Algorithm 1 Procedure to find the EAD threshold.

1: Set ion channel conductances in cell model to new values based on drug block.

2: Run cell model to steady state and then save this state to reset to later.

3: Set upper and lower limits α, β for intervention value.

4: Repeat

5: Reset cell model to earlier state.

6: Set intervention to (α + β) ÷ 2 (e.g. multiply ICaL conductance by this factor).

7: Run model for 12 s.

8: Check for early afterdepolarisation (upwards trajectory after initial depolarisation).

9: Adjust α or β using interval bisection.

10: Until |α – β| < 10–4