RESUMO
AIM: The aim of the present study was to evaluate [123I] MIBG uptake and clearance in patients with hypertrophic cardiomyopathy (HCM) and to assess their relationships with left ventricular function (systolic and diastolic) and perfusion. METHODS: Eleven consecutive patients with HCM (8 men and 3 women; mean age 38+/-12 years, none in the dilated phase) underwent (in separate days, in random order) [123I]-MIBG scintigraphy, [(99m)Tc]-MIBI SPET at rest, and echocardiography. All patients were studied in fasting condition, and all medications were discontinued. [(99m)Tc]-MIBI SPET study was performed 1 hour after tracer injection. [123I]-MIBG study was acquired 5 minutes (planar) and 4 hours (planar and SPET) after the i.v. injection of [123I]-MIBG. Heart to mediastinum ratio (H/M) was computed at 4 hours. Wash out rate (WOR) was computed as: (H early - H delayed)/(H early), after decay correction. Both [123I]-MIBG and [(99m)Tc]-MIBI SPET were analyzed on 3 short axis views (apical, middle, and basal). Left ventricular outflow tract gradient (LVOTG), ejection fraction, volumes, septum thickness, and left atrial fractional shortening (LAFS) were evaluated on echocardiography. RESULTS: [123I]-MIBG WOR showed a positive relationship with LVOTG (r=0.84, p<0.001) and septum thickness (r=0.76, p<0.01), while a negative one was found with LAFS (r= -0.66, p<0.05). The study group was divided into: Group A (n=5) with higher, and Group B (n=6) with lower WOR than the median value (i.e. 11%). Group A patients had significantly lower LAFS (17.6+/-4.8 vs 26.8+/-7.2%, p<0.05), higher LVOTG (49+/-35 vs 3+/-3 mmHg), and thicker septum (21+/-2 vs 17+/-2 mm) than Group B patients. Inferior and septal wall [123I]-MIBG uptake on 4 hour SPET was significantly lower in Group A than in Group B. On the other hand, no differences were found in (99m)T-MIBI SPET rest regional uptake between the 2 subgroups of patients. CONCLUSION: These results suggest that cardiac sympathetic activity correlates to cardiac anatomy (i.e. degree of hypertrophy) and diastolic function in patients with HCM.
