Effect of Verapamil on threshold potential

[Northerncardinal]

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a question in uworld mentions that verapamil raises the threshold potential of cardiac slow response fibers. how does it affect threshold potential?

 

[Ven0m]

weird. because i know if a patient has hyperkalemia, which decreases the threshold potential (indirectly), then you give calcium gluconate to raise the threshold potential, countering the effects of hyperkalemia. but since verapamil is a ca2+ blocker, i would think it has the opposite effect. any ideas?