Ann Thorac Surg 2003;75:1631-1633
© 2003 The Society of Thoracic Surgeons
Case report
Detection of pannus by multidetector-row computed tomography
Hideki Teshima, MDa*,
Nobuhiko Hayashida, MDa,
Naofumi Enomoto, MDa,
Shigeaki Aoyagi, MDa,
Koji Okuda, MDa,
Masafumi Uchida, MDb
a Department of Surgery, Kurume University, School of Medicine, Kurume, Japan,
b department of Radiology, Kurume University, School of Medicine, Kurume, Japan
Accepted for publication October 21, 2002.
* Address reprint requests to Dr Teshima, Department of Surgery, Kurume University, School of Medicine, 67 Asahi-machi, Kurume 830-0011, Japan
e-mail: tesshi{at}med.kurume-u.ac.jp
 |
Abstract
|
|---|
Prosthetic valve dysfunction (PVD) due to pannus formation is an infrequent but serious complication. A 72-year-old man who underwent aortic valve replacement was diagnosed with PVD and aneurysm of the Sinus of Valsalva. Multidetector-row computed tomography (MDCT) was used to examine the cause of PVD before reoperation. MDCT demonstrated that tissue regarded as pannus extended from the left ventricular septum into the pivot guard. These findings were confirmed by observations during reoperation. MDCT can be a useful diagnostic technique for the anatomical and functional evaluation of PVD.
|
Introduction
|
|---|
Prosthetic valve dysfunction (PVD) due to pannus formation is an infrequent but serious complication [1]. However the mechanism of pannus formation has not been fully proven yet. Multidetector-row computed tomography (MDCT) has many detectors for the direction of axis from head to foot and permits high-speed scanning of large volumes with high resolution [2]. A combination of MDCT and gating electrocardiography may enable the detection of images without the unique artifacts that result from leaflet motion. We examined valvular anatomy and function after aortic valve replacement (AVR) in a patient with PVD and aneurysm of the Sinus of Valsava using MDCT. The MDCT findings were validated by observations during reoperation.
A 72-year-old man who underwent AVR with a 25-mm St. Jude Medical valve (St. Jude Medical Inc, St. Paul, MN) was diagnosed as PVD by transthoracic echocardiography (peak pressure gradient and aortic valve area were 25.7 mm Hg and 0.84 cm2/m2, respectively), and cineradiography (the opening angle was 24 degrees calculated as the distance between the two leaflets in the fully open position) [3].
The patient’s condition was New York Heart Association functional class II. Electrocardiography showed a heart rate of 60 beats per minute and sinus rhythm without arrhythmia. To examine the anatomical and morphologic mechanism of the PVD a MDCT scanner was used. The MDCT system was a Light Speed ULTRA (GE Medical Systems, Yokogawa Medical System, Tokyo, Japan) of the 8 slice/8 DAS type with electrocardiographic gated half reconstruction. Contrast medium, 120 mL, using nonionic iodide was infused through an intravenous rapid injector. Scanning was started from 30 seconds after the beginning of contrast medium administration. Images were viewed using the workstation version of INTAGE RV version 1.3 (KGT, Kubota, Tokyo, Japan) after being converted into DICOM data.
MDCT scanning enabled clear detection of the prosthetic valve in the closed position without the artifacts associated with cardiac and leaflet motion. The aortic prosthetic valve was located within the hypertrophic ventricular septum (25 mm in maximum thickness) and narrowed left ventricular outflow tract (15 mm in diameter), which was detected in the long left ventricular axis view by the two-dimensional technique of multiplanner reformation. A small amount of tissue extending from the left ventricular septum into the pivot guard was detected (Fig 1).
Based on the CT attenuation value, the tissue with the same attenuation as interventricular septum was regarded as periannular pannus rather than prosthetic valve-related thrombus. The other dark pixels near the pannus in the image were considered as fatty degeneration or necrotic tissue around the sewing cuff. Dilation of the Sinus of Valsalva (60 mm in diameter) was also detected by MDCT.
View larger version (112K):
[in this window]
[in a new window]
|
Fig 1. (A) The aortic prosthetic valve is demonstrated in the closing position and located within the hypertrophic ventricular septum and narrowed left ventricular outflow tract. A small amount of tissue (arrowhead) that extended from the left ventricular septum into the pivot guard was detected. The dilation of the sinus of Valsalva was also detected by multidetector-row computed tomography. (B) This image is a reversed black and white image of Figure A. (C) The image that detected the pannus (arrowhead) extending into the pivot guard is shown on the lateral side of Figure A. (AO = aorta; IVS = interventricular septum; LA = left ventricular; LV = left atrium.)
|
|
Based upon these findings the patient underwent reoperation. A full aortic root replacement was performed using a 25-mm Freestyle aortic root bioprosthesis (Medtronic Inc, Minneapolis, MN) and 26-mm Hemashield Gold (Boston Scientific Corporation, Natick, MA) with coronary reconstruction using an aortic button technique. Similar to the MDCT findings, pannus formation without thrombus was observed in the left ventricular aspect on the septum intraoperatively. The pannus had two linear prints interfering with the straight edge of leaflet movement in the pivot guard (Fig 2).
