Comparison of nitrate augmented Tc-99m tetrofosmin gated SPECT with FDG PET for the assessment of myocardial viability in patients with severe LV dysfunction

Objectives Of various nuclear medicine techniques, 18F-FDG PET is considered as the best modality for the assessment of viable myocardium (VM). 99m Tc -Tetrofosmin SPECT is widely available and inexpensive. However, there is a scarcity in the literature comparing the 99mTc Tetrofosmin SPECT with FDG PET for detection of VM. In this study, we compared the diagnostic accuracy of nitrate augmented 99mTc-tetrofosmin G- SPECT with FDG PET.

Methods 31 consecutive cases of angiographically proven CAD with severe LV dysfunction were enrolled in the study. The patients underwent 99mTc-tetrofosmin G-SPECT (pre & post nitrate) and FDG PET. 99mTc-tetrofosmin G-SPECT study was analysed with and without attenuation correction (AC & NAC) and the findings were compared with FDG PET.

Results SPECT data analysis indicated functional abnormalities in 376/527 myocardial segments. 18F-FDG-PET revealed viable myocardium in 270/376 segments. The diagnostic accuracy of baseline NAC, postnitrate-NAC, baseline AC and postnitrate-AC 99mTc-tetrofosmin SPECT was 87%, 88%, 92% and 95% respectively. Agreement between SPECT and FDG-PET findings was done using kappa statistics. Kappa values for NAC baseline, NAC postnitrate, AC and baseline and AC post nitrate Tc-99m tetrofosmin G-SPECT were 0.71, 0.72, 0.82 and 0.87 respectively. Attenuation correction revealed viability additionally in 27 segments which were non viable on NAC post nitrate study (p=0.001). Nitrate augmentation showed viability additionally in 9 segments which were non viable on AC baseline scan (p=0.04). On patient based analysis FDG PET changes the management only in 10% (3/31) of patients, compared to AC post nitrate 99mTc-tetrofosmin G-SPECT.

Conclusions Nitrate augmented AC 99mTc-Tetrofosmin G-SPECT shows excellent (k=0.87) agreement with FDG PET. FDG-PET changes management only in 10% of the patients. 99mTc-Tetrofosmin G-SPECT being more widely available and cheaper imaging modality can be reliably used to detect VM where FDG PET is not available