tachycardia (AVRT) in Wolff-Parkinson-White syndrome. The steps are as follows: Leads V1-V6 are inspected to detect an RS complex (ie, a biphasic QRS complex with both positive R and negative S wave components). If there are no RS complexes, concordance is present, and the diagnosis of VT can be made ( waveform 2). (See 'Concordance' above.) If an RS complex is present, measure the interval between the onset of the R wave and the nadir of the S wave (RS interval). If the longest RS interval in any lead is >100 milliseconds and the R wave is wider than the S wave, the diagnosis of VT can be made. This reflects that https://www.uptodate.com/contents/wide-qrs-complex-tachycardias-approach-to-the-diagnosis/print 12/38 7/5/23, 10:41 AM Wide QRS complex tachycardias: Approach to the diagnosis - UpToDate with VT, the entire QRS complex is wide and abnormal (even the initial R wave portion), while aberration is due to a terminal delay resulting in a wider terminal portion of the QRS complex (ie, S wave). This criterion, however, may be limited in the presence of an underlying diffuse cardiomyopathy, as in this situation, even initial ventricular activation may be slow and abnormal. If the longest RS interval is <100 milliseconds, the presence or absence of AV dissociation is assessed. If AV dissociation is seen, the diagnosis of VT is made. (See 'AV dissociation' above.) If AV dissociation cannot clearly be demonstrated, the QRS morphology criteria for V1- positive and V1-negative wide QRS complex tachycardias are considered. QRS morphology criteria consistent with VT must be present in leads V1 or V2 and in lead V6 to diagnose VT. If either the V1-V2 or the V6 criteria are not consistent with VT, an SVT is assumed. (See 'QRS morphology' above.) Alternative approaches Several alternative approaches have been proposed in the literature, although none are as commonly used as the Brugada criteria. These approaches are generally best performed in consultation with an electrophysiologist with expertise in the diagnosis of WCT. An alternative algorithm (Vereckei approach) uses a stepwise approach similar to the Brugada criteria but includes different ECG features ( algorithm 3) [15]. Two unique features of this algorithm include: An initial R wave in aVR (diagnostic of VT). Vi:Vt ratio. Vi and Vt are the magnitude of voltage change in the initial and terminal 40 milliseconds of a QRS, respectively. Vi and Vt should be measured from the same biphasic or multiphasic QRS complex. A Vi:Vt ratio 1 is diagnostic of VT. One study of 51 patients with WCT induced during electrophysiology study showed equivalent sensitivity for diagnosis between the Vereckei and Brugada approaches (89 versus 90 percent), but the Vereckei approach yielded significantly fewer incorrect diagnoses following the first step (2 versus 27 percent) and was slightly faster to perform (9.1 versus 9.9 seconds) [17]. An additional algorithm (limb leads algorithm) diagnoses VT in the presence of at least one of the following criteria: https://www.uptodate.com/contents/wide-qrs-complex-tachycardias-approach-to-the-diagnosis/print 13/38 7/5/23, 10:41 AM Wide QRS complex tachycardias: Approach to the diagnosis - UpToDate Monophasic R wave in lead aVR Predominantly negative QRS complex in leads I, II, III Opposing QRS complex in the limb leads (concordant monophasic QRS complex in all inferior leads [II, III, aVF] and concordant monophasic QRS complex in two or three of the remaining limb leads [I, aVR, aVL] with opposite polarity of the inferior leads) Among a series of 528 wide QRS complex tachycardias (397 VT, 131 SVT), the limb leads algorithm had similar overall accuracy compared to other algorithms (88 percent versus 85 percent with Brugada criteria and 88 percent with Vereckei approach); in general, the limb leads algorithm had lower sensitivity but higher specificity for diagnosing VT [18]. A Bayesian approach utilizes likelihood ratios (LR) for