Author + information
- Published online July 3, 2017.
- Claire Bouleti, MD, PhD,
- Guillaume Baudry, MD,
- Bernard Iung, MD,
- Dimitri Arangalage, MD,
- Jérémie Abtan, MD,
- Gregory Ducrocq, MD,
- Philippe-Gabriel Steg, MD, PhD,
- Alec Vahanian, MD,
- Marie-Cécile Henry-Feugeas, MD, PhD,
- Nicoletta Pasi, MD,
- Sylvie Chillon, MS,
- Francesca Pitocco, MD,
- Jean-Pierre Laissy, MD, PhD and
- Phalla Ou, MD, PhD∗ ()
- ↵∗Department of Radiology, Assistance Publique-Hôpitaux de Paris, Bichat Hospital, 46 rue Henri Huchard, 75018 Paris, France
Clinical presentation of acute myocarditis is heterogeneous and often leads to coronary angiography to rule out acute coronary syndrome (ACS). Noninvasive evaluation relies on cardiac magnetic resonance (CMR), with late gadolinium enhancement (LGE) being one of the main parameters (1). However, CMR examination may be limited by contraindications (mainly claustrophobia and metallic implants), long-time scanning, and/or machine availability. Spectral cardiac computed tomography (CT) allows for tissue characterization based on late iodine enhancement (LIE) and could represent an interesting substitute for CMR, as well as an alternative to coronary angiography (2). The aim of this study was to compare LIE on spectral CT with the reference LGE on CMR in acute myocarditis.
Between 2013 and 2015, 20 consecutive patients who presented with CMR-proven acute myocarditis based on the modified Lake Louise criteria were enrolled for cardiac spectral CT. CMR examinations were performed using a 3-T machine (GE Healthcare, Milwaukee, Wisconsin). LGE was defined as a signal intensity >5 SDs above that of the reference myocardium, and was imaged 6 min after gadolinium injection (3). The number and localization of positive segments were assessed in each of the 17 segments of the left ventricle. CT was performed with a 64-slice machine (GE Discovery CT 750HD) with a prospective electrocardiographically gated mode with iodine contrast agent injection (Iomeprol 350 [Bracco, Evry, France], 70 to 90 ml). The first acquisition was performed to evaluate the coronary arteries. At 3 min post-injection, a spectral mode with a multienergy single-source emission was acquired that allowed for LIE mapping and iodine quantification in inflamed areas of myocardium. A 180° one-half reconstruction was applied with the Adaptive Statistical Iterative Reconstruction algorithm. Iodine concentrations and tissue density were measured in both nonenhanced and enhanced myocardium. Comparisons between CT and CMR findings were obtained on a segment-by-segment analysis using LIE and LGE (Figure 1), using the McNemar test. The images were analyzed by 2 experienced radiologists to assess the interobserver variability.
All patients were admitted for chest pain and elevated troponin I. Median age was 31 years, and 90% were men. Seventeen patients (85%) had an abnormal electrocardiogram upon admission, mainly with ST-segment elevation (16 of 17; 94%). ACS was ruled out in all patients, 6 (30%) by coronary angiography and the other 14 (70%) by coronary CT angiography.
The median time between admission and CMR or CT examinations was 2 days. On CMR, all 20 patients presented with positive LGE. They accounted for 340 segments, of which 72 (21%) were positive on LGE; the median number of inflammatory segments was 3 per patient. On CT, all patients also presented with positive LIE, with a median number of inflamed segments of 3 per patient. The iodine concentration and tissue density in nonenhanced segments were 17.4 ± 3.5 μg/cm3 and 49 ± 17 HU, respectively. They increased to 28.9 ± 4.9 μg/cm3 and 78 ± 19 HU in enhanced segments.
In patient-based analysis, the sensitivity of spectral CT was 100%. On a segment-to-segment comparison, the sensitivity of spectral CT was 82% (59 of 72 positive segments), its specificity was 99% (264 of 268 negative segments), its positive predictive value was 94% (59 of 63 segments), and its negative predictive value was 95% (264 of 277 segments). Finally, the overall accuracy of spectral CT was 95% (59 + 264)/340 compared with CMR. The interobserver variability was excellent, with a kappa value of 0.84.
The duration of the CMR examination was 41 ± 5 min, including 10 ± 2 min for LGE imaging and only 15 ± 4 min for CT examination, including 3 ± 1 min for LIE imaging. The median radiation dose due to spectral acquisition was 1.2 mSv (range 1.1 to 1.3), which is 4 times less than the dose received when undergoing coronary CT angiography.
In this proof-of-concept study, spectral CT thus appears to be a valid alternative to CMR for the evaluation of inflamed myocardium in acute myocarditis. Acute myocarditis may be easily misclassified as ACS. These results provide new perspectives because CMR remains of limited availability in some centers. The large availability of CT combined with the possibility to rule out ACS with coronary CT angiography during the same examination, makes it promising for refining acute myocarditis imaging.
Please note: Dr. Iung has been a consultant for Boehringer Ingelheim and has received speaker’s fees from Edwards Lifesciences. Dr. Ducrocq has received speaking and consulting fees from Lilly, AstraZeneca, and Bristol-Myers Squibb. Dr. Steg has received research grants from Merck, Sanofi, and Servier; and has received speaking or consulting fees from Amarin, AstraZeneca, Bayer, Boehringer Ingelheim, Bristol-Myers Squibb, CSL-Behring, Daiichi-Sankyo, GlaxoSmithKline, Janssen, Lilly, Merck Novartis, Pfizer, Regeneron, Roche, Sanofi, Servier, and The Medicines Company. Dr. Vahanian has received speaker fees from Abbott, Valtech, and Edwards Lifesciences. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose. Drs. Bouleti and Baudry contributed equally to this work.
- 2017 American College of Cardiology Foundation
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