The postoperative course was uneventful and the patient was followed up for 3 months postoperatively without any complications.
View larger version (158K):
[in this window]
[in a new window]
|
Fig 2. (A) Pannus formation without thrombus was observed in the left ventricular aspect on the septum intraoperatively (arrows). (B) Pannus had two linear prints, which interfered with the straight edge of the leaflet movement in the pivot guard (arrows). Pannus extended into the pivot guard (arrowheads). (C) Aortic view of the resected prosthetic valve. (D) Left ventricular view of the prosthetic valve covered with resected pannus of Figure B (arrowheads).
|
|
|
Comment
|
|---|
Many recent clinical and histologic studies have reported pannus formation related to prosthetic valves especially in the mitral position [4, 5]. These studies suggested that the overgrowth of periannular pannus was associated with persistent inflammation [4, 5]. We also reported 9 patients with severe PVD who underwent reoperation [3]. We found that 7 of the 9 PVD cases were caused by pannus formation solely whereas pannus overgrowth was observed in the left ventricular aspect of the SJM valve on the septum in all 9 cases [3]. Although cineradiography is essential to diagnose obstructive leaflet movement, the method is unable to determine the cause of PVD. Echocardiography is also a noninvasive and feasible diagnostic method but artifacts resulting from leaflet movement and lower resolution of the ultrasonic image [6] may interfere with detailed observations of the periannular morphology. Magnetic resonance imaging also presents a problem; a prosthetic valve is detected as a defective image of a so-called void. Helical CT can more clearly detect the shape of the prosthetic valve than conventional CT; still it is not sufficient for examining the anatomical and functional consequences of pannus formation owing to various problems including mechanical artifacts. The use of more advanced diagnostic imaging, MDCT, enabled us to determine the morphologic cause of PVD, which was confirmed by intraoperative observations. This technique also provided anatomical information regarding the Sinus of Valsalva and the left ventricular outflow tract in detail, which is essential for making the decision about operative procedure.
To determine an appropriate treatment strategy for PVD, whether thrombolysis or reoperation, it is important to differentiate pannus from thrombus in the MDCT image. The attenuation level, position in the prosthetic valve, and size of abnormal tissue observed in MDCT images may be important indices. Pannus in the aortic position is observed as a small amount of tissue at the same attenuation as interventricular septum, of concentric or eccentric morphology [5], in the left ventricular aspect on the septum [3]. In contrast, thrombus appears to be of various sizes, at low or heterogeneous attenuation. Because pannus is occasionally accompanied by secondary thrombi, however, careful inspection is required.
To obtain a useful image it is essential to minimize artifacts associated with leaflet motion, contrast medium, and banding. Moreover, awareness of patient conditions such as sinus rhythm, low heart rate without arrhythmia, and negligible transvalvular leakage is mandatory to obtain minute images. Further studies involving more PVD cases are required to resolve these problems and to refine this diagnostic technique.
In conclusion, MDCT clearly demonstrated pannus formation, which extended from the left ventricular septum into the pivot guard with resulting PVD. MDCT can be a useful diagnostic technique for the anatomical and functional evaluation of PVD.
|
Acknowledgments
|
|---|
This work was supported in part by a Grant-in-Aid for Scientific Research, Japan Society for the Promotion of Science (Grant C-14571290 and Grant C-13671416).
|
References
|
|---|
- Barbetseas J., Nagueh S.F., Pitsavos C., Toutouzas P.K., Quinones M.A., Zoghbi W.A. Differentiating thrombus from pannus formation in obstructed mechanical prosthetic valves: an evaluation of clinical, transthoracic and transesophageal echocardiographic parameter. J Am Coll Cardiol 1998;32:1410-1417.[Abstract/Free Full Text]
- Nieman K., Oudkerk M., Rensing B.J., et al. Coronary angiography with multi-slice computed tomography. Lancet 2001;357:599-603.[Medline]
- Aoyagi S, Nishimi Y, Tayama E, et al. Obstruction of St. Jude Medical valves in the aortic position: a consideration for pathogenic mechanism of prosthetic valve obstruction. Cardiovasc Surg 2002;10:339–44
- Ibrahim M.F., David T.E. Mitral stenosis after mitral valve repair for nonrheumatic mitral regurgitaion. Ann Thorac Surg 2002;73:34-36.[Abstract/Free Full Text]
- Vitale N., Renzulli A., Agozzino L., et al. Obstruction of mechanical mitral prostheses: analysis of pathological findings. Ann Thorac Surg 1997;63:1101-1106.[Abstract/Free Full Text]
- Lengyel M., Vandor L. The role of thrombolysis in the management of left-sided prosthetic valve thrombosis: a study of 85 cases diagnosed by transesophageal echocardiography. J Heart Valve Dis 2001;10:636-649.[Medline]
This article has been cited by other articles:
|
|
|
|
 
H. Teshima, N. Hayashida, and S. Aoyagi
Reply to the Editor
J. Thorac. Cardiovasc. Surg.,
June 1, 2004;
127(6):
1851 - 1852.
[Full Text]
[PDF]
|
|
|
Top
Abstract
Introduction
