37 patients with either chronic atrial fibrillation (AF), atrial premature beats (APBs) or ventricular premature beats (VPBs) received tiapamil as antiarrhythmic treatment. Tiapamil reduced A-V conduction by an average 20% in the group with AF (10 patients), the magnitude of response being dependent on the initial ventricular rate. In 3 of the 7 patients with APBs, the frequency of ectopic beats was reduced following a single i.v. injection of 1 mg/kg tiapamil. In patients with VPBs (n = 20), tiapamil (i.v. injection of 1 mg/kg followed by 4-hour i.v. infusion of 50 µg/kg/min in 10 patients) reduced ectopic beats by 30-50% in 6 cases, these all being patients who had not responded to previous antiarrhythmic therapy. The antiarrhythmic effect was maintained by i.v. infusion of 50 µg/kg/min for 4 h. The antiarrhythmic effect of tiapamil consists essentially in slowing A-V conduction and reducing chronic VPBs.
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-methylty-rosine 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.
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