Significance of Cardiac Sympathetic Nervous System Abnormality for Predicting Origin of Tachyarrhythmia in Patients with a History of Paroxysmal Palpitation

Cardiac sympathetic nervous system abnormality can predict sudden cardiac death due to arrhythmia. However, it is unknown whether the sympathetic nerve abnormality is related to the origin of tachyarrhythmia. We hypothesized that such a relationship exists and tested it by uptake of iodine-123 metaiodobenzylguanidine (123I-MIBG) in 184 patients (mean ± standard deviation, age : 52.7 ± 18.8 years, 106 males) with a history of paroxysmal palpitation. Patients with organic heart disease or left ventricular dysfunction were excluded. Cardiac sympathetic nerve abnormality was assessed from the heart l mediastinum (H / M) later index and washout ratio (WR) . Sustained ventricular tachycardia (VT) in 46 patients and sustained supraventricular tachycardia (SVT) in 103 patients were diagnosed by ECG during onset of arrhythmia or by electrophysiologic tests employing programmed cardiac stimulation. The tachyarrhythmia was not proven in 35 patients (Control groups) . The H I M index was significantly lower and WR significantly higher in tachyarrhythmia groups compared to controls (H I M index : 2.75 ± 0.55 in VT group, 3.01 ± 0.78 in SVT group vs. 3.34 ± 0.48 in control group, p < 0.001 and p < 0.05, WR : 39.6 ± 12.1% in VT group, 38.1 ± 8.5% in SVT group vs. 34.2 ± 6.8% in Control group, p < 0.05 in each) . The mean H / M index was lower in the VT group than the SVT group (p < 0.05) . Cardiac sympathetic nerve abnormality thus predicts the origin of tachyarrhythmia, and we propose 123I-MIBG scintigraphy as an important tool to discriminate the life-threatening tachyarrhythmia from benign episodes in patients with a history of palpitation.