digoxin & QT interval

[DJtiesto]

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can someone explain how digoxin decreases the QT interval?

Thanks,

Jay

 

[Phloston]

The QT-interval is largely determined by the rate of calcium influx during phase-II (plateau) of the cardiomyocyte AP.

My guess would be that because digoxin increases intracellular [Ca2+], there is a concomitant lesser amount of time needed for extracellular Ca2+ to flow down its gradient in order to balance electrical charge during the plateau phase; this would be similar to the state induced by hypercalcaemia. Therefore the QT would shorten.

Once again, not a cardiac expert, but that's my reasoning.