Cardiac neurotransmission imaging with 123I-meta-iodobenzylguanidine in postural tachycardia syndrome.

BACKGROUND: Postural orthostatic tachycardia syndrome (POTS) is a disorder of orthostatic intolerance characterised by excessive tachycardia of unknown aetiology. Whether this condition involves abnormal cardiac sympathetic innervation or function remains elusive. Meta-iodobenzylguanidine (MIBG) resembles guanethidine and is a pharmacologically inactive analogue of norepinephrine, which is similarly metabolised in noradrenergic neurons. MIBG myocardial scintigraphy is used clinically to estimate local myocardial sympathetic nerve damage in some forms of heart disease and autonomic neuropathy. The objective of this study was to evaluate cardiac sympathetic innervation in patients with POTS. METHODS: 20 patients with POTS were studied using (123)I-MIBG-single photon emission computed tomography, standardised autonomic testing, assessment of catecholamine plasma levels and sympathetic skin response. RESULTS: In four POTS patients (20.0%), myocardial MIBG uptake was markedly decreased. The mean heart to mediastinum ratio was reduced to 1.22+/-0.08 compared with the normal range of >1.7. No correlation was found between myocardial MIBG uptake and degree of postural tachycardia, baroreflex sensitivity, catecholamine plasma levels or other autonomic parameters. Sympathetic skin responses were normal in all patients. CONCLUSIONS: These findings suggest that POTS may be, in part, a manifestation of autonomic cardiac neuropathy. MIBG myocardial scintigraphy may be helpful to distinguish patients with neuropathic POTS from patients with orthostatic intolerance of other origin.

Cardiac denervation in postural tachycardia syndrome.

Myocardial 123I-Meta-iodobenzylguanidine uptake was markedly reduced in a patient with postural tachycardia syndrome (POTS). This finding suggests that loss of sympathetic autonomic neurons in the heart may play a role in the etiology of POTS.

Three-dimensional localization of sentinel lymph nodes using combined emission and transmission SPECT data.

PURPOSE: With conventional planar imaging, preoperative anatomic localization of a sentinel lymph node is possible in only two dimensions. To improve spatial localization of sentinel lymph nodes, a dual-head camera equipped with a transmission source was used to create combined transmission-emission SPECT images in a patient with a malignant melanoma of the left forearm. METHODS: Lymph node scintigraphy was performed after injection of Tc-99m-labeled nanocolloid around the tumor site 1 day before operation. SPECT was performed using a gamma camera equipped with a transmission collimator system originally designed to correct attenuation. Transmission and emission images were created simultaneously, matched, and displayed in three dimensions. RESULTS: In the combined emission-transmission images, the sentinel lymph node was clearly located in the left axilla. The lymph nodes could be identified during operation at the same location as that detected by SPECT. Based on preoperative information, the sentinel lymph node was identified rapidly and the extent and duration of the operation were minimized. CONCLUSIONS: This method provides better anatomic information, especially in deep structures such as the axilla or pelvis. With accurate three-dimensional preoperative information, intraoperative access is quicker and less invasive for the patient.