Diagnostic Efficacy of Cardiac Scintigraphy with 99mTc-Pyrophosphate for Latent Myocardial Inflammation in Patients with Atrial Fibrillation

Objectives. This work aimed to study the efficacy of hybrid Tc-99m-Pyrophosphate SPECT/CT for diagnosis of latent inflammatory processes in the myocardium of patients with atrial fibrillation (AF). Methods. The study comprised 34 patients aged 44 +/- 9 years with AF of unknown etiology referred for radiofrequency ablation. The data were acquired using hybrid Tc-99m-Pyrophosphate SPECT/CT. To evaluate and interpret the results of hybrid study and to determine localization of radiopharmaceutical accumulation, scintigraphic and CT images were fused. SPECT/CT results were compared with data of endomyocardial biopsy. Results. Sensitivity, specificity, and accuracy of Tc-99m-Pyrophosphate SPECT/CT in diagnosing myocarditis were 91%, 100%, and 94%, respectively. Proposed diagnostic criteria for myocarditis comprised intensity of the radiopharmaceutical accumulation in the myocardium and the ratios of focus/lung, focus/vertebral column, and focus/LV pool. Minimum cutoff values for the histologically verified myocarditis were >1.47 for focus/lung index, >0.11 for focus/vertebral column ratio, and >1.26 for focus/lung index. Conclusions. SPECT/CT-based quantitative assessment of Tc-99m-Pyrophosphate accumulation in the myocardium is a highly informative noninvasive method for diagnosis of inflammatory process in the heart in patients with AF of undefined etiology.