Force-frequency relations in nonfailing and failing animal myocardium.

This paper reviews the recent data concerning the force-frequency relations in experimental animals with heart failure. After a brief overview of the nature of these relations, which are induced by 2 opposite phenomena, the potentiation of force of contraction by heart rate and the restitution process, the paper reviews first the force-frequency relations in isolated failing myocardium. This is followed by a review of recent data obtained in the in situ failing heart. The cellular mechanisms of the force-frequency relations are then discussed.