Blanked flutter

Patient

This 57-year-old woman presented with pulmonary arterial hypertension, on a treatment of anticoagulation and amiodarone for episodes of paroxysmal AF, underwent implantation of a dual chamber pacemaker for management of syncopal episodes due to paroxysmal AV conduction disorder; she was hospitalized for cardiac decompensation with palpitations for 2 weeks.

Trace

Tracing 5a: the first channel is lead I of the surface ECG with the markers superimposed, the second shows the atrial EGM and the third shows the ventricular EGM;

rapid atrial rhythm at approximately 130 bpm (upper synchronous rate programmed at 140 bpm) followed by 1:1 ventricular pacing; the atrial EGM reveals that the rhythm is atrial tachycardia with every other event not sensed by the device, as they fell in the post-ventricular atrial blanking period;

Tracing 5b: interrogation of the pacemaker indicated that the blanked flutter search algorithm was not programmed ‘on’; the algorithm was then turned ON;

continuation of the rapid AS-VP rhythm;
successful programming of the blanked flutter search algorithm;
over 8 consecutive cycles, the AA interval is shorter than twice the sum of the AV delay + atrial post-ventricular blanking period, and shorter than twice the programmed rate sensing interval: suspicion of 2:1 flutter; at the 9th cycle, the PVARP is lengthened; the event previously labeled AS is now labeled AR and no longer followed by ventricular pacing; the following atrial event, thus far concealed in the post-ventricular pacing atrial blanking period, is visualized in absence of ventricular pacing and labeled AS; diagnosis of blanked 2:1 flutter;
switch (MS) to mode DDIR;
gradual slowing of the ventricular pacing rate;
return of the spontaneous ventricular rhythm; Tracing

Tracing 5c: the 12-lead ECG is consistent with typical flutter;

the tracing shows persistent atrial flutter with variable AV conduction;

Tracing 5d: the patient undergoes successful anticoagulation; an attempt is made at conversion of the atrial arrhythmia with rapid atrial pacing, using the pacemaker;

burst of rapid atrial pacing; the 2 – 3 sec duration and the rate (slightly faster than the flutter) of pacing were chosen by the cardiologist;
unsuccessful burst and persistence of atrial flutter;

Tracing 5e: new conversion attempt;

another burst, faster than the previous attempt;
conversion of atrial flutter to AF; the atrial EGM are faster and irregular in rate and morphology;

Comments

In this patient, the initial absence of fallback for this undiagnosed episode of flutter was the cause of prolonged, rapid ventricular pacing, which promoted the development of cardiac decompensation. She complained of palpitations of 2-week duration, day and night. The programming of the blanked flutter search algorithm interrupted this inappropriate pacing and returned ventricular conduction to a more acceptable rate. The attempt at conversion of the arrhythmia could be made only after effective anticoagulation had been achieved (>2 INR for >3 weeks). Pacing at a rate faster than the flutter was ineffective and further acceleration of pacing transformed flutter to AF.
This patient returned spontaneously to sinus rhythm a few minutes after the cessation of pacing. Atrial flutter often persists for prolonged periods of time. An attempt at conversion might be immediately successful and restore sinus rhythm, or the success might be delayed after an initial transformation of flutter to AF.

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