The tachycardia algorithm in ACLS asks the basic questions:
Signs and symptoms due to tachycardia:
Narrow complex tachycardia: Usually more than 150 bpm.
Narrow complex QRS:
1. Look at the 12-lead ECG and ask:
Irregular + no P = Atrial fibrillation (may be junctional tachycardia)
Irregular + P: Multifocal atrial tachycardia (3 different P morphologies)
Regular: most everything else
2. Where is the P wave located with respect to the R?
*Compare QRS complex with resting; retrograde P manifesting as pseudo s in II, III,
aVR, or r’ in V1 may be a subtle finding.
P closely follows R: typical AVNRT (“slow-fast”), junctional tachycardia
R follows P closely: sinus tachycardia, atypical (“fast-slow”)
No P: Usually AVNRT (P hidden in QRS complex)
P halfway: any of the above. Consider atrial flutter.
AV dissociation with intermittent retrograde P. Junctional tachycardia.
3. Shape of the P wave?
Sawtooth shape: atrial flutter
P same as resting: Sinus Tachycardia; rarely, atypical flutter
P wave morphology different from sinus: ectopic atrial rhythm or retrograde P seen
in junctional tachycardia.
4. Delta wave or shortened PR interval:
Suggests WPW or pre-excitation.
150: consider atrial flutter with 2:1 block.
Above 250? Consider bypass tract.
6. Response to adenosine? *Avoid in COPD/asthma/WPW with atrial
fibrillation (usually wide complex QRS) because adenosine block of the AV
nodal pathway can speed up the rate.
-Underlying atrial rhythm as ventricular rate slows?
-Any retrograde P at the end of the tachycardia?
-AVRT and AVNRT terminate frequently with retrograde P. MAT splits 40%
of the time. Ectopic atrial tachycardia can split.
-Sinus tachycardia resulting from sinus nodal reentry can be terminated by
7. Junctional tachycardia is rare. AVNRT is more common than junctional tachycardia.
Usual junctional tachycardia rate 70-120. Usually VA 1:1 conduction.
-Diff DX: cardiac ischemia, dig toxicity, post cardiac surgery, metabolic, COPD
Automatic junctional tachycardia (rare, rare, rare): rate 110-250, with frequent AV
dissociation. Benign in adults, but dangerous in peds.
AVNRT: atrio-ventricular nodal re-entry tachycardia
AVRT: Atrial ventricular re-entrant tachycardia (bypass tract)
WPW: Wolff Parkinson White
MAT: Multi-focal atrial tachycardia