crucial for subsequent management of the patient (see 'Initial diagnostic and treatment decisions' above): Narrow QRS complex tachycardias If the QRS complex is narrow ( algorithm 2), the approach to acute management is based on whether the patient is stable ( algorithm 3) or unstable ( algorithm 1). (See 'Narrow QRS complex tachyarrhythmias' above.) Wide QRS complex tachycardias If the QRS complex is wide ( algorithm 2), the approach to acute management is based on whether the patient is stable or unstable; pulseless patients should be treated according to the adult cardiac life support algorithm ( algorithm 5). (See 'Wide QRS complex tachyarrhythmias' above.) ACKNOWLEDGMENTS The UpToDate editorial staff acknowledges Philip Podrid, MD, FACC, and Leonard Ganz, MD, FHRS, FACC, who contributed to an earlier version of this topic review. Use of UpToDate is subject to the Terms of Use. REFERENCES https://www.uptodate.com/contents/overview-of-the-acute-management-of-tachyarrhythmias/print 13/28 7/5/23, 10:17 AM Overview of the acute management of tachyarrhythmias - UpToDate 1. Link MS. Clinical practice. Evaluation and initial treatment of supraventricular tachycardia. N Engl J Med 2012; 367:1438. 2. Page RL, Joglar JA, Caldwell MA, et al. 2015 ACC/AHA/HRS Guideline for the Management of Adult Patients With Supraventricular Tachycardia: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. J Am Coll Cardiol 2016; 67:e27. 3. Brugada J, Katritsis DG, Arbelo E, et al. 2019 ESC Guidelines for the management of patients with supraventricular tachycardiaThe Task Force for the management of patients with supraventricular tachycardia of the European Society of Cardiology (ESC). Eur Heart J 2020; 41:655. 4. Kalbfleisch SJ, el-Atassi R, Calkins H, et al. Differentiation of paroxysmal narrow QRS complex tachycardias using the 12-lead electrocardiogram. J Am Coll Cardiol 1993; 21:85. Topic 936 Version 43.0 https://www.uptodate.com/contents/overview-of-the-acute-management-of-tachyarrhythmias/print 14/28 7/5/23, 10:17 AM Overview of the acute management of tachyarrhythmias - UpToDate GRAPHICS Algorithm for the evaluation of narrow QRS complex tachycardias in unstable patients IV: intravenous. Graphic 109811 Version 2.0 https://www.uptodate.com/contents/overview-of-the-acute-management-of-tachyarrhythmias/print 15/28 7/5/23, 10:17 AM Overview of the acute management of tachyarrhythmias - UpToDate Algorithm for the initial ECG review and differential diagnosis of tachycardia ECG: electrocardiogram; AVNRT: atrioventricular nodal reentrant tachycardia; AVRT: atrioventricular reciprocating (bypass-tract mediated) tachycardia; AT: atrial tachycardia; SANRT: sinoatrial nodal reentrant tachycardia; AF: atrial fibrillation; AV: atrioventricular; VT: ventricular tachycardia; SVT: supraventricular tachycardia; WPW: Wolff-Parkinson-White. A narrow QRS complex is <120 milliseconds in duration, whereas a wide QRS complex is 120 milliseconds duration. Refer to UpToDate topic reviews for additional details on specific ECG findings and management of individu arrhythmias. Monomorphic VT accounts for 80% of wide QRS complex tachycardias; refer to UpToDate topic on diagnosi wide QRS complex tachycardias for additional information on discriminating VT from SVT. Graphic 117571 Version 3.0 https://www.uptodate.com/contents/overview-of-the-acute-management-of-tachyarrhythmias/print 16/28 7/5/23, 10:17 AM Overview of the acute management of tachyarrhythmias - UpToDate Algorithm for the evaluation of narrow QRS complex tachycardias in stable pati AVNRT: atrioventricular nodal reentrant tachycardia; AVRT: atrioventricular reentrant tachycardia (due to an a electrocardiogram; SANRT: sinoatrial nodal reentrant tachycardia. Graphic 76920 Version 3.0 https://www.uptodate.com/contents/overview-of-the-acute-management-of-tachyarrhythmias/print 17/28 7/5/23, 10:17 AM Overview of the acute management of tachyarrhythmias - UpToDate Approach to adenosine dosing in stable adults with suspected supraventricular tachyarrhythmia This figure summarizes the initial dosing, administration, and need for repeat dosing of adenosine in a hemo stable adult with suspected AV node-dependent SVT. Adenosine can be used as a diagnostic aid to identify th rhythm or as a therapy to terminate SVTs that rely on AV node conduction. AV node-dependent SVTs include A reentrant tachycardia (AVNRT) and AV reentrant (or reciprocating) tachycardia (AVRT). The management of su node-dependent SVT in hemodynamically stable adults commonly starts with a trial of 1 or more vagal mane proceeding to adenosine therapy. If the patient has hemodynamically unstable SVT, cardioversion is indicate UpToDate content for details on management of SVTs. https://www.uptodate.com/contents/overview-of-the-acute-management-of-tachyarrhythmias/print 18/28 7/5/23, 10:17 AM Overview of the acute management of tachyarrhythmias - UpToDate AV: