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

PURPOSE: 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).
METHODS: Iodine-123 metaiodobenzylguanidine ((123)I-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.
RESULTS: 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).
CONCLUSION: 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. (123)I-MIBG scintigraphy can provide prognostic information of VT patients without conventional risk.