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May 3, 1965


JAMA. 1965;192(5):411. doi:10.1001/jama.1965.03080180069022

Recovery of electrical excitability of the heart precedes recovery of contractile activity. Establishment of this physiologic principle in 19591 has resulted in a novel method of heart stimulation which possesses major clinical potential. It is possible to introduce an electric impulse immediately after termination of the absolute refractory period, which results in electrical stimulation without an effective mechanical response. When paired electrical stimuli are appropriately timed, only the first results in cardiac contraction; this technique increases the number of electrical events but results in a decrease in the number of mechanical contractions. The strength of a post-extrasystolic ventricular contraction increases with the degree of prematurity of the extrasystole. Paired pulse stimulation can be timed to effect maximum prematurity of the extrasystole; therefore, maximal potentiation of the post-extrasystolic contraction can be achieved. Chardack, Gage, and Dean2 have demonstrated recently that slowing of the heart by this technique leads to

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