Sandbox/WCT

Wide Complex Tachycardia Resident Survival Guide Microchapters
Overview
Causes
FIRE
Diagnosis
Treatment
Do's
Don'ts

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Rim Halaby, M.D. [2]

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Overview

Wide complex tachycardia is characterized by a heart rate more than 100 beats per minute associated with a QRS interval of more than 120 ms. When wide complex tachycardia is present, it is important to determine whether the tachycardia is of a supraventricular or a ventricular origin. The diagnosis of wide complex tachycardia is very challenging as there is no fixed criteria to accurately determine the cause and type of the WCT. Hemodynamically unstable patients should receive urgent synchronized cardioversion. If the QRS complex and the T wave can't be distinguished in unstable patients, then we proceed with unsynchronized cardioversion.

Causes

Life Threatening Causes

Wide complex tachycardia may be a life-threatening condition and must be treated as such irrespective of the causes.

Common Causes

• Atrial fibrillation with aberrancy
• Atrial fibrillation with pre-excitation
• Supraventricular tachycardia (SVT) with aberrancy
• Ventricular tachycardia

Click here for the complete list of causes.

FIRE: Focused Initial Rapid Evaluation

A Focused Initial Rapid Evaluation (FIRE) as shown below should be performed to identify patients in need of immediate intervention.

Boxes in salmon signify that an urgent management is needed.

Identify cardinal findings that increase the pretest probability of wide complex tachycardia ❑ Palpitations ❑ QRS complex > 120 ms ❑ Heart rate > 150 beats/min

Does the patient have any of the following findings that require urgent cardioversion? ❑ Hemodynamic instability ❑ Hypotension ❑ Cold extremities ❑ Peripheral cyanosis ❑ Mottling ❑ Altered mental status ❑ Chest discomfort suggestive of ischemia ❑ Decompensated heart failure

❑ Yes

❑ No

❑ Continue with the complete diagnostic approach below

Prepare the patient for immediate cardioversion and simultaneously do the following: ❑ Maintain patent airway; assist breathing as necessary ❑ Adminster oxygen (if the patient is hypoxemic) ❑ Cardiac monitor to identify rhythm; monitor blood pressure and oximetry ❑ Give IV sedation if the patient is conscious (don't delay cardioversion to sedate the patient) ❑ Consider expert consultation

VT/VF in the form of cardiac arrest Click here for Cardiac arrest resident survival guide

Unsynchronized cardioversion ❑ If a patient has polymorphic VT and is unstable, treat the rhythm as VF and deliver high-energy unsynchronized shocks ❑ Provide an initial shock of 200 Joules ❑ Increase the dose if no response to the first shock (eg, 300 J, 360 J, 360 J)

Synchronized cardioversion

Atrial fibrillation with aberrancy ❑ Provide an initial dose of biphasic cardioversion of 120-200 Joules (Class IIa, level of evidence A) ❑ If the initial shock fails, increase the dose in a stepwise fashion

Arial flutter and other SVTs with aberrancy ❑ Provide an initial dose of biphasic cardioversion of 50-100 Joules (Class IIa, level of evidence B) ❑ If the initial shock fails, increase the dose in a stepwise fashion ❑ If monophasic wave form is used, begin at 200 Joules and increase in stepwise fashion if not successful

Monomorphic VT (regular form and rate) ❑ Provide an initial dose of biphasic cardioversion of 100 Joules (Class IIb, level of evidence C) ❑ If the initial shock fails, increase the dose in a stepwise fashion

❑ After the stabilization of the patient, continue with the complete diagnostic approach below

Complete Diagnostic Approach

A complete diagnostic approach should be carried out after a focused initial rapid evaluation is conducted and following initiation of any urgent intervention.

Abbreviations: ECG: electrocardiogram; VT: ventricular tachycardia; VF: ventricular fibrillation; ICD: implantable cardioverter-defibrillator; BPM: beat per minute

Characterize the symptoms: ❑ Palpitations ❑ Lightheadedness ❑ Dyspnea ❑ Diaphoresis ❑ Chest discomfort ❑ Shock ❑ Syncope ❑ Seizures ❑ Cardiac arrest Characterize the timing of the symptoms: ❑ Onset ❑ First episode ❑ Recurrent ❑ Duration ❑ Frequency ❑ Termination of the episode ❑ Spontaneous ❑ Medication use ❑ Not terminated

