[Sympathetic reinnervation of the transplanted heart. Study using iodine-123 labeled meta-iodobenzylguanidine].
OBJECTIVE
Metaiodobenzylguanidine (MIBG) is an analogue of norepinephrine and its cardiac uptake shows sympathetic innervation. During the heart transplantation the allograft becomes completely denervated. The present study was conducted to assess the evolution of sympathetic re-innervation after transplantation, and to related re-innervation with functional status.


METHODS
We studied 31 patients from 6 months to 12 years after transplantation by 123I-MIBG studies to evaluate re-innervation and by rest/exercise radionuclide ventriculography to evaluate cardiac function. Myocardial MIBG uptake was quantified by calculating a heart-to-mediastinum ratio (HMR). An HMR > 1.8 was considered normal, moderate between 1.8 and 1.6, mild between 1.6 and 1.3, and absent < 1.3.


RESULTS
HMR correlated with time after transplantation (r = 0.607; p < 0.001). HMR of patients studied after 2 years of transplantation was significantly higher (1.62 +/- 0.2 vs 1.34 +/- 0.2; p < 0.05). MIBG uptake was in the anterior region in 3 patients, in the antero-lateral region in 25, and in the antero-lateral and septal regions in 3. From a functional point of view, peak filling rate at exercise was higher in patients studied 2 years after the transplantation (2.7 +/- 0.8 edv/s vs 2.16 +/- 0.5 edv/s; p = 0.02). These patients also showed a higher increase of heart rate with exercise (p < 0.005 vs p < 0.01).


CONCLUSIONS
Sympathetic re-innervation increase with time after heart transplantation, and is more frequently seen 2 years after transplantation. Sympathetic re-innervation first appears in the anterior or the antero-lateral regions. A complete re-innervation of the transplanted heart does not occur 12 years after transplantation.
Estorch Cabrera
M
M
Servicio de Medicina Nuclear, Hospital de la Santa Creu i Sant Pau, Barcelona. mnu@santpau.es
Flotats Giralt
A
A
Campreciós Crespo
M
M
Marí Aparici
C
C
Bernà Roqueta
L
L
Catafau Alcántara
A M
AM
Ballester Rodés
M
M
Carrió Gasset
I
I
D019797:3-Iodobenzylguanidine / Q000493:pharmacokinetics; D000328:Adult; D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D006321:Heart / Q000000981:diagnostic imaging / Q000294:innervation*; D016027:Heart Transplantation / Q000502:physiology*; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000378:metabolism; D009416:Nerve Regeneration; D015635:Radionuclide Ventriculography; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D012044:Regression Analysis; D013564:Sympathetic Nervous System / Q000502:physiology*; D013997:Time Factors; D015899:Tomography, Emission-Computed, Single-Photon
D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D019797:3-Iodobenzylguanidine
Reinervación simpática del corazón trasplantado. Estudio realizado con metayodobenzilguanidina marcada con yodo-123.