Management of tachycardia

Tachycardia is defined as a heart rate that exceeds 100/minute. Signs of unstable tachycardia include chest pain, shock, and impaired consciousness. Unstable tachycardia is considered an emergency and should be managed with immediate electrical cardioversion. In stable tachycardias, both the cardiac rhythm (i.e., regular or irregular) and the QRS complex (i.e., narrow-complex tachycardia and wide-complex tachycardias) should be evaluated. Undifferentiated regular supraventricular tachycardia (SVTs) should be initially managed with a trial of vagal maneuvers and, if necessary, IV adenosine. Irregular SVTs are usually caused by atrial fibrillation (Afib) or atrial flutter, which are managed either with a rate control strategy (e.g., with β-blockers or calcium channel blockers) or a rhythm control strategy (i.e., with antiarrhythmics or electrical cardioversion) in combination with risk-based anticoagulation therapy. Undifferentiated wide-complex tachycardias (WCTs) should be managed with electrical cardioversion or pharmacological cardioversion. If a stable patient becomes unstable at any point during management, immediate electrical cardioversion is recommended regardless of the rhythm. The content in this article is organized to first provide management steps for undifferentiated arrhythmias but also includes management for specific rhythms, once identified. Unstable tachycardia without a pulse, ventricular fibrillation, and cardiac arrest are not addressed here (see “ACLS”).

Initial approach

1. ABCDE survey
2. Determine if the patient is stable or unstable
3. Obtain a 12-lead ECG
4. Identify and treat the cardiac rhythm according to acute management algorithm
   • See “Management of unstable tachycardia with pulse.”
   • See “Management of stable, regular narrow-complex tachycardia.”
   • See “Management of stable, irregular narrow-complex tachycardia.”
   • See “Management of stable wide-complex tachycardia.”

1. ABCDE survey ^[1]

• No pulse: Start CPR (see “ACLS”).
• Pulse present: Continue stepwise approach through ABCDE and proceed to the next step.
  • Continuous telemetry
  • Continuous pulse oximetry
  • Crash cart at the bedside
  • Frequent blood pressure assessment
  • Supplemental oxygen as needed
  • Obtain IV access.
  • Identify and treat reversible causes

2. Determine if the patient is stable or unstable

• Unstable signs of tachycardia present: immediate synchronized electrical cardioversion (See “Management of unstable tachycardia with pulse.”)
• No unstable signs present: Proceed to the next step.

Examine patients for unstable signs of tachycardia so that immediate electrical cardioversion can be initiated if indicated.

3. Obtain a 12-lead ECG

1. Evaluate whether it is a wide-complex tachycardia (WCT) or narrow-complex tachycardia (NCT).
   • Narrow QRS complex : suggests supraventricular tachycardia (SVT)
   • Wide QRS complex : suggests either ventricular tachycardia (VT), SVT with aberrancy, or SVT with an accessory pathway
2. Determine whether the rhythm is regular or irregular (e.g., RR intervals regular or irregular).
3. Review previous ECGs if available to look for pre-existing abnormalities that may affect treatment choices, e.g.:
   • AV block greater than first degree
   • Episodes of bradycardia suggesting sinus node dysfunction
   • Presence of an accessory pathway

4. Identify and treat the cardiac rhythm according to acute management algorithm

• See “Management of unstable tachycardia with pulse.”
• See “Management of stable, regular narrow-complex tachycardia.”
• See “Management of stable, irregular narrow-complex tachycardia.”
• See “Management of stable wide-complex tachycardia.”

For unstable tachycardia without a pulse, start CPR (see “ACLS”).

Signs of unstable tachycardia ^[1]

• Acutely altered mental state or loss of consciousness
• Hypotension
• Shock
• Acute heart failure
• Ischemic chest pain

Initial management of unstable tachycardia with pulse

• Obtain a crash cart, defibrillator device, suction, bag-mask device, and airway and intubation equipment.
• Call for help (e.g., urgent cardiology consult and/or anesthesia consult)
• Administer supplemental oxygen, if needed.
• If unstable signs of tachycardia are present and instability is likely due to tachycardia, perform immediate electrical cardioversion.
  • HR > 150/min: Unstable signs are likely due to tachycardia.
  • HR 100–150/min: Suspect another underlying condition.