Identify possible triggers: ❑ Infection ❑ Caffeine ❑ Alcohol ❑ Nicotine ❑ Recreational drugs ❑ Hypovolemia ❑ Hyperthyroidism ❑ Hypoxia ❑ Acidosis ❑ Hypokalemia ❑ Hyperkalemia ❑ Hypoglycemia ❑ Hypothermia ❑ Toxins ❑ Pulmonary embolism ❑ Coronary thrombosis ❑ Cardiac tamponade ❑ Trauma

Examine the patient: Vitals ❑ Pulse ❑ Rate ❑ Tachycardia (> 100 bpm) ❑ Rhythm ❑ Regular ❑ Irregular ❑ Strength ❑ Weak ❑ Alternating in strength (atrial fibrillation with aberrancy) ❑ Respiration ❑ Tachypnea ❑ Blood pressure ❑ Hypotension (in hemodynamically unstable patients) ❑ Marked fluctuation of blood pressure (suggestive of AV dissociation in VT) Neck ❑ Canon A waves on examining the jugular venous pressure of the neck (suggestive of AV dissociation in VT) Cardiovascular examination ❑ Auscultation ❑ Heart sounds ❑ Rapid regular or irregular beats ❑ Murmurs (suggestive of valvular diseases) ❑ Variability in the occurrence and the intensity of heart sounds especially S1 (suggestive of AV dissociation in VT) ❑ Inspection ❑ Midsternal incision (sugestive of previous cardiothoracic surgery) ❑ Palpation ❑ Pace maker or ICD are usually palpapable on the left pectoral area

Order labs and tests: ❑ Order and monitor the ECG Perform urgent cardioversion in unstable patients ❑ Chest x ray ❑ Cardiomegaly (suggestive of heart disease) ❑ Pace maker and ICD appear in the x ray ❑ Invasive electrophysiological studies ❑ Electrolytes ❑ Hypomagnesemia ❑ Hypokalemia ❑ Plasma concentration of drugs (eg,digoxin, quinidine or procainamide

Wide QRS complex tachycardia (QRS duration greater than 120 ms)

Regular or irregular?

Regular

Irregular

Is QRS identical to that during SR? If yes, consider: - SVT and BBB - Antidromic AVRT

Atrial fibrillation Atrial flutter / AT with variable conduction and: a) BBB or b) Antegrade conduction via AP

Vagal maneuvers or adenosine

Previous myocardial infarction or structural heart disease? If yes, VT is likely.

1 to 1 AV relationship?

Yes or unknown

No

V rate faster than A rate

A rate faster than V rate

QRS morphology in precordial leads

VT

Atrial tachycardia Atrial flutter

Typical RBBB or LBBB

Precordial leads: - Concordant - No R/S pattern - Onset of R to nadir longer than 100ms

RBBB pattern: - qR, Rs or Rr' in V1 - Frontal plane axis range from +90 degrees to -90 degrees

LBBB pattern: - R in V1 longer than 30 ms - R to nadir of S in V1 greater than 60 ms - qR or qS in V6

SVT

VT

VT

VT

The above algorithm is adapted from the 2003 American College of Cardiology.

Treatment

A complete diagnostic approach should be carried out after a focused initial rapid evaluation is conducted and following initiation of any urgent intervention.

ABC: Air, breathing and circulation; Afib: Atrial fibrillation; BBB: Bundle branch block; LV: Left ventricle; SVT: Supraventricular tachycardia; VT: Ventricular tachycardia; WPW: Wold Parkinson White

Click on boxes to expand/collapse detailed information.                     Wide complex tachycardia QRS ≥ 120ms                                                                                             Begin initial management                                                                                             Determine if the patient has any unstable sign or symptom                                                                                                                 No               Yes                                                                         Determine the regularity of the rhythm               Perform immediate synchronized cardioversion                                                                           Regular rhythm               Irregular rhythm                                                                                                           VT or uncertain rhythm   SVT with aberrancy   Afib with aberrancy   Pre-excited Afib (Afib + WPW)   Recurrent polymorphic VT   Torsade de pointes

