I recovered almost completely from a dilated left ventricle. The underlying cause was ischemic meaning there was in adequate blood flow to an area of the heart that caused an impairment of heart wall movement and as a consequence less blood was pumped with each heart beat. Medication and stent provided sufficient blood flow and the left ventricle size returned to normal and the ventricle pumped sufficiently. It seems the underlying cause for your heart attack is different as I never required a pacer/defribillator treatment.
My limitations are limited by any symptoms such as chest pain (angina), but my med relieves that symptom. If your prior activities don't increase your heart rate over 220 minus your age, the exercise can be beneficial, and whether that is appropriate for you should be approved by your doctor.
Thanks for the question, and if you have any followup questions you are welcome to respond. Take care.