atrioventricular; SVT: supraventricular tachycardia; IV: intravenous; ACC: American College of Cardiology; American Heart Association; HRS: Heart Rhythm Society; ECG: electrocardiogram. Lower adenosine doses are indicated in certain clinical settings. If central venous administration is perform adenosine dose is 3 mg; if needed (SVT persists and there is no AV block), the dose may be increased to 6 mg mg for subsequent doses. For heart transplant recipients, the initial adenosine dose is 1 mg; if needed (SVT p there is no AV block), the dose may be increased to 2 mg and then 3 mg for subsequent doses. An 18 mg dose is more likely to be required to produce AV block in patients with a body weight >70 kg, par [1] those weighing >110 kg. When a third dose is indicated, an alternative approach is to administer 12 mg (in mg) as described in the 2015 ACC/AHA/HRS Guideline for the Management of Adult Patients with Supraventr Tachycardia. [2] SVT termination in response to adenosine includes SVT termination closely followed by SVT recurrence. Refer to UpToDate content on treatment of SVT for dosing of second-line AV nodal blockers. If the SVT pers second-line AV nodal blocker therapy, electrical cardioversion is performed, as discussed in UpToDate conten treatment of SVT. SVTs that are not AV node dependent include atrial flutter, atrial fibrillation, and atrial tachycardia. When AV is induced by adenosine, the ECG may reveal atrial activity diagnostic of these rhythms. References: 1. Prabhu S, Mackin V, McLellan AJA, et al. Determining the optimal dose of adenosine for unmasking dormant pulmonary vein co following atrial brillation ablation: Electrophysiological and hemodynamic assessment. DORMANT-AF study. J Cardiovasc Electr 28:13. 2. Page RL, Joglar JA, Caldwell MA, et al. 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Hea Society. Circulation 2016; 133:e506. Graphic 141417 Version 3.0 https://www.uptodate.com/contents/overview-of-the-acute-management-of-tachyarrhythmias/print 19/28 7/5/23, 10:17 AM Overview of the acute management of tachyarrhythmias - UpToDate Medical therapy of arrhythmias associated with Wolff-Parkinson-White syndrome Arrhythmia Treatment options Contraindicated therapies Orthodromic AV reentrant tachycardia Acute termination* Unstable patients: Synchronized cardioversion Stable patients: First line: Vagal maneuvers Second line: IV adenosine Third line: IV verapamil OR IV diltiazem Other therapies: IV procainamide OR IV beta blocker; synchronized cardioversion if other therapies are ineffective or not feasible Chronic prevention First line: Catheter ablation of the accessory pathway Second line: Oral flecainide or propafenone in the absence of structural or ischemic heart disease Third line: Oral IA antiarrhythmic agent OR oral amiodarone Antidromic AV reentrant tachycardia Acute termination* Unstable patients: Adenosine, verapamil, diltiazem, Synchronized cardioversion beta blockers, digoxin should all be avoided if NOT certain of diagnosis Stable patients (if CERTAIN of the diagnosis): Same progression of therapies as acute termination of orthodromic AVRT Stable patients (if NOT certain of the diagnosis): IV procainamide, synchronized cardioversion if procainamide is ineffective or not available https://www.uptodate.com/contents/overview-of-the-acute-management-of-tachyarrhythmias/print 20/28 7/5/23, 10:17 AM Overview of the acute management of tachyarrhythmias - UpToDate Chronic prevention First line: Catheter ablation of the accessory pathway Digoxin Beta blockers Second line: Oral flecainide or propafenone in the absence of Verapamil, diltiazem structural or ischemic heart disease Other therapies: Oral IA antiarrhythmic agent OR oral amiodarone Pre-excited atrial fibrillation Acute termination* Unstable patients: Amiodarone Synchronized cardioversion Stable patients: Digoxin Beta blockers First line: IV ibutilide or IV procainamide Adenosine Other therapies: IC antiarrhythmic agent or dofetilide; synchronized cardioversion if other therapies are ineffective or not available Verapamil, diltiazem Chronic prevention First line: Catheter ablation or the accessory pathway Oral digoxin Second line: Oral flecainide or propafenone in the absence of structural or ischemic heart disease Third line: Oral IA antiarrhythmic agent OR oral amiodarone AVRT: atrioventricular reciprocating tachycardia; IV: intravenous; class IC: flecainide, propafenone; class IA: quinidine, procainamide, disopyramide. Cardioversion is indicated if hemodynamically unstable or drugs are ineffective. Ablation of the accessory pathway is generally preferred to cure the arrhythmia. Procainamide is the intravenous drug of choice for acute termination of suspected antidromic AVRT. If the tachycardia is definitely known to be antidromic AVRT, and it has been verified that the AV node (rather than a second accessory pathway) is acting as the retrograde limb of