How much any patient, big or little, feels when the ICD corrects the heart rhythm usually depends on the type of therapy delivered. If defibrillation is called for and the device delivers a shock, it may feel like a kick in the chest. Shock is uncomfortable and can be moderatiely painful. Research suggests patients rate it as a "6" on a scale from 1 to 10. Some say it feels like a mild shock from an electrical outlet. Either way, the feeling does not last long. Usually the patient is awake when it happens, but occasionally, one might lose consciousness before the therapy comes. Often the rhythm is corrected with pacing, a series of more subtle nudges. Patients usually don't notice that at all.