Assessment of Myocardial Viability Using Nuclear Medicine Imaging in Dextrocardia

Abstract

Imaging of dextrocardia in humans requires an understanding of the orientation of the heart chambers and walls. There are many types of cardiac malpositioning, such as dextrocardia (with or without situs inversus), mesocardia, and levocardia. Myocardial perfusion scintigraphy of dextrocardia has been explained in case reports and imaging atlases; however, myocardial viability assessment using nuclear medicine imaging techniques is less documented in the literature. Methods: In 2 cases of dextrocardia with situs inversus and 1 case of mesocardia, myocardial viability was assessed using 99m Tc-sestamibi rest perfusion scintigraphy and 18 F-FDG PET. Cardiac SPECT images of dextrocardia with situs inversus were acquired using the feet-first supine position with a 180°arc from left anterior oblique to right posterior oblique, whereas a rightlateral-to-left-lateral arc was used for mesocardia. The processing and reconstruction were done by entering the dataset for the feetfirst supine position and repeating after entering the dataset for the feet-first prone position. The 2 sets of reconstructed images were compared for orientation of walls and cardiac chambers. Results: The first processing, using the feet-first supine position, revealed an interchanged septum and lateral wall in reconstructed images of dextrocardia with situs inversus. This interchange was corrected by changing the position to prone during processing of the rest perfusion and PET raw data. The display of cardiac slices in various axes matched the conventional nomenclature for the septum and lateral wall, leading to easy interpretation. However, this change was not required in the mesocardia, for which the location of the heart chambers was not interchanged. Conclusion: Because the acquisition protocol for SPECT is a semicircular orbit, the various types of dextrocardia require careful selection of the arc, with the patient positioning kept feet-first supine. Processing and reconstruction of data by changing the patient position to prone was found to be most useful method of matching the septum and lateral wall orientation for interpretation of images.

Situs Inversus Totalis: A Clinical Review

“…41 Nuclear medicine imaging is also feasible in situs inversus, but technical details need to be considered, like detector position during cardiac SPECT imaging. 42 If available, fusion with CT or MRI can help to understand the anatomy that may not be visible on functional imaging. SPECT/CT with 99m Tc-labeled native red blood cells can be useful to differentiate between polysplenia and abdominal masses.…”

Medication and ECG Patterns That May Hinder SPECT Myocardial Perfusion Scans

“…Various imaging modalities have been proposed for SPECT acquisition, including changing the arc of rotation and proning the position. The latter was deemed to potentially be the best suited option to keep the heart in the usual spot in the field of view, as well as reduce soft tissue attenuation [ 80 , 81 ].…”