Relationship between myocardial 123I-metaiodobenzylguanidine scintigraphic uptake and heart rate variability in patients with syndrome X.
BACKGROUND
We have recently demonstrated a striking impairment in cardiac uptake of 123I-metaiodobenzylguanidine (MIBG) in most patients with syndrome X. In this study we investigated the relationship between cardiac MIBG defects and cardiac autonomic activity in these patients.


METHODS
MIBG myocardial scintigraphy and time-domain and frequency-domain heart rate variability (HRV) were compared in 11 syndrome X patients and 10 healthy controls. Cardiac MIBG uptake was assessed by the heart/mediastinum ratio and a cardiac MIBG uptake defect score (higher values = lower uptake).


RESULTS
The heart/mediastinum ratio was lower (1.71 +/- 0.6 vs 2.19 +/- 0.3, p = 0.03) and MIBG uptake score higher (37.1 +/- 32 vs 4.0 +/- 2.5, p = 0.005) in syndrome X patients, whereas average HRV values did not differ between the two groups. However, while there were no correlations between MIBG uptake and HRV in controls, in syndrome X patients both the heart/mediastinum ratio and MIBG uptake score correlated significantly with two HRV parameters, specific for vagal activity: the square root of the mean squared differences of consecutive RR intervals (r = 0.73, p = 0.01, and r = -0.67, p = 0.02, respectively), and high frequency (r = 0.64, p = 0.03, and r = -0.74, p = 0.009, respectively). CONCLUSIONS; In patients with syndrome X, the impairment in cardiac MIBG uptake was associated with a reduction in HRV indexes mainly reflecting vagal modulation of sinus node, thus suggesting that a predominance of cardiac adrenergic activity may be present in those with abnormal cardiac MIBG scintigraphy.
Lanza
G A
GA
Institute of Cardiology, Catholic University of the Sacred Heart, 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
D019797:3-Iodobenzylguanidine; D000328:Adult; D015716:Electrocardiography, Ambulatory; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D017566:Microvascular Angina / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D008875:Middle Aged; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals
D019275:Radiopharmaceuticals; D019797:3-Iodobenzylguanidine