Study objective: The presence of defects on rest thallium 201 myocardial scintigraphy, reversible after dipyridamole infusion, was already demonstrated in myocardial localization of sarcoidosis. The present study compared the respective efficiency of a new tracer of myocardial blood flow, 99mTc sestamibi (sestamibi), vs thallium 201 (TI) for the diagnosis and follow-up of myocardial sarcoidosis.
Methods: Quantitative single photon emission computed tomography (SPECT) was performed in 37 consecutive patients with confirmed sarcoidosis and clinical suspicion of myocardial localization. Three successive scans were performed in all patients within the same day: rest TI SPECT, rest sestamibi SPECT, and dipyridamole sestamibi SPECT. Thirteen patients were reinvestigated after 3 months of corticosteroid therapy. The size and intensity of the defects were compared using a computerized quantitative analysis of bull's eye.
Results: At rest, sestamibi SPECT is more sensitive than TI, demonstrating significantly larger defects (28.1 +/- 13.2% vs 17.2 +/- 12.8% of bull's eye area, p < 0.001) and detecting abnormalities in seven more patients (24 vs 17). All patients with abnormal TI scans also had sestamibi abnormalities. After dipyridamole infusion, sestamibi defects decreased significantly (28.1 +/- 13.2% vs 15.2 +/- 12.3%, p < 0.001). This improvement correlated with the evolution of sestamibi SPECT performed in the 13 patients reinvestigated after corticosteroid therapy (r = 0.85, p < 0.001).
Conclusions: We conclude that sestamibi SPECT is suitable for the diagnosis of myocardial sarcoidosis and represents an objective tool for the follow-up. The improvement after vasodilatation supports the hypothesis of reversible abnormalities in most of these patients and accurately predicts corticosteroid efficiency.