Transcatheter Aortic Valve Implantation with Preexisting Mechanical Mitral Prosthesis — Use of CT Angiography

ABSTRACT: A 72-year-old Chinese female with prior mitral valve replacement with a mechanical prosthesis 13 years before was diagnosed with severe symptomatic aortic stenosis. She was considered a high-risk surgical candidate and was considered for transcatheter aortic valve implantation using a balloon-expandable device. The close proximity of the non-compliant mechanical mitral prosthesis to the aortic annulus raised concerns that the deployment of the device may be affected. Gated cardiac computed tomographic angiography was used to assess the distance between the mitral prosthesis and the aortic annulus. Transcatheter aortic valve implantation using the transapical approach was subsequently performed successfully.

J INVASIVE CARDIOL 2010;22:339–340

Key words: valvular heart disease, computed tomography, catheterization, diagnostic

Case Report. A 72-year-old Chinese female presented with decreasing exertional tolerance (New York Heart Association [NYHA] Class III) over 1 year due to severe aortic stenosis (valve area 0.6 cm², mean gradient 46 mmHg, ejection fraction 60%). She had a history of hypertension, hyperlipidemia, osteoporosis and lumbar compression fractures. Thirteen years before, she underwent a mitral valve replacement with a St. Jude mechanical prosthesis (St. Jude Medical, Inc., St. Paul, Minnesota). Coronary angiography showed minor coronary disease. Her logistic Euro- SCORE was 15%, and STS score was 5.3%. Despite the risk scores, she was considered a high-risk surgical candidate due to frailty. She was evaluated for transcatheter aortic valve implantation (TAVI) via the transapical approach because of small ilio-femoral vessels. Her aortic annulus as assessed by transesophageal echocardiography (TEE) was 21 mm. Gated cardiac computerized tomographic angiography (CTA) was performed. This showed a 3.7 mm clearance between the mitral valve prosthesis and aortic annulus (Figure 1A). The procedure was performed under general anesthesia, with fluoroscopy and TEE guidance. TEE confirmed a 3 mm aorto-mitral distance (Figure 2). The apex was exposed with a left anterior minithoracotomy. Access was obtained, and balloon aortic valvuloplasty with a 20 mm balloon showed complete expansion and stability of the balloon with no indentation seen. A 23 mm Edwards Sapien transcatheter heart valve (THV) (Edwards Lifesciences, Irvine, California) was then deployed. During the inflation of the deployment balloon, a distinct pull towards the aortic direction was felt, and strong tension was maintained on the delivery catheter to maintain position of the device during the entire deployment. Subsequently, TEE and fluoroscopy showed good positioning of the aortic prosthesis with mild aortic paravalvular leak. Post-procedural echocardiography showed mean aortic gradient of 11 mmHg, and trivial aortic valve regurgitation. The patient was discharged on the 7th post-operative day. Three months after discharge, she was in NYHA Class II. The post-procedural CTA showed a fully expanded aortic bioprosthesis with obliteration of the aorto-mitral space (Figure 1B). Discussion Transcatheter aortic valve implantation is a promising alternative to high-risk aortic valve replacement.¹ With mitral valve injury reported after TAVI, the close proximity of the aortic and mitral annuli has been reemphasized in this new context.² The presence of a mechanical prosthesis in the mitral position may complicate TAVI due to: 1) significant reduction or absence of the aorto-mitral space; 2) a non-compliant mechanical prosthesis. Both factors may limit the expansion of the valve, resulting in inadequate valve stent expansion or embolization due to the “melon-seeding” effect.^3,4 Various methods have been used to assess this risk, which include: 1) using TEE to assess the aorto-mitral distance; 2) using a valvuloplasty balloon of a similar size to the valve stent for aortic valvuloplasty and observing for adequate balloon expansion and stability as an indicator of the effect that the existing mitral prosthesis might have on the valve stent to be deployed later.⁴ The authors used gated cardiac CTA as a complementary imaging modality to assess the aorto-mitral distance preoperatively instead of solely relying on intraoperative TEE. In the previous 3 reported cases of TAVI using a balloon-expandable valve stent in the presence of a mechanical mitral valve prosthesis — 2 transapical^3,5 and the other transfemoral⁴ — all prostheses were fully deployed with no evidence of embolization or displacement. This might suggest that the risks of incomplete expansion and embolization may not hold true. However, the total obliteration of the aorto-mitral space in the post-operative CTA showed the compressive effect of the fully inflated balloon-expandable valve stent on the surrounding tissue, demonstrating the close proximity of the aortic and mitral annuli. In addition, during the procedure, the tension applied by the operator on the delivery catheter in response to the opposing pull towards the aorta may have prevented the valve stent from melon-seeding and embolizing. This suggests that in spite of prior reported successes, TAVI in the patient with a preexisting mechanical valve should be regarded with caution, especially when using a balloon-expandable valve stent in those with small aortic roots where there is significant oversizing of the prosthesis. In this instance, gated cardiac CTA is a useful modality for preprocedural assessment of the amount of excursion available for valve-stent expansion. Acknowledgements. The authors would like to thank Dr Anson Cheung from St Paul’s Hospital, Vancouver, British Columbia, Canada, for his technical assistance during the procedure. References

1. Webb JG, Altwegg L, Boone RH, et al. Transcatheter aortic valve implantation: Im- pact on clinical and valve-related outcomes. Circulation 2009;16;119:3009–3016. 2. Wong DR, Boone RH, Thompson CR, et al. Mitral valve injury late after tran- scatheter aortic valve implantation. J Thorac Cardiovasc Surg 2009;137:1547–1549. 3. Rodes-Cabau J, Dumont E, Miro S, et al. Apical aortic valve implantation in a patient with a mechanical valve prosthesis in mitral position. Circ Cardiovasc Intervent 2008;1:233. 4. Dumonteil N, Marcheix B, Berthoumieu P, et al. Transfemoral aortic valve implan- tation with pre-existent mechanical mitral prosthesis: Evidence of feasibility. JACC Cardiovasc Interv 2009;2(9):897–898. 5. Scherner M, Strauch JT, Haldenwang PL, et al. Successful transapical aortic valve replacement in a patient with a previous mechanical mitral valve replacement. Ann Thorac Surg 2009;88:1662–1663.

_________________________________________________________________________ From the Departments of *Cardiothoracic Surgery and †Cardiology, National Heart Centre Singapore. The authors report no conflicts of interest regarding the content herein. Manuscript submitted December 14, 2009, provisional acceptance given January 7, 2010, final version accepted March 2, 2010. Address for correspondence: Dr. Victor T. Chao, Department of Cardiothoracic Surgery, National Heart Centre Singapore, 17 Third Hospital Avenue, Singapore 168752. E-mail: ttvchao@gmail.com