Endocardial control of myocardial performance.

ABSTRACT

Impairment of the endocardial surface has a profound influence on the mechanical performance of the underlying undamaged myocardium. It immediately and irreversibly shortens the duration of twitch tension development, particularly at a physiological extracellular [Ca++] and temperature, thereby affecting the relationship of peak isometric twitch tension development to both [Ca++]0 and length. Accordingly, the endocardium as the most primitive structure of the heart, may help to control the performance of the underlying myocardium by modulating the onset of early tension decline. These effects will result in important variations of peak contractile performance and of relaxation of the underlying myocardium.