Contraction without depolarization in the in vivo heart: Kinetic and electronmicroscopic studies

Abstract

Contraction without depolarization was demonstrated in the in vivo heart after very rapid single or paired stimulation. This occurred when the restitution curves exhibited a descending phase. Electronmicroscopic studies indicated that during the high contractile states induced by rapid electrical heart rates the myofilaments were flooded by Ca⁺⁺ from their intracellular storage sites.