Dual-Source Computed Tomography Demonstrating Obstruction of Left Ventricular Outflow Tract

Dual-Source Computed Tomography Demonstrating Obstruction of Left Ventricular Outflow Tract Hiroshi Imagawa, MD, Fumiaki Shikata, MD, Teruhito Kido, MD, Kouhei Hosokawa, MD, Masahiro Ryugo, MD, Teruhito Mochizuki, MD, and Kanji Kawachi, MD Cardiothoracic Surgery, Ehime University School of Medicine, and Radiology, Ehime University School of Medicine, Ehime, Japan

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69-year-old woman with a medical history of mitral valve replacement was admitted to our hospital with atrial fibrillation tachycardia and dyspnea. She underwent an implantation of the Starr-Edwards mitral disk prosthesis (6520, 2M [Edwards Lifesciences, Irvine, CA]) for mitral stenosis 30 years ago. Transthoracic continuous wave Doppler echocardiography showed a pressure gradient between the left ventricle and ascending aorta (greater than 90 mm Hg), suggesting the presence of marked subaortic stenosis. The cause of her disease could not be identified. A computed tomographic scan on a dual-source system [1] (Somation Definition [Siemens Medical Systems, Forchheim, Germany]) revealed a left ventricular outflow tract obstruction due to anterior projection of the Starr-Edwards mitral disk prosthesis (Edwards Lifesciences) and stenosis between the prosthetic valve and the interventricular septum. Preoperative volume-rendered images of the left two-chamber axis view by dual-source computed tomographic scan showed diastolic and almost occluded left ventricular outflow tract in the systolic phase (Figs 1A and 1B; A ⫽ diastolic; B ⫽ systolic; white arrow indicates StarrEdwards mitral disk valve; AAo ⫽ ascending aorta; LA ⫽ left atrium; LV ⫽ left ventricle). The patient received a mitral valve re-replacement with a 23-mm St. Jude valve (St. Jude Medical, St. Paul, MN). Operative findings showed a projected cage of the Starr-Edwards disk valve, which seemed to have compressed the left ventricular muscle, causing secondary Address correspondence to Dr Imagawa, Cardiothoracic Surgery, Ehime University School of Medicine, To-on, Ehime, 791-0295, Japan; e-mail: [email protected].

© 2010 by The Society of Thoracic Surgeons Published by Elsevier Inc

fibrosis hyperplasia and calcification of the interventricular septum. Fibrotic or calcified tissue was partially excised, but not totally, because of concerns that too much excision of thickened connective tissue might cause damage to the left ventricular muscle. The patient had an uneventful recovery. Postoperative echocardiography showed improved left ventricular outflow tract pressure gradient (20 mm Hg) and a well-functioning mitral prosthetic valve. A postoperative dual-source computed tomographic scan revealed the widened outflow tract and well-functioning prosthetic valve (Figs 2A and 2B; A ⫽ diastolic; B ⫽ systolic; black arrow indicates St. Jude Medical mitral valve; AAo ⫽ ascending aorta; LA ⫽ left atrium; LV ⫽ left ventricle). Recently, dual-source computed tomography with improved temporal resolution was introduced into clinical routine, bringing the hope that some of the earlier problems might be overcome. The high temporal resolution (dual-source computed tomography, 83 msec; conventional computed tomography, 150 to 200 msec) is expected to make a diagnostic assessment of the heart with atrial fibrillation rhythm feasible. We had an impression that the dual-source computed tomography offered a clear depiction of the heart valve, and the image quality was considerably improved compared with that of the previous scanner generation.

Reference 1. Johnson TR, Nikolaou K, Wintersperger BJ, et al. Dual-source CT cardiac imaging: initial experience. Eur Radiol 2006;16: 1409 –15. Ann Thorac Surg 2010;90:314 • 0003-4975/$36.00 doi:10.1016/j.athoracsur.2009.09.004