Intense uniform FDG myocardial uptake during anti-tuberculous therapy

Background: The treatment of active tuberculosis lasts at least six months using multiple drugs. Myocarditis may occur as a result of anti-tuberculous therapy (ATT). Intense uniform myocardial FDG uptake during chemotherapy for cancers has been observed and suggested to be a sign of early myocardial dysfunction. A similar uptake has been observed during the treatment of TB that may similarly be related to early myocardial dysfunction. The aim of the study was to determine the prevalence of intense increased myocardial FDG uptake in patient’s ATT and its relation to treatment duration.

Methods: We retrospectively reviewed 96 FDG PET/CT studies done for patients while on anti-tuberculous therapy. All patient were fasted for at least 6 hours before the scan and blood sugar before the study was less than 10mmol/L. We scanned the patients according to international guidelines on the same PET/CT camera. We excluded patients with pericarditis or known myocardial dysfunction. We drew regions of interest around the heart and recorded the maximum standardized uptake value (SUVmax). We also drew regions of interest in the liver avoiding areas of abnormal tracer uptake when present and recorded the SUVmax. We calculated the heart-liver ratio for each patient. We determined the proportion of patients with intense uptake at SUVmax defined as patients with SUVmax of more than 10 and a heart-liver ratio of greater than three for the entire study population. We also calculated these proportion in the patients who received therapy for less than two months of therapy and more than two months of therapy to determine whether the proportion increased with longer duration of ATT.

Results: The mean age at the time of the scan was 37.36 ±11.67, and 49 (51%) were in females. Sixty-four (67%) patients had their scan within the first two months of starting ATT. The median myocardial FDG SUVmax and the heart-liver ratio of the SUVmax was 3.81 (range, 1.62-52.62) and 1.3 (range, 0.51-13.19) respectively. We found 21 (21.9%) of all the scans studied had the SUVmax ≥10 and 26 (27%) had a heart-liver ratio ≥3. The proportion of patients with myocardial SUVmax ≥10 was higher in patients who had a longer duration of ATT 11/32 (34.4%) vs. 10/64 (15.6%), p=0.037. We also found a higher proportion of patient with heart-liver ratio ≥3 in the patients who had a longer duration of ATT, 12/64 (18.6%) vs. 14/32 (43.8), p = 0.009.

Conclusions: More than one in five patients on anti-tuberculous therapy have a uniform and intense myocardial uptake on FDG PET/CT imaging. The proportion of patients with the intense FDG uptake increases with the duration of anti-tuberculous therapy.