In silico study of action potential and QT interval shortening due to loss of inactivation of the cardiac rapid delayed rectifier potassium current.
The rapid delayed rectifier K(+) current, I(Kr), plays a key role in repolarisation of cardiac ventricular action potentials (APs). In recent years, a novel clinical condition denoted the short QT syndrome (SQTS) has been identified and, very recently, gain in function mutations in the gene encoding the pore-forming sub-unit of the I(Kr) channel have been proposed to underlie SQTS in some patients. Here, computer simulations were used to investigate the effects of the selective loss of voltage-dependent inactivation of I(Kr) upon ventricular APs and on the QT interval of the electrocardiogram. I(Kr) and inactivation-deficient I(Kr) were incorporated into Luo-Rudy ventricular AP models. Inactivation-deficient I(Kr) produced AP shortening that was heterogeneous between endocardial, mid-myocardial, and epicardial ventricular cell models, irrespective of whether heterogeneity between these sub-regions was incorporated of slow delayed rectifier K(+) current (I(Ks)) alone, or of I(Ks) together with that of transient outward K(+) current. The selective loss of rectification of I(Kr) did not augment transmural dispersion of AP repolarisation, as AP shortening was greater in mid-myocardial than in endo- or epicardial cell models. Simulated conduction through a 1 D transmural ventricular strand was altered by incorporation of inactivation-deficient I(Kr) and the reconstructed QT interval was shortened. Collectively, these results substantiate the notion that selective loss of I(Kr) inactivation produces a gain in I(Kr) function that causes QT interval shortening.
Zhang
Henggui
H
Biological Physics Group, Physics Department, UMIST, Manchester M60 1QD, UK. h.zhang-3@umist.ac.uk
Hancox
Jules C
JC
D000200:Action Potentials / Q000502:physiology*; D003198:Computer Simulation; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; D006801:Humans; D007700:Kinetics; D009206:Myocardium / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism; D024642:Potassium Channels, Voltage-Gated
D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D011188:Potassium