Characteristics of the time-dependent slow inward current in adult human atrial single myocytes

The slow inward current isi plays a prominent role in impulse formation and slow conduction in the human heart. For this reason, it may be involved in a great variety of arrhythmias that occur clinically, particularly at the supraventricular level. isi also appears to be the major target of numerous cardioactive drugs daily administered to many patients. Difficulties encountered in voltage clamping human tissues, inevitably dissected from restricted zones of myocardium with inadequate geometry, may explain why direct measurements of this current have never been performed on multicellular human preparations. The recent development of enzymatic techniques allowing the isolation of calcium-tolerant myocytes has provided a solution to these problems. To our knowledge only one abstract has presented until now records of isi in human ventricular myocytes. We describe here the result of experiments carried out to investigate the slow inward current in single cells isolated from adult human atria. The present work provides the first quantitative description of this current in human myocytes.