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 in 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.