Abnormalities of cardiac sympathetic neuronal and left ventricular function in chronic mitral regurgitation: Assessment by iodine-123 metaiodobenzylguanidine scintigraphy

Myocardial uptake of iodine-123 meta-iodobenzylguanidine (¹²³I-MIBG) was measured using scintigrams at rest in 12 patients with isolated, nonischemic mitral regurgitation (MR; regurgitant fraction 64% ± 7%) and was related to the left ventricular (LV) function assessed by cardiac catheterization. Iodine-123 meta-iodobenzylguanidine activity at the upper mediastinum, liver, and lung was comparable between MR and control (n = 8) patients. The heart to mediastinum ¹²³I-MIBG activity ratio 4 hours after injection was significantly (p < 0.01) decreased in MR (2.0 ± 0.1, mean ± SE) compared with control (2.7 ± 0.1) with the increased clearance of MIBG. In addition, MR patients had significantly greater heterogeneity in the ¹²³I-MIBG distribution within the myocardial images (26.1% ± 2.1% intraimage variability for MR versus 15.6% ± 0.8% for control, p < 0.01). Myocardial ¹²³I-MIBG activity correlated positively with cardiac index and negatively with pulmonary capillary wedge pressure and LV volume indexes. Thus, ¹²³I-MIBG scintigrams can be a noninvasive method for assessing the contractile dysfunction in MR.