- Cardiac or other medical contraindications for stimulant trial (e.g., family history of heart attack at age younger than 40 years, personal history of heart disease, history of fainting while exercising, structural cardiac abnormalities, cardiomyopathy, serious cardiac arrhythmias, coronary artery disease, or other serious cardiac problems. If any doubt, children will be referred to a cardiologist for a cardiac clearance.