the circuit, one could consider treatment with an agent such as adenosine similar to therapy for orthodromic AVRT, https://www.uptodate.com/contents/overview-of-the-acute-management-of-tachyarrhythmias/print 21/28 7/5/23, 10:17 AM Overview of the acute management of tachyarrhythmias - UpToDate but it is rare to have all of the necessary data in the acute setting to justify use of AV nodal blocking agents. Graphic 62762 Version 7.0 https://www.uptodate.com/contents/overview-of-the-acute-management-of-tachyarrhythmias/print 22/28 7/5/23, 10:17 AM Overview of the acute management of tachyarrhythmias - UpToDate Adult cardiac arrest algorithm https://www.uptodate.com/contents/overview-of-the-acute-management-of-tachyarrhythmias/print 23/28 7/5/23, 10:17 AM Overview of the acute management of tachyarrhythmias - UpToDate https://www.uptodate.com/contents/overview-of-the-acute-management-of-tachyarrhythmias/print 24/28 7/5/23, 10:17 AM Overview of the acute management of tachyarrhythmias - UpToDate Reprinted with permission. Highlights of the 2020 American Heart Association Guidelines for CPR and ECC. Copyright 2020 American Association, Inc. Graphic 129983 Version 9.0 https://www.uptodate.com/contents/overview-of-the-acute-management-of-tachyarrhythmias/print 25/28 7/5/23, 10:17 AM Overview of the acute management of tachyarrhythmias - UpToDate Revised (2018) Vaughan Williams classification of antiarrhythmic drugs abridged table Class 0 (HCN channel blockers) Ivabradine Class I (voltage-gated Na+ channel blockers) Class Ia (intermediate dissociation): Quinidine, ajmaline, disopyramide, procainamide Class Ib (rapid dissociation): Lidocaine, mexilitine Class Ic (slow dissociation): Propafenone, flecainide Class Id (late current): Ranolazine Class II (autonomic inhibitors and activators) Class IIa (beta blockers): Nonselective: carvedilol, propranolol, nadolol Selective: atenolol, bisoprolol, betaxolol, celiprolol, esmolol, metoprolol Class IIb (nonselective beta agonists): Isoproterenol Class IIc (muscarinic M2 receptor inhibitors): Atropine, anisodamine, hyoscine, scopolamine Class IId (muscarinic M2 receptor activators): Carbachol, pilocarpine, methacholine, digoxin Class IIe (adenosine A1 receptor activators): Adenosine Class III (K+ channel blockers and openers) Class IIIa (voltage dependent K+ channel blockers): Ambasilide, amiodarone, dronedarone, dofetilide, ibutilide, sotalol, vernakalant Class IIIb (metabolically dependent K+ channel openers): https://www.uptodate.com/contents/overview-of-the-acute-management-of-tachyarrhythmias/print 26/28 7/5/23, 10:17 AM Overview of the acute management of tachyarrhythmias - UpToDate Nicorandil, pinacidil Class IV (Ca++ handling modulators) Class IVa (surface membrane Ca++ channel blockers): Bepridil, diltiazem, verapamil Class IVb (intracellular Ca++ channel blockers): Flecainide, propafenone Class V (mechanosensitive channel blockers): No approved medications Class VI (gap junction channel blockers) No approved medications Class VII (upstream target modulators) Angiotensin converting enzyme inhibitors Angiotensin receptor blockers Omega-3 fatty acids Statins HCN: hyperpolarization-activated cyclic nucleotide-gated; Na: sodium; K: potassium; Ca: calcium. Graphic 120433 Version 3.0 https://www.uptodate.com/contents/overview-of-the-acute-management-of-tachyarrhythmias/print 27/28 7/5/23, 10:17 AM Overview of the acute management of tachyarrhythmias - UpToDate Contributor Disclosures Jordan M Prutkin, MD, MHS, FHRS No relevant financial relationship(s) with ineligible companies to disclose. James Hoekstra, MD No relevant financial relationship(s) with ineligible companies to disclose. Hugh Calkins, MD Grant/Research/Clinical Trial Support: Adagio Medical [Atrial fibrillation]; Boston Scientific [ARVC]; Farapulse [Atrial fibrillation]; Medtronic [Atrial fibrillation]. Consultant/Advisory Boards: Abbott [Atrial fibrillation]; Atricure [Atrial fibrillation]; Biosense Webster [Catheter ablation]; Boston Scientific [ARVC and atrial fibrillation]; Medtronic [Atrial fibrillation]; Sanofi [Atrial fibrillation]. Other Financial Interest: Atricure [Lecture honoraria]; Biosense Webster [Lecture honoraria]; Boston Scientific [Lecture honoraria]; Medtronic [Lecture honoraria]. All of the relevant financial relationships listed have been mitigated. Todd F Dardas, MD, MS No relevant financial relationship(s) with ineligible companies to disclose. Contributor disclosures are reviewed for conflicts of interest by the editorial group. When found, these are addressed by vetting through a multi-level review process, and through requirements for references to be provided to support the content. Appropriately referenced content is required of all authors and must conform to UpToDate standards of evidence. Conflict of interest policy https://www.uptodate.com/contents/overview-of-the-acute-management-of-tachyarrhythmias/print 28/28