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Patient
67-year-old woman, hypertensive treated with flecainide for paroxysmal atrial fibrillation; palpitations with lipothymia; recording of this tracing at entry;
Trace
Very rapid tachycardia (over 200 bpm) with wide QRS (left axis, left delay); there is no typical conduction aberration pattern (right bundle branch block or left bundle branch block); atrial activation is difficult to visualize; it is therefore not possible to formally differentiate between ventricular tachycardia and 1:1 flecainide associated atrial flutter;
Trace
This second tracing was recorded after the intravenous infusion of beta-blockade; slowing of the ventricular rate, narrowing of the QRS complexes (left anterior fascicular block); the presence of long diastoles (2:1 or 3:1 conduction) allows evidencing a characteristic pattern of common atrial flutter; the first tracing corresponds to a 1:1 conducted flecainide associated atrial flutter with rate-dependent prolongation of the QRS duration (the ventricular rate on the first tracing is very similar to that of the atrial flutter rate);
Exergue
A wide QRS tachycardia in a patient receiving class Ic antiarrhythmic treatment should trigger the diagnosis of 1:1 flutter. The electrical pattern of this rhythm disorder is difficult to differentiate from that of a ventricular tachycardia with very wide QRS complexes of atypical morphology and an atrial activity that is often problematic to identify.
The electrophysiological properties of the atrioventricular node (decremental conduction) normally allows filtering the rapid atrial activation observed during a common flutter with the onset of a protective atrioventricular conduction block (2:1, 3:1, etc.).