six ECG criteria [8]. Patients are presumed to start with a "prior odds ratio" of 4.0 (4:1) in favor of VT. As each criterion is evaluated sequentially, the associated LR is multiplied by the prior odds ratio to calculate the new probability of VT. The final odds ratio (posterior probability) is considered consistent with VT if the value is 1.0 and SVT if the value is <1.0. Intravenous adenosine may be administered as both a diagnostic and potentially therapeutic agent. (See "Wide QRS complex tachycardias: Approach to management", section on 'Pharmacologic interventions'.) VT versus AVRT Differentiation between VT and antidromic AVRT is particularly difficult. Because there is direct myocardial activation (since ventricular activation begins outside of the normal conduction system) in both VT and antidromic AVRT, many of the standard criteria are not able to discriminate antidromic AVRT from VT. The clinical significance of this problem is often limited, however, because pre-excitation is an uncommon cause of WCT (6 percent in one series), particularly if other clinical factors (eg, age, underlying heart disease) suggest VT [11]. For cases in which pre-excitation is thought to be likely (such as a young patient without structural heart disease, or a patient with a known accessory pathway), a separate algorithm was developed that consists of the following three steps ( algorithm 4) [14]: The predominant polarity of the QRS complex in leads V4 through V6 is defined either as positive or negative. If predominantly negative, the diagnosis of VT can be made. If the polarity of the QRS complex is predominantly positive in V4 through V6, the ECG should be examined for the presence of a qR complex in one or more of the precordial leads V2 through V6. If a qR complex can be identified, VT can be diagnosed. https://www.uptodate.com/contents/wide-qrs-complex-tachycardias-approach-to-the-diagnosis/print 14/38 7/5/23, 10:41 AM Wide QRS complex tachycardias: Approach to the diagnosis - UpToDate If a qR wave in leads V2 through V6 is absent, the AV relationship is then evaluated (AV dissociation). If a 1:1 AV relationship is not present and there are more QRS complexes present than P waves, VT can be diagnosed. When any of these criteria are met, VT is likely. However, if the ECG does not display any of the three morphologic characteristics diagnostic of VT in this algorithm, the diagnosis of antidromic AVRT must be considered. Importantly, the QRS complex morphology and ST-T waves are uniform with AVRT as every impulse to the ventricle is conducted through the same accessory pathway. Algorithm performance Algorithms often perform well in initial reports. However, such studies include selected populations and experienced ECG analysts. In its initial description, the reported sensitivity and specificity of the Brugada criteria were 98.7 and 96.5 percent, respectively [14]. However, in two subsequent reports in which a total of nine clinicians (two cardiologists, two emergency department clinicians, and five internists) used these criteria in interpreting a total of 168 WCTs that had been diagnosed with electrophysiologic testing, the sensitivity ranged from 79 to 92 percent and specificity ranged from 43 to 70 percent [19,20]. In a comparison of the Brugada criteria and the Bayesian approach, the two approaches performed similarly, with sensitivities of 92 and 97 percent and specificities of 44 and 56 percent, respectively [20]. In the initial description of the alternative algorithm (Vereckei approach), it was significantly more accurate than the Brugada criteria [15]. Further study is necessary to confirm both the overall accuracy of this approach and its superiority to the Brugada criteria. SOCIETY GUIDELINE LINKS Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Arrhythmias in adults" and "Society guideline links: Ventricular arrhythmias" and "Society guideline links: Supraventricular arrhythmias".) INFORMATION FOR PATIENTS https://www.uptodate.com/contents/wide-qrs-complex-tachycardias-approach-to-the-diagnosis/print 15/38 7/5/23, 10:41 AM Wide QRS complex tachycardias: Approach to the diagnosis - UpToDate UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." th th The Basics patient education pieces are written in plain language, at the 5 to 6 grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more th th sophisticated, and more detailed. These articles are written at the 10 to 12 grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon. Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.) Basics topics (see "Patient education: Ventricular tachycardia (The Basics)") SUMMARY AND RECOMMENDATIONS The first priority when evaluating a patient with a wide QRS complex tachycardia (WCT) is an immediate assessment of patient stability, including the patient's symptoms, vital signs, and the level of consciousness. An unstable patient will have evidence of hemodynamic compromise, such as hypotension, altered mental status, chest pain, or heart failure. A patient who is unresponsive or pulseless should be treated according to standard advanced cardiac life support (ACLS) algorithms ( algorithm 5). (See 'Assessment of hemodynamic stability' above and "Advanced cardiac life support (ACLS) in adults".) For a patient who is unstable, with evidence of hemodynamic compromise but who remains conscious, emergency synchronized cardioversion (after intravenous sedation, whenever possible) is the treatment of choice regardless of the mechanism of the arrhythmia. (See 'Assessment of hemodynamic stability' above and "Wide QRS complex tachycardias: Approach to management", section on 'Unstable patients'.) In a stable patient, or following cardioversion to stabilize an unstable patient, our initial approach includes the following: A succinct history and physical examination, focusing on the presence of structural heart disease, especially coronary heart disease and/or a previous myocardial infarction, as well as the history of any arrhythmias and the presence of a https://www.uptodate.com/contents/wide-qrs-complex-tachycardias-approach-to-the-diagnosis/print 16/38 7/5/23, 10:41 AM Wide QRS complex tachycardias: Approach to the diagnosis - UpToDate pacemaker or implantable cardioverter-defibrillator. (See 'History' above and 'Physical examination' above.) Review of the patient s medications for drugs that may be proarrhythmic (by prolonging the QT interval or promoting electrolyte disturbances). (See 'Medications' above.) Initial review of the ECG, with a focus on whether the rhythm is regular or irregular, the width of the QRS complex, the presence or absence of AV dissociation, and any preexisting arrhythmias. (See 'ECG initial impressions' above.) Ancillary testing including serum electrolyte levels, cardiac troponin, and a chest radiograph in all patients. (See 'Ancillary testing' above.) In most patients with WCT, a probable diagnosis (ventricular tachycardia [VT] or supraventricular tachycardia [SVT]) may be made by closely reviewing the ECG, although definitive diagnosis is not always possible and may be time consuming. The standard initial approach to ECG interpretation includes an assessment of rate, regularity, axis, QRS duration, and QRS morphology. (See 'Evaluation of the electrocardiogram' above.) Most patients with WCT will have some, but not all, of the ECG features favoring VT. There is no single criterion or combination of criteria that provides complete diagnostic accuracy in evaluating a WCT, even when employing an algorithmic approach to the diagnosis of a WCT. (See 'Diagnosis' above.) We prefer using the Brugada algorithm to evaluate for VT versus SVT in patients with WCT when the diagnosis is uncertain and when patient hemodynamic stability allows. ECG features consistent with VT include concordance ( waveform 2), AV dissociation, fusion/capture beats, and specific QRS morphologies. The absence