Narrow complex tachycardia resident survival guide

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Hilda Mahmoudi M.D., M.P.H.^[2]

Definition

Narrow complex tachycardia (NCT) is defined as a rhythm with heart rate > 100 beats per minute and a QRS complex duration < 120 milliseconds.

Differential Diagnosis for NCT

Supraventricular tachycardia	Any tachyarrhythmia that is initiated and maintained in atrial tissue or atrioventricular junctional tissue.
Sinus tachycardia	Rhythm with heart rate > 100 bpm, originating in SA node due to its increased automaticity.
Sinus node re-entry tachycardia	Rare paroxysmal tachycardia arising due to re-entry circuits with in SA node.
Atrial fibrillation	Supraventricular tachycardia with irregularly irregular rhythm and absent P waves on EKG.
Atrial flutter	Cardiac rhythm characterized by an atrial rate ranging from 240 to 400 beats per minute and regular continuous wave-form.
AVNRT	Most common form of PSVT with a heart rate of 140-250 bpm, re-entrant circuit involves two separate anatomical pathways (slow and fast) loacted in perinodal tissue.
AVRT	Re-entrant tachycardia, re-entrant circuit involves an accessory pathway in addition to AV node, accessory pathway is essential for initiation and maintenance of tachycardia.
Focal atrial tachycardia	Focal atria tachycardia refers to a rhythm originating from a single site either in the left or right atrium with an atrial rate of 100-250 bpm.
Nonparoxysmal junctional tahcycardia	Benign tachycardia occurring due to increased automaticity arising from a high junctional focus.
Multifocal atrial tachycardia	Irregular tachycardia characterized by 3 different P wave morphologies on EKG.

Causes

Life Threatening Causes

Life-threatening causes include conditions which result in death or permanent disability within 24 hours if left untreated.

Management

Shown below is an algorithm summarizing a stepwise approach to the initial diagnosis of an arrhythmia. Algorithm is according to the 2003 ACC/AHA/ESC guidelines for the management of patients with supraventricular arrhythmias.

Characterize the symptoms: ❑ Asymptomatic ❑ Palpitations ❑ Dyspnea ❑ Fatigue ❑ Chest discomfort ❑ Lightheadedness ❑ Syncope Characterize the timing of the symptoms: ❑ Onset ❑ Duration ❑ Frequency

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

❑ Examine the patient ❑ Order an EKG

❑ Analyze EKG

Documented arrhythmia (Arrhythmia mechanism is documented on EKG)

Undocumented arrhythmia (EKGis normal or does not suggest mechanism of arrhythmia)

Unstable patient

Stable patient

❑ History suggests extra premature beats.

❑ History suggests paroxysmal arrhythmia.

❑ Immediate direct current cardioversion.

❑ Confirm diagnosis of narrow QRS complex tachycardia.

Rule out following: ❑ Caffeine ❑ Alcohol ❑ Nicotine ❑ Recreational drugs ❑ Hyperthyroidism

❑ Refer for an invasive electrophysiological study AND/OR ❑ Catheter ablation ❑ Teach vagal maneuvers to patients. ❑ Consider beta blocking agent.

Acute management: ❑ Perform vagal maneuvers ❑ Valsalva maneuver ❑ Carotid massage ❑ Facial immersion in cold water

If vagal maneuvers fail: ❑ Administer IV adenosine† ❑ First dose: 6 mg; second dose: 12 mg; third dose: 18mg if required. ❑ 50-250 ug/Kg in pediatric patients

❑ Continuous EKG monitoring

If adenosine fails: ❑ Administer IV verapamil/diltiazem ❑ Verapamil: 5 mg IV over 2 minutes followed in 5-10 min by 5-7.5 mg if required. ❑ Diltiazem: 20 mg followed by 25-35 mg if required. ❑ Administer IV beta blocker

❑ Perform EKG simultaneously with drug administration

❑ Analyze changes on ECG

No change

Gradual slowing then re-acceleration of rate

Abrupt termination

Persisting atrial tachycardia with transient high-grade AV block

❑ Consider inadequate dose or inadequate delivery ❑ Consider VT

❑ Consider following ❑ Sinus tachycardia ❑ Focal AT ❑ Nonparoxysmal junctional tachycardia

Consider following causes: ❑AVNRT ❑AVRT ❑ Sinus node re-entry ❑Focal AT

❑ Consider atrial flutter OR ❑ Atrial tachycardia (AT)

Arrhythmia terminated

Persistent arrhythmia

No further therapy required if: ❑ Patient is stable ❑ LV function is normal ❑ Normal sinus rhythm on EKG

