It will largely depend on your individual circumstances and medical conditions but common suspension periods are as follows:
If you had a heart attack as the cause of your cardiac arrest and it was remedied with medications and/or stents then the suspension period is 1 month.
If you had to have an ICD fitted then the suspension period will be 6 months from the date of the implant. If you have any shocks further suspensions will apply and the length will vary depending on a number of factors. See “Can I drive if I get a shock from my ICD” for more information.
You may also have to temporarily stop driving if your anti-arrhythmic medications are changed, typically for 1 month.
If your driving licence was revoked you’ll have to wait until all medical enquiries are complete. You will also need to have your driving licence back before you can start driving again.
You can check the DVLA information for medical professionals regarding assessing fitness to drive here, and this shows the rules regarding whether you can drive or not and if not, for how long.