Begin initial management ❑ Assess and support ABC's as needed ❑ Give oxygen ❑ Monitor ECG, blood pressure, oxymetry ❑ Establish IV access ❑ Identify and treat reversible causes Determine if the patient has any unstable sign or symptom ❑ Chest pain ❑ Congestive heart failure ❑ Hypotension ❑ Loss of consciousness ❑ Seizures Perform immediate synchronized cardioversion ❑ Perform immediate synchronized cardioversion ❑ Give IV sedation if the patient is conscious ❑ Consider expert consultation VT or uncertain rhythm ❑ Give amiodarone 150 mg IV over 10 min ❑ Repeat amiodarone as needed for a maximal dose of 2.2g/24h ❑ Prepare for elective synchronized cardioversion SVT with aberrancy ❑ Attempt vagal maneuvers ❑ Give adenosine 6 mg rapid IV push ❑ If no conversion give 12 mg IV push ❑ May repeat 12 mg dose once Afib with aberrancy ❑ Consider expert consultation ❑ Control rate e.g diltiazem or beta blockers Pre-excited Afib (Afib + WPW) ❑ Consider expert consultation ❑ Avoid AV nodal blocking agents e.g adenosine, digoxin, diltiazem and verapamil ❑ Consider amiodarone 150 mg IV over 10 min Recurrent polymorphic VT ❑ Consider expert consultation Torsade de pointes ❑ Load with magnesium 1-2 g over 5-60 min, then infusion

Differentiating SVT from VT

Shown below is a table summarizing some clues that help differentiate SVT from VT.

Clues	Type of arrhythmia
Irregularly irregular rhythm	Atrial fibrillation or atrial flutter with aberrancy
Previous myocardial infarction or structural heart disease	Ventricular tachycardia
Ventricular rate faster than atrial rate	Ventricular tachycardia
Typical RBBB or LBBB	Supraventricular tachycardia
Precordial leads: ❑ Concordant ❑ No R/S pattern ❑ Onset of R to nadir longer than 100ms	Ventricular tachycardia
RBBB pattern: ❑ qR, Rs or Rr' in V1 ❑ Frontal plane axis range from +90 degrees to -90 degrees	Ventricular tachycardia
LBBB pattern: ❑ R in V1 longer than 30 ms ❑ R to nadir of S in V1 greater than 60 ms ❑ qR or qS in V6	Ventricular tachycardia

For more details about differentiating VT from SVT, click here

Antiarrhythmics

Shown below is a table summarizing the choices of the antiarrhythmic drugs for the different types of tachycardia according to the 2003 ACC/AHA/ESC guidelines for the management of patients with supraventricular arrhythmias.

BBB: Bundle branch block; LV: Left ventricle; SVT: Supraventricular tachycardia

Management of wide complex tachycardia Ventricular tachycardia or wide QRS tachycardia of unknown origin ▸ Procainamide (Class I, level of evidence B) OR ▸ Sotalol (Class I, level of evidence B) OR ▸ Amiodarone OR ▸ Cardioversion (Class I, level of evidence B) OR ▸ Lidocaine (Class IIb, level of evidence B) OR ▸ Adenosine (Class IIb, level of evidence C) OR ▸ Beta blocker (Class III, level of evidence C) OR ▸ Verapamil (Class III, level of evidence B) Wide QRS tachycardia of unknown origin + poor LV function ▸ Amiodarone (Class I, level of evidence B) OR ▸ Cardioversion (Class I, level of evidence B) SVT + BBB ▸ Vagal maneuvers (Class I, level of evidence B) OR ▸ Adenosine (Class I, level of evidence A) OR ▸ Verapamil (Class I, level of evidence A) OR ▸ Diltiazem (Class I, level of evidence A) OR ▸ Beta blocker (Class IIb, level of evidence C) OR ▸ Amiodarone (Class IIb, level of evidence C) OR ▸ Digoxin (Class IIb, level of evidence C) SVT or atrial fibrillation + Preexcitation ▸ Flecainide (Class I, level of evidence B) OR ▸ Ibutilide (Class I, level of evidence B) OR ▸ Procainamide (Class I, level of evidence B) OR ▸ Cardioversion (Class I, level of evidence C)

Do's

• Refer the patient to an arrhythmia specialist when the tachycardia causes syncope or dyspnea as well as when the wide complex tachycardia is of unknown cause.
• Place an ambulatory 24 hour Holter when the tachycardia is frequent and transient.
• Treat the patient as having a ventricular tachycardia when the diagnosis of supraventricular tachycardia can not be made.
• Suspect ventricular tachycardia in a patient with wide complex tachycardia and previous myocardial infarction or a history of structural heart disease.
• Use beta blockers with caution in pulmonary diseases or congestive heart failure.

Dont's

• Don't rely on the hemodynamic status of the patient and the heart rate to differenciate SVT from VT.

References