Neurogenic cardiac arrhythmias during 5 cases of subarachnoid rebleeding in 4 patients were analyzed by using long-term ECG (Holter). The initial onset of rebleeding was characterized by an abrupt decrease of heart rate from 93.3 +/- 7.85 (beats/min) to 63.3 +/- 14.6 (beats/min). This was immediately followed by pronounced tachycardia of 163.0 +/- 20.9 (beats/min) and subsequently, alterations of the P wave, ST depression with an increase in T wave amplitude. Frequent premature ventricular contractions, couplets, and self-terminating episodes of ventricular tachycardia for 2-8 minutes were observed during 2 episodes of rebleeding, an idioventricular rhythm in one case. The ECG returned to normal in the 3 non-lethal cases. Pathogenetically, the initial heart rate decrease with varying P wave configuration can be explained through activation of the baroreceptor reflex. Elevated intracranial pressure causes a blood pressure increase thus stimulating the baroreceptors and consequently, the afferent and efferent tracts of the vagus nerve. The sympathicotonus appears to have a modulating effect.