Adverse cardiac events appear to increase among children infected with HIV as the disease progresses. Heart function was assessed among 81 young children infected with HIV. Elevated heart rate, which was seen in 52 (64%) of the children, was the most common heart abnormality. An abnormally slow heart rate was noted in nine (11%) of the children. Fifteen of the children had high blood pressure, and 16 had low blood pressure. Dysrhythmia, which is an abnormality in the heart rhythm, occurred in 28 (35%) of the children. Seven children experienced cardiac arrest, and eight had congestive heart failure. Heart abnormalities were more severe and more frequent in children with advanced HIV disease. Heart dysfunction was associated with death in 10 of the 37 children who died. Encephalopathy, which is degeneration of the brain, was the strongest predictor of cardiac arrest, and infection with Epstein-Barr virus was the strongest predictor of the development of congestive heart failure., Objective.--Dysrhythmias, hemodynamic instability, congestive heart failure, and sudden death are serious complications of human immunodeficiency virus (HIV) infection that, to our knowledge, have not been studied systematically. We sought to determine the cumulative incidence and clinical predictors of these adverse events in a cohort of HIV-infected children. Design.--Historical cohort study. Setting.--University-affiliated, primary and tertiary care pediatric hospital and ambulatory care center. Participants.--Eighty-one HIV-infected children who had one or more cardiac evaluations between 1984 and 1991 form the study cohort. The initial cardiac evaluation occurred at a median age of 1.5 years, and children were followed up to a median age of 3.6 years. Main Outcome Measures.--Mortality (related to cardiac dysfunction as well as noncardiac causes), tachycardia, bradycardia, hypertension, hypotension, marked sinus arrhythmia, cardiac arrest, and chronic congestive heart failure. Results.--Hemodynamic abnormalities and dysrhythmias occurred frequently. Eight unexpected cardiorespiratory arrests occurred in seven children (9%). Chronic congestive heart failure was noted in 10% of patients. Thirty children died, 10 with significant cardiac dysfunction. As HIV-infected children progressed from acquired immunodeficiency syndrome (AI DS)-related complex to AI DS, significant cardiac problems were more likely to occur. Both nonneurologic AIDS and encephalopathy were strongly associated with most severe cardiac outcomes. However, encephalopathy was the strongest correlate of cardiorespiratory arrest (P=-.002). Epstein-Barr virus coinfection was the strongest correlate of chronic congestive heart failure (P Conclusions.---Cardiac morbidity and mortality are more common with advanced HIV infection. The presence of encephalopathy or Epstein-Barr virus coinfection identifies HIV-infected children at especially high risk for adverse cardiac outcomes. (JAMA. 1993;269:2869-2875)