Allied Professional Corner

Atypical AFL: redo-ablation following prior PVI

This 77-year-old male, with a history of Paroxysmal Atrial Fibrillation, received a Pulmonary Vein Isolation ablation, in May 2019.The electrophysiology operator used a cryo balloon (Freezor Medtronic, MN)to perform the PVI in 2019. Following the completion of the PVI, an eccentric CS-activated flutter arose. In hopes of terminating the atypical flutter, the operator performed two additional lines of ablation in the left atrium; a mitral isthmus line and an anterior wall line. The additional RF energy did not terminate this atypical flutter, and a DCCV was administered to restore sinus rhythm, prior to the completion of the case. Upon follow-up, the patient presented to clinic in a 12-lead interpreted flutter. Pharmacologically treated following the initial ablation, the patient opted for a second ablation to cure this atypical flutter. On the procedure date, the patient presented in this atypical flutter, which exhibited a varying 3:1P:QRSratio. The atrial cycle length was consistently measured at a rate of 260ms.Via femoral venous access, a transeptal puncture was made to access the left atrium. An Advisor HD Grid (Abbott Laboratories Abbott Park, IL) was inserted to create an impedance-based geometry, a Local Activation Timing map, and a voltage map simultaneously.

What is interpretation of the following 3D maps acquired at the start of the procedure?

  • a. Clockwise Mitral Flutter
  • b. Counterclockwise Mitral Flutter
  • c. LA Roof Flutter
  • d. RA Flutter with passive LA activation
  • e. Septal Flutter due to previous transseptal access

Answer: b. Counterclockwise Mitral Flutter.


Upon map creation, a counterclockwise mitral valve dependent flutter was diagnosed. 


Figure 1) Left atrial geometry, denoting an electrical leak through the previously created mitral isthmus ablation line. Left: Local Activation Timing map (reentrant) Right: Voltage map (0.2mV-0.5mV)

Additionally, a second electrical leak was identified, near the previously performed anterior wall ablation line. It was determined that the CCW mitral flutter, was using substrate that remained electrically active, from the two previous incomplete ablation lines.


To terminate an atrial flutter, whether typical or atypical, a complete line of block must be created from a non-conductive area to another non-conductive area. Here, the physician performed an RF ablation from the LIPV to the RIPV. The area of termination was marked with a blue lesion.

Are we done? What is the next step? 


After a line of block is created, it should be tested for completeness. If there is a gap in the line, then the tachycardia may continue. The line was tested for block by pacing the heart below the ablation line. Here, this was performed by pacing the coronary sinus. The impulse traveled from the coronary sinus up both the posterior and anterior wall. When it traveled up to the posterior wall it reached the line of block created by RF ablation and was unable to continue. Notice the red near the ablation site followed by orange, and then the impulse could not continue.


The activation cannot travel from orange to purple (seen on the opposite side of the line) therefore block is observed. The wave of depolarization traveled up the anterior wall, over the roof, and down the posterior wall until it reached the line of block created.

This ablation line was successful in treating the patient’s atypical atrial flutter. There is still activation and voltage in the pulmonary veins. If the patient has a history of or at risk for atrial fibrillation, a PVI (pulmonary vein isolation) ablation may be performed next.