Clinical significance of I-123 MIBG myocardial scintigraphy for evaluating the severity of congestive heart failure

We studied the significance of I-123 MIBG (metaiodobenzylguanidine) myocardial scintigraphy for evaluating the severity of congestive heart failure. I-123 MIBG scintigraphy was performed in 7 patients with congestive heart failure (CHF) of NYHA class I-III (6 with dilated cardiomyopathy and 1 with Adriamycine cardiomyopathy) and in 2 normals. The SPECT and anterior planar myocardial images were obtained 15 minutes after (initial images) and 4 hours after (delayed images) an injection of I-123 MIBG (111 MBq). Compared with normals, patients with CHF demonstrated (1) low myocardial uptake and (2) rapid myocardial washout of I-123 MIBG, indicating myocardial sympathetic disarrangement. Then, quantitating these abnormalities with the heart to upper mediastinum uptake ratio (H/B) and the percent washout rate (%WR) during 4 hours, respectively, we compared these two indices with LV ejection fraction (EF) at rest measured by echocardiography and exercise capacity (max VO2 and VO2 at anaerobic threshold (AT] determined with respiratory gas exchange analysis during maximal bicycle exercise. H/B was lower and %WR was greater in patients with CHF than in normals. H/B correlated with EF (r = 0.77, p less than 0.05) and AT (r = 0.74, p less than 0.05). On the other hand, %WR significantly correlated with EF (r = 0.79, p less than 0.05), max VO2 (r = -0.74, p less than 0.05) and AT (r = -0.81, p less than 0.05). Thus, H/B and %WR were closely related to the severity of CHF. These results suggest that I-123 MIBG myocardial scintigraphy and the quantitative analysis of I-123 MIBG myocardial uptake provide useful information about the severity of CHF.