of the historical or ECG features of VT does not confirm a diagnosis of SVT. The diagnosis of SVT should be considered primarily in young patients, whose hearts are structurally normal, in whom none of the historical (eg, family history of sudden cardiac death), physical, or ECG criteria supporting VT are present, or in patients with a history of SVT with a similar presentation. When the diagnosis of a WCT is uncertain despite a careful initial evaluation, the patient should be treated as if the rhythm is VT. (See "Wide QRS complex tachycardias: Approach to management".) https://www.uptodate.com/contents/wide-qrs-complex-tachycardias-approach-to-the-diagnosis/print 17/38 7/5/23, 10:41 AM Wide QRS complex tachycardias: Approach to the diagnosis - UpToDate ACKNOWLEDGMENT The UpToDate editorial staff acknowledges Philip Podrid, MD, 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 1. Akhtar M, Shenasa M, Jazayeri M, et al. Wide QRS complex tachycardia. Reappraisal of a common clinical problem. Ann Intern Med 1988; 109:905. 2. Morady F, Baerman JM, DiCarlo LA Jr, et al. A prevalent misconception regarding wide- complex tachycardias. JAMA 1985; 254:2790. 3. Dancy M, Camm AJ, Ward D. Misdiagnosis of chronic recurrent ventricular tachycardia. Lancet 1985; 2:320. 4. Tchou P, Young P, Mahmud R, et al. Useful clinical criteria for the diagnosis of ventricular tachycardia. Am J Med 1988; 84:53. 5. Baerman JM, Morady F, DiCarlo LA Jr, de Buitleir M. Differentiation of ventricular tachycardia from supraventricular tachycardia with aberration: value of the clinical history. Ann Emerg Med 1987; 16:40. 6. Griffith MJ, de Belder MA, Linker NJ, et al. Multivariate analysis to simplify the differential diagnosis of broad complex tachycardia. Br Heart J 1991; 66:166. 7. Wellens HJ. Electrophysiology: Ventricular tachycardia: diagnosis of broad QRS complex tachycardia. Heart 2001; 86:579. 8. Lau EW, Pathamanathan RK, Ng GA, et al. The Bayesian approach improves the electrocardiographic diagnosis of broad complex tachycardia. Pacing Clin Electrophysiol 2000; 23:1519. 9. Crijns HJ, van Gelder IC, Lie KI. Supraventricular tachycardia mimicking ventricular tachycardia during flecainide treatment. Am J Cardiol 1988; 62:1303. 10. Murdock CJ, Kyles AE, Yeung-Lai-Wah JA, et al. Atrial flutter in patients treated for atrial fibrillation with propafenone. Am J Cardiol 1990; 66:755. 11. Miller JM, Das MK. Differential diagnosis of narrow and wide complex tachycardias. In: Cardi ac Electrophysiology From Cell to Bedside, 7th, Zipes DP, Jalife J, Stevenson WG (Eds), W.B. Sa unders, Philadelphia 2018. https://www.uptodate.com/contents/wide-qrs-complex-tachycardias-approach-to-the-diagnosis/print 18/38 7/5/23, 10:41 AM Wide QRS complex tachycardias: Approach to the diagnosis - UpToDate 12. Militianu A, Salacata A, Meissner MD, et al. Ventriculoatrial conduction capability and prevalence of 1:1 retrograde conduction during inducible sustained monomorphic ventricular tachycardia in 305 implantable cardioverter defibrillator recipients. Pacing Clin Electrophysiol 1997; 20:2378. 13. Haley JH, Reeder GS. Images in cardiovascular Medicine. Wide-complex tachycardia. Circulation 2000; 102:E52. 14. Brugada P, Brugada J, Mont L, et al. A new approach to the differential diagnosis of a regular tachycardia with a wide QRS complex. Circulation 1991; 83:1649. 15. Vereckei A, Duray G, Sz n si G, et al. Application of a new algorithm in the differential diagnosis of wide QRS complex tachycardia. Eur Heart J 2007; 28:589. 16. Al-Khatib SM, Stevenson WG, Ackerman MJ, et al. 2017 AHA/ACC/HRS Guideline for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death: 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 2018; 72:e91. 17. Kaiser E, Darrieux FC, Barbosa SA, et al. Differential diagnosis of wide QRS tachycardias: comparison of two electrocardiographic algorithms. Europace 2015; 17:1422. 