Transient Outward Current, I to1 , Is Altered in Cardiac Memory

Publisher Website
Google Scholar
Abstract
Background —Cardiac memory refers to an altered T-wave morphology induced by ventricular pacing or arrhythmias that persist for variable intervals after resumption of sinus rhythm. Methods and Results —We induced long-term cardiac memory (LTM) in conscious dogs by pacing the ventricles at 120 bpm for 3 weeks. ECGs were recorded daily for 1 hour, during which time pacing was discontinued. At terminal study, the heart was removed and the electrophysiology of left ventricular epicardial myocytes was investigated. Control (C) and LTM ECG did not differ, except for T-wave amplitude, which decreased from 0.12±0.18 to −0.34±0.21 mV (±SEM, P P P I to ) was investigated by whole-cell patch clamp. No difference in capacitance was seen in C and LTM myocytes. I to activated on membrane depolarization to −25±1 mV in C and −7±1 mV ( P I to density was reduced in LTM myocytes, and a decreased mRNA level for Kv4.3 was observed. Recovery of I to from inactivation was significantly prolonged: it was 531±80 ms (n=10) in LTM and 27±6 ms (n=9) in C ( P Conclusions — I to changes are associated with and can provide at least a partial explanation for action-potential and T-wave changes occurring with LTM.