Long-term ECG in pheochromocytoma.

In 13 patients with pheochromocytoma (in all but 2 cases localization by scintigraphy) investigations using Holter long-term ECG were performed under medication with alpha- and beta-sympathicolytic drugs under bed rest conditions. The incidence of ventricular dysrhythmias hardly exceeded the extent of a normal control group. In 1 case alpha-methyltyrosine caused a first to second degree AV block and beyond this a stable high frequency sinus rate without any adaptation to the environmental requests. In 12 patients the frequency profile showed sudden and inadequate rises of heart rate up to 200% of very short duration, reaching their maximum within about 20 s of the onset of muscular activity. Although less pronounced, these characteristics were still found 1-2 weeks after operation. In our opinion the heart rate profiles described reveal a dysfunction of the entire autonomus nervous system in pheochromocytoma.