Silvehtssen, Egil; Bay, Orxnar; Grendahl., Helgk
September 1975
Angiology;Sep1975, Vol. 26 Issue 8, p605
Academic Journal
The atrial effective (ERP) and relative (RRP) refractory periods were examined at high atrial pacing rates in 12 patients before and after intravenous injection of propranolol. and in ;") patients before and after injection of verapamil. using the technique of paired pacing. Seven of the patients had A-V block grade II-III and 10 patients had sinus rhythm. The range of atrial ERP in all patients was found to be 200 to 270 msee. and the range of atrial RRP was 230 to 330 msec. the atria ERP and RHP were longer at a pacing rate of 160 per minute then at a pacing rate of 240 per minute. The conduction delay between the second impulse and the atrial depolarization was found to be due to increased interval between the stimulus and the start of the depolarization wave. The atrial ERP increased after injection of propranolol in 8 of 12 patients, decreased in :5 patients and was unchanged in one patient. The atrial RRP increased in 7 patients, decreased in one patient and was unchanged in 4 patients. In all patients the changes were of moderate degree. The conduction delay between the stimulating impulse and the atrial response was shorter after propranolol in 7 patients, longer in one pain and unchanged in 4 patients. The ERP of the atrioventricular conducting tissue was 220 to more than ;180 millisec. After injection of proprauolol it increased in all of H patients in whom it could be measured. After injection of verapamil no significant effects on the atrial ERP and RRP were found. ERP of the atrioventricular conducting tissue was lengthened in 4 of 5 patients, and tbe degree of A-V block during rapid atrial pacing increased after injection of verapamil. It is suggested that the effect of propranolol on atrial arrhythmias is due to its effect on ectopic pacemaker activity rather then any effect on the refractory period of the atrium. The effects of verapamil on the atrioventricular conducting tissue may explain some of the antiarrhythmic effects of this drug.


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