Snapshot A 28-year-old woman presents to the emergency department for palpitations and lightheadedness. She reports that her symptoms began approximately 20 minutes ago and it has not subsided. Medical history is significant for hyperthyroidism. Vital signs are significant for a blood pressure of 135/95 mmHg and a pulse of 155/min. An electrocardiogram is performed that shows a narrow QRS-complex tachyarrhythmia. Carotid sinus massage is performed and her symptoms do not improve. Intravenous adenosine is instituted and her pulse decreases to 79/min. Introduction Definition a tachyarrhythmia that originates above the ventricles (e.g., atrial or atrioventricular node tissues) also known paroxysmal supraventricular tachycardia (SVT) Types atrial fibrillation atrial flutter focal atrial tachycardia multifocal atrial tachycardia atrioventricular reentrant tachycardia atrioventricular nodal reentrant tachycardia Wolff-Parkinson-White syndrome Associated conditions acute myocardial infarctions preexcitation syndromes atrial septal defects chronic lung disease Epidemiology Precipitating factors excessive caffeine or alcohol hyperthyroidism illicit drug use Etiology Reentrant circuit involved atrial and/or atrioventricular nodal tissue Presentation Symptoms palpitations anxiety presyncope/lightheadedness chest pain Physical exam tachycardia Studies Electrocardiogram tachycardia narrow or wide QRS complex if a wide QRS complex is noted, it must be differentiated from a ventricular tachycardia a wide QRS complex can be seen in SVT if there is bundle branch block accessory pathway Holter monitor consider a 24-hour Holter monitor in patients if the tachycardia is not present Differential Atrial fibrillation differentiating factor narrow QRS complex with an irregularly irregular rhythm Treatment Conservative vagal maneuvers indication first-step in management in a stable patient examples carotid sinus massage Valsalva facial immersion in ice or a cold wet towel Medical intravenous adenosine indication administered in stable patients who are unresponsive to vagal maneuvers AV nodal blocking agents beta-blockers calcium channel blockers contraindicated in patients < 12 months old (can cause hypotension and pulselessness) Procedural synchronized cardioversion indication performed in hemodynamically unstable patients radiofrequency catheter ablation indication best long-term therapy for SVT Complications Tachycardia-mediated cardiomyopathy