echocardiography in, 1151–1152, 1152f–1153f electrocardiography in, 1150, 1151f ambulatory, 1150 epidemiology of, 1145 etiology of, 1147–1149, 1148t adenosine monophosphate-activated protein kinase mutations and, 1148 Anderson-Fabry disease and, 1149 Danon disease and, 1147–1148 Friedreich ataxia and, 1148–1149 LEOPARD syndrome and, 1147 mitochondrial cardiomyopathies and, 1148 Noonan syndrome and, 1147 Pompe disease and, 1149 sarcomeric protein disease and, 1147 magnetic resonance imaging in, 1152, 1154f management of, 1153–1155 for nonobstructive disease, 1154 to prevent sudden cardiac death, 1154–1155 for symptoms caused by obstruction of left ventricular outflow tract, 1154 pacing for, 366 pathology of, 1149, 1149f pathophysiology of, 1149–1150 Hyperventilation, terminal, 384 Hypoplastic branch pulmonary arteries, in diagnostic catheterization, 248, 248f Hypoplastic left heart syndrome (HLHS), 132 established, with intact or highly restrictive atrial septum, 154–155 patient selection for, 155, 155f postnatal outcome and management of, 155 technical aspects of, 155, 155f evolving, severe midgestation aortic stenosis with, 149–153, 150f patient selection for, 150, 151f postnatal outcome and management of, 152–153, 152f–153f technical aspects of, 150–152, 151f–152f novel treatments for, 276–277, 277f in univentricular hearts, 1248–1249, 1248f–1250f Hypoplastic right heart syndrome, evolving, pulmonary atresia with intact ventricular septum and, 153–154 patient selection for, 153–154, 154f postnatal outcome and management of, 154 technical aspects of, 154 Hypoplastic right ventricle, in diagnostic catheterization, 246 Hypoplastic ventricular cavities, 804–806, 805f–807f Hypotension brain injury and, 192–194, 194f in prematurity, 200–204 etiology of, 200, 201t therapeutic approach to, 201–204, 202f–203f, 202t–203t Hypothetical patient, medical summary for, 1488, 1489b Hypothyroidism cardiac involvement in, 1096 pericarditis and, 1069 Hypovolemia, in prematurity, 201 Hypoxemia long-standing and severe, consequences of, 1524–1525, 1525f, 1525t unanticipated, 1268–1270, 1268f, 1269t Hypoxia, human fetal circulatory adaptation to, 117–118, 119f I I-cell disease, cardiac involvement in, 1092 Iduronate sulfatase deficiency, cardiac involvement in, 1090–1091 α-L-iduronidase deficiency, cardiac involvement in, 1089–1090 Iloprost, for pulmonary hypertension, 1389 Immune system, extracardiac anomalies of, 453–454 Immunoglobulin, for atrial tachyarrhythmias, 139t Immunologic abnormalities, in Fontan circulation, 1330–1331 Immunomodulatory agents, for myocarditis, 1177 Immunosuppression, 1437 for cardiac transplantation, 1229, 1230f Immunosuppressive therapy, for myocarditis, 1177