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DOI:10.2214/AJR.05.1021
AJR 2007; 189:W228-W230
© American Roentgen Ray Society

Case Report

Combined Assessment of Tricuspid Valve Endocarditis and Pulmonary Septic Embolism with ECG-Gated 40-MDCT of the Whole Chest

Latifa Fellah1, Frederic Waignein2, Xavier Wittebole3 and Emmanuel Coche1

1 Department of Medical Imaging, Université Catholique de Louvain, Cliniques Universitaires St-Luc, Av. Hippocrate, 10-1200 Brussels, Belgium.
2 Department of Anatomo-pathology, Université Catholique de Louvain, Cliniques Universitaires St-Luc, Brussels, Belgium.
3 Department of Intensive Care, Université Catholique de Louvain, Cliniques Universitaires St-Luc, Brussels, Belgium.

Received June 15, 2005; accepted after revision September 18, 2005.

 
Address correspondence to E. Coche (coche{at}rdgn.ucl.ac.be).

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Keywords: cardiopulmonary imaging • embolism • heart • lung • MDCT


Introduction
Top
 Introduction
Case Report
 Discussion
 References
 
Infective endocarditis is one of the most serious complications of IV drug abuse [1], and Staphylococcus aureus is the most frequent infective organism. Cardiac echocardiography is usually the first-line study performed to establish the diagnosis and to identify complicated cardiac involvement that may warrant surgical intervention [2]. ECG-gated MDCT allows visualization of the entire chest, coronary arteries, and other mobile cardiac structures [3]. In this context, MDCT may be useful for identifying in one CT acquisition valvular vegetation; potential thoracic causes of septic emboli, such as coronary artery fistula [4]; and complications such as coronary artery occlusion [5] and septic pulmonary embolism [6–8]. We present a case of tricuspid valve endocarditis complicated by septic pulmonary embolism documented on ECG-gated 40-MDCT of the entire chest.


Case Report
Top
 Introduction
 Case Report
Discussion
 References
 
A 41-year-old man with drug addiction was referred to our institution because of fever and respiratory distress. A bedside chest radiograph revealed multiple lung nodules disseminated throughout both lungs. Analysis of a blood sample showed a WBC count of 18.76 x 103/µL and C-reactive protein level of 19.8 mg/dL (normal value, < 1 mg/dL). Blood culture revealed Staphylococcus aureus. Transesophageal echocardiography (Fig. 1A) revealed vegetation implanted on the tricuspid valve.


Figure 1
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  		Fig. 1A —41-year-old man with drug addiction and suspected tricuspid valve endocarditis. Transesophageal echocardiogram obtained during systole shows vegetation (arrow) attached to tricuspid valve.

 
Retrospective ECG-gated 40-MDCT (MX Brilliance 40, Philips Medical Systems) of the entire chest was performed with 40 x 0.625 mm collimation, 0.8-mm interval reconstruction, 600 mAs at 120 kV per slice, 250-mm field of view, and 512 x 512 matrix size. After injection of 120 mL of iobitridol (Xenetix 350, Codali Guerbet) at a rate of 3 mL/s, the entire chest was imaged in one breath-hold lasting 24 seconds. CT acquisition started 10 seconds after the beginning of contrast injection. The heart rate was 110 beats/min and regular during CT acquisition. The radiation dose delivered to the patient was 42 mGy. Frontal images of the entire chest reformatted with maximum intensity projection (Fig. 1B) and the mediastinal window setting showed a large filling defect occupying the left inferior pulmonary artery. Multiple nodules of various sizes, some excavated and suggestive of septic emboli, were well depicted with the lung window setting (Fig. 1C). During the same examination, CT images were reconstructed retrospectively in the diastolic (Fig. 1D) and systolic (Fig. 1E) phases. These images revealed a rounded hypodense mass implanted on the tricuspid valve. An operation was performed, and the pathologic specimen (Fig. 1F) showed a large vegetation attached to the tricuspid valve. The clinical outcome was favorable.


Figure 2
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  		Fig. 1B —41-year-old man with drug addiction and suspected tricuspid valve endocarditis. Coronal ECG-gated chest CT scan obtained with thin slab and mediastinal window setting shows large filling defect (arrows) in left inferior pulmonary artery consistent with acute pulmonary embolism.

