IODINE-123-METAIODOBENZYLGUANIDINE MYOCARDIAL IMAGING IN PATIENTS WITH RIGHT-VENTRICULAR PRESSURE-OVERLOAD

Iodine-123-metaiodobenzylguanidine ([I-123]MIBG) has been used to eval uate the cardiac sympathetic nervous system, particularly that of the left heart. To clarify whether the right ventricular (RV) sympathetic neuronal function could be evaluated by [I-123]MIBG myocardial imaging , we applied the technique in patients with pulmonary hypertension tha t was associated with either chronic pulmonary diseases or pulmonary v ascular diseases. Methods: All patients underwent right heart catheter ization, and right heart hemodynamics were determined during a clinica lly stable state. SPECT was performed in the resting state 15 min (ear ly imaging) and 4 hr (delayed imaging) postadministration of [I-123]MI BG, Seven regions of interest (ROI) were selected on the delayed short -axis images on the RV free wall, left ventricular (LV) free wall and interventricular septum (IVS). We calculated the IVS-to-LV uptake rati o from the scintillation counts of the ROI. Thallium-201 myocardial im aging was also performed within 1 wk after [I-123]MIBG imaging. Result s: Images obtained with these techniques were analyzed for the RV-to-L V uptake ratio. The IVS-to-LV ratio on [I-123]MIBG correlated negative ly and significantly with the mean pulmonary arterial pressure (PAm). The RV-to-LV uptake ratio on Tl-201 images correlated significantly wi th PAm. Conclusion: Our results suggest that the uptake ratio of [I-12 3]MIBG in the IVS is a useful index for evaluating the severity of pul monary hypertension, and that chronic RV pressure overload contributes to disturbances of the cardiac sympathetic nervous system.