❑ Administer IV ibutilide‡ ❑ Administer IV procainamide ❑ Administer IV flecainide ❑ AV-nodal-blocking agent with above mentioned drugs ❑ DC cardioversion,

† Adenosine should be used cautiously in patients with severe coronary artery disease and may produce AF.
‡ Ibutilide is especially indicated for patients with atrial flutter but should not be used in patients with EF less than 30% as it increases risk of polymorphic VT.
AF: Atrial fibrillation; AV: Atrioventricular; BBB: Bundle-branch block; IV:Intravenous; QRS: Ventricular activation on ECG; VT: Ventricular tachycardia; LV: Left ventricle; SVT: Supraventricular tachycardia; SVT: Supra ventricular tachycardia; ECG: Electrocardiograph; AVNRT: Atrioventricular nodal reciprocating tachycardia; AVRT: Atrioventricular reciprocating tachycardia

Differential Diagnosis for Narrow QRS Tachycardia

Shown below is an algorithm summarizing the approach to differentiate various types of narrow complex tachycardia. Algorithm is according to the 2003 guidelines issued by ACC/AHA/ESC for the management of patients with supraventricular arrhythmias.

Narrow QRS tachycardia (QRS duration less than 120 ms)

❑ Determine the regularity of rhythm

Regular rhythm

Irregular rhythm

Consider following causes: ❑ AVRT ❑ AVNRT ❑ Atypical AVNRT ❑ Atrial tachycardia ❑ Atrial flutter

Consider following causes: ❑ Atrial fibrillation ❑ Atrial tachycardia/flutter with variable AV conduction ❑ MAT

❑ Determine if P waves are visible.

P waves are not visible

P waves are visible

❑ Consider AVNRT

❑ Determine if atrial rate is greater than ventricular rate.

Atrial rate > Ventricular rate

Atrial rate ≤ Ventricular rate

❑ Consider Atrial flutter or atrial tachycardia

❑ Determine if RP interval > PR interval

No (RP < PR)

Yes (RP > PR)

❑ Determine the duration of RP interval.

Consider following causes: ❑ Atrial tachycardia ❑ PJRT ❑ Atypical AVNRT

< 70 ms

> 70 ms

AVNRT

AVRT AVNRT Atrial tachycardia

† Echocardiographic examination is required in patients with documented sustained supraventricular tachycardia to rule out structural heart disease.

• Patients with focal junctional tachycardia may mimic the pattern of slow-fast AVNRT and may show AV dissociation and/or marked irregularity in the junctional rate.
  

AV: Atrioventricular; AVNRT: Atrioventricular nodal reciprocating tachycardia; MAT: Multifocal atrial tachycardia; ms: miliseconds; PJRT: Permanent form of junctional reciprocating tachycardia; QRS: Ventricular activation on ECG

Strength of Recommendations for Treatment of Stable and Regular Tachycardia

Management of narrow complex tachycardia SVT ▸ 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)

Additional Management

Order tests ❑ ECG ❑ Echocardiography ❑ In patients with sustained SVT† ❑ 24 hour holter monitor ❑ In patients with frequent but transient tachycardia ❑ Loop recorder ❑ In patients with less frequent arrhythmias ❑ Trans-esophageal atrial recordings ❑ If other investigations have failed to document an arrhythmia

Do's

• Refer narrow complex tachycardic patients with following characteristics to a cardiac arrhythmia specialist:

• Patients with drug resistance
• Patients with intolerance to drugs
• Patients who do not want any drug therapy.
• Patients with severe symptoms such as syncope and dyspnoea during palpitations.

• Refer all the patients with Wolff-Parkinson-White syndrome (WPW syndrome) to a cardiac arrhythmia specialist.
• Consider invasive electrophysiological investigation in presence of pre-excitation and severe disabling symptoms.
• Order a 12 lead ECG during use of adenosine or carotid massage.
• Consider esophageal pill electrodes in cases of invisible P waves.
• Administer higher doses of adenosine in patients taking theophylline.
• Administer IV adenosine or DC cardioversion in patients with PSVT requiring a rapid therapeutic effect.
• Perform following tests when indicated:

• Echocardiography

• In patients with sustained SVT to rule out structural heart disease.

Don'ts

• Do not perform esophageal stimulation if an invasive electrophysiological investigation is planned.
• Do not initiate treatment with anti-arrhythmic agents in a patient with undocumented arrhythmia.
• Do not administer adenosine in patients with severe bronchial asthma, heart transplant recipients.

References

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