DOI:10.2214/AJR.08.1553
AJR 2009; 192:W77
© American Roentgen Ray Society
Role of MDCT in the Evaluation of Prosthetic Heart Valves
Murat Biteker,
Sabahattin Gündüz and
Mehmet Özkan
Kosuyolu Heart and Research Hospital, Istanbul, Turkey
WEB—This is a Web exclusive article.
We would like to comment on the recent article by Konen and colleagues
[1] titled "The Role of
ECG-Gated MDCT in the Evaluation of Aortic and Mitral Mechanical Valves:
Initial Experience." In addition to the inclusion of a relatively small
number of patients and the unblinded retrospective design, the study has some
other limitations.
First, we note the absence of multiplane transesophageal echocardiography
(TEE), which is known to be the most useful diagnostic tool in the evaluation
of prosthetic valve dysfunction. Konen et al.
[1] did not use TEE for the
evaluation of any patient and regarded fluoroscopy as the reference standard.
Fluoroscopy may detect the restriction of mechanical valve leaflets but cannot
reveal the reason for the obstruction. To determine the appropriate management
strategy for prosthetic valve dysfunction—thrombolysis or re
operation—differentiating pannus from thrombus formation is useful. In
addition to differentiating pannus from thrombus, TEE can also detect the
location and size of an abnormal mass that is causing prosthetic valve
dysfunction.
Second, on fluoroscopy and MDCT, prosthetic valve dysfunction is defined as
occurring when the motion of a leaflet or leaflets is persistently restricted,
with a calculated opening angle of more (for bileaflet valves) or less (for
disk valves) than the values for a normal valve, as specified by the
manufacturer. However, the features of abnormal tissues that cause prosthetic
valve dysfunction, such as the attenuation level, position, and size observed
on MDCT, are not defined. Konen et al.
[1] referred to another article
[2] they considered as showing
the usefulness of MDCT in the diagnosis of pannus in only two patients.
However, in that article, Teshima et al.
[2] described the CT properties
of pannus formation in 16 patients with prosthetic aortic valves, such as
attenuation values that were the same as those of the interventricular septum,
ranged from 1 to 4 mm in size, and extended from the left ventricular septum
into the pivot guard. In an ongoing trial, we have evaluated the role of MDCT
in more than 40 patients with prosthetic valve dysfunction. We have determined
that attenuation values of the abnormal masses adjacent to the prosthetic
valves may provide quantitative data for the differentiation of pannus from
thrombus formation. MDCT can also predict the response of the masses to
thrombolytic therapy, with masses of > 200 HU resistant to thrombolytic
therapy. Concordant with Konen et al., we determined that the role of MDCT in
the evaluation of monoleaflet valves is limited because of excessive
artifacts.
Third, we note the absence of the use of contrast material in four patients
with prosthetic valve dysfunction in the Konen et al.
[1] study. In contrast, we
determined that for detecting the cause of prosthetic valve dysfunction, in
most of the cases, the use of contrast material may allow clear delineation
and border detection of abnormal masses as well as visualization of the
abnormal tissues adjacent to prosthetic valves.
We include an example of a patient with mitral prosthetic valve dysfunction
because of pannus formation surrounding the valve
(Fig. 1A), which was confirmed
using the surgically excised valve (Fig.
1B).
References
- Konen E, Goitein O, Feinberg MS, et al. The role of ECG-gated MDCT
in the evaluation of aortic and mitral mechanical valves: initial experience.
AJR 2008; 191:26
–31[Abstract/Free Full Text]
- Teshima H, Hayashida N, Fukunaga S, et al. Usefulness of a
multidetector-row computed tomography scanner for detecting pannus formation.
Ann Thorac Surg 2004;77
: 523–526[Abstract/Free Full Text]
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