Iodine-123-metaiodobenzylguanidine myocardial imaging in patients with right ventricular pressure overload

Iodine-123-metaiodobenzylguanidine ([123I]MIBG) has been used to evaluate 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 [123I]MIBG myocardial imaging, we applied the technique in patients with pulmonary hypertension that was associated with either chronic pulmonary diseases or pulmonary vascular diseases.

All patients underwent right heart catheterization, and right heart hemodynamics were determined during a clinically stable state. SPECT was performed in the resting state 15 min (early imaging) and 4 hr (delayed imaging) postadministration of [123I]MIBG. 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 ratio from the scintillation counts of the ROI. Thallium-201 myocardial imaging was also performed within 1 wk after [123I]MIBG imaging.

Images obtained with these techniques were analyzed for the RV-to-LV uptake ratio. The IVS-to-LV ratio on [123I]MIBG correlated negatively and significantly with the mean pulmonary arterial pressure (PAm). The RV-to-LV uptake ratio on 201Tl images correlated significantly with PAm.

Our results suggest that the uptake ratio of [123I]MIBG in the IVS is a useful index for evaluating the severity of pulmonary hypertension, and that chronic RV pressure overload contributes to disturbances of the cardiac sympathetic nervous system.