U havent explained digoxin action correctly at ca Na exchange pump. Normally ca is expoted out and Na in while digoxin block this exchange and so in turn ca remains intracellular and its levels are increased in this way digoxin causes contractility
You're right. It also confused me because in first aid I found out the opposite concept. Actually, Na biluds up inside the cell due to Digoxin due to which Na Ca exchanger slows down and Ca is unable to exit the cell and it's also starts to accumulate, as a result contractility is increased
