Alterations in muscarinic K + channel response to acetylcholine and to G proteinmediated activation in atrial myocytes isolated from failing human hearts. Circulation

Background A variety of previous studies have demon-strated reduced diastolic potential and electrical activity in atrial specimens from patients with heart disease. Although K' channels play a major role in determining resting membrane potential and repolarization of the action potential, little is known about the effects of preexisting heart disease on human atrial K ' channel activity. Methods and Results We characterized the inwardly recti-fying K ' channel (IKI) and the muscarinic K ' channel [IK(ACh)I in atrial myocytes isolated from patients with heart failure (HF) and compared electrophysiological characteristics with those from donors (control) by the patch-clamp technique. Resting membrane potentials of isolated atrial myocytes from HF were more depolarized (-51.1±9.7 mV, mean-SD, n=30 patients) than those from donors (-73.0±7.2 mV, n=4 pa