I-123-MIBG cardiac uptake imaging, in familial dilated cardiomyopathy.
The pathological significance of myocardial adrenergic activity in patients with heart failure is well documented. No previous study has assessed the usefulness of I123-metaiodobenzylguanidine (123I-MIBG) cardiac uptake imaging for the evaluation of familial dilated cardiomyopathy (DCM).


OBJECTIVE
To evaluate cardiac adrenergic activity, using 123I-MIBG cardiac uptake imaging, in members of a genotyped family with DCM.


METHODS
Clinical evaluation, 12-lead ECG, 2D echocardiogram, heart rate variability analysis by 24h Holter, plasma B-type natriuretic peptide (BNP) measurements and 123I-MIBG cardiac imaging were performed in all participants. Anterior projection planar images and single photon emission computed tomographies of the thorax were obtained 20 min and 4 hours after the intravenous administration of 370 MBq of 123I-MIBG (early and late images). Heart/mediastinal (H/M) ratio and myocardial washout (MW) rate were obtained based on the anterior planar images. In polar maps, segmental uptake of 123I-MIBG was evaluated using a 4-grade visual score: grade 1 - uptake > 75% of maximum myocardial uptake (MMU); grade 2 - uptake 51-75% of MMU; grade 3 - uptake 26-50% of MMU; grade 4 - uptake < or = 25% of MMU.


RESULTS
Eleven adults were included: 4 with DCM, 4 with isolated left ventricular enlargement (LVE), and 3 with normal echocardiogram. Patients with DCM and LVE presented higher MW rates, lower H/M ratios and higher visual score grades than those with normal 2D echocardiograms. One patient with a normal echocardiogram but carrying the disease locus also presented an abnormal MIBG cardiac scintigram.


CONCLUSIONS
Patients with the phenotypic expression of the disease (DCM and LVE) and even carriers of the DCM gene with normal echocardiograms may present an abnormal MIBG cardiac scintigram, probably reflecting cardiac adrenergic hyperactivity. If confirmed in larger numbers, this method may be useful for the evaluation of DCM families.
Martins
Elisabete
E
Faculdade de Medicina do Porto, Serviço de Cardiologia, Hospital de São João, Porto, Portugal. elisabetemartins09@gmail.com
Faria
Teresa
T
Silva-Cardoso
J
J
Oliveira
Ana
A
Campelo
Manuel
M
Amorim
Sandra
S
Moura
Brenda
B
Rocha-Gonçalves
F
F
Pereira
Jorge G
JG
Maciel
M Júlia
MJ
D019797:3-Iodobenzylguanidine / Q000378:metabolism; D000328:Adult; D000368:Aged; D002311:Cardiomyopathy, Dilated / Q000000981:diagnostic imaging* / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000378:metabolism; D010865:Pilot Projects; D011877:Radionuclide Imaging
D019797:3-Iodobenzylguanidine