A 26-year-old woman, who has complained of palpitations in the past, presents to the emergency department ....

A 26-year-old woman, who has complained of palpitations in the past, is admitted via the A & E department with palpitations. Her ECG is shown below:

What does the ECG show and what should you do?

The ECG shows:
• Narrow-complex tachycardia, rate about 200/min
• No P waves visible
• Normal axis
• Regular QRS complexes
• Normal QRS complexes, ST segments and T waves

Clinical interpretation
This is a supraventricular tachycardia, and since no P waves are visible this is a junctional, or
atrioventricular nodal, tachycardia.

Diagnosis: Junctional (atrioventricular nodal re-entry) tachycardia.

What to do
Junctional tachycardia is the commonest form of paroxysmal tachycardia in young people, and

presumably explains her previous episodes of palpitations. Attacks of junctional tachycardia
may be terminated by any of the manoeuvres that lead to vagal stimulation - Valsalva's manoeuvre carotid sinus pressure, or immersion of the face in cold water. If these are unsuccessful, intravenous adenosine should be given by bolus injection.
Adenosine has a very short half-life, but can cause flushing and occasionally asthma. If adenosine
proves unsuccessful, verapamil 5-10 mg given by bolus injection will usually restore sinus rhythm.
Otherwise, DC cardioversion is indicated.