Influence of alpha-adrenergic blockade on ventricular arrhythmias, QTc interval and heart rate variability in phaeochromocytoma.
There are strong experimental evidences that alpha 1-adrenergic stimulation significantly influences cardiac arrhythmogenesis, especially during myocardial ischaemia and reperfusion. However, anti-arrhythmic effects of alpha-blockade in humans were scarcely utilised. Thus the purpose of our study was to assess these effects in patients with phaeochromocytoma. In 22 patients simultaneous 24 h ECG and blood pressure (BP) monitoring, as well as estimation of the urinary 24 h free catecholamine excretion, were performed twice: before and during the treatment with the non-selective alpha-blocker, phenoxybenzamine. The heart rate variability was measured during four 5 min periods, at 10.00, 16.00, 22.00 and 04.00. During alpha-blockade systolic blood pressure (SBP) decreased from 137.6 +/- 23.8 to 126.5 +/- 15.7 mm Hg (P < 0.01), heart rate increased from 83.0 +/- 9.9 to 88.5 +/- 10.0/min (P < 0.02) and duration of QTc interval unsignificantly increased. Incidence of frequent or repetitive ventricular arrhythmias was significantly higher before treatment (in 9 vs 3 of 22 patients, P < 0.05). Heart rate variability significantly decreased during the treatment, with regard to all parameters, representing both the sympathetic and parasympathetic activity. We conclude that non-selective alpha-blockade significantly decreases the incidence of frequent or repetitive ventricular arrhythmias in patients with phaeochromocytoma, although the lack of QTc interval shortening suggests that the effect of class I drugs may participate in the anti-arrhythmic effects of phenoxybenzamine. Moreover, non-selective alpha-blockade in phaeochromocytoma significantly diminishes vagal activity.
Dabrowska
B
B
Department of Hypertension and Angiology, Warsaw Medical Academy, Central Clinical Hospital MMA, Poland.
Pruszczyk
P
P
Dabrowski
A
A
Feltynowski
T
T
Wocial
B
B
Januszewicz
W
W
D000310:Adrenal Gland Neoplasms / Q000150:complications / Q000188:drug therapy* / Q000503:physiopathology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology / Q000627:therapeutic use*; D000328:Adult; D000368:Aged; D001145:Arrhythmias, Cardiac / Q000150:complications / Q000209:etiology; D001794:Blood Pressure / Q000187:drug effects; D002395:Catecholamines / Q000652:urine; D004452:Echocardiography; D004562:Electrocardiography; D015716:Electrocardiography, Ambulatory; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D017379:Hypertrophy, Left Ventricular / Q000150:complications / Q000209:etiology; D008297:Male; D008875:Middle Aged; D010643:Phenoxybenzamine / Q000494:pharmacology / Q000627:therapeutic use*; D010673:Pheochromocytoma / Q000150:complications / Q000188:drug therapy* / Q000503:physiopathology; D016896:Treatment Outcome
D000317:Adrenergic alpha-Antagonists; D002395:Catecholamines; D010643:Phenoxybenzamine