Abnormal cardiac adrenergic nerve function in patients with syndrome X detected by [123I]metaiodobenzylguanidine myocardial scintigraphy.
BACKGROUND
Previous studies have suggested that an abnormal cardiac adrenergic tone may have a pathophysiological role in syndrome X (effort angina, positive exercise testing, angiographically normal coronary arteries).


RESULTS
To evaluate cardiac adrenergic nerve function, we performed [123I]metaiodobenzylguanidine (MIBG) myocardial scintigraphy in 12 patients with syndrome X and 10 control subjects. Cardiac MIBG uptake was assessed by the heart/mediastinum (H/M) ratio and by an MIBG uptake defect score (higher values=lower uptake). In syndrome X patients, we also correlated MIBG scintigraphic findings with stress myocardial perfusion as assessed by 201Tl scintigraphy. An inferior MIBG defect was observed in only 1 control subject, whereas 9 patients (P<.01) showed MIBG defects. The heart was totally or almost totally invisible on MIBG images in 5 patients, and predominantly regional defects were observed in 4. The H/M ratio was lower (1.70+/-0.6 versus 2.2+/-0.3, P=.03) and MIBG uptake defect score higher (35+/-31 versus 4+/-2, P=.003) in syndrome X patients. Reversible stress thallium perfusion defects were found in 62% of patients with MIBG defects but in no patient with normal MIBG uptake. MIBG defects persisted unchanged in 7 patients at a 5+/-3-month follow-up study.


CONCLUSIONS
In this study, obvious defects in global and/or regional cardiac MIBG uptake, indicating an abnormal cardiac adrenergic nerve function, were detected in 75% of patients with syndrome X. These findings strongly support the cardiac origin of chest pain in syndrome X, although the mechanisms and the pathophysiological meaning of the abnormal cardiac MIBG uptake in these patients deserve further investigation.
Lanza
G A
GA
Istituto di Cardiologia, Università Cattolica del Sacro Cuore, Rome, Italy.
Giordano
A
A
Pristipino
C
C
Calcagni
M L
ML
Meduri
G
G
Trani
C
C
Franceschini
R
R
Crea
F
F
Troncone
L
L
Maseri
A
A
D019797:3-Iodobenzylguanidine; D000368:Aged; D003287:Contrast Media; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging*; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D007457:Iodine Radioisotopes; D007462:Iodobenzenes; D008297:Male; D017566:Microvascular Angina / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D008875:Middle Aged; D011877:Radionuclide Imaging; D015203:Reproducibility of Results; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D013794:Thallium Radioisotopes
D003287:Contrast Media; D007457:Iodine Radioisotopes; D007462:Iodobenzenes; D013794:Thallium Radioisotopes; D019797:3-Iodobenzylguanidine