Picture of two heads

Open Access research that challenges the mind...

The Strathprints institutional repository is a digital archive of University of Strathclyde research outputs. Strathprints provides access to thousands of Open Access research papers by University of Strathclyde researchers, including those from the School of Psychological Sciences & Health - but also papers by researchers based within the Faculties of Science, Engineering, Humanities & Social Sciences, and from the Strathclyde Business School.

Discover more...

The contribution of ionic currents to changes in refractoriness of human atrial myocytes associated with chronic atrial fibrillation

Workman, A.J. and Kane, Kathleen and Rankin, A.C. (2001) The contribution of ionic currents to changes in refractoriness of human atrial myocytes associated with chronic atrial fibrillation. Cardiovascular Research, 52 (2). pp. 226-235. ISSN 0008-6363

Full text not available in this repository. (Request a copy from the Strathclyde author)

Abstract

Objective: To investigate changes in human atrial single cell functional electrophysiological properties associated with chronic atrial fibrillation (AF), and the contribution to these of accompanying ion current changes. Methods: The whole cell patch clamp technique was used to record action potentials, the effective refractory period (ERP) and ion currents, in the absence and presence of drugs, in enzymatically isolated myocytes from 11 patients with chronic (<6 months) AF and 39 patients in sinus rhythm. Results: Stimulation at high rates (up to 600 beats/min) markedly shortened late repolarisation and the ERP in cells from patients in sinus rhythm, and depolarised the maximum diastolic potential (MDP). Chronic AF was associated with a reduction in the ERP at physiological rate (from 203±16 to 104±15 ms, P<0.05), and marked attenuation in rate effects on the ERP and repolarisation. The abbreviated terminal phase of repolarisation prevented fast rate-induced depolarisation of the MDP in cells from patients with AF. The density of L-type Ca2+ (ICaL) and transient outward K+ (ITO) currents was significantly reduced in cells from patients with AF (by 60–65%), whilst the inward rectifier K+ current (IK1) was increased, and the sustained outward current (IKSUS) was unaltered. Superfusion of cells from patients in sinus rhythm with nifedipine (10 micromol/l) moderately shortened repolarisation, but had no effect on the ERP (228±12 vs. 225±11 ms). 4-Aminopyridine (2 mmol/l) markedly prolonged repolarisation and the ERP (by 35%, P<0.05). However, the combination of these drugs had no effect on late repolarisation or refractoriness. Conclusion: Chronic AF in humans is associated with attenuation in adaptation of the atrial single cell ERP and MDP to fast rates, which may not be explained fully by accompanying changes in ICaL and ITO.