Sympathetic nervous function in patients with hypertrophic cardiomyopathy assessed by [123I]-MIBG: relationship with left ventricular perfusion and function.
OBJECTIVE
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.


CONCLUSIONS
These results suggest that cardiac sympathetic activity correlates to cardiac anatomy (i.e. degree of hypertrophy) and diastolic function in patients with HCM.
Pace
L
L
Department of Biomorphologic and Functional Sciences, Federico II University, Naples, Italy. pace@unina.it
Betocchi
S
S
Losi
M A
MA
Della Morte
A M
AM
Ciampi
Q
Q
Nugnez
R
R
Chiariello
M
M
Salvatore
M
M
D019797:3-Iodobenzylguanidine; D000328:Adult; D002312:Cardiomyopathy, Hypertrophic / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D003326:Coronary Circulation; D004452:Echocardiography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction; D019275:Radiopharmaceuticals; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D017256:Technetium Tc 99m Sestamibi; D015899:Tomography, Emission-Computed, Single-Photon; D016277:Ventricular Function, Left
D019275:Radiopharmaceuticals; D019797:3-Iodobenzylguanidine; D017256:Technetium Tc 99m Sestamibi