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Published on: February 16, 2016
Assessment of Myocardial Viability Using Nuclear Medicine Imaging in Dextrocardia
Shwetal U Pawar1, Suruchi S Shetye2, Mangala K Ghorpade2
1Department of Nuclear Medicine, King Edward Memorial Hospital, Seth G.S. Medical College, Mumbai, India shwetal13@yahoo.com.
Insights
Accurate myocardial viability assessment in dextrocardia (heart positioned on the right) requires specific imaging protocols. Adjusting patient positioning during data processing, particularly to a prone position, corrects septal and lateral wall orientation for clear interpretation.
Area of Science:
- Nuclear medicine imaging
- Cardiology
- Medical diagnostics
Background:
- Dextrocardia involves cardiac malpositioning, with varying chamber and wall orientations.
- Myocardial viability assessment in dextrocardia using nuclear medicine is not well-documented.
- Accurate interpretation of cardiac imaging requires understanding heart chamber and wall orientation.
Purpose of the Study:
- To assess myocardial viability in patients with dextrocardia and mesocardia using nuclear imaging.
- To determine optimal processing and reconstruction methods for accurate cardiac imaging in dextrocardia.
- To improve the interpretation of myocardial perfusion scintigraphy and PET scans in cardiac malpositioning.
Main Methods:
- Evaluated 2 cases of dextrocardia with situs inversus and 1 case of mesocardia.
- Utilized 99mTc-sestamibi rest perfusion scintigraphy and 18F-FDG PET for myocardial viability assessment.
- Acquired SPECT images using specific arcs and patient positions (feet-first supine/prone) for dextrocardia and mesocardia, comparing processing methods.
Main Results:
- Standard feet-first supine processing inverted septum and lateral wall orientation in dextrocardia with situs inversus.
- Switching to a prone position during data processing corrected the orientation, enabling accurate interpretation.
- This positional adjustment was not necessary for mesocardia, where chamber orientation was not reversed.
Conclusions:
- Careful selection of acquisition arc and patient positioning (feet-first supine) is crucial for dextrocardia SPECT imaging.
- Processing data with a prone position adjustment is the most effective method for aligning cardiac anatomy for interpretation.
- Standardized imaging and processing protocols are essential for reliable myocardial viability assessment in cardiac malpositioning.
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 99mTc-sestamibi rest perfusion scintigraphy and 18F-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 right-lateral-to-left-lateral arc was used for mesocardia. The processing and reconstruction were done by entering the dataset for the feet-first 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.
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