Autonomic Vasovagal a Breath-holding spell a Situational (micturition, defecation, hair grooming, coughing) Cardiac b Electrical disturbances a Pre-excitation syndromes (Wolff–Parkinson–White syndrome) Long QT syndromes (congenital and acquired) Brugada syndrome Polymorphic ventricular tachycardia (e.g., in arrhythmogenic right ventricular cardiomyopathy or catecholaminergic polymorphic ventricular tachycardia) Bradycardia (complete heart block) Structural heart disease (obstruction to blood flow) Hypertrophic obstructive cardiomyopathy Aortic valve stenosis Pulmonary hypertension Myocardial Dysfunction Dilated cardiomyopathy Ischemia (coronary artery anomalies, Kawasaki disease, and atherosclerotic disease) Myocarditis Pericarditis Postoperative cardiac repair Others Hypoglycemia a Anaphylaxis b Environmental Heat syncope b Orthostatic a Dehydration or hemorrhage b Toxins a Carbon monoxide poisoning b Inhalant abuse (volatile inhalants, nitrites) b Hypoxia b Drugs