Calculation of the effective orifice area of Edwards SAPIEN balloon expandable valve: AVA-TAVI study

Abstract Background Calculation of the aortic valve effective orifice area (EOA) is essential for the patient’s follow-up after transcatheter aortic valve implantation (TAVI). When using the Bernoulli equation for the Edwards SAPIEN (ES) valve, positioning of the pulsed-wave (PW) spectral Doppler sample volume for velocity-time integral (VTI) measurement just apical to the valve stent frame at peak systole is suggested. For the neo-left ventricular outflow tract (neo-LVOT) diameter, measurement of the outer-to-outer stent diameter from parasternal long-axis view (PLAX) is recommended. Aim To compare 1. the neo-LVOT diameters derived from transthoracic echocardiography (TTE), computed tomography (CT) and fluoroscopy (X-ray) and 2. EOAs calculated using these diameters and the nominal valve size as a neo-LVOT diameter with invasively calculated EOA. Methods We prospectively enrolled patients indicated for TAVI with ES valve in our institution. The neo-LVOT was measured as outer-to-outer (oo), inner-to-inner (ii) and leading-to-leading (ll) edge diameters at the ventricular tip of the valve stent in PLAX at peak systole and on corresponding reconstructed CT planes. The PW sample volume for VTI measurement was positioned at the same place. X-ray of the valve in its long axis was obtained at the end of TAVI procedure, mid-stent to mid-stent diameter was used for the neo-LVOT diameter. Invasive EOA was calculated using Gorlin equation. The sphericity index was determined as the ratio of max./min. CT neo LVOT diameter at the short axis plane, the neo-LVOT CT planimetry was measured at the inner stent tip border. Results 103 patients were enrolled in the study, 38 were excluded. (Table 1) In 65% (n=42) S3 valve and in 35% (n=23) S3 Ultra valve was implanted, in majority of sizes 26 (52%) or 23 (37%). Although the CT neo-LVOT was not circular (sphericity index 1.08), there was no difference in EOA calculated using CT derived neo-LVOT ii diameter and corresponding CT stent planimetry area (1.90 ± 0.46 vs 1.81 ± 0.46 cm2, p=0.16). Significant differences between TTE and corresponding CT neo-LVOT diameters were observed, the smallest for the oo neo-LVOT. Furthermore, only the oo neo-LVOT did not differ from the X-ray diameter. Consequently, EOAs calculated from neo-LVOT diameters were significantly smaller than X-ray diameter calculated EOA, apart from oo neo LVOT diameter. (Table 2) No difference was found between EOAs calculated using X-ray, oo neo LVOT stent diameter and the nominal valve size as the neo-LVOT diameter for the whole group (p=0.22) and for the valve size 23 (p=0.70) and 26 (p=0.12) subgroups. These EOAs were larger than invasively measured EOA (p=0.01). Conclusion For ES EOA calculation, the oo TTE neo-LVOT, X-Ray diameter and valve size provide the same result. Non-circular neo-LVOT shape does not affect the accuracy of EOA calculation. Non-invasive calculation seems to overestimate EOA in comparison with invasive measurement.Post enrolment exclusions. The neo-LVOT diameters/EOAs comparison.