Electromechanical mapping of the myocardium does not match the information gained by 18F-FDG PET

Abstract
Aim: an initial evaluation of the clinical relevance of catheter-aided electromechanical mapping (EMM) in coronary heart disease (CHD) for diagnosis of normal, hibernating and anormal (non-viable) myocardium using ²⁰¹Tl-SPECT and ¹⁸F-FDG-PET as a gold standard. Methods: fourteen patients (13 male, 1 female; mean age 59 yrs.) with a history of CHD and limited left ventricular function (EF at rest < 50%) underwent myocardial scintigraphy with ²⁰¹Tl-SPECT and Cardio-PET with ¹⁸F-FDG using an insulin/glucose clamp and Acipimox. Within 5 days all patients also underwent EMM of the left ventricle using the EMM-system. Comparison of the results was made using polar-plots and a segmental analysis with the left ventricle being divided into 5 segments. Normal myocardium in PET was considered under conditions of normal glucose consumption and normal SPECT results. Using EMM, the definition of normal myocardium was a basic potential (> 11 mV) and normal myocardial contractility. Hibernating myocardium was detected where there was a PET/SPECT mismatch and/or an EMM showing reduced contractility and a potential of 6 - 11 mV. Non-viable myocardium was considered if a match of defects was found in PET and SPECT and/or if there was a basic potential of less than 6 mV in EMM. Results: correlating results for hibernating and abnormal tissue were found in 13 segments. In 16 segments PET proved viability while the EMM-system detected scar tissue. Another 14 myocardial segments which were considered as hibernating or scar by EMM could also be shown to be normal using PET. In 10 segments PET detected hibernating myocardium while EMM suggested that these segments were normal and EMM also classified 13 segments to be normal while PET and SPECT showed a corresponding defect indicating these segments represented scar tissue. The sensitivity of the EMM-system to detect normal (viable) / hibernating and infarcted myocardium was 86 / 64 / 9%. The specificity was 55 / 71 and 82% for normal / hibernating and infarcted myocardium. Conclusion: the majority of myocardial segments was correctly classified as Normal by all methods being applied. There remains, however, a subset of segments with discrepancies between the results of the EMM and functional imaging, especially for the detection of hibernating myocardium. Methodological difficulties of the rather novel technique for EMM may account for some of these results.

Key words
FDG-PET, electromechanical mapping

Bibliografía del artículo

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