>> it was very scary. because we know the risk with the myocarditis of sunday sudden cardiac death, my first night was the scary one. all i kept thinking to myself was please let me wake up in the morning. >> reporter: a large study from washington university found in the year after getting covid, patients were at increased risk for developing 20 cardiac problems, including stroke, heart attack, myocarditis, and irregular heart rhythms. even younger, healthier people were at risk, as were those who were not hospitalized for covid. do you worry that we're going to be seeing more and more cardia...