A symptomatic sinus bradycardia is a very common situation in cardiology for which the diagnostic and therapeutic management are far from being well codified. After ruling out the obvious and reversible causes, the differential diagnosis between sinus bradycardia caused by vagal hypertonia and sinus dysfunction is often not easy subjecting the patient to electrophysiological exploration. We report 2 cases of permanent sinus bradycardia for which a non-invasive exploration of the autonomic nervous system (ANS) has led to the diagnosis of vagal hypertone bradycardia, in the first case after electrophysiological exploration, whereas in the second case the electrophysiological study was not performed.