This is a very topical question. A link between sudden death or fatal arrhythmia and stimulant medication has been postulated (though not proven), and that has caused much consternation. Recently, the Canadian Child Psychiatric Association and Cardiology Association joined up to put out some new advice on this. It’s now advised to do a thorough cardiologic history and physical on every child you are about to prescribe stimulants to, and (not surprisingly) investigate if there’s anything to suspect a problem, such as exertional syncope. There were no recommendations regarding a baseline ECG, however, so I don’t routinely order one.