Di Palma, Joseph R.
April 1960
Angiology;Apr1960, Vol. 11 Issue 2, p126
Academic Journal
In open chest anesthetized dogs the heart was driven at rates from 90 to 210 per minute with the sinuaurieular node intact or crushed. A second pulse produced a premature systole measuring the refractory period of the normal cyclic systole. A third pulse was applied producing a second premature systole so as to measure the refractory period of the first premature systole. Latency of response to the second and third pulses was also measured. It was found that in all heart rates studied, the refractory period and latency were much shorter for the premature systole as compared to the previous cyclic systole. In nodal rhythm the same results were obtained. Latency was progressively shorter for the premature systoles induced in successive cycles. The results substantiate the view that a single premature systole may make the heart muscle more susceptible to rapid ventricular rhythms.


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