AimTranscatheter mitral valve implantation (TMVI) is a novel technology for patients with severe mitral valve disease but at high surgical risk. Imaging guidance during the procedure is critical for successful device deployment. Identification of the mitral annular plane (MAP) with fluoroscopy during the procedure is limited by lack of clearly defined landmarks. We hypothesized that a plane defined by left circumflex-right coronary arteries (LCX-RCA) would have a consistent relationship to MAP. Methods and resultsWe studied 25 patients with gated cardiac computed tomography. We identified the MAP and the LCX-RCA plane in mid systole and diastole. The distance between the two planes in prespecified four points (anterior, posterior, medial, and lateral) in the apical 2 and 3-chamber views. Alignment of the planes was described by cranial/caudal angulation for both planes in RAO 30 degrees and LAO 90 degrees (lateral) angulation. Mean age was 819 years, 56% of patients had 2+ mitral regurgitation. In mid systole, the distances between the LCX-RCA plane and the MAP in the four points were<5 mm in 92% of patients. In mid diastole, distances were<5 mm in 100% of patients. In mid systole, the correlation between the caudal/cranial orientations of the 2 planes was 0.85 and 0.80 in the LAO 90 degrees and RAO 30 degrees, respectively (P=<0.001). In mid diastole, this was 0.92 and 0.92 in the LAO 90 degrees and RAO 30 degrees, respectively (P=<0.001). Conclusion LCX-RCA plane has a close and consistent relationship to the MAP and can be useful to guide TMVI. Accurate imaging of mitral valve annular plane during TMVI procedure is challenging. MAP guided by fluoroscopy might be crucial to guide successful prosthesis deployment. A plane defined by the left circumflex- right coronary arteries in the atrioventricular grove has a consistent relationship with MAP; this can be used aided by pre-procedural MDCT to guide TMVI procedure. (c) 2016 Wiley Periodicals, Inc.