18. Chen Q, Xu J, Gianni C, et al. Simple electrocardiographic criteria for rapid identification of wide QRS complex tachycardia: The new limb lead algorithm. Heart Rhythm 2020; 17:431. 19. Isenhour JL, Craig S, Gibbs M, et al. Wide-complex tachycardia: continued evaluation of diagnostic criteria. Acad Emerg Med 2000; 7:769. 20. Lau EW, Ng GA. Comparison of the performance of three diagnostic algorithms for regular broad complex tachycardia in practical application. Pacing Clin Electrophysiol 2002; 25:822. Topic 920 Version 45.0 https://www.uptodate.com/contents/wide-qrs-complex-tachycardias-approach-to-the-diagnosis/print 19/38 7/5/23, 10:41 AM Wide QRS complex tachycardias: Approach to the diagnosis - UpToDate GRAPHICS 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/wide-qrs-complex-tachycardias-approach-to-the-diagnosis/print 20/38 7/5/23, 10:41 AM Wide QRS complex tachycardias: Approach to the diagnosis - UpToDate Some reported causes and potentiators of the long QT syndrome Congenital Jervell and Lange-Nielsen syndrome (including "channelopathies") Romano-Ward syndrome Idiopathic Acquired Metabolic disorders Other factors Androgen deprivation therapy Hypokalemia Myocardial GnRH agonist/antagonist therapy ischemia or infarction, Hypomagnesemia Bilateral surgical orchiectomy Hypocalcemia Diuretic therapy via electrolyte disorders especially with Starvation particularly hypokalemia and hypomagnesemia prominent T-wave inversions Anorexia nervosa Herbs Liquid protein diets Cinchona (contains quinine), iboga (ibogaine), licorice extract in overuse via electrolyte disturbances Intracranial disease Hypothyroidism Bradyarrhythmias HIV infection Sinus node dysfunction Hypothermia Toxic exposure: Organophosphate insecticides AV block: Second or third degree Medications* High risk Adagrasib Cisaparide Lenvatinib Selpercatinib (restricted availability) Ajmaline Levoketoconazole Sertindole Amiodarone Methadone Sotalol Delamanid Arsenic trioxide Mobocertinib Terfenadine Disopyramide Astemizole Papavirine Vandetanib Dofetilide (intracoronary) Bedaquline Vernakalant Dronedarone Procainamide Bepridil Ziprasidone Haloperidol (IV) Quinidine Chlorpromazine Ibutilide Quinine Ivosidenib Moderate risk Amisulpride (oral) Droperidol Inotuzumab ozogamacin Propafenone Azithromycin Encorafenib Propofol Isoflurane Capecitabine Entrectinib Quetiapine Carbetocin Erythromycin Ribociclib https://www.uptodate.com/contents/wide-qrs-complex-tachycardias-approach-to-the-diagnosis/print 21/38 7/5/23, 10:41 AM Wide QRS complex tachycardias: Approach to the diagnosis - UpToDate Certinib Escitalopram Levofloxacin Risperidone (systemic) Chloroquine Etelcalcetide Saquinavir Lofexidine Citalopram Fexinidazole Sevoflurane Meglumine Clarithromycin Flecainide Sparfloxacin antimoniate Clofazimine Floxuridine Sunitinib Midostaurin Clomipramine Fluconazole Tegafur Moxifloxacin Clozapine Fluorouracil Terbutaline Nilotinib (systemic) Crizotinib Thioridazine Olanzapine Flupentixol Dabrafenib Toremifene Ondansetrol (IV > Gabobenate dimeglumine Dasatinib Vemurafenib oral) Deslurane Voriconazole Osimertinib Gemifloxacin Domperidone Oxytocin Gilteritinib Doxepin Pazopanib Halofantrine Doxifluridine Pentamidine Haloperidol (oral) Pilsicainide Imipramine Pimozide Piperaquine Probucol Low risk Albuterol Fingolimod Mequitazine Ranolazine (due to bradycardia) Alfuzosin Fluoxetine Methotrimeprazine Relugolix Amisulpride (IV) Fluphenazine Metoclopramide (rare reports) Rilpivirine Amitriptyline Formoterol Metronidazole (systemic) Romidepsin Anagrelide Foscarnet Roxithromycin Apomorphine Fostemsavir Mifepristone Salmeterol Arformoterol Gadofosveset Mirtazapine Sertraline Artemether- Glasdegib Mizolastine lumefantrine Siponimod Goserelin Nelfinavir Asenapine Solifenacin Granisetron Norfloxacin Atomoxetine Sorafenib Hydroxychloroquine Nortriptyline Benperidol (rare reports) Sulpiride Ofloxacin (systemic) Bilastine Hydroxyzine Tacrolimus Olodaterol (systemic) Bosutinib Iloperidone Osilodrostat Tamoxifen