Electrical cardioversion ^[1][4]

• Synchronized electrical cardioversion is indicated in almost all unstable patients with tachycardia and a pulse. ^[1]
• Defibrillation is only indicated if either of the following is the case: ^[5]
  • An irregular wide-complex cardiac rhythm is identified.
  • The device fails to synchronize with the patient's cardiac rhythm.
• If Afib with RVR or rapid atrial flutter is identified, administer anticoagulation as soon as possible (see “Pericardioversion anticoagulation for Afib”). ^[6]
• Procedural sedation for cardioversion is typically necessary if the patient is conscious, but should not delay lifesaving intervention.
  • Administer any one of the following: ^[7][8]
    • Etomidate : preferred for hemodynamically unstable patients
    • Propofol
    • Midazolam
  • Consider the addition of an analgesic (e.g., fentanyl ).
  • See “Sedatives for procedural sedation” for details.

Avoid using sedatives for procedural sedation at doses that can worsen hypotension in unstable patients.

Ensure oxygen is turned off or that the flow of oxygen is moved away from the patient during the procedure since cardioversion may trigger combustion.

Synchronized electrical cardioversion ^[1][4][5]

• Definition: A form of electrical cardioversion in which a low-energy shock is delivered at or just after the peak of the R-wave of the QRS complex.
• Indications
  • Unstable narrow-complex tachycardia with pulse (e.g., supraventricular tachycardia, including Afib with RVR and atrial flutter)
  • Unstable regular wide-complex tachycardia with pulse (e.g., monomorphic ventricular tachycardia)
• Steps
  1. Preparation and procedural sedation for cardioversion
  2. Place paddles or electrode pads firmly on the thorax of the patient (anteroapical or anteroposterior position).
  3. Choose the synchronized (SYNC) mode of shock on the defibrillator device.
  4. Select the recommended dose of electrical energy according to the patient's cardiac rhythm. ^[1][4][5]
     • Regular narrow-complex tachycardia: 50–100 J biphasic waveform
     • Irregular narrow-complex tachycardia: 120–200 J biphasic waveform (preferred) OR 200 J monophasic ^[9]
     • Regular wide-complex tachycardia: 100 J biphasic waveform
  5. “Clear” the patient.
  6. Deliver shock.
  7. Reassess the rhythm and check the pulse.

Defibrillation ^[10]

• Definition: A form of electrical cardioversion in which a high energy shock is delivered transthoracically to the precordium but not timed with any part of the cardiac cycle
• Indications
  • Unstable irregular wide-complex tachycardia with pulse (e.g., polymorphic ventricular tachycardia with a pulse)
  • Pulseless patient/cardiac arrest (See “ACLS.”)
• Steps
  1. Preparation and procedural sedation for cardioversion
  2. Place paddles or electrode pads firmly on the thorax of the patient (anteroapical or anteroposterior position).
  3. Choose the unsynchronized mode of shock on the defibrillator device.
  4. Select the defibrillator dose: 120–200 J biphasic waveform. ^[1]
  5. “Clear” the patient.
  6. Deliver shock.
  7. Reassess the rhythm and check the pulse.

Subsequent management

• Reversion to sinus rhythm (i.e., successful cardioversion)
  • Urgent cardiology consult
  • Consider anticoagulation.
  • Transfer to ICU or CCU.
  • Continuous telemetry and pulse oximetry
• Persistent arrhythmia (i.e., failure to cardiovert)
  • Administer a second dose of cardioversion
  • Call for expert help.
  • Consider antiarrhythmic infusion in consultation with a cardiologist.
  • Continue resuscitation.
• Deterioration to a life-threatening rhythm or pulseless patient: Start CPR (see “ACLS”).

