TY - JOUR
T1 - Cardiac resynchronization therapy improves altered na channel gating in canine model of dyssynchronous heart failure
AU - Aiba, Takeshi
AU - Barth, Andreas S.
AU - Hesketh, Geoffrey G.
AU - Hashambhoy, Yasmin L.
AU - Chakir, Khalid
AU - Tunin, Richard S.
AU - Greenstein, Joseph L.
AU - Winslow, Raimond L.
AU - Kass, David A.
AU - Tomaselli, Gordon F.
PY - 2013/6
Y1 - 2013/6
N2 - Background-Slowed Na+ current (INa) decay and enhanced late INa (INa-L) prolong the action potential duration (APD) and contribute to early afterdepolarizations. Cardiac resynchronization therapy (CRT) shortens APD compared with dyssynchronous heart failure (DHF); however, the role of altered Na+ channel gating in CRT remains unexplored. Methods and Results-Adult dogs underwent left-bundle branch ablation and right atrial pacing (200 beats/min) for 6 weeks (DHF) or 3 weeks followed by 3 weeks of biventricular pacing at the same rate (CRT). INa and INa-L were measured in left ventricular myocytes from nonfailing, DHF, and CRT dogs. DHF shifted voltage-dependence of INa availability by -3 mV compared with nonfailing, enhanced intermediate inactivation, and slowed recovery from inactivation. CRT reversed the DHF-induced voltage shift of availability, partially reversed enhanced intermediate inactivation but did not affect DHF-induced slowed recovery. DHF markedly increased INa-L compared with nonfailing. CRT dramatically reduced DHF-induced enhanced INa-L, abbreviated the APD, and suppressed early afterdepolarizations. CRT was associated with a global reduction in phosphorylated Ca2+/Calmodulin protein kinase II, which has distinct effects on inactivation of cardiac Na+ channels. In a canine AP model, alterations of INa-L are sufficient to reproduce the effects on APD observed in DHF and CRT myocytes. Conclusions-CRT improves DHF-induced alterations of Na+ channel function, especially suppression of INa-L, thus, abbreviating the APD and reducing the frequency of early afterdepolarizations. Changes in the levels of phosphorylated Ca2+/Calmodulin protein kinase II suggest a molecular pathway for regulation of INa by biventricular pacing of the failing heart.
AB - Background-Slowed Na+ current (INa) decay and enhanced late INa (INa-L) prolong the action potential duration (APD) and contribute to early afterdepolarizations. Cardiac resynchronization therapy (CRT) shortens APD compared with dyssynchronous heart failure (DHF); however, the role of altered Na+ channel gating in CRT remains unexplored. Methods and Results-Adult dogs underwent left-bundle branch ablation and right atrial pacing (200 beats/min) for 6 weeks (DHF) or 3 weeks followed by 3 weeks of biventricular pacing at the same rate (CRT). INa and INa-L were measured in left ventricular myocytes from nonfailing, DHF, and CRT dogs. DHF shifted voltage-dependence of INa availability by -3 mV compared with nonfailing, enhanced intermediate inactivation, and slowed recovery from inactivation. CRT reversed the DHF-induced voltage shift of availability, partially reversed enhanced intermediate inactivation but did not affect DHF-induced slowed recovery. DHF markedly increased INa-L compared with nonfailing. CRT dramatically reduced DHF-induced enhanced INa-L, abbreviated the APD, and suppressed early afterdepolarizations. CRT was associated with a global reduction in phosphorylated Ca2+/Calmodulin protein kinase II, which has distinct effects on inactivation of cardiac Na+ channels. In a canine AP model, alterations of INa-L are sufficient to reproduce the effects on APD observed in DHF and CRT myocytes. Conclusions-CRT improves DHF-induced alterations of Na+ channel function, especially suppression of INa-L, thus, abbreviating the APD and reducing the frequency of early afterdepolarizations. Changes in the levels of phosphorylated Ca2+/Calmodulin protein kinase II suggest a molecular pathway for regulation of INa by biventricular pacing of the failing heart.
KW - Arrhythmias
KW - Cardiac resynchronization therapy
KW - Electrophysiology
KW - Heart failure
KW - Na+ channels
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U2 - 10.1161/CIRCEP.113.000400
DO - 10.1161/CIRCEP.113.000400
M3 - Article
C2 - 23650309
AN - SCOPUS:84883016295
SN - 1941-3149
VL - 6
SP - 546
EP - 554
JO - Circulation: Arrhythmia and Electrophysiology
JF - Circulation: Arrhythmia and Electrophysiology
IS - 3
ER -