PURPOSE

Hypericin (Hyp) is a natural compound with a newly discovered necrosis-avidity, which can be exploited as a necrosis-avid tracer once labeled with radioactive iodine as has been tested in rodent models. This study was to evaluate the effect of radioiodinated Hyp (I-Hyp) for imaging detection of acute myocardial infarction (AMI) in conditions closer to clinical scenarios.

METHODS

We established swine AMI models (n = 6) which were intravenously given I-Hyp and Tc-sestamibi and underwent SPECT-CT imaging with high- and low-energy collimators. The acquired SPECT images were fused with cardiac CT images and correlated with postmortem autoradiography and macro- and microscopic pathology. Tissue γ counting was performed to determine biodistribution of I-Hyp.

RESULTS

I-Hyp based SPECT indicated clearly hot regions on ventricular walls which were all histologically proved as AMI. Complementally, the hot AMI regions on I-Hyp SPECT (infarct/myoc ratio of 15.3 ± 7.7) were inversely cold regions on Tc-sestamibi SPECT (infarct/myoc ratio of 0.029 ± 0.021). Autoradiography of heart slices showed 9.8 times higher I-Hyp uptake in infarcted over normal myocardium. With γ counting, the mean I-Hyp uptake in infarcts was 10.69 ID%/g, 12.05 times of that in viable myocardium.

CONCLUSION

I-Hyp shows a potential for clinical detection of AMI once I-131 is substituted by its isotope like I-124 or I-123 for PET or SPECT, respectively.