Electrocardiographic repolarization changes, comprising QT prolongation, T-wave flattening or inversion, and ST-segment alterations, are most commonly seen after subarachnoid and intracerebral hemorrhage, but may occur in other neurologic conditions. They may presage arrhythmias. The effects likely are mediated by the sympathetic nervous system. Cerebral arrhythmogenesis may underlie sudden death in both normal and epileptic populations. Experimental evidence suggests that the insula has a cardiac chronotropic organization, and may be involved in the genesis of arrhythmias seen in epilepsy or after cerebral hemorrhage or stroke.