Gated myocardial perfusion scintigraphy in children with myocarditis: can it be considered as an indicator of clinical outcome?

Purpose: Myocarditis is an inflammation of the heart muscle and represents a challenge for diagnosis and treatment. On account of the lack of sensitivity and specificity of routine cardiac tests, there is a need for accurate diagnostic imaging. The aim of this study is to review the role of gated 99Tc-methoxyisobutylisonitrile myocardial perfusion scintigraphy (G-MPS) in the diagnosis and follow-up of the patients with myocarditis in comparison with gallium scintigraphy.

Materials And Methods: Thirteen patients with a clinical diagnosis of myocarditis were included in the study. All underwent rest G-MPS and the images were then evaluated by quantitative perfusion single-photon emission computed tomography and quantitative gated single photon emission computed tomography software program. Visual evaluation of perfusion was performed as well as analysis of motion with thickening function [expressed as summed rest score, summed motion score, and summed thickening score (STS)] with calculation of ejection fraction (EF) and lung-to-heart (L/H) ratio. Eight patients underwent 67Ga scintigraphy. Clinical, echocardiography, and cardiac enzymes (creatinine kinase-MB, myoglobulin, troponin T, brain natriuretic peptide) data were gathered from the patients' charts. Clinical outcome was grouped according to prognosis. Spearman's correlation (SC) test was used for comparison analysis.

Results: Myocardial perfusion defects were observed in eight patients. Perfusion defects in the left ventricle involve a mean of 7.25% (range: 1-11%), whereas wall motion abnormality on G-MPS was more prominent, which showed to be a better marker for myocardial inflammation and necrosis. The 67Ga scintigraphy findings were normal in all, but two. The G-MPS EF (33+/-21%) was slightly lower than the echocardiography EF (40+/-15%), but with close correlation (SC coefficient: 0.635). Comparison of scintigraphic findings with clinical parameters showed that summed motion score with G-MPS EF and STS with L/H ratios were highly correlated (0.932 and 0.622, respectively). The maximum brain natriuretic peptide and L/H ratio with STS were highly correlated with the patients' outcomes (SC coefficient: -0.621, 0.821, and 0.579, respectively), as well.

Conclusion: Tc-methoxyisobutylisonitrile G-MPS is therefore helpful in providing additional diagnostic and prognostic information in patients with myocarditis.