In a 4 years old girl with hypo plastic left heart and Fontan surgery you encounter the following ECG tracing on the monitor:
There is sinus rhythm (upright P waves, PR interval 190ms - AVB I°) with frequent premature atrial contractions (PAC; negative P waves, short PR interval).
A few minutes later the ECG changes:
First beat is a PAC, followed by a sinus beat and subsequent run of atrial ectopy (beats 3-5). Further beats in the strip are atrial tachycardia with negative P waves preceding QRS complexes. Cycle lengths is regular (400ms, ie 150 bpm).
Due to associated symptoms of dizziness and impaired consciousness, the caring physician decided to terminate tachycardia by electrical cardioversion.
Synchronized eCV successfully converted tachycardia.
Atrial tachycardia (AT) is the 3rd most common form of supra ventricular tachycardia in children. Patients who had atriotomy or who might have atrial scar regions are at higher risk for AT. PACs are common in these patients. Origins of AT are not restricted to the right atrium as they may frequently originate from the left atrium as well.
Acute therapy includes class I anti-arrhythmic drugs (propafenone, flecainide), class III AADs (sotalol, amiodarone) or eCV.
Adenosine may be of diagnostic value, blocking the AV node and thus revealing continuing P waves at a regular cycle lengths.
Long term therapy may include class I AADs or ivabradine. However, AT usually very well amenable to catheter ablation, which should be considered first choice.