Slow bolus injection of ribose in the identification of thallium-201 redistribution following combined adenosine/dynamic exercise stress.
AIM
A simple stress/redistribution thallium-201 myocardial perfusion imaging protocol may underestimate the degree of thallium redistribution in a defect identified on the stress images. We sought to investigate whether a slow-bolus injection of D-ribose improves the identification of thallium redistribution following combined adenosine/dynamic exercise stress.


MATERIALS AND METHODS
Fifteen patients (10 males, five female, median age 63 years, range 50-75) were enrolled in the study. All underwent two successive adenosine plus exercise myocardial perfusion scintigraphy protocols 7-14 days apart. Adenosine was infused at 140 micrograms.kg-1.min-1 coupled with 25 W ergometer pedalling for 6 min with 74 Mbq of thallium-201 being injected at 4 min. Immediately following the stress image acquisition, patients received the one of either 60 mg.kg-1 of D-ribose or normal saline, injected over 5 min. Redistribution images were acquired after 4 h. The identical stress procedure was conducted in the crossover arm of the study, and patients received the alternative test article. SPECT images were visually analysed and scored in a nine segment model by two blinded observers. In addition, circumferential profile analysis was conducted.


RESULTS
By visual interpretation 25 segments displayed redistribution of the ribose, but not in the saline study, 14 reversible segments were seen on the saline study alone and 18 were seen on both studies (P = ns). In six patients ribose identified a greater number of redistributing segments and in a further six patients saline identified more reversible segments. Comparison of mean values of defect extent severity and percentage reversibility scores generated from the circumferential profile analysis showed no significant difference between the two arms of the study.


CONCLUSION
A 5 min bolus injection of D-ribose following combined adenosine/dynamic exercise stress confers little benefit on the identification of redistribution of thallium-201. These results differ from those of previous studies which showed that a 30 min infusion of D-ribose following treadmill exercise significantly enhanced thallium redistribution. The duration of the ribose infusion is likely to be an important factor influencing the effect brought to bear on the redistribution of the tracer, and should be run over 30 min, or longer.