Affiliation:
1. University Department of Cardiology and Clinical Physiology Wilhelmina Gasthuis, Amsterdam, the Netherlands
2. Department of Defense the Hague, the Netherlands
Abstract
In exposed hearts of anesthetized dogs with total A-V block, a sudden increase or decrease in heart rate changes the duration of refractoriness immediately. A steady state is established only after a few hundred beats. The time course of shortening of the refractory period caused by an increase in driving rate ("on" effect) has the following characteristics. The first beat shortens the refractory period, as determined from strength-interval curves, about 30% of the total shortening; the second beat shortens it 10% more. After the second beat, the rate of change in the duration of the refractory period suddenly becomes slower. Alternation of the refractory period begins with a slightly prolonged refractory period of the third beat and then diminishes rapidly in about the following 10 beats. These changes are in phase throughout the ventricular myocardium.
Following sudden transition to a slower rhythm, the time course of lengthening of the refractory period ("off" effect) is opposite to the "on" effect: the alternation that occurs is less marked. Changes in the duration of the functional refractory period near the stimulus site are parallel to those in the threshold curves.
These results demonstrate a long persistence of the effect on myocardial refractoriness of a previous cardiac frequency.
Publisher
Ovid Technologies (Wolters Kluwer Health)
Subject
Cardiology and Cardiovascular Medicine,Physiology
Reference12 articles.
1. BROOKS CH. M C C HOFFMAN B. F. SUCKLINC E. E. AND ORIAS O.: Excitability of the heart. New York Grune & Stratton 1955.
2. HOFFMAN B. F. AND CHANEFIELD P. F.: Electrophysiology of the Heart. New York Mc-Graw Hill Book Co. Inc. 1960.
3. Influence of cycle length upon refractory period of auricles, ventricles and A-V node in the dog;MENDEZ C.;Am. J. Physiol.,1956
4. Influence du rythme sur la duree du potentiel d'action ventriculaire cardiaque;CARMELIET E. E.;Arch. Intern. Physiol.,1955
5. Spread of activation in the left ventricular wall of the dog. I.
Cited by
208 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献