Sandbox/NCT
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]
Narrow Complex Tachycardia Resident Survival Guide Microchapters |
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Overview |
Causes |
Diagnosis |
Treatment |
Do's |
Don'ts |
Overview
Narrow complex tachycardia (NCT) is characterized by heart rate > 100 beats per minute and QRS complex of duration < 120 milliseconds. The NCT may originate in the sinus node, the atria, the AV node, the His bundle, or combination of these tissues causing rapid activation of the ventricles. Diagnosis of NCT is established by surface ECG in correlation with history and physical examination. Hemodynamically unstable patients should receive urgent cardioversion.
Causes
Life Threatening Causes
Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated.
Common Causes
Diagnosis
Shown below is an algorithm summarizing the approach for diagnosing narrow complex tachycardia according to the 2003 ACC/AHA/ESC guidelines for the management of patients with supraventricular arrhythmias.[1]
ECG: electrocardiogram; SVT: supraventricular tachycardia; ms: Milliseconds; bpm: beats per minute; NCT: Narrow complex tachycardia; AV: atrioventricular; AVNRT: atrioventricular nodal reciprocating tachycardia; MAT: multifocal atrial tachycardia; ms: milliseconds; PJRT: permanent form of junctional reciprocating tachycardia
Characterize the symptoms: ❑ Asymptomatic (most common presentation) | |||||||||||||||||||||||||||||||||||||||||||||
Identify possible triggers: | |||||||||||||||||||||||||||||||||||||||||||||
Differential Diagnosis of NCT | |||||||||||||||||||||||||||||||||||||||||||||
Examine the patient: General appearance Vitals
Neck
Cardiovascular examination
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❑ Assess hemodynamic stability
❑ Order and monitor the ECG
❑ Give oxygen if needed | |||||||||||||||||||||||||||||||||||||||||||||
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 | Consider the following causes: ❑ Atrial fibrillation | ||||||||||||||||||||||||||||||||||||||||||||
❑ 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 | ||||||||||||||||||||||||||||||||||||||||||||
❑ Determine if RP interval > PR interval | |||||||||||||||||||||||||||||||||||||||||||||
RP < PR | RP > PR | ||||||||||||||||||||||||||||||||||||||||||||
❑ Determine the duration of RP interval | |||||||||||||||||||||||||||||||||||||||||||||
< 70 ms | > 70 ms | ||||||||||||||||||||||||||||||||||||||||||||
Consider the following cause: ❑ AVNRT | |||||||||||||||||||||||||||||||||||||||||||||
Treatment
Initial Approach
Shown below is an algorithm summarizing the initial approach for narrow complex tachycardia according to the 2003 ACC/AHA/ESC guidelines for the management of patients with supraventricular arrhythmias.[1]Assess the hemodynamic stability of the patient | |||||||||||||||||||||||||||||||||||||||||||||
❑ Unstable patient | ❑ Stable patient | ||||||||||||||||||||||||||||||||||||||||||||
❑ If the rythm isn't sinus tachycardia: Urgent cardioversion | ❑ If the rythm is sinus tachycardia: ❑ Control the rate:
| Documented arrhythmia | Undocumented arrhythmia (ECG is normal) | ||||||||||||||||||||||||||||||||||||||||||
History suggestive of extra premature beats ❑ Sensation of a pause followed by a strong heart beat OR | History suggestive of paroxysmal arrhythmia ❑ Regular palpitations with sudden onset and termination | ||||||||||||||||||||||||||||||||||||||||||||
❑ Refer for an invasive electrophysiological study AND/OR ❑ Catheter ablation ❑ Educate about vagal maneuvers ❑ Consider beta blocker | |||||||||||||||||||||||||||||||||||||||||||||
Short Term Treatment of SVT in a Hemodynamically Stable Patient
Shown below is an algorithm summarizing the management of narrow complex tachycardia according to the 2003 ACC/AHA/ESC guidelines for the management of patients with supraventricular arrhythmias.[1]
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
Acute management: ❑ Perform vagal maneuvers (Class I, level of evidence B) | |||||||||||||||||||||||||||
If vagal maneuvers fail: ❑ Administer IV adenosine† (Class I, level of evidence A)
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❑ Assess changes on ECG following adenosine administration
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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)[2]
❑ IV beta blocker (Class IIb, level of evidence C)
❑ 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
OR | ||||||||||||||||||||||||||
† 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.
Type of Arrhythmia | EKG (lead II)† | Clues |
Supraventricular tachycardia | ![]() |
Any tachyarrhythmia that is initiated and maintained in atrial tissue or atrioventricular junctional tissue.[1] |
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.[3] | |
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.[4] |
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 occurring due to an accessory pathway in addition to AV node, accessory pathway is essential for the initiation and the 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 tachycardia | ![]() |
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. |
† EKG strips are a courtesy from ECGpedia.