A clinical protocol for analysis of the structural integrity of the Medtronic CoreValve System (R) frame and its application in patients with 1-year minimum follow-up

Aims: The optimal clinical protocol to detect fractures of transcatheter aortic valves is unknown. To the best of our knowledge, there are no published reports describing stent or frame fractures following transcatheter aortic valve implantation. The purpose of this study is two-fold: (1) to determine the optimal fluoroscopic protocol to identify potential fractures of the Medtronic CoreValve (R) frame; and (2) to implement this protocol in the analysis of the fluoroscopic films of patients implanted with the CoreValve (R) device with 1-year minimum follow-up. Methods and results: Considering the resolution of fluoroscopy (similar to 0.2 mm), we used a 0.2 mm diamond-cutter to create a single fracture in a single strut of two CoreValve (R) frames. An intact CoreValve (R) prosthesis was used as control. These prostheses were subsequently implanted in post-mortem heart specimens. A protocol involving still frames and rotational (left-right and cranial-caudal) fluoroscopic imaging was then applied to the heart specimens. The experimentally induced fractures were detectable on the rotational cine runs (left-right and cranial-caudal); in some of the fixed acquisition sequences, however, the fractures were undetectable. The fluoroscopic protocol was retrospectively applied to the films of 58 patients who underwent implantation with the CoreValve System (R) between October 2005 and August 2008 and had at least 1-year follow-up. The mean and median follow-up times were 22 months and 24 months, respectively (range 12 to 36 months). Rotational cine films (only left-right lateral) were available in 39 patients (60%). No frame fractures of the CoreValve (R) frame were identified. Conclusions: Rotational cine runs in the left-right and cranial-caudal directions should be mandatory in the clinical assessment of the structural integrity of the CoreValve (R) frame. No frame fractures were identified in 58 patients implanted with the Medtronic CoreValve (R) device with 2-year mean follow-up.