Assessment of the geometric interaction between the Lotus transcatheter aortic valve prosthesis and the native ventricular aortic interface by 320-multidetector computed tomography.

OBJECTIVES: This study sought to assess the geometric interaction between the Lotus Valve System transcatheter aortic prosthesis (Boston Scientific, Natick, Massachusetts) and the native aortoventricular interface using multidetector computed tomography (MDCT).

BACKGROUND: The interaction between transcatheter aortic valve prostheses and native anatomy is variable, although potentially predictable. The Lotus transcatheter device uses a novel mechanical means of expansion, the effect of which on native anatomic geometry has not previously been described.

METHODS: Forty patients treated with the Lotus prosthesis were enrolled. The patients underwent 320-MDCT imaging before and after implantation. Prosthesis dimensions and relevant interaction parameters, including circularity and expansion, were assessed. The degree of paraprosthetic regurgitation (PAR) and prosthesis gradient were measured by transthoracic echocardiography at the same time points.

RESULTS: The mean baseline annular eccentricity index (EI) was 0.21 ± 0.06 and left ventricular outflow tract EI was 0.31 ± 0.09. The deployed prostheses had high rates of circularity with a mean EI across all device segments of 0.06 ± 0.04. In noncircular device deployment, an EI >0.1 was identified in 25% of prostheses and was associated with greater native annular eccentricity at baseline compared with circular devices (0.24 ± 0.04 vs. 0.19 ± 0.06; p = 0.01). The median percent of expansion was 97.5 ± 3.8% in the inflow portion of the prosthesis. Twenty-five percent of prostheses were <90% expanded in at least 1 segment with a numerical, but not statistically significant, association between oversizing and underexpansion. No correlation was found between device underexpansion and the mean transprosthesis gradient or between noncircularity and PAR.

CONCLUSIONS: The Lotus prosthesis results in nearly full device expansion and circularization of the native basal plane. Awareness of the anatomic interaction between this unique device and the native architecture may help in the formulation of appropriate device-specific sizing algorithms.