Narrow complex tachycardia resident survival guide

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Hilda Mahmoudi M.D., M.P.H.^[2]; Twinkle Singh, M.B.B.S. [3]; Rim Halaby, M.D. [4]

Definition

Narrow complex tachycardia (NCT) is characterized by a heart rate > 100 beats per minute associated with a QRS complex duration < 120 milliseconds.

Causes

Life Threatening Causes

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

• Wolff-Parkinson-White syndrome
• VT

Common Causes

• Atrial fibrillation
• Atrial flutter
• Atrial tachycardia
• AVNRT
• AVRT

Management

Initial Management

Shown below is an algorithm summarizing the initial management of narrow complex tachycardia 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 ❑ Polyuria 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 ❑ Pulmonary embolism ❑ Coronary thrombosis ❑ Trauma

❑ Examine the patient ❑ Order an ECG

❑ Assess the ECG

Documented arrhythmia

Undocumented arrhythmia (ECG is normal)

Unstable patient

Stable patient

History suggestive of extra premature beats ❑ Sensation of a pause followed by a strong heart beat OR ❑ Irregularities in heart rhythm

History suggestive of paroxysmal arrhythmia ❑ Regular palpitations with sudden onset and termination

❑ Immediate direct current cardioversion

❑ Confirm diagnosis of narrow QRS complex tachycardia ❑ Identify and treat SVT

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

❑ Refer for an invasive electrophysiological study AND/OR ❑ Catheter ablation ❑ Educate about vagal maneuvers ❑ Consider beta blocker

ECG: electrocardiogram; SVT: supraventricular tachycardia

Identification of the Rhythm on ECG

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

Narrow QRS tachycardia ❑ Heart rate > 100 beats/min ❑ QRS duration < 120 ms

❑ Determine the regularity of rhythm

Regular rhythm

Irregular rhythm

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

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

❑ Determine P wave morphology

❑ Determine P wave morphology

❑ P waves are not visible

❑ P waves are visible

❑ > 3 P wave morphologies

❑ Absent P waves

❑ Sawtooth appearance of P waves

❑ Consider AVNRT

❑ Determine if atrial rate is greater than ventricular rate

MAT

Atrial fibrillation

Atrial flutter

Atrial rate > ventricular rate

Atrial rate ≤ ventricular rate

Consider the following causes: ❑ Atrial flutter ❑ atrial tachycardia

❑ Determine if RP interval > PR interval

RP < PR

RP > PR

❑ Determine the duration of RP interval

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

< 70 ms

> 70 ms

Consider the following cause: ❑ AVNRT

Consider the following causes: ❑ AVRT ❑ AVNRT ❑ Atrial tachycardia

Note: 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: milliseconds; PJRT: permanent form of junctional reciprocating tachycardia

Short Term Treatment of SVT in a Hemodynamically Stable Patient

Shown below is an algorithm summarizing the initial management of narrow complex tachycardia according to the 2003 ACC/AHA/ESC guidelines for the management of patients with supraventricular arrhythmias.

Acute management: ❑ Perform vagal maneuvers (Class I, level of evidence B) ❑ Valsalva maneuver ❑ Carotid massage ❑ Monitor ECG continuously

If vagal maneuvers fail: ❑ Administer IV adenosine† (Class I, level of evidence A) ❑ First dose: 6 mg rapid IV push, followed by 20 mL of normal saline bolus ❑ Second dose: 12 mg (if no response in 1-2 min) ❑ Monitor ECG continuously

❑ Assess changes on ECG following adenosine administration Changes on ECG Possible causes No change ❑ Inadequate delivery of the medication ❑ Inadequate dose ❑ VT Gradual slowing then re-acceleration of rate ❑ Sinus tachycardia ❑ Focal AT ❑ Nonparoxysmal junctional tachycardia Abrupt termination ❑ AVNRT ❑ AVRT ❑ Sinus node re-entry ❑ Focal AT Persisting atrial tachycardia with transient high-grade AV block ❑ Atrial flutter ❑ Atrial tachycardia

If adenosine fails, administer ONE of the following: ❑ IV verapamil 5 mg IV every 3-5 min, maximum 15 mg (Class I, level of evidence A) ❑ IV diltiazem (Class I, level of evidence A) ❑ 0.25 mg/kg over 2 minutes ❑ Additional 0.35 mg/kg over 2 minutes ❑ Maintenance infusion of 5-15 mg/hour ❑ IV beta blocker (Class IIb, level of evidence C) ♦ Metoprolol ❑ 5 mg over 2 minutes ❑ Up to 3 doses within 15 minutes ♦ Esmolol ❑ 250-500 μg/kg over 1 minute ❑ Maintenance with 50-200 μg/kg over 4 minutes (if needed) ♦ Propranolol ❑ 0.15 mg/kg over 2 minutes ❑ Monitor ECG continuously

Terminated arrhythmia

Persistent arrhythmia

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

❑ Administer AV-nodal-blocking agent AND one of the following ❑ IV ibutilide‡ ❑ 1 mg over 10 minutes (if ≥ 60 kg) ❑ 0.01 mg/kg over 10 minutes (if <60 kg) ❑ Repeat once after 10 minutes if needed ❑ IV procainamide ❑ 30 mg/min infusion, maximum 17 mg/kg ❑ Maintenance 2-4 mg/min ❑ IV flecainide 2mg/kg over 10 min OR ❑ 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 ejection fraction less than 30% as it increases risk of polymorphic VT.

AF: atrial fibrillation; AV: atrioventricular; AVNRT: atrioventricular nodal reciprocating tachycardia; AVRT: atrioventricular reciprocating tachycardia; BBB: bundle-branch block; ECG: electrocardiography; IV: intravenous; LV: left ventricle; SVT: supraventricular tachycardia; VT: ventricular tachycardia

Do's

• Refer patients with narrow complex tachycardia with any of the following to a cardiac arrhythmia specialist:

• Drug resistance
• Intolerance to drugs
• Refusal of drug therapy
• Severe symptoms such as syncope and dyspnea
• Wolff-Parkinson-White syndrome

• Consider trying different types of anti-arrhythmic agents in case the SVT is refractory; however, closely monitor the blood pressure and heart rate.

• Consider invasive electrophysiological investigation in presence of pre-excitation and severe disabling symptoms.

• Monitor the 12 lead ECG during the administration ofadenosine or carotid massage.

• Make sure the equipment for resuscitation is available during the administration of adenosine in case of the occurrence of any complication, such as ventricular fibrillation or bronchospasm.

• Consider esophageal pill electrodes in cases of invisible P waves.
• Administer higher doses of adenosine in patients taking theophylline.
• Perform the following tests when indicated:

• Echocardiography in case of sustained SVT to rule out structural heart disease
• 24 hour holter monitor in case of 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

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 or heart transplant recipients.

References

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