 

Figure 3
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  		Fig. 1C —41-year-old man with drug addiction and suspected tricuspid valve endocarditis. Coronal ECG-gated chest CT scan obtained with thin slab and lung window setting shows lung nodules (arrows), some excavated, consistent with septic emboli.

 

Figure 4
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  		Fig. 1D —41-year-old man with drug addiction and suspected tricuspid valve endocarditis. CT scan in transaxial plane of body axis reconstructed in diastolic phase (75% of R-R interval) shows vegetation (thick arrow) implanted on tricuspid valve (thin arrow).

 

Figure 5
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  		Fig. 1E —41-year-old man with drug addiction and suspected tricuspid valve endocarditis. CT scan in transaxial plane of body axis reconstructed at systolic phase (12.5% of R-R interval) shows vegetation (arrow) protruding into right ventricle.

 

Figure 6
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  		Fig. 1F —41-year-old man with drug addiction and suspected tricuspid valve endocarditis. Photomicrograph shows vegetation attached to tricuspid valve (curved arrows). Vegetation is composed of thrombotic material (T), bacterial proliferation, and polynuclear exudate (star) and is covered by fibrin (straight arrows).

 

Discussion
Top
 Introduction
 Case Report
 Discussion
References
 
In this case MDCT depicted complications related to migration of infected material within the pulmonary arteries. Lung nodules depicted with the lung window setting were consistent with peripheral septic emboli [6, 7]. The presence of hypodense material in the left inferior pulmonary artery was probably due to migration of septic material from the tricuspid valve into the main pulmonary artery [8]. This case highlights the clinical importance of combined assessment of the heart and thoracic blood vessels in a single CT acquisition. Because they improve temporal and spatial resolution and volume coverage, 16-, 40-, and 64-MDCT make it possible to obtain in a single acquisition high-quality images of cardiac and surrounding thoracic structures. White et al. [9] found that emergency ECG-gated 16-MDCT of the entire chest in one breath-hold was feasible for evaluating the coronary arteries [3], thoracic aorta, and pulmonary arteries of patients with acute chest pain in stable condition.

To our knowledge, the use of ECG-gated MDCT to depict tricuspid valve vegetation and its complications has not been described in the literature. Imaging of cardiac valves with ECG-gated MDCT was studied by Willmann et al. [10], who evaluated the usefulness of MDCT in assessment of aortic valve structure and stenosis. Those investigators obtained good agreement with surgical findings in regard to quantification of the degree of aortic valve calcification. Bootsveld et al. [11] described papillary fibroelastoma on the aortic valve as an incidental finding on 16-MDCT.

The main limitation of ECG-gated MDCT of the entire chest is associated with the delivered radiation dose, which was measured at 42 mGy in our patient. This dose may be lowered by adjusting tube current, scanning time, tube voltage, and slice collimation and by use of ECG-controlled dose-modulation techniques. Retrospective ECG-gated MDCT of the heart has shown that ECG-controlled tube current modulation allows a dose reduction of 37–44% [12]. Future studies are needed to evaluate whether an adapted MDCT protocol is useful for imaging of the cardiac valves. Optimization of contrast medium injection also is mandatory for decreasing the total amount of injected contrast medium, for reducing artifacts in the right atrium, and for obtaining the optimal delay time for visualizing opacified pulmonary arteries, the aorta, coronary arteries, and cardiac valves in one acquisition.

In this case, use of ECG-gated MDCT of the chest led to a combined diagnosis of acute pulmonary embolism, tricuspid valve endocarditis, and lung septic embolism with one imaging technique. Further clinical studies are warranted to define the exact role of MDCT in the diagnostic evaluation of infective endocarditis.


Acknowledgments
 
We thank Gebrin El Khoury for surgical and clinical follow-up information.


References
Top
 Introduction
 Case Report
 Discussion
 References
 

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  8. Kasper W, Meinertz T, Henkel B, et al. Echocardiographic findings in patients with proved pulmonary embolism. Am Heart J1986; 112:1284 –1290[CrossRef][Medline]
  9. White CS, Kuo D, Kelemen M, et al. Chest pain evaluation in the emergency department: can MDCT provide a comprehensive evaluation? AJR 2005; 185:533 –540[Abstract/Free Full Text]
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