Correlation between severity of pulmonary arterial hypertension and I-123-metaiodobenzylguanidine left ventricular imaging

It remains unclear whether cardiac sympathetic nervous function is disturbe d in patients with pulmonary arterial hypertension (PH) and how sympathetic dysfunction is related to PH. Methods: in this study, I-123-metaiodobenzyl guanidine (MIBG) imaging of the heart, which reveals the sympathetic innerv ation of the left ventricle, was performed in 7 healthy volunteers without cardiopulmonary disease (control subjects); 55 patients with PH, including 27 with chronic thromboembolic pulmonary hypertension (CTEPH) of major vess els; and 28 patients with primary pulmonary hypertension (PPH). Results: Ca rdiac I-123-MIBG uptake, assessed as the heart-to-mediastinum activity rati o (H/M), was significantly lower in the CTEPH and PPH groups compared with that in the control group (P < 0.01), Myocardial MIBG turnover, expressed a s the washout rate (WR [%]) from 15 to 240 min, was significantly higher in the CTEPH and PPH groups than that in the control group (P < 0.01). In the PPH group, H/M and WR values of MIBG correlated with the severity of pulmo nary hypertension (represented by total pulmonary vascular resistance deter mined by right heart catheterization), the right ventricular ejection fract ion determined by electron beam CT, and other variables but did not correla te well in the CTEPH group. In both groups, patients with H/M greater than or equal to 2.0 showed better cumulative survival than did those with H/M < 2.0 (P < 0.05). Conclusion: Patients with PH have significant left ventric ular myocardial sympathetic nervous alteration. I-123-MIBG imaging of the h eart is useful for assessing the severity of pulmonary hypertension caused by PPH or CTEPH.