FORCE-FREQUENCY-RELATION IN HUMAN ATRIAL AND VENTRICULAR MYOCARDIUM

In human heart failure, an increase in frequency of stimulation is followed by a reduced force of contraction in vivo and in vitro. The present study aimed to investigate whether a different origin of the myocardial sample or pretreatment with the cardioprotective agent 2,3-butanedione-monoxime (BDM) influences the force-frequency-relationship in electrically driven muscle strips taken from failing and nonfailing human myocardium. With as well as without pretreatment with BDM, the altered force-frequency-relationship in failing compared to nonfailing human ventricular myocardium can be observed. The effectiveness and the potency to increase force of contraction following an increase in frequency of stimulation was significantly higher in atrial than in ventricular myocardium in nonfailing and failing tissue. The different observations in atrial and ventricular myocardium provide evidence for functionally relevant differences in the electromechanical coupling between the human atrial and ventricular myocardium.