Does a heart infection like myocarditis show up on ecg or echo?

Yes: Typically, there in patients with myocarditis, there are abnormalities on both ECG and echocardiogram. In fact, if both the ECG and the echocardiogram were normal, the likelihood of myocarditis would be very low. Typical ECG findings are st and t wave changes, and perhaps low amplitude qrs complexes. Echocardiographic findings are decrease ventricular function and perhaps pericardial effusion.