FIELD : medicine.SUBSTANCE : invention relates to medicine, namely, to pediatrics, cardiology, and is a method for diagnosing heart disease in infectious diseases in children and adolescents by assessing electrocardiographic parameters, characterized in that they determine atrioventricular conduction in relation to the heart rate in the percentiles and markers of infectious diseases : when detecting PQ>75 percentile to eliminate hidden violations of AV-conduction, stress tests or Holter ECG monitoring are carried out with determination of PQ at different heart rates and with persistent atrioventricular block I degree, identified latent impairments of atrioventricular conduction and markers of acute or previous infectious disease diagnose infections associated with damage to the cardiac conduction system. Method can be used to diagnose infection-associated lesions of the heart, including early diagnosis of myocarditis with an isolated lesion of the cardiac conduction system.EFFECT : invention provides the possibility of early detection of a cardiac lesion developing on the background of an acute or chronic infectious disease with further development of severe cardiac pathology and, as a result, a timely delivery of anti-infective and cardiotropic therapy, which improves the outcome of the disease.1 cl, 4 ex, 9 dwg