valve replacement by us because of lack of symptoms and very unfavorable anatomy. Indeed he had been irradiated at the age of 3 due to Hodgkin’s Lymphoma and presented with porcelain aorta, small ascending aorta and aortic annulus. The patient returned to us with a 3–month history of progressive dyspnea (NYHA class IIa) and one episode of lipothymia during physical exercise. Physical examination, hematologic and biochemical investigations at admission were normal. Our trans–thoracic echocardiogram confirmed a trileaflet aortic valve (AV) that was severely stenotic and calcified with a mean gradient of 60 mmHg and an AV area of 0.5 cm2 (0.3 cm2/m2), in presence of good left ventricular systolic function with an ejection fraction (EF) of 60%. CT excluded coronary disease but, confirmed severe calcified aortic stenosis and porcelain aorta with small calcific sino–tubular junction and ascending aorta and protruding LVOT calcium. (Ascending aorta 19 mm; STJ 19 mm). The heart–team judged the patient not suitable for AVR and decided to perform a high–risk TAVI, leaving apical conduit as the last resort. From a technical standpoint, the LVOT calcium and the short and narrow STJ were high risk features for rupture with balloon expandable devices. On the other hand the short and narrow STJ with the narrow ascending aorta would represent a serious issue for the expansion of self–expanding devices and an even more troublesome feature for future coronary access and coronary occlusion in the setting of TAVI–in–TAVI down the road. Given the patient’s young age, a balloon expandable SAPIEN ultra 23 mm was chosen to be implanted with a two–step inflation to minimize the risk of STJ rupture. The prosthesis was partially expanded until anchoring was achieved on the aortic leaflets then, on continuous pacing, the balloon was rapidly collapsed, pushed down deeper under the STJ and fully inflated to achieve prosthesis’ inflow expansion. Intra–procedural and post–procedural course were uneventful and the patient was discharged home in 5th Day. Transthoracic echocardiogram at the dismission reveal a trans–aortic mean gradient of 18 mmhg, the absence of significant paravalvular leaks and a preserved ejection fraction. Pre–discharge CT scan confirmed feasibility of future TAVI–in–TAVI in case of need.

Intravascular ultrasound for valve frame expansion and orifice area measurement as well as paravalvular leak assessment during transcatheter aortic valve replacement

Abstract Introduction Valve frame expansion (measured outer valve frame area/nominal valve dimension), but not oversizing (nominal valve dimension/annulus area, %) determines pattern of restored blood flow after transcatheter aortic valve replacement (TAVR). There is no online measure of frame expansion, and error in current echocardiographic assessment of effective orifice area (EOA) and paravalvular leak (PVL) are common. Purpose To evaluate large imaging field intravascular ultrasound (IVUS) during TAVR for measuring valve geometry [frame expansion, minimal geometric orifice area (min GOA), and mechanism of PVL] with transthoracic echo and angio-CT serving for comparative measures, along with the nominal EOA as established by Hahn et al. Methods After successful TAVR either a 10MHz Vision PV 0.035" (60mm imaging field) or 20MHz Vision PV 0.018" (24mm imaging field plus Chr omaFlo) IVUS catheter (Philips) was slowly pulled from the left ventricle outflow (LVOT) to the aorta with continuous imaging of the aortic root. Results There were 16 pts (80.8±7.1 yrs, 8 female) treated for de novo aortic stenosis (n=15) or failed bioprosthesis (n=1), 7 of whom were treated with balloon-expandable TAVR. PV 0.35" catheters were used in 8 pts (including valve-in-valve) and allowed complete geometry assessment of 26.6±2.7mm nominal prosthesis Ø (Figure 1A) whereas PV 0.018" allowed complete geometry assessment in only 4 of 8 pts with nominal prosthesis Ø of 26.1±2.8mm (Figure 1B). Actual % valve inflow expansion (IVUS outer frame/valve nominal dimension) was significantly smaller than % valve oversizing (80%±19% vs 125±19%, p=0.005). Min GOA was substantially bigger than corresponding nominal EOA and EOA calculated using the post-procedural LVOT diameter (272±84mm2 vs 174±25mm2 vs 181±59mm2, p=0.001 correspondingly). However, min GOA was similar to EOA calculated using baseline LVOT area (272±84mm2 vs 230±90mm2; r=0.713, p=0.009). IVUS and angio-CT measurements of outer prosthesis frame area were similar for inflow, coaptation site, and outflow (460±143mm2 vs 454±134mm2 and 455±134mm2 vs 447±114mm2 and 722±174mm2 vs 725±180; p≤0.001 for all paired correlations). Inflow expansion (IVUS outer frame/baseline CT annulus area) tended to be smaller among valves with ≥mild vs no PVL (95±14% vs 107±11%, p=0.156), with clear ChromaFlo signal seen in the space between the aortic annulus wall and outer-valve frame surface (Figure 1C). Conclusions Large imaging field IVUS during TAVR allows for peri-procedural assessment of actual valve geometry that differs substantially from nominal. IVUS offers online tomographic perspective and highest accuracy in anatomy evaluation corresponding with valve function. Funding Acknowledgement Type of funding sources: None. Figure 1

TCT-663 Anatomic and Procedural Predictors of Paravalvular Leak following Transcatheter Aortic Valve Replacement with a Self-expanding Prosthesis at a High Volume Center Including a Novel Variable of Inflow Expansion

Transcatheter Aortic Valve Replacement (TAVR) is frequently used to treat patients with symptomatic, severe aortic stenosis in whom surgery is considered to be high-risk or contraindicated. Post-procedural para-valvular leak (PVL) remains a significant issue with a complex etiology. Our objective

Exergy analysis of radial inflow expansion turbines for power recovery

The paper presents an exergy analysis of the performance of a single-stage, radial-inflow expansion turbine. The analysis considers the effect of the design controlling parameters on the power output, and the first law and second law efficiencies of the turbine. The design parameters include: inlet temperature, wheel tip speed, exhaust Mach number and expansion pressure ratio. Limitations imposed by the second law of thermodynamics are presented and discussed, and the admissible ranges of variation of the controlling parameters are outlined and discussed. The analysis enables the process designer to quickly and realistically estimate the amount of power available from the exhaust gases of a process stream, the maximum effective pressure ratio and the temperature drop across the turbine and the exit Mach number.

Effect of an Unsteady Three‐Dimensional Wake on Elastic Blade‐Flapping Eigenvalues in Hover

This paper describes the formulation of a finite-state inflow model based on an acceleration potential and a helical wake geometry. The states of the model are coefficients of an inflow expansion in terms of a Fourier series (azimuthally) and of special polynomials (radially). The integrals over the wake are done in closed-form to obtain a set of ordinary differential equations for the inflow coefficients. The forcing functions for these equations are generalized forces which are integrals of the blade loading exactly as in structural dynamics. This model implicitly includes (for the hover case) Prandtl-Goldstein tip losses, dynamic inflow, and Theodorsen/Loewy lift deficiency. Thus, it is a fully three-dimensional unsteady wake model. Here, this model is coupled with elastic-blade equations in hover and eigenvalues are found. The results show that the three-dimensional wake has a large effect on the flap damping of all modes.

Radial Inflow Expansion Turbines for Power Recovery

Performance data for single-stage, radial inflow, expansion turbines is presented in a manner to enable the process designer to quickly estimate the amount of power available from a process stream, the maximum effective pressure ratio and the temperature drop. All data presented is based on the current state of the art and recognizes the different levels of technology which may be applied.