Cardiac sympathetic nerve abnormality predicts ventricular tachyarrhythmic events in patients without conventional risk of sudden death

Patients with structural heart disease, severe left ventricular dysfunction, or history of cardiac arrest are at increased risk of sudden cardiac death. However, a useful marker for predicting sudden cardiac death is not clarified in low-risk patients without those conventional risks. We hypothesized that cardiac sympathetic nerve system (SNS) abnormality would be associated with ventricular tachyarrhythmic events in low-risk patients with ventricular tachycardia (VT). Iodine-123 metaiodobenzylguanidine (123I-MIBG) scintigraphy was performed in 50 patients (mean±standard deviation, age 54 ± 16 years, 52% males) with VT who did not have structural heart disease, severe left ventricular dysfunction, or history of cardiac arrest, and SNS activity was assessed from heart/mediastinal (H/M) ratio on delayed images. Over 11 years of follow-up, three patients had sudden deaths (6%) and nine patients had sustained ventricular tachyarrhythmic events (18%). SNS abnormality, defined as H/M ratio <2.8, was predictive of sudden death or ventricular tachyarrhythmic events (45% in nine of 20 patients with SNS abnormality vs 16.7% in three of 30 patients without SNS abnormality, p = 0.005). After adjustment for potential confounding variables including slight left ventricular dysfunction, SNS abnormality remained independently predictive of ventricular tachyarrhythmic events with a hazard ratio of 5.3 (95% confidence interval = 1.4 to 20.8, p = 0.016). SNS abnormality is a readily available and powerful predictor of recurrent ventricular tachyarrhythmic events in patients with VT who did not have conventional risk of sudden cardiac death. 123I-MIBG scintigraphy can provide prognostic information of VT patients without conventional risk. (orig.)