Narrow complex tachycardia

ECG shows rate of >100bpm and QRS complex duration of <120ms (<3 small squares at the rate of 25mm/s).

Differential diagnosis : Sinus tachycardia, Atrial fibrillation (AF), Atrial flutter, Atrial tachycardia, Multifocal atrial tachycardia, AV nodal re-entry tachycardia, AV re-entry tachycardia (e.g. WPW)

Management

Be guided by patient status.

If the patient is compromised, use DC cardioversion

• Oxygen if SaO2 <90%
• IV access
• 12-lead ECG
• If the patient has adverse signs (shock, myocardial ischemia (chest pain or ECG changes), syncope, heart failure)
• Sedation
• Synchronized DC Up to 3 shocks 70–120J for the first shock (120–150J for AF)*
• Then120–360J for subsequent shocks
• Check and correct K+, Mg2+, Ca2+
• Amiodarone 300mg IV over ≥20min
• Consider repeat shock
• Then Amiodarone 900mg/24h IVI (via central line)
• If No adverse signs
• Identify the underlying rhythm and treat accordingly
• Decide whether the rhythm is regular or not
• If Irregular, treat as AF (the most likely diagnosis) (see below)
• If regular
• Start continuous ECG trace
• Vagal maneuvers (caution if possible digoxin toxicity, acute ischemia or carotid bruit)
• If it fails, Adenosine: 6mg IV bolus into a large vein, followed by 0.9% saline flush
• If unsuccessful, after 2min give 12mg bolus, then one further 12mg bolus (if necessary).
• If adenosine fails or contraindicated
• Verapamil 2.5–5mg over 2min is an alternative (see below for Verapamil alternatives)
• If Sinus rhythm achieved
• Probable paroxysmal re-entrant SVT
• Assess ECG for e.g. WPW If recurrent consider referral for electrophysiology/prophylaxis (see below)
• If Sinus rhythm Not achieved, Possible atrial flutter (Control rate with, e.g. Beta-blocker) (see below)

Specific Management

Sinus tachycardia

Identify and treat underlying cause

Supraventricular tachycardia

• If adenosine fails
• Use verapamil 2.5–5mg IV over 2min. (NOT if on a beta-blocker)
• If no response, a further 5mg IV over 3min (if age <60yrs)
• Verapamil alternatives are:
• Atenolol 2.5mg IV repeated at 5min intervals until 10mg given
• Or Amiodarone
• If all unsuccessful, use DC cardioversion

Atrial fibrillation

• If the patient is stable & AF started <48h ago: rate or rhythm control may be tried.
• For rhythm control, DC cardiovert under sedation
• Or give flecainide 300mg oral (only if definitely no structural heart damage) (CI: structural heart disease, IHD)
• Or amiodarone 300mg IVI over 20–60min, then 900mg over 24h.
• Startheparin in case cardioversion is delayed
• If the patient is stable & AF started >48h ago or unclear time of onset
• Rate control with one of the following:
• Beta-blocker: e.g. metoprolol 1–10mg IV, give small increments to slow rate
• Or Verapamil 5–10mg IV
• Or Digoxin is an alternative in heart failure (load with e.g. 500mcg oral then 500mcg oral after 8h and further 250mcg oral after 8h)
• Or Amiodarine (may also control rhythm, see above)
• Consider anticoagulation with warfarin or NOAC.
• If rhythm control is chosen, the patient must be anticoagulated for >3wks first.
• Correct electrolyte imbalances (K+, Mg2+, Ca2+)
• Treat associated illnesses (e.g. MI, pneumonia)

Atrial flutter

• Similar to AF regarding rate and rhythm control and the need for anticoagulation.
• DC cardioversion is preferred to pharmacological cardioversion; start with 70–120J.
• Amiodarone IV may be needed if rate control is proving difficult.
• Radiofrequency ablation is often recommended for long-term management as recurrence rates are high.

Atrial tachycardia

• Rare, maybe due digoxin toxicity or withdraw digoxin
• Consider Digoxin-specific antibody fragments
• Maintain K+ at 4–5mmol/L.

Multifocal atrial tachycardia

• Most commonly occurs in COPD
• Correct hypoxia and hypercapnia
• Consider verapamil if rate remains >110bpm.

Junctional tachycardia

• Vagal maneuvers
• If it fails, Adenosine
• If it fails or recurs, Beta-blockers (or verapamil—not with Beta-blockers, digoxin, or class I agents such as quinidine)
• If all fails, consider radiofrequency ablation

Wolff -Parkinson-White (WPW) syndrome

• Flecainide, propafenone, sotalol, or amiodarone.
• Electrophysiology and ablation of the accessory pathway.