Tachyarrhythmias SVT represents the most common tachyarrhythmia of childhood (see Chapter 86 Cardiac Emergencies ) The typical heart rate in infants with SVT exceeds 220 beats per minute, whereas older children usually have a heart rate in excess of 180 beats per minute Infants and children with SVT demonstrate a range of physical signs including no symptoms, palpitations, chest pain, tachypnea (often with feeding in infants), diaphoresis, and severe cardiogenic shock TABLE 77.1 DIFFERENTIAL DIAGNOSIS OF TACHYCARDIA Sinus tachycardia Fever Crying Pain Hypoglycemia Hypoxemia Hypercarbia Shock Anemia Poisoning (see Table 63.4 ) Sepsis Anaphylaxis Hyperthyroidism Pheochromocytoma Drug induced (e.g., antihistamines, caffeine, dietary supplements) Withdrawal (e.g., alcohol, benzodiazepines, opiates) Anxiety Myocarditis Acute rheumatic fever Kawasaki disease Pericardial effusion with tamponade Tachyarrhythmias Supraventricular tachycardia Atrial flutter Ventricular tachycardia (monomorphic and polymorphic/torsades de pointes)