Erythromycin as an alternative to reduce interfering extra-cardiac activity in myocardial perfusion imaging

OBJECTIVES: We sought to determine whether taking oral erythromycin prior to SPECT myocardial perfusion imaging with Tc99m-sestamibi would reduce the amount of interfering extra-cardiac activity and improve the image quality. METHODS: A total of 96 patients who were routinely referred for myocardial perfusion imaging were randomly assigned to one of two groups. Patients in group A received 500 mg of non-enterically coated erythromycin orally one hour prior to image acquisition (45 patients). Patients in group B received diluted lemon juice which comprises the current standard of care in our department (51 patients). A two-day protocol was followed and study participants received the same intervention on both days. Planar images of both the stress and rest images were assessed visually by three experienced nuclear medicine physicians for the presence of interfering extra-cardiac activity. Physicians were blinded to the detail of the protocol and independently assessed the images. RESULTS: The qualitative results favoured lemon juice in reducing the amount of interfering extra-cardiac activity. The overall incidence of interfering extra-cardiac activity was 46.15% in the lemon juice group vs 55.56% in the erythromycin group. However, this difference was not found to be statistically significant (p = 0.36). The use of a MYO:EXT ratio similar to the one described by Peace and Lloyd,11 appeared promising in quantifying interfering extra-cardiac activity. CONCLUSION: The difference between the effect of erythromycin and lemon juice on interfering extra-cardiac activity appears statistically insignificant and erythromycin could therefore be considered as a suitable alternative to lemon juice.