Initial management of stable, regular narrow-complex tachycardia ^[11]

1. Determine the underlying rhythm.
   • If the underlying rhythm cannot be identified, see “Management of undifferentiated SVT.”
   • If AVNRT, AVRT, or focal atrial tachycardia can be identified, treat the same as undifferentiated SVT (see “Management of undifferentiated SVT”).
   • If sinus rhythm is identified, identify and treat the underlying cause.
   • Management of rapid atrial flutter is the same as management of Afib with RVR.
2. Consult cardiology for definitive management and follow-up.

Management of undifferentiated SVT ^[11][12]

1. Perform vagal maneuvers. ^[12]
2. Reassess the rhythm.
   • Rhythm reverts to normal sinus rhythm: Monitor for recurrence.
   • Regular SVT is identified:
     • No contraindications to adenosine: Administer adenosine.
     • Contraindications to adenosine present: Administer an AV-nodal blocking agent.
   • Irregular SVT is identified: See “Management of stable, irregular narrow-complex tachycardia.”
3. If regular or undifferentiated SVT persists despite adenosine, administer one of the following:
   • A nondihydropyridine calcium channel blocker
     • Verapamil
     • Diltiazem
   • OR a β-blocker
     • Metoprolol
     • Esmolol
4. If regular or undifferentiated SVT persists despite the above measures:
   • Start an antiarrhythmic
     • Amiodarone (preferred in patients with heart failure)
     • Ibutilide
   • OR perform synchronized electrical cardioversion.
5. Consult cardiology for definitive management.

If the patient becomes hemodynamically unstable, perform synchronized electrical cardioversion.

Calcium channel blockers should be avoided if there is any concern for ventricular tachycardia, as they can precipitate ventricular fibrillation.

Differential diagnoses

If it is not possible to differentiate between the different types of SVT and expert consultation is not available, treat tachycardia as undifferentiated SVT.

Initial management of stable, irregular narrow-complex tachycardia ^[1]

1. Determine the underlying rhythm.
   • If the underlying rhythm cannot be identified, see “Management of undifferentiated SVT.”
   • If the patient has rapid Afib or atrial flutter, choose between rate control or rhythm control strategy and start anticoagulation (see “Management of Afib with RVR”).
   • If the patient has MAT, start medications to control heart rate (See “Management of MAT”).
   • If the distinction between MAT and atrial fibrillation/flutter cannot be made and expert consultation is not immediately available, start rate control (preferably with diltiazem ) until expert opinion can be obtained.
2. Consult cardiology for definitive management and follow-up.

Differential diagnoses

Afib is the most common cause of irregular NCT, followed by atrial tachycardia. MAT is an uncommon cause of tachyarrhythmia; it is often associated with congestive heart failure and COPD. ^[11][19]

Establishing the underlying rhythm in a patient with wide-complex tachycardia can be extremely challenging and requires a multifaceted approach. The most critical aspect is to distinguish between ventricular tachycardia (VT) and SVT with accessory pathway, but if this cannot be done in a timely manner any wide-complex tachycardia should be treated as VT, as wide-complex tachycardias are most commonly caused by ventricular arrhythmias. Ventricular fibrillation is an unstable rhythm and is not addressed here. ^[11][20]

Initial management of stable wide-complex tachycardia

1. Attach defibrillator pads to the patient.
2. Ensure that the rhythm is stable.
   • If any sign of hemodynamic instability: Deliver unsynchronized electrical cardioversion (at 200 J for biphasic defibrillators).
   • If the patient at any point becomes unresponsive or no pulse is palpable, start CPR (see “ACLS”).
3. Check 12-lead ECG and perform a brief, focused history (if there is time).
4. Determine whether the rhythm is more likely to be ventricular or supraventricular in origin (e.g., Brugada criteria) ^[1]
   • VT (∼80%): Determine the morphology. ^[20]
     • Monomorphic VT: pharmacological cardioversion or synchronized electrical cardioversion (100 J)
     • Polymorphic VT: pharmacological cardioversion or defibrillation (120–200 J)
       • Torsades de pointes (most common): IV magnesium
   • SVT (< 20%): Determine if an accessory pathway is present. ^[20]
     • Findings suggestive of an accessory pathway: synchronized electrical cardioversion or IV procainamide ^[21]
       • HR > 200
       • Irregular rhythm
       • No bundle branch block on ECG
       • Signs of impending instability (e.g., clammy skin)
       • Baseline ECG findings that support the diagnosis
     • No signs of an accessory pathway: consider managing as SVT (See “Management of undifferentiated SVT.”)
   • Undifferentiated wide-complex tachycardia: Treat as VT, with either electrical cardioversion or IV procainamide (see “Management of stable, undifferentiated ventricular tachycardia”).
5. Urgent cardiology consultation for definitive rhythm identification, management, and follow-up (see “Differential diagnoses of wide-complex tachycardia”)
6. Identify and treat the underlying cause (e.g., cardiac glycoside poisoning, myocardial ischemia).

