[Contractile force and myocardial ischemia--electrical and ionic mechanisms].

In early myocardial ischemia we find several characteristic electrical and ionic alterations, like action potential shortening K(+)-accumulation or contractile failure. Trautwein and Dudel were 1954 the first to discuss action potential shortening as an important characteristic of myocardial ischemia. They already demonstrated that the action potential shortening is due to an enhanced outward current, while recently KATP-channels have been found to play an important role in the context. It has been suggested that contractile failure due to myocardial ischemia is caused by the shortening of action potential duration, reduced cytoplasmic free calcium levels, intracellular acidification, and a rise in inorganic phosphate and Mg. All of these phenomena may be related to the opening of KATP-channels. The different ionic and molecular mechanisms of contractile failure in myocardial ischemia will be discussed in this paper.