Bromperidol Indacaterol Oxaliplatin Telavancin Buprenorphine Itraconazole Ozanimod Telithromycin Buserelin Ketoconazole (systemic) Pacritinib Teneligliptin Ciprofloxacin (Systemic) Lacidipine Paliperidone Tetrabenazine Cocaine (Topical) Lapatinib Panobinostat Trazodone Degarelix Lefamulin Pasireotide Triclabendazole https://www.uptodate.com/contents/wide-qrs-complex-tachycardias-approach-to-the-diagnosis/print 22/38 7/5/23, 10:41 AM Wide QRS complex tachycardias: Approach to the diagnosis - UpToDate Desipramine Leuprolide Pefloxacin Triptorelin Deutetrabenazine Leuprolide- Periciazine Tropisetron norethindrone Dexmedetomidine** Pimavanserin Vardenafil Levalbuterol Dolasetron Pipamperone Vilanterol Levomethadone Donepezil Pitolisant Vinflunine Lithium Efavirenz Ponesimod Voclosporin Loperamide overdose in Eliglustat Primaquine Vorinostat Eribulin Promazine Zuclopenthixol Lopinavir Ezogabine Radotinib Macimorelin Mefloquine This is not a complete list of all corrected QT interval (QTc)-prolonging drugs and does not include drugs with either a minor degree or isolated association(s) with QTc prolongation that appear to be safe in most patients but may need to be avoided in patients with congenital long QT syndrome depending upon clinical circumstances. A more complete list of such drugs is available at the CredibleMeds website. For clinical use and precautions related to medications and drug interactions, refer to the UpToDate topic review of acquired long QT syndrome discussion of medications and the Lexicomp drug interactions tool. AV: atrioventricular; IV: intravenous; QTc: rate-corrected QT interval on the electrocardiogram. Classifications provided by Lexicomp according to US Food & Drug Administration guidance: Clinical Evaluation of QT/QTc Interval Prolongation and Proarrhythic Potential for Non-Antiarrhythmic Drugs Questions and Answers; Guidance for Industry US Food and Drug Administration, June 2017 (revision 2) available at: https://www.fda.gov/downloads/Drugs/GuidanceComplianceRegulatoryInformation/Guidances/UCM 073161.pdf with additional data from CredibleMeds QT drugs list criteria may lead to some agents being classified differently by other sources. [1,2] . The use of other classification Not available in the United States. In contrast with other class III antiarrhythmic drugs, amiodarone is rarely associated with torsades de pointes; refer to accompanying text within UpToDate topic reviews of acquired long QT syndrome. Withdrawn from market in most countries due to adverse cardiovascular effects. IV amisulpride antiemetic use is associated with less QTc prolongation than the higher doses administered orally as an antipsychotic. Other cyclic antidepressants may also prolong the QT interval; refer to UpToDate clinical topic on cyclic antidepressant pharmacology, side effects, and separate UpToDate topic on tricyclic antidepressant poisoning. The "low risk" category includes drugs with limited evidence of clinically significant QTc prolongation or TdP risk; many of these drugs have label warnings regarding possible QTc effects or recommendations to avoid use or increase ECG monitoring when combined with other QTc prolonging drugs. https://www.uptodate.com/contents/wide-qrs-complex-tachycardias-approach-to-the-diagnosis/print 23/38 7/5/23, 10:41 AM Wide QRS complex tachycardias: Approach to the diagnosis - UpToDate Rarely associated with significant QTc prolongation at usual doses for treatment of opioid use disorder, making buprenorphine a suitable alternative for patients with methadone-associated QTc prolongation. Refer to UpToDate clinical topic reviews. * The United States FDA labeling for the sublingual preparation of dexmedetomidine warns against use in patients at elevated risk for QTc prolongation. Both intravenous (ie, sedative) and sublingual formulations of dexmedetomidine have a low risk of QTc prolongation and have not been implicated in TdP. Over-the-counter; available without a prescription. Not associated with significant QTc prolongation in healthy persons. Refer to UpToDate clinical topic for potential adverse cardiovascular (CV) effects in patients with CV disease. Data from: 1. Lexicomp Online. Copyright 1978-2023 Lexicomp, Inc. All Rights Reserved. 