Late sodium current in cardiac cells is very small compared with the fast component, but as it flows throughout the action potential it may make a substantial contribution to sodium loading during each cardiac cycle. Late sodium current may contribute to triggering arrhythmia in two ways: by causing repolarisation failure (early afterdepolarisations); and by triggering late afterdepolarisations attributable to calcium oscillations in sodium–calcium overload conditions. Reduction of late sodium current would therefore be expected to have therapeutic benefits, particularly in disease states such as ischaemia in which sodium–calcium overload is a major feature.
- EAD, early afterdepolarisation
- IbNa, sodium background current
- ICa, L, L-type inward calcium current
- IKr, rapid delayed potassium current
- IpNa, persistent sodium current
- [Na+]i, intracellular sodium concentration
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Competing interests: None declared.