If it is not possible to quickly identify the underlying rhythm as SVT or VT, it is safest to treat empirically as VT with synchronized electrical cardioversion (100 J) or with IV procainamide.

Adenosine and AV nodal blocking agents are contraindicated in unstable, irregular, and polymorphic (e.g., Torsades des pointes) wide-complex tachycardias. In SVT with accessory pathway (e.g., Afib with WPW), the AV blockade caused by adenosine can lead to V-Fib due to unrestricted conduction of rapid atrial impulses through the accessory pathway.

Differentiating between VT and SVT

• There are multiple tools and strategies available, all with advantages and disadvantages.
• See “VT vs. SVT with aberrancy” for a comparison of common clinical and ECG features between these two.
• The Brugada criteria is a commonly used ECG-based algorithm to differentiate between VT and SVT in regular WCT. ^[22]

Management of stable, undifferentiated ventricular tachycardia ^[1][24][25]

• Prepare for potential decompensation, resulting in unstable tachycardia or cardiac arrest (see “Unstable tachycardia with pulse” and “ACLS”).
• Choose between pharmacological cardioversion or electrical cardioversion.
• Electrical cardioversion preferred in patients with structural heart disease.

Pharmacological cardioversion (IV antiarrhythmics)

• Procainamide is generally preferred. ^[25][26][27]
  • Avoid in patients with HFrEF or QTc prolongation.
• Consider also:
  • Amiodarone ^[1][25]
  • Sotalol (avoid in patients with HFrEF or QTc prolongation) ^[1][25]
• In confirmed regular monomorphic VT: Consider adenosine. ^[1]

Do not administer a second antiarrhythmic without expert consultation. ^[1]

Adenosine is contraindicated in polymorphic WCT and irregular WCT because of the risk of triggering ventricular fibrillation. Verapamil is contraindicated in WCT because of the risk of profound hypotension and cardiac arrest.

Electrical cardioversion

• Indications
  • Unsuccessful pharmacological cardioversion
  • Contraindications to pharmacological cardioversion
  • Structural heart disease: Consider electrical cardioversion as a first-line option. ^[25]
• Procedure: See “Electrical cardioversion” and “Procedural sedation.” ^[1]
  • Monomorphic VT: synchronized electrical cardioversion
    • Dose: 100 J (monophasic or biphasic); increase in a stepwise manner as needed
  • Polymorphic VT: defibrillation
    • Dose: 120–200 J (biphasic)

If it is unclear if a ventricular tachycardia is monomorphic or polymorphic, use defibrillation.

Further management

• Cardiology consult
• Persistent VT: Consider repeating electrical cardioversion and/or advanced therapies.
• Termination of VT: Identify and treat any underlying cause.
  • Suspected MI: See “Treatment” in acute coronary syndrome.
  • CHF: See “Treatment” in congestive heart failure.
  • Digoxin toxicity: See “Cardiac glycoside poisoning.”
  • Stop or replace drugs that cause prolongation of QTc interval.
  • Obtain electrolyte levels and correct electrolyte imbalance: See “Electrolyte repletion” and “Hyperkalemia.”
• If ≥ 3 episodes in 24 hours: Treat as electrical storm.
  • Identify and treat any underlying cause.
  • Refer for advanced therapies. ^[28]
• Admit to CCU/ICU.

Differential diagnoses