2. CredibleMeds QT drugs list website sponsored by Science Foundation of the University of Arizona. Available at http://crediblemeds.org/. Graphic 57431 Version 142.0 https://www.uptodate.com/contents/wide-qrs-complex-tachycardias-approach-to-the-diagnosis/print 24/38 7/5/23, 10:41 AM Wide QRS complex tachycardias: Approach to the diagnosis - UpToDate Calculation of frontal plane axis If the QRS complex is positive in leads I and II, it falls between -30 and 90 and is normal, as indicated by the yellow area. If the QRS complex is negative in I and positive in aVF, there is right axis deviation. If the QRS complex is positive in I and negative in II, there is left axis deviation. If the QRS complex is negative in I and aVF, there is extreme axis deviation. Graphic 85682 Version 1.0 https://www.uptodate.com/contents/wide-qrs-complex-tachycardias-approach-to-the-diagnosis/print 25/38 7/5/23, 10:41 AM Wide QRS complex tachycardias: Approach to the diagnosis - UpToDate Ventricular tachycardia An example of concordance/absence of rS complex and initial R wave in AVR. Courtesy of Leonard Ganz, MD. Graphic 129901 Version 1.0 https://www.uptodate.com/contents/wide-qrs-complex-tachycardias-approach-to-the-diagnosis/print 26/38 7/5/23, 10:41 AM Wide QRS complex tachycardias: Approach to the diagnosis - UpToDate Wide complex tachycardia with wide concordance Extreme tachycardia with wide complex. Courtesy of Leonard Ganz, MD. Graphic 129926 Version 2.0 https://www.uptodate.com/contents/wide-qrs-complex-tachycardias-approach-to-the-diagnosis/print 27/38 7/5/23, 10:41 AM Wide QRS complex tachycardias: Approach to the diagnosis - UpToDate Ventricular tachycardia with positive concordance Monophasic R waves are noted in all the precordial leads; this is positive concordance. Dissociated P waves a evident in the lead II rhythm strip and in lead aVR. Thick arrow shows artifact. Arrowheads show P waves, marching out at approximately 54 beats per minute. P waves are less evident on the left side of the lead II rh strip. Courtesy of Leonard Ganz, MD. Graphic 129857 Version 1.0 https://www.uptodate.com/contents/wide-qrs-complex-tachycardias-approach-to-the-diagnosis/print 28/38 7/5/23, 10:41 AM Wide QRS complex tachycardias: Approach to the diagnosis - UpToDate Atrioventricular dissociation Independent activation of the atria and ventricles results in no fixed relationship between the P waves (arrows) and the QRS complexes; the PR intervals are variable in a random fashion. Graphic 52123 Version 2.0 Normal rhythm strip Normal rhythm strip in lead II. The PR interval is 0.15 sec and the QRS duration is 0.08 sec. Both the P and T waves are upright. Courtesy of Morton F Arnsdorf, MD. Graphic 59022 Version 3.0 https://www.uptodate.com/contents/wide-qrs-complex-tachycardias-approach-to-the-diagnosis/print 29/38 7/5/23, 10:41 AM Wide QRS complex tachycardias: Approach to the diagnosis - UpToDate Fusion beats The rhythm strip in a patient with sustained ventricular tachycardia shows a fusion beat and a capture beat. The fusion beat occurs when a supraventricular impulse (following the first P wave) causes ventricular activation, which fuses with the complex originating in the ventricle, producing a hybrid complex. The complex following the second P wave has the appearance of a normal QRS complex and is known as a capture beat. Graphic 72600 Version 4.0 Normal rhythm strip Normal rhythm strip in lead II. The PR interval is 0.15 sec and the QRS duration is 0.08 sec. Both the P and T waves are upright. Courtesy of Morton F Arnsdorf, MD. Graphic 59022 Version 3.0 https://www.uptodate.com/contents/wide-qrs-complex-tachycardias-approach-to-the-diagnosis/print 