Differential Diagnosis and Management of Narrow Complex Regular Tachycardia
| Arrhythmia | Comment | Management |
|---|---|---|
Sinus tachycardia AV nodal re-entrant tachycardia (AVNRT) | May sometimes be difficult to distinguish from other causes of tachycardia Adenosine causes gradual deceleration of sinus rate followed by acceleration, with or without AV block The commonest cause of paroxysmal SVT Typically presents in teenagers or young adults with no underlying cardiac disease, though may present at any age Retrograde P wave usually hidden within or inscribed at the end of the QRS complex (simulating S wave in inferior leads, partial RBBB in V1) Heart rate usually 140–200/min | Identify and treat the underlying cause IV adenosine (Table 42.3) may be appropriate to exclude other causes of narrow- complex regular tachycardia if in doubt DC cardioversion if there is haemodynamic instability (uncommon) or other measures are ineffective In stable patient try vagotonic manoeuvres. If these fail, use IV adenosine, or verapamil* if adenosine is not tolerated or is contraindicated (Table 42.3) Record 12-lead ECG after sinus rhythm restored to check for pre-excitation (WPW syndrome) Refer to a cardiologist if episodes are frequent or severe or if pre-excitation is found |
| AV re-entrant tachycardia involving accessory pathway (AVRT) (Fig. 42.1) | Typically presents in children, teenagers or young adults with no underlying cardiac present | DC cardioversion if there is haemodynamic instability or other measures are ineffective |
| Retrograde P wave may be seen inscribed in the ST segment or the ascending limb of the T wave | In stable patient try vagotonic manoeuvres. If these fail, use IV adenosine, or | |
| Heart rate usually 140–230/min | verapamil* if adenosine is not tolerated or is contraindicated (Table 42.3) Record 12-lead ECG after sinus rhythm restored to check for pre-excitation (WPW syndrome) Refer to a cardiologist if episodes are frequent or severe or if pre-excitation is found | |
| Atrial flutter (Figure42.2) | Suspect atrial flutter with 2:1 block when the rate is 150/min | See Chapter 43 |
| Often associated with structural heart disease | DC cardioversion if there is haemodynamic instability or other measures are ineffective | |
| Vagotonic manoeuvres and adenosine slow the ventricular rate to reveal flutter waves | In stable patient, aim for rate control with AV node-blocking drugs (Table 42.4) Discuss further management with a cardiologist | |
| Atrial tachycardia | Caused by discrete focus of electrical activity | DC cardioversion if there is haemodynamic instability or other measures are ineffective |
| P wave usually of abnormal morphology, at a rate 130–300/min, conducted with varying degree of AV block | In stable patient, aim for rate control with AV node-blocking drugs (Table 42.4) | |
| May be associated with structural heart disease in older patients | Discuss further management with a cardiologist |
AV, atrioventricular; RBBB, right bundle branch block; SVT, supraventricular tachycardia; WPW, Wolff-Parkinson-White.
ALERT Atrial flutter and atrial tachycardia may be irregular if there is variable AV conduction.
NOTE: 1. In up to 50% of patients with AVRT the accessory pathway is concealed and a delta wave is never present in sinus rhythm. These patients do not have Wolff-Parkinson-White syndrome.
2. It may be impossible to distinguish AVRT from AVNRT on the surface ECG. Initial treatment is identical.