30/38 7/5/23, 10:41 AM Wide QRS complex tachycardias: Approach to the diagnosis - UpToDate Brugada algorithm for the diagnosis of ventricular tachycardia or supraventricular tachycardia in a patient with wide QRS complex tachycardia Brugada algorithm for distinguishing VT from SVT. VT: ventricular tachycardia; SVT: supraventricular tachycardia. Adapted from: Brugada P, Brugada J, Mont L, et al. A new approach to the di erential diagnosis of a regular tachycardia with a wide QRS complex. Circulation 1991; 83:1649. Graphic 73159 Version 4.0 https://www.uptodate.com/contents/wide-qrs-complex-tachycardias-approach-to-the-diagnosis/print 31/38 7/5/23, 10:41 AM Wide QRS complex tachycardias: Approach to the diagnosis - UpToDate Vereckei algorithm for the diagnosis of ventricular tachycardia (VT) or supraventricular tachycardia (SVT) in a patient with wide QRS complex tachycardia Vereckei algorithm for the diagnosis of wide complex tachycardias. In step 4, V represents the magnitude of voltage change in the initial 40 milliseconds of the QRS complex, while V represents the i t magnitude of voltage change in the terminal 40 milliseconds of the QRS complex. The initial V and terminal V voltages should be i t measured from the same biphasic or multiphasic QRS complex. A-V: atrio-ventricular; BBB: bundle branch block; FB: fascicular block; SVT: supraventricular tachycardia; VT: ventricular tachycardia. Reproduced with permission from: Vereckei A, Duray G, Szenasi G, et al. Application of a new algorithm in the di erential diagnosis of wide QRS complex tachycardia. https://www.uptodate.com/contents/wide-qrs-complex-tachycardias-approach-to-the-diagnosis/print 32/38 7/5/23, 10:41 AM Wide QRS complex tachycardias: Approach to the diagnosis - UpToDate Eur Heart J 2007; 28:589. Copyright 2007 Oxford University Press. Graphic 79624 Version 6.0 https://www.uptodate.com/contents/wide-qrs-complex-tachycardias-approach-to-the-diagnosis/print 33/38 7/5/23, 10:41 AM Wide QRS complex tachycardias: Approach to the diagnosis - UpToDate Algorithm for the diagnosis of wide QRS tachycardia in the setting of ventricular pre- excitation Algorithm for distinguishing VT from SVT in the setting of pre- excitation syndrome. VT: ventricular tachycardia; AV: atrioventricular; SVT: supraventricular tachycardia; ECG: electrocardiography; EP: electrophysiologic. Graphic 59336 Version 8.0 https://www.uptodate.com/contents/wide-qrs-complex-tachycardias-approach-to-the-diagnosis/print 34/38 7/5/23, 10:41 AM Wide QRS complex tachycardias: Approach to the diagnosis - UpToDate Adult cardiac arrest algorithm https://www.uptodate.com/contents/wide-qrs-complex-tachycardias-approach-to-the-diagnosis/print 35/38 7/5/23, 10:41 AM Wide QRS complex tachycardias: Approach to the diagnosis - UpToDate https://www.uptodate.com/contents/wide-qrs-complex-tachycardias-approach-to-the-diagnosis/print 36/38 7/5/23, 10:41 AM Wide QRS complex tachycardias: Approach to the diagnosis - 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/wide-qrs-complex-tachycardias-approach-to-the-diagnosis/print 37/38 7/5/23, 10:41 AM Wide QRS complex tachycardias: Approach to the diagnosis - UpToDate Contributor Disclosures Peter J Zimetbaum, MD Consultant/Advisory Boards: Abbott Medical [Lead extraction]. All of the relevant financial relationships listed have been mitigated. Ary L Goldberger, MD Other Financial Interest: Elsevier book royalties [Clinical electrocardiography]. All of the relevant financial relationships listed have been mitigated. James Hoekstra, MD No relevant financial relationship(s) with ineligible companies to disclose. N A Mark Estes, III, MD Consultant/Advisory Boards: Boston Scientific [Arrhythmias]; Medtronic [Arrhythmias]. All of the relevant financial relationships listed have been mitigated. Nisha Parikh, MD, MPH 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/wide-qrs-complex-tachycardias-approach-